Front Cover
 Title Page
 The cover
 Table of Contents
 Program development
 Outreach activities
 Field programs
 Supporting research
 Research utilization
 Associated research activities
 International visitors
 Participation in meetings, conferences,...

Annual progress report
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00054172/00001
 Material Information
Title: Annual progress report
Cover title: Vertebrate damage control research in agriculture annual report
Investigaciones sobrre el control de daños causados por los vertebrados en la agricultura infore anual
Physical Description: v. : ill. ; 27 cm.
Language: English
Creator: Denver Wildlife Research Center -- Cali, Colombia Field Station
Instituto Colombiano Agropecuario
United States -- Agency for International Development. -- Office of Agriculture and Fisheries
Publisher: Research Center, Centro de Investigaciones.
Place of Publication: Palmira Columbia
Creation Date: 1978
Frequency: annual
Subjects / Keywords: Pests -- Control -- Periodicals -- Colombia   ( lcsh )
Genre: federal government publication   ( marcgt )
serial   ( sobekcm )
Language: Cover title also in Spanish.
Statement of Responsibility: Cali, Colombia, Field Station.
Dates or Sequential Designation: 1970-
Issuing Body: Cooperating agencies: Instituto Colombiano Agropecuario, Office of Agriculture and Fisheries, Bureau of Technical Assistance, U.S. Agency for International Development, Denver Wildlife Research Center, Bureau of Sport Fisheries, U.S. Dept. of the Interior.
 Record Information
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 05024769
System ID: UF00054172:00001

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Title Page
        Page i
        Page ii
    The cover
        Page iii
        Page iv
    Table of Contents
        Page v
        Page vi
        Page vii
        Page viii
        Page ix
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        Page xi
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
    Program development
        Page 7
        Page 8
    Outreach activities
        Page 9
        Page 10
        Page 11
        Page 12
    Field programs
        Page 13
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            Page 55
            Page 56
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            Page 58
            Page 59
            Page 60
    Supporting research
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
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    Research utilization
        Page 99
        Page 100
        Page 101
        Page 102
    Associated research activities
        Page 103
        Page 104
        Page 105
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        Page 107
        Page 108
        Page 109
        Page 110
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        Page 113
        Page 114
    International visitors
        Page 115
        Page 116
    Participation in meetings, conferences, seminars
        Page 117
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Full Text



Denver Wildlife Research Center
U.S. Fish and Wildlife Service

U.S. Agency for International Development


Edited by
Donald J. Elias


U.S. Fish and Wildlife Service

U.S. Agency for International Development

Agricultural Agencies in Africa, Asia, and Latin America

International Agricultural Agencies



This work was conducted with funds provided to the U.S. Fish and
Wildlife Service by the U.S. Agency for International Development
under the following Participating Agency Service Agreements:

"Control of Vertebrate Pests"
"Control of Vampire Bats"
"Consultants and Seminars"
"Vertebrate Pest Component"



The photographs on the cover (from left to right, top to bottom)
illustrate the scope of research involved in the AID-sponsored Inter-
national Programs of the Denver Wildlife Research Center.

The common vampire bat has long been a source of economic loss and
hardship for livestock producers in Latin America. The trans-
mission of paralytic rabies and possibly other diseases, blood
loss, myiasis, and reduced production contribute to a multimillion
dollar problem annually.

Systemic treatment of cattle, by intraruminal injection of the
anticoagulant diphenadione, is one of two highly effective, safe,
and economical means of vampire bat control developed by DWRC

Rodents cause severe losses of coconuts in almost all countries
where they are grown. A control method developed by DWRC biolo-
gists has yielded dramatic results in field tests in Colombia and
the Philippines.

Quantification of the magnitude of food losses to vertebrate pests
on a worldwide basis is meager at best. Most published discus-
sions of food losses inevitably focus on micro-organisms or
arthropods and make only passing mention of vertebrate pests. The
development of reliable survey methods for measuring vertebrate
damage will result in a greater appreciation of the role of these
pests in food losses.

Laboratory research at DWRC by specialists in such fields as wild-
life biology, toxicology, animal behavior, physiology, statistics,
electronics, and chemistry play a major role in the development of
effective and appropriate control technology.

Vertebrate damage in agriculture involves a variety of crops and
species of animals, primarily birds and rodents. Direct losses
occur typically at planting and sprouting, during the milk or
dough stages (for grains), just before harvest, or under posthar-
vest storage conditions. Some damage may be mechanical, as when
crops are trampled or dislodged by animals. Losses may alter the
food value, as when rats selectively remove the germ from stored
corn, or may result from contamination with urine, feces, feath-
ers, or hair.

In many areas of the world, rodent damage to field crops causes
severe reduction of the human food supply and increases the risks
of small-farm agriculture. In localized areas, rodents may be a
principal factor limiting crop production; more often, rodents
unobtrusively remove a share of production before harvest--crop
after crop, season after season. Although there are more than
6,000 kinds of rodents, only about 50 can be considered signifi-
cant agricultural pests.

A central difficulty in development of vertebrate damage control
technology has been a tendency to ascribe minor importance to
species and environmental differences and to attempt transfer of
results from the laboratory to field areas where different
species, crops, and environmental factors prevail. Hence, on-site
field testing is requisite to a successful program. In addition,
such an approach affords excellent opportunities for training of
local specialists who will ultimately bear the responsibility for
vertebrate damage control programs in their countries.

Losses to birds are less well documented than those to rodents.
Various species of parrots, parakeets, blackbirds, weavers, doves,
seedeaters, pheasants, and waterfowl are among the types of birds
known to cause damage in agriculture around the world. Actual
losses are difficult to assess because damage is usually concen-
trated in limited areas and, due to the mobility of birds, is
often seasonal, sporadic, and hard to predict.

Research at DWRC and in the field involves evaluation of different
control methods including chemical, physical (such as this sub-
lethal electric barrier), cultural, or other techniques which have
potential for providing positive benefits by reducing vertebrate
damage in agriculture. The species, crop, farming methods, envi-
ronmental factors, and a host of other considerations may influ-
ence the manner in which a particular problem is approached.

The Denver Wildlife Research Center is well equipped with modern
scientific instrumentation, a broad-based technical library, and
linkages to computer systems. These tools provide the capability
for research into many facets of a vertebrate damage problem.

The results of research undertaken by DWRC staff and cooperators
around the world are regularly published in scientific and tech-
nical journals, progress reports, or special publications, often
in the language of the country or countries suffering a particular
pest problem. Nearly 200 publications have resulted from the
international activities of the DWRC since inception of the

The cover .

Contents .

Frontispiece .












Current s


NT . . . .
. .ES .. . . . .

e pest survey . . . .

e programs . . ...

tatus and future goals . .

. . . . . .

Behavior of rats in relation to coconut damage . .

Diffusion of the sustained baiting method among
Masagana-99 farmers in Laguna, Philippines . .

Development of an anticoagulant resistance monitoring
program on rats in the Philippines . .. .

Sugarcane yield losses due to rodents with reference to
species distribution, in-field stalk damage, varietal
preference, and movement under Philippine conditions .



Management of limiting factors in anticoagulant baiting
of lowland ricefield rats . . .... .29

Assessment of rat damage to corn . .. . 29

Glue stakes reduce bird damage in ricefields . 30

Use of crown baiting with wax blocks to reduce rat
damage in coconut palms . . . 31

Anticoagulant residues in the ricefields . .. 36

Preliminary trial of an electric rat barrier in a
farmer's ricefield . . . .. .36

Training . . . . .. ... 37

SUDAN . . . . . . 39

Indirect (population suppression) control efforts 40

Some economic aspects . . . . 40

Basis for estimates of cereal grain losses to quelea in
Africa . ............ . . . . 51

Summary of major bird damage problems in the Sudan 51

Repellent testing: efficacy of methiocarb for
protecting sorghum from house sparrow damage . .. 54

Field trials: Upper Nile, Blue Nile, Kordofan, and
Kassala Provinces . . . .... .55

Blue Nile Integrated Agriculture Development Project 56

Rodent problems in the Sudan . . .... 56

Personnel and training . . . .... .59

Cooperation with international and national
organizations . . . . 59


Toxicity of 1,3-difluoro-2-propanol (DFP) . .. 61

Laboratory bioassays of diphacinone baits . ... 62

Acute oral toxicity of CAT (DRC-2698;
N-(3-chloro-4-methylphenyl) acetamide) to male albino rats 65

Markers for toxic grease formulations . . .. 66

Evaluation of adhesives for foliar application of methiocarb 66

Evaluation of rodent glues . . . ... .67

Automatic data-acquisition system for measuring the bait
intake of ricefield rats (R. r. mindanensis) . ... 67

Drug-induced taste aversion in ricefield rats (R. r.
mindanensis): factors affecting drug effectiveness and
feasibility of use for reducing crop damage . ... 68

Laboratory tests of the repellent activity of selected
chemicals for protecting corn from damage by cotton rats
(Sigmodon hispidus) . . . . ... 75

Nonlethal electric barriers for control of ricefield rats 76

Development of highly preferred baits for quelea . .. 78

Design modification trials of sublethal electric barriers 82

Coulometric event counter problems corrected . ... 85

Chemical analyses of Philippine ricefield samples for
diphacinone and warfarin residues . . .... .85

A potential new wildlife marking agent . . .. 85

Bird-resistant sorghum research . . ... .92


Socio-economic evaluation of vampire bat control in Latin
America . . . . ... ....... .99

Vampire bat control workshop . . . .... 100


Vertebrate pests in the Dominican Republic . ... 103

Assessment of postharvest losses in Jamaica due to rodents 105

Vertebrate pests in Peruvian agriculture . ... 106

Losses and lesions in swine caused by vampire bats .... 108

Rodent control in coconut plantations on San Andres Island
(Colombia) . . . .... . 110

Observations on rodent problems in Latin American
agriculture . . . . ... ..... 111



PUBLICATIONS . . . ... . .. 121

SUMMARY .. ..... . . . ....... 123



The black-faced dioch or red-billed weaver (Quelea quelea) is a seri-
ous pest to small-grain farmers in Africa. It has the distinction of
being the most numerous and perhaps the most destructive bird in the
world. It is known to adversely affect the agricultural economies of
between twenty and twenty-five nations by its depredations of cereal
crops such as millet, sorghum, wheat, and rice.



About one-half of the world's population is actively engaged in agri-
culture. In spite of this, and in spite of many advances in agricul-
tural technology, millions of people in scores of nations still suffer
hunger, malnutrition, and starvation. The reasons for this are many
and complex, but certainly one important factor is food loss to crop
pests. Vertebrate pests (primarily rodents and birds) are responsible
for much of this loss but, historically, they have not received the
degree of attention given to other agricultural pests. Most published
discussions on food losses or agricultural pests inevitably focus on
pathogenic organisms or arthropods, while making only passing mention
of vertebrate pests. Hence, with few exceptions, little organized and
reliable information on the species involved, degree of damage, or the
resultant economic impact, is available.

In recent years, however, the role of vertebrate depredations in agri-
culture is attracting more interest in developing nations. Recognizing
this, the U.S. Agency for International Development (AID) has sup-
ported a research program at the Denver Wildlife Research Center
(DWRC) to evaluate these situations and, when circumstances warrant,
develop means to reduce or eliminate the damage. The overall objec-
tive of this project is to increase the available human food supply in
developing countries and reduce the risk of severe losses caused by
vertebrate pests. The ultimate goal of the research program is to
develop biologically sound, safe, effective, and economical control
methods which are suitable and practical for small farmers and accept-
able in the broader context of agricultural development.

Attainment of these goals is approached by: (1) in-country programs;
(2) outreach activities from the DWRC as requested by AID/Washington
or AID Missions; and (3) problem-oriented research activities at DWRC.
Vertebrate damage problems in Africa, Asia, and Latin America are
continuously reviewed. Current bird and mammal damage research and
development is also reviewed with the aim of adapting new techniques
or materials to specific problem situations.

The Denver Wildlife Research Center has, for many years, been recog-
nized throughout the world as a leader in development of vertebrate
pest control technology. The large, experienced staff is comprised of
specialists in diverse fields such as ecology, physiology, pharma-
cology, wildlife biology, nutrition, statistics, animal psychology and
behavior, chemistry, and electronics. Several staff members have

foreign experience and fluency in foreign languages. Denver Center
laboratories are well equipped with the instrumentation necessary to
conduct research in each of the disciplines involved. Although the
field staff is quite small, the Section of International Programs may
call upon the services and expertise of more than one hundred pro-
fessional and support personnel from other units of the Denver Center.

The Section of International Programs provides support and direction
to field personnel, assists in establishing relevant research objec-
tives for laboratory personnel, and coordinates the team efforts of
DWRC and cooperating scientists. Administrative support is provided
in the areas of fiscal management, personnel matters, commodity pro-
curement, records management, and coordination of correspondence,
reports, and manuscripts. Related activities include representing
the program to other organizations, coordinating DWRC-based training
for AID participants, briefing visitors, developing cooperative pro-
grams with international organizations, providing technical informa-
tion to USAID Missions or other cooperators, and assisting AID
personnel in program development and negotiations with foreign


Section of International Programs1

John W. De Grazio
Wayne H. Bohl
Michael W. Fall
Lynwood A. Fiedler*
G. Clay Mitchell
Richard M. Poch6**
Russell F. Reidinger, Jr.***
Donna J. Scott
Anneliese E. M. Valvano

Section of Supporting Sciences2

R. Daniel Thompson
Jean B. Bourassa3
Roger W. Bullard
Joseph Butler3
Kenneth A. Crane
Donald J. Elias
Stanley E. Gaddis3
Melvyn V. Garrison
David J. Hayes3
Diane C. Horton3
Paulette L. Isenmann3
Brad E. Johns3
Richard E. Johnson3
Stephen R. Kilburn
A. Lawrence Kolz
Dennis L. Meeker3
Iwao Okuno3
Lela A. Riebe
Carole M. Rowland3
Peter J. Savarie
Stephen A. Shumake
Dolores K. Steffen3
Ray T. Sterner3
James A. Whitehead3

Section Chief
Biologist (Sudan)
Biologist (Philippines)
Biologist (Bangladesh)
Biologist (Philippines)
Administrative Assistant

Section Chief
Electronics Technician
YACC Enrollee
Biology Technician
Biology Technician
Biology Technician
Biology Aid
Electronics Technician
Chemistry Technician
Electronics Engineer
Chemistry Technician
YACC Enrollee
Electronics Technician

Section of Bird Damage Control

Jerome F. Besser3


M. Z. Alam
Parvin Sultana
Yousuf Mian
Emdadul Haque

Counterpart Personnel (Sudan)4

Yousif Mohamed Ahmad
Salah Hassan Ali
Obeid Awad El Kariem
El Safi Mohamed El Mahadi
Ahmad Abo El Rahman
Ismail El Hag Khier El Seed
Ali Abdel Halim
Awad Moustafa Mahmoud
Babiker A. Ali
Abdel Latif Zarrough
El Sadig Awad Beshir

Counterpart Personnel (Philippines)4

Aurora K. Ammayao1
Edwin A. Benigno
Jose C. Castillo
Melanda M. Hoque
Justiniano L. Libay1
Jaime L. Olvidal
Danilo C. Sanchez
Fernando F. Sanchez
Jesus P. Sumangil

Cooperators, Participants,

Daniel B. Jayasingh
J. Fernando Londono
Danilo Valencia G.
Pedro Aguilar F.
Alberto Fernandez B.
Daniel Evans
Marcos Pefa F.
John D. Axtell
Martin L. Price
Richard A. Creelman
J. 0. York
Enrique Sanchez

and Graduate Students5

Dominican Republic
Dominican Republic
Purdue University
Purdue University
Texas A&M University
University of Arkansas

(Banal adesh )4

Counterpart Personnel

Cooperators, Participants, and Graduate Students5 (cont'd)

Francisco B. Castro
Romeo C. Dizon
Bienvenido R. Estioko
Agapito dela Paz
Roberto Rubio
Zosimo M. Sultan
Mohamed Hamza
Saeed Mohamed Suliman



Daniel D. Badger
Robert E. Rhoades
Denny G. Constantine

Oklahoma State University
University of Kansas
California State Health

1 Fully funded under a Participating Agency Service Agreement (PASA).

2 Partially funded under a PASA except as otherwise indicated.

3 Personnel not funded under a PASA but who participated in work
associated with or pertinent to this project.


nationals assigned to the project and funded by their
governments except as otherwise indicated.

5 Individuals who cooperated with the project in research,
extension, or project development activities or who participated as
students or trainees.

6 Hired under contract for specific assignment.
Badger was provided under contract AID/ta-C-1484.
Rhoades was provided under USAID RSSA/USDA 0176.
Constantine was provided partially under contract
partially under PASA ID/TAB-000-10-76.

Funding for
Funding for
Funding for

Lynwood A. Fiedler replaced Russell F. Reidinger, Jr., as DWRC
project leader at the Vertebrate Pest Control Unit, Philippine
National Crop Protection Center, in September.

** Richard M. Pochd entered on duty in March as project leader for
the AID/DWRC/Bangladesh vertebrate pest control project and reported
to his post in Dacca in November.

*** Russell F. Reidinger, Jr., left his post as project leader in the
Philippines in August, and was reassigned to the DWRC project at the
Monell Chemical Senses Center, Philadelphia, Pennsylvania.


Program development activities involved continued planning for new or
expanded vertebrate damage control research programs under the aus-
pices of both AID and the Food and Agriculture Organization (FAO) of
the United Nations. These are briefly discussed here. Detailed
information is given in the appropriate Project Papers or other perti-
nent documents.

FAO Vertebrate Pest Project for East Africa

At the request of FAO and AID, project personnel participated in the
design of a proposed FAO-funded regional project for East Africa.
This project is intended to promote technical cooperation between the
national governments of Ethiopia, Sudan, Somalia, Kenya, and Tanzania,
and FAO, the German Technical Assistance Program (GTZ), and AID/DWRC
(Denver Wildlife Research Center) for a period of 3 years.

The development objective is to establish a regional office for the
coordination of national bird damage control programs covering the
range of the two Quelea populations, aethiopica and intermedia. The
aim of the coordinated bird control program is to increase cereal crop
production by developing improved techniques for the control of damage
caused by birds, strengthening of government bird control services,
and by advising investors in cereal production of potential bird
damage problems and how to avoid them.

An office will be temporarily provided by the Desert Locust Control
Organization for Eastern Africa, DLCO(EA), for the purpose of using
this radio network for project communications. Each of the African
countries cooperating in the project is a member of DLCO(EA). During
the course of the project, the most appropriate international body
under which to permanently establish this office will be sought.

Immediate project objectives will be to: (a) increase the quantity
and improve the quality of professional survey and bird damage control
staffs in the plant protection services; (b) clarify the picture of
bird damage control problems in the member countries; (c) collaborate
with the USAID/DWRC project in the Sudan, the GTZ project in Tanzania,
and national FAO-assisted projects in Kenya, Ethiopia, and Somalia in
improving present methods of bird damage control and introducing new
methods where possible; and (d) assist in planning bird damage control
activities through development and implementation of a granivorous
bird reporting service.


As discussed in our 1977 report, the Rodent Research Center (RRC) was
incorporated into the National Crop Protection Center as a unit enti-
tled "Control of Vertebrate Pests." The RRC was originally estab-
lished and operated in conjunction with the AID/DWRC vertebrate pest
control program. Our association with and support of the project is


An amendment to the existing AID Agricultural Research Project for
Bangladesh proposed the inclusion of a vertebrate pest component (see
1977 report). We are pleased to report that all negotiations and
administrative matters have been completed and the project is under-
way. Further details are presented in the Field Programs section of
this report.

Latin America

The Latin America Bureau (AID/Washington) proposed the establishment
of regional programs in Latin America to address problems of verte-
brate pest damage to agriculture with special emphasis placed on
those crops predominantly produced by small farmers (see 1977
report). Work on this proposal continued during 1978 and culminated
with the completion of a Project Paper. This document is presently
being reviewed by AID/Washington.


DWRC staff and consultants traveled extensively in Africa, Asia,
Europe, and Latin America during the year. This travel was undertaken
in conjunction with ongoing field research activities; at the request
of foreign governments through AID Missions or AID Washington; to par-
ticipate in international meetings; or to review, evaluate, and coor-
dinate present and future research programs. Such travel involved 435
man-days in the following countries.

Kenya Bangladesh Colombia France
Kuwait Indonesia Costa Rica
Somalia Philippines Dominican Republic
Sudan Ecuador
Tanzania El Salvador

The dates, persons involved, countries visited, and the purpose of
each trip are outlined briefly in Table 1. Detailed information is
contained in individual trip reports on file at the Denver Wildlife
Research Center, Section of International Programs.

Table 1. Travel associated with DWRC international program activities.

Date Name Location Purpose of Visit

Jan 3-14

Feb 2-27

Feb 10-Mar 1

o Feb 14-Mar 17

Mar 5-14

Apr 14-May 4

Apr 16-21

May 2-5

D. D. Badger'

M. W. Fall

J. W. De Grazio

G. C. Mitchell

D. D. Badger'

A. L. Kolz

D. D. Badger'

M. W. Fall



Tanzania, Kenya,
Somalia, Sudan

Paraguay, Dominican
Republic, Costa
Rica, Nicaragua,
El Salvador,





Socio-economic evaluation of vampire bat
control program

Conduct rodent damage surveys; assist
Sudan project leader with administrative

Review AID/DWRC project in Sudan; member
of FAO formulation team for FAO Regional
Vertebrate Pest Project

Conduct classroom and field demonstra-
tions on vampire control in Paraguay;
present paper at symposium in Dominican
Republic; assess vertebrate pest prob-
lems in Central American agriculture

Socio-economic evaluation of vampire bat
control program

Field evaluation of nonlethal electric
barrier for ricefield rat control; pro-
vide training in electronics to NCPC
personnel; field test wildlife telemetry
and other electronic equipment

Socio-economic evaluation of vampire bat
control program

Participate in OECD/FAO/WHO Expert Con-
sultation meeting on rodent problems,
control, and research

Date Name Location Purpose of Visit

May 17-Jun 24

Jun 2-24

Jun 10-23

Jun 24-Jul 10

Jul 9-20

Jul 17-21

D. J. Elias
G. C. Mitchell

R. E. Rhoades2

D. D. Badger'
D. G. Constantine3

J. W. De Grazio

D. D. Badger'

D. J. Elias
J. F. Besser

Colombia, Ecuador,
Peru, Costa Rica,
Dominican Republic,
Haiti, Jamaica

Dominican Republic

Venezuela, Panama,



Weslaco, Texas

Project development: review and assess-
ment of vertebrate pest losses in agri-
culture for proposed Latin American
regional projects

Project development: social soundness
analysis, proposed L. A. projects

Socio-economic evaluation of vampire bat
control program

Review AID/NCPC/DWRC research activities
in the Philippines; confer with USAID
and government officials regarding
proposed vertebrate pest project in

Socio-economic evaluation of vampire bat
control program

Field tests; work associated with Sudan
quelea program. For economic and logis-
tic reasons, work could more easily be
accomplished in Texas, serving as a
model for later studies in Africa


Date Name Location Purpose of Visit

Aug 15-Sep 25

Sep 18-26

Oct 18-29

Oct 20-Dec 5

Nov 25-Dec 20

M. W. Fall

J. W. De Grazio

P. J. Savarie

J. F. Besser

M. W. Fall


Dominican Republic




Assist with ongoing research studies and
graduate training programs at NCPC
during interval between departure of
previous project biologist and arrival
of replacement

Project development: consultation with
AID Mission and local government offi-
cials regarding proposed L. A. regional

Participate as U.S. representative in
International Discussion Conference to
assess and recommend alternative control
methods for commensal rodents

Assist in field and laboratory research

Discuss rodent control activities with
government and WHO authorities in Indo-
nesia; assist new project leader in
planning and coordinating research pro-
gram in the Philippines

1 Funding for Dr. Badger provided unter contract AID/ta-C-1484.
2 Funding'for Dr. Rhoades provided under contract USAID RSSA/USDA 0176.

3 Funding for Dr. Constantine provided partially under contract AID/ta-C-1484 and partially
under PASA ID/TAB-000-10-76.


Three field projects, involving resident U.S. technicians, are cur-
rently operated under the AID/DWRC program. These are located in the
Philippines, the Sudan, and Bangladesh. The objectives of these field
projects and activities undertaken during the year toward achievement
of these objectives are summarized below.


The Bangladesh Agricultural Research Council of the Government of
Bangladesh requested assistance from the AID Mission in Dacca in
assessing the status of rodent research and control programs in the
country and to determine the type of program necessary to address the
problem. AID/Dacca, in turn, sought assistance from the DWRC in
accomplishing this review and formulating an appropriate response.

The review led to a proposed amendment of the existing AID Agricul-
tural Research Project for Bangladesh to include a vertebrate pest
component. The purpose of the proposed 5-year project is to establish
an ongoing research capability to adapt and/or develop vertebrate pest
management techniques suited to the needs of small farmers. Because
of its geographical limitations, Bangladesh must plan its economic
development almost exclusively around agriculture; hence, the impor-
tance of vertebrate pest control takes on even greater significance.
The proposal was favorably received and the project became reality in
November 1978. Laboratory facilities are presently under construction
at Joydebpur, 20 miles north of Dacca. This facility will contain
office space, animal rooms, and laboratory facilities. Mr. Richard M.
Pochg, the DWRC representative, is working with four Bangladeshi

Vertebrate pest survey

Vertebrate pests (especially rodents) are a recognized menace to agri-
cultural crops in Bangladesh but no systematic nor reliable documenta-
tion as to the extent of losses incurred is available. Therefore, one
of the first priorities of the project is to develop an effective
means of assessing damage, identifying species involved, and evalu-
ating the economic impact. To this end, a nationwide survey of verte-
brate pest problems was initiated in late 1978. Since the staple food
grain is rice, this initial survey will focus primarily on vertebrate
pest problems in rice and similar grain crops and will involve inter-
views with 1,000 farmers throughout the 20 districts of Bangladesh.
Rice is harvested in three seasons: aman (rain-fed, harvested


Three field projects, involving resident U.S. technicians, are cur-
rently operated under the AID/DWRC program. These are located in the
Philippines, the Sudan, and Bangladesh. The objectives of these field
projects and activities undertaken during the year toward achievement
of these objectives are summarized below.


The Bangladesh Agricultural Research Council of the Government of
Bangladesh requested assistance from the AID Mission in Dacca in
assessing the status of rodent research and control programs in the
country and to determine the type of program necessary to address the
problem. AID/Dacca, in turn, sought assistance from the DWRC in
accomplishing this review and formulating an appropriate response.

The review led to a proposed amendment of the existing AID Agricul-
tural Research Project for Bangladesh to include a vertebrate pest
component. The purpose of the proposed 5-year project is to establish
an ongoing research capability to adapt and/or develop vertebrate pest
management techniques suited to the needs of small farmers. Because
of its geographical limitations, Bangladesh must plan its economic
development almost exclusively around agriculture; hence, the impor-
tance of vertebrate pest control takes on even greater significance.
The proposal was favorably received and the project became reality in
November 1978. Laboratory facilities are presently under construction
at Joydebpur, 20 miles north of Dacca. This facility will contain
office space, animal rooms, and laboratory facilities. Mr. Richard M.
Pochg, the DWRC representative, is working with four Bangladeshi

Vertebrate pest survey

Vertebrate pests (especially rodents) are a recognized menace to agri-
cultural crops in Bangladesh but no systematic nor reliable documenta-
tion as to the extent of losses incurred is available. Therefore, one
of the first priorities of the project is to develop an effective
means of assessing damage, identifying species involved, and evalu-
ating the economic impact. To this end, a nationwide survey of verte-
brate pest problems was initiated in late 1978. Since the staple food
grain is rice, this initial survey will focus primarily on vertebrate
pest problems in rice and similar grain crops and will involve inter-
views with 1,000 farmers throughout the 20 districts of Bangladesh.
Rice is harvested in three seasons: aman (rain-fed, harvested

November-January); boro (irrigated, harvested April-June); and aus
(irrigated, harvested June-August). The aman harvest accounts for
about 60 percent of annual production. Therefore, the number of
interviews in each district is based on total aman rice production.
The sample size per district is: Rangpur, 91; Rajshahi, 76;
Mymensinjh, 67; Barisal, 65; Comilla, 64; Sylhet, 63; Dinajpur, 56;
Faridpur, 52; Noakhali, 51; Dacca, 51; Jessore, 43; Patuakhali, 42;
Pabna, 41; Bogra, 40; Chittagong, 39; Kishorganj, 36; Tangail, 31;
Kushtia, 12; and Chittagong Hill tracts, 5. For each farmer inter-
viewed, four rice- or wheatfields will be sampled for rodent damage.
The Dacca and Comilla districts are scheduled for completion in
February 1979.

This survey will require about 1 year to complete. It will provide
basic information on pest species distribution, damage accumulation
during various crop growth stages, and the primary periods of damage.
In wheat, for example, we have determined that damage begins 30-40
days after planting and increases to 2.8 percent by 70-75 days after
planting (based on a sample of 200,000 stems in 154 wheatfields).
Extrapolation of these preliminary data suggests that rodent damage
to wheat will average 6-8 percent throughout most of Bangladesh.

The following is a summary of major vertebrate pest problems in
Bangladesh, based on presently available information. Knowledge
gained from current and planned damage surveys and other research
activities may change the picture as time goes on.


The Indian mole rat (Bandicota bengalensis) and the short-tailed mole
rat (Nesokia indica) inflict heavy damage in all cereal crops. Rattus
fulvescens, Rattus rattus, and Bandicota bengalensis infest godowns
(grain storage facilities) throughout Bangladesh.

The Indian porcupine (Hystrix indica) destroys much pineapple and
groundnut production in many areas of the country. The hoary-bellied
Himalayan squirrel (Callosciurus pygerythrus) damages fruits and nuts
in the Chittagong Hill tracts region. Damage they inflict on betel
nut trees (an important cash crop) retards production for 2 years. In
the Barisal, Jessore, and Khulna districts, the five-striped palm
squirrel (Funambulus pennanti) and the three-striped palm squirrel
(F. palmarum) damage many crops including corn, peanuts, and coconuts.
The Indian hare (Lepus nigricollis) causes problems in pulses,
sprouting corn, and soy beans.

In sugarcane, rodents damage young (4-6 month) plants by severing the
canes at ground level or digging into the root system and retarding

-i C~' 7 'I~rF


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Bandicoot rats (Bandicota bengalensis) and mole rats (Nesokia indica) do considerable damage
in agricultural crops. These animals burrow extensively and may severely damage irrigation
systems by tunneling through canal walls. They are among the more serious vertebrate pests in

I Z.


growth. Damage by rodents is reportedly light, averaging from 1 to 4
percent. Jackals (Canis aureus) are apparently a more serious pest in
sugarcane than rodents. They attack the crop when it is nearly mature
and the sugar content is high. Packs of jackals invade cane fields
at night and chew on the cane stalks, rendering them unmarketable. In
areas where sugarcane production averages only 6-10 tons/acre, damages
of 40-80 percent are having a severe economic impact. The Sugarcane
Research Institute (SRI) is very interested in developing a solution
to this problem. Jackals also damage ripening corn.

The Indian flying foxes (Pteropus giganteus and Cynopterus spp.)
reportedly cause heavy damage to bananas, mangoes, guava, and other
fruits. Many farmers complain that these bats also damage the inflo-
rescence of banana trees, resulting in decreased fruit production.


The major bird damage problems in Bangladesh occur in sprouting wheat.
Mynas (Acridotheres spp. and Sturnus spp.), crows (Corvus spp.), and
sparrows (Passer spp.) destroy much of the crop. Weaverbirds (Ploceus
spp.), munias (Lonchura spp.), and parakeets (Psittacula spp.) inflict
severe damage in mature rice and wheat. Corn, a recently introduced
crop, is fast becoming a favorite target of parakeets.


In preparation for the aforementioned vertebrate pest survey, a 1-week
training program was held at the BARI Central Library. The DWRC
project leader provided instruction on completion of the interview
questionnaire, sampling designs in rice and wheat, random vs. area
sampling methods, study skin preparation, and trapping methods and
configurations. In addition, a visit to the central godown in Dacca
gave trainees an opportunity to examine evidence of rodent activity.
Participants in this training session included six BARI officers, six
Plant Protection staff members, and two Bangladesh Rice Research
Institute (BRRI) officers.

Cooperative programs

A German government (GTZ) rodent control program was initiated at
about the same time as the BARI/DWRC Vertebrate Pest project. The
BARI and the Plant Protection Department (host agency for GTZ) are
jointly undertaking the vertebrate pest survey. The Bangladesh Agri-
cultural Research Council is assisting in coordination of activities.
Two field teams (one directed by GTZ and the other by DWRC) are
working simultaneously. The outcome of this effort will be a joint
report outlining the major rodent problems and areas of concern.

Current status and future goals

The BARI/DWRC vertebrate pest project existed for a total of 33 days
in 1978. Thus, most research activities are still in the planning
stage and are pending nomination of a permanent staff, completion of
project facilities, receipt of equipment, vehicles, etc. Among
planned research projects are the following:

1. Completion of vertebrate pest survey: this will include distribu-
tion of pest species; identification of problem areas, cropping
patterns, and season of damage; evaluation of traditional control
methods; economic evaluations of damage and control technology; and
evaluation of farmer attitudes toward control.

2. Damage assessments in rice and wheat: continuation of the current
evaluation of rodent damage during various growth stages of these
crops and development of accurate and sensitive vertebrate damage
assessment methods.

3. Rodent control in deep-water rice: one-third of Bangladesh floods
under 0.60-3.60 m of water during the monsoons (June-September), and
deep-water rice is becoming an increasingly important crop. Rodent
damage becomes more concentrated and significant during these periods.

4. Ecology of major rodent pest species: effective control of these
pests may be dependent on a knowledge of their burrowing and other

5. Toxicology: efficacy of different chemical control agents on
major rodent pests.

These and other research projects are currently being planned for
initiation in 1979, however, a definitive schedule has not been

Bangladeshi counterparts learn the art of preparing study skins. Proper identification of
species and a knowledge of their habits are important in the development of effective control

-- -


The goal of the project is to reduce vertebrate damage to agricultural
crops in the Philippines and other Southeast Asian countries. Dr.
Russell F. Reidinger, Jr. (January-August) and Mr. Lynwood A. Fiedler
(November-December), representing the DWRC, nine Filipino biologists,
and a number of graduate students and cooperating personnel worked
toward attainment of this goal through developmental and adaptive
research projects, training programs, and extension activities.

Research projects during 1978 involved investigations aimed at
reducing vertebrate pest damage to rice, coconut, corn, and sugarcane
crops. Emphasis was placed on: development of delivery systems,
including bait station comparisons and evaluation of various bait for-
mulations; damage assessment and yield loss determinations; evaluation
of traditional farm level control technology; behavioral studies; and
development of a rodenticide resistance monitoring program. Training
continued to be a major part of the program both at the individual and
group level.

These activities are summarized below. Many of the studies were con-
ducted by graduate students as partial fulfillment of their degree
requirements (acknowledged in parentheses). In several cases, the
reports are partially repetitious since the work was initiated prior
to 1978 and has been discussed in previous (1976 or 1977) annual

Behavior of rats in relation to coconut damage

Rat damage is a common problem in coconut plantations and is a special
concern in the Philippines, the world's leading exporter of copra.
This study was aimed at developing a better understanding of the rela-
tionship between rat behavior and coconut production.

Field data were collected near Calauan, Laguna, in six 1-ha study
plots within a 120-ha coconut plantation with a history of chronic rat
damage. Trapping was used as a representative control method in two
plots (treatment), it was simulated in two plots (reference), and
radio telemetry was used in the remaining two plots to study rat move-
ment patterns. Feeding preference studies were conducted in labora-
tory cages. Damage and harvest data were recorded in both treatment
and reference plots and rat activity was monitored in both with
tracking tiles. Biological data were collected from rats trapped in
both treatment and reference plots during the final trapping period.

Rattus rattus mindanensis, R. exulans, and Suncus murinus were common
at ground level. R. r. mindanensis and R. exulans were also trapped

at the crown level, but both were relatively less abundant there than
on the ground. Trapping reduced both damage and activity in the
treatment plots while these remained high in the reference plots. R.
r. mindanensis exhibited a larger home range (963.2 m2) than R.
exulans (610.7 m2) and preferred a denser, more shrubby cover.

Medium-sized nuts were commonly damaged in the field but R. r.
mindanensis seemed to prefer the developing button stage in cage
tests. R. exulans did not respond well in cage preference tests
regardless of nut size. The relatively greater numbers of R. r.
mindanensis caught at the crown level and their more active feeding
during cage tests strongly suggest that R. r. mindanensis is the major
coconut pest; a conclusion consistent with the findings of other

The taking of a large number of S. murinus (an important insectivore
and a nontarget species) as a result of trapping at ground level,
indicates that this and similar control techniques might lead to
undesirable environmental consequences if they are not based on a
thorough understanding and consideration of all relevant ecological
and behavioral factors. Trapping in the crowns was much more selec-
tive in reaching target species and more effective from the standpoint
of long-term damage reduction. However, too selective a control can,
in some cases, lead to replacement of one species (e.g., R. r. minda-
nensis) with the other less dominant form (e.g., R. exu-lans) rather
than a general reduction in damage. Effective rat control in coconut
plantations can be influenced by numerous factors (i.e., species
composition, behavior, meteorological conditions, etc.), and each of
these factors must be taken into consideration and evaluated prior to
the design and implementation of a control program. (Sultan, M.S.

Diffusion of the sustained baiting method among Masagana-99 farmers
in Laguna, Philippines

The Masagana 99 (M-99) rice program in the Philippines is a noncollat-
eral credit program which allows repayable loans to small rice
farmers, provided that they follow recommended farming methods. This
program was considered a logical mechanism by which to disperse infor-
mation and establish the use of ricefield rodent control technology
developed by DWRC and Filipino biologists at the Philippine National
Crop Protection Center (formerly Rodent Research Center). The
inclusion of rat control technology into the M-99 program represented
the first attempt to implement a control program through an extension-
type program. The technology itself is based on the results of
intense scientific study and has received the endorsement of the
Philippine scientific community. With the effectiveness of the method

Rat damage is a common problem in coconut plantations and is a special concern in the
Philippines, the world's leading exporter of copra.

fairly well established, its inclusion in the M-99 program presented a
unique opportunity to follow the effectiveness of the extension pro-
gram in diffusing information to farmers.

Most of the results from this study were given in the 1977 annual
report. The information given here discusses the effectiveness of
M-99 agricultural technicians' (extension workers) efforts to promote
adoption of rodent control technology.

Of the 252 farmers who were frequently visited (once a week or at
least twice a month) by the technicians, only 32 were adopters. Only
eight of the 68 farmers who were visited less frequently (once a month
or less) by the technicians were adopters. In both cases, only two of
the four recommended practices were adopted and the promotional
efforts of the technicians did not have a significant relationship to
this acceptance. This was due to the fact that only 17 percent of the
technicians had received formal training in rat control.

A lack of proper information about rat control technology and an
absence of rat damage (5-20 percent cut tillers was not considered
high by farmers) were the two reasons most frequently given by farmers
when they explained their reasons for not adopting the technology.
The basis for this reasoning (especially concerning the lack of infor-
mation) was traced back to the lack of technical adequacy of the M-99
technicians themselves and also to the absence of a mass media (e.g.,
radio-TV, newspapers, etc.) informational effort.

No evidence was found to indicate that the adoption of two of the four
recommended rat control practices was triggered by the M-99 rice pro-
gram itself. However, the technology is apparently compatible with
the farmers' existing practices under the M-99 program and is effec-
tive. This is evidenced by the fact that rat damage was reduced in
sample barangays where partial adoption of the technique occurred. In
places where it was not accepted, rat damage was considerably higher.
(Dizon, M.S. thesis.)

Development of an anticoagulant resistance monitoring program on rats
in the Philippines

While acute toxicants, such as zinc phosphide and sodium fluoroacetate
(Compound 1080), have long been the favored rodenticides of farmers in
the Philippines and other Southeast Asian countries, the advantages
offered by chronic (anticoagulant) rodenticides are now generally
recognized and their use is increasing. However, intensive use of
anticoagulant rodenticides can lead to resistant rat populations.
This is because anticoagulants kill susceptible individuals and favor
the development of genetically resistant populations. This problem

has occurred in parts of Europe and the United States in locations
where anticoagulants were used intensively for a decade or so.

The purpose of this study was to: (1) gather baseline information
required to develop an efficient monitoring system for the control of
anticoagulant resistant rats in the Philippines including (a) develop-
ment of methods suitable for screening anticoagulant resistant rats
in two local pest species--R. r. mindanensis and R. argentiventer, and
(b) testing of compounds known to counteract deveTopment of anticoagu-
lant resistance in rat populations; (2) propose a system, based on the
above information, that could be used to regulate anticoagulant
resistance within acceptable ranges.

No-choice feeding tests, using 0.025-percent warfarin bait, were per-
formed on R. r. mindanensis (14 days) and R. argentiventer (10 days)
as a method for screening warfarin-resistant individuals. Animals
that survived for 10 days after withdrawal of the treated bait were
considered resistant.

The mean pretreatment plasma clotting time of R. r. mindanensis was
12.3 s. Animals treated (gavage) with 5 mg warfarin or 2.5 mg
diphacinone per kilogram of body weight had mean clotting times of
80.3 and 58.2 s, respectively, 48 h after treatment. These results
can be used to quantify anticoagulant-resistant or susceptible animals
of this species, granting that resistant rats will have lower clotting
times than the nonresistant animals used to establish the baseline

Feeding tests with 0.1-percent calciferol, 0.1-percent calciferol plus
0.025-percent warfarin, 0.025-percent warfarin, 0.005-percent broma-
diolone, and 0.002-percent biodifacoum resulted in similar mean num-
bers of days to death--6.7, 4, 5.9, 6.5, and 5.6, respectively, for R.
r. mindanensis. All treatments resulted in 100 percent mortality.

The information gathered in this study may serve as a guideline in
establishing a national anticoagulant monitoring program. This pro-
gram would detect resistant rat populations and offer alternate
rodenticide recommendations to control crop damage by anticoagulant-
resistant rats (Hoque, Ph. D. thesis, in progress).

Sugarcane yield losses due to rodents with reference to species
distribution, in-field stalk damage, varietal preference, and movement
under Philippine conditions

Sugarcane fields, in 14 locations within 14 mill districts on Negros
Island, were surveyed for rat damage and yield losses. Five sampling
areas (4 m X 10 m) in fields of not less than 1 ha were selected

randomly. Total stalks, both damaged and undamaged, were counted at
the onset of hand harvest. An equal number of damaged and undamaged
stalks were weighed and the juice extracted. Laboratory analysis of
the extracted juice permitted an estimate of total sugar loss due to
rat damage. Two other sampling methods (random row sampling and cane
car or "Vagon" sampling) were not as efficient as the area method
which was the most practical, reliable, and least expensive.

R. r. mindanensis was, by far, the predominant species. Only one R.
norvegicus, and no R. exulans, were trapped. Rat damage increased
from the edges toward the interior of the fields, contrary to findings
reported from Hawaii, Florida, and British Guyana. This may be attri-
butable to the small average farm size (24.71 ha), clean culture at
the edges, and the use of boundaries as common pathways by work ani-
mals, overseers, and farm machinery in Negros.

These studies showed a mean total sugar loss of 2.30 percent due to
rats in Negros (Table 2). Dead stalks, tonnage reduction, and juice
deterioration resulted in high correlations between rat damage and
total sugar loss. Rat damage (RD) ranged from 1.80 percent to 13.19
percent with a mean of 6.70 percent. The relationship between percent
total sugar loss (TSL) and the percentage of RD is expressed by the

TSL = -0.77803 + 0.5555 RD 0.01450 RD2.

The significance of this equation means that reduction in yields can
be estimated from rat damage data, a simplified approach for extensive

Of 15 locally bred varieties that were tested for rat preference, five
were found less preferred by rats. Phil. 6559, Phil. 6553, Phil.
6421, Phil. 6019, and Phil. 6111 exhibited erect to reclining and
erect to recumbent growth habits, medium to large solid stalks, and
medium to high fiber content, all characteristics which favor resist-
ance to rat damage.

Seven radio-monitored rats traveled 2.5 times more (36.38 m/h) during
onset of harvest than during preharvest (13.93 m/h). Males averaged
less area covered than females. (Estioko, Ph. D. thesis.)

Table 2. Sugar loss due to rat damage to sugarcane in mill districts
of Negros Island, Philippines.


Dacong-cogon 3.17 0.30 11.76 0.37 0.10 0.77

Sonedco 10.12 0.19 36.32 3.68 3.04 6.91

Biscom 2.62 0.14 17.84 0.47 0.18 0.79

La Carlota 6.86 0.44 14.18 1.04 0.44 1.92

Ma-ao 4.91 0.08 9.13 0.45 0.29 0.82

Bacolod-Murcia 2.36 0.05 32.86 0.78 0.50 1.33

Talisay-Silay 12.88 0.85 31.77 4.09 1.67 6.61

Victorias 11.08 0.69 7.08 0.79 0.83 2.31

Lopez 7.39 0.18 14.00 1.03 1.40 2.61

Sagay 13.19 0.55 6.98 0.92 2.37 3.84

Danao 7.86 0.53 6.06 0.48 0 0.81

San Carlos 4.47 0.25 9.65 0.43 0.45 1.13

Bais 1.80 0.26 9.85 0.18 0.45 0.89

Tolong 5.14 0.34 11.19 0.58 0.62 1.54

Means 6.70 0.33 15.62 1.09 0.88 2.30

a RD--rat damage
SLDS--sugar loss due to dead stalks
LW--loss in weight
SLTR--sugar loss due to tonnage reduction
SLPS/TC--sugar loss due to deterioration of juice
TSL--total sugar loss

Management of limiting factors in anticoagulant baiting of lowland
ricefield rats

The effectiveness of an agricultural rodent control program (e.g.,
sustained baiting with anticoagulants) may be influenced by a number
of variables. The identification of these limiting factors and appro-
priate modifications relative to the species, crop, or other condi-
tions would contribute to increased effectiveness in reducing damage,
greater economic return, and increased acceptance of the technology by
farmers. The purpose of this study was to determine: (1) the rela-
tive acceptance by ricefield rats of several common bait carriers; (2)
the effects of shape, size, and structural material used for bait sta-
tions; (3) the effect of location or placement of bait stations; and
(4) the ability of ricefield rats to discriminate between fresh and
moldy baits. Data were collected in a study area established within a
40-ha ricefield along the western rim of Laguna de Bay at barrio
Lungus, 2 km NE of Kalaya-an, Laguna, Philippines.

Populations of R. r. mindanensis in ricefields showed marked
responses to a variety of factors pertinent to the effective use of
sustained anticoagulant baiting. In bait acceptance trials, for
example, significantly greater amounts of rice shorts were taken when
compared to corn grits (p <0.005), cornmeal (p <0.001), rice bran (P
<0.001) and polished rice (p<0.005). Apparently, the shape, size,
and material used to construct bait stations caused discrimination
among animals. Ricefield rats preferred standard bamboo tube bait
stations to the nipa baiting hut (p<0.01), coconut husk (p <0.001),
plastic quart oil can (p <0.001), narrow-gauge bamboo (p <0.001) and
plastic "floating saucer" bait platforms (p <0.005).

Intake from bamboo tube bait stations located in three different sites
during the vegetative and booting stages of rice varied significantly.
During the vegetative stage, bait stations located either atop or
alongside paddy dikes were preferred (p <0.001) to in-paddy stations.
No statistical difference in intake was demonstrated between bait
stations located along paddy dikes and within paddies during booting
stage, but both sites had greater consumption than those atop the

Ricefield rats consumed significantly greater (p<0.001) amounts of
fresh bait (1,365 g) than moldy bait (41 g) over a 13-day field trial
using 12 paired bamboo bait stations. (Castro, M.S. thesis.)

Assessment of rat damage to corn

Actual crop losses caused by vertebrate pests, both in terms of yield
reduction and economic significance, are not readily defined without a

reliable means of damage assessment. The purpose of this study was to
develop a damage assessment method for accurately determining the loss
of corn as a result of rat damage.

Two procedures were required to assess rat damage to corn. First, a
sampling method was needed to determine the proportion of rat damaged
ears in the field. Secondly, a means of relating corn weight and some
parameter of damage to define the extent of loss on individual ears
was needed. In situations where partial damage to an ear means a com-
plete loss (as in sweet corn grown for commercial markets), only the
first sampling procedure would be required to estimate economic loss.
Where partially damaged ears are measured, both procedures are
required to obtain estimates of yield loss.

Rat damage in corn occurred mostly at the periphery of the fields,
probably as a result of proximity to adjacent uncultivated areas which
provide good cover for rats. Damaged plants were generally restricted
to certain areas of the field rather than being widely distributed. A
more uniform distribution of damage noted in one field was associated
with a relatively higher rat population.

Areas of intact kernels on an ear of corn can be determined by the use
of a compensating polar planimeter or by the "cut-and-weigh" method
using cardboard materials that simulate the damaged area. The rela-
tionship between corn loss (g) and surface area (cm2) on intact ears
and those with simulated rat damage can be best described by a simple
linear regression. These factors were highly.correlated for both the
planimeter and "cut-and-weigh" methods on damaged and undamaged areas.
The relationship between corn loss (g) and area (cm2) occupied on
ears of corn could be used for predicting the extent of damage to ears
of corn. (dela Paz, M.S. thesis, in progress.)

Glue stakes reduce bird damage in ricefields

The use of "glues" on tree branches or artificial perches as a means
to capture or repel depredating birds is a traditional practice in
many countries. This study was conducted to evaluate the effective-
ness and potential of this technique for reducing bird damage in
Philippine ricefields.

Four contiguous 0.25-ha plots were selected within a 6-ha ricefield
near Namanparan, Diodi, Nueva Vizcaya. Rice plants within the plots
were nearly mature while surrounding fields contained plants from
booting to mature stages. The numbers of birds visiting each plot
were recorded at 10-min intervals from sunrise (0600) to early evening
(1700) during four consecutive days. Bird (Lonchura spp.) damage in
each plot was estimated by counting total tillers and bird-damaged

tillers in samples comprised of five adjacent rice plant hills.
Twenty such samples were checked in each plot. Sample locations were
marked so posttreatment appraisals could be repeated on the same

At the end of the pretreatment evaluation period, two of the sample
plots were selected for treatment and 120 stakes were placed in each.
These stakes were coated with a "bird glue" (prepared from sap of
local trees) and placed in the paddies so that the coated ends pro-
truded 15-20 cm above the rice plants. The two remaining plots were
left untreated and served as reference areas. Bird counts and damage
appraisals were then repeated as described above. The resultant data
were subsequently analyzed by a two-factor analysis of variance.

The average number of birds per 10-min interval were similar (11.6 in
treated plots and 7.9 in reference plots) prior to placement of the
glue stakes. After treatment, bird numbers dropped to as low as 0.2
bird per interval in treated areas and increased to as high as 17.1
birds per interval in untreated areas. During the pretreatment sur-
vey, damage averaged 14.5 percent in test plots and 11.8 percent in
reference plots. Posttreatment surveys revealed increased damage in
all plots. These increases were slight (up to 19.9 percent) and not
significant (p <0.005) in treated plots, but quite large (up to 63.2
percent) in reference plots. Although the stakes lost their adhesive
quality within 3 days, Lonchura learned to avoid plots containing them
for a full 8 days after treatment.

Use of crown baiting with wax blocks to reduce rat damage in coconut
Crown baiting with anticoagulant rodenticides has been proven effec-
tive in reducing rodent damage to coconuts. However, ease of place-
ment of bait in the crowns and deterioration of loose bait materials
are among the problems encountered in the use of this technique.
Incorporation of the bait into wax blocks might eliminate some of
these difficulties.

Two 1-ha study plots were selected within a large area of coconut
plantations near Victoria, Mindoro Oriental. The plots were separated
by over 200 m, and each contained 100 palms of a local variety. One
plot was selected for treatment, the other served as a reference. For
treatment, 25 randomly chosen palms were baited monthly with paraffin-
ized cubes containing polished rice, talc, and warfarin (0.025 per-
cent). The cubes were placed in the palm crowns with a long bamboo
pole. Monthly records of bait additions, rat activity (tracking
tiles), damaged nuts, and coconut production were kept for 1 year.

During the pretreatment survey, 164 rat-damaged nuts were counted on
the ground within the reference plot and 76 within the test plot
(Table 3). Rat activity, determined by tracking tiles, averaged 82.7
percent in the reference plot and 76.0 percent in the test area. R.
r. mindanensis, R. exulans, R. argentiventer, and Suncus murinus were
collected in both areas. In the treated plot, rat activity had
dropped to a negligible level by the seventh month after initial
treatment and remained low thereafter. Similarly, rat-damaged nuts
were found in the test plot after 5 months of treatment. Both rat
activity and numbers of damaged nuts were much greater in the refer-
ence plot than in the test area (53.1 percent vs. 12.1 percent, and
349 vs. 33, respectively). Production in the test plot averaged 3.2
nuts/tree/month, which was 2.2 times greater than production in the
reference plot and indicates that the wax-block treatment provided
effective rodent control.


Effective control of rodents can increase coconut production and harvests by two or three times
the precontrol levels.


Table 3. Rat activity, damage, and coconut production in two plots
near Victoria, Mindoro Oriental.

after % Rat activity
treatment Reference Treated











































No. of
rat-damaged nuts
Reference Treated















Reference Treated

1.1a 1.3b

2.6 2.8

2.3 4.1














a Based on 8 months
before treatment.

b Based on 16 of 19

(when complete records were available) of 19 months

months before treatment.

Anticoagulant residues in the ricefields

The possibilities for food chain concentration and secondary hazard
are generally considered low when anticoagulant rodenticides are used
according to manufacturers' recommendations. A study is in progress
to examine the potential for residue accumulation in paddy water,
soil, plants, and polished grain in two simulated "worst-case"
situations: (1) when exceptionally high levels of bait (5 kg/ha/week
at manufacturers' recommended concentration) are used throughout the
growing season, and all bait is "spilled" into the paddy; and, (2)
when even greater levels (50 kg/ha/week) are used, and all bait is
"spilled" into the paddy.

Sixty-six contiguous (7 m X 8 m) paddies were constructed in experi-
mental fields at the International Rice Research Institute (IRRI),
and planted with C-168, a tall, high-yielding variety. Paddies were
constructed and maintained by IRRI field crews. Fifteen paddies were
selected for treatment. Each treated paddy was surrounded on three
sides by untreated paddies and on the fourth by an affluent canal.
For treatment, a bait formulation (polished rice plus toxicant) was
broadcast evenly over the paddy each week from the second week after
transplant (WAT) until harvest. Paddies were assigned randomly, three
paddies per combination, to five combinations of bait formulation/
application rates: (1) warfarin (0.05 percent), 5 kg/ha/week; (2)
warfarin (0.05 percent), 50 kg/ha/week; (3) diphacinone (0.005 per-
cent), 5 kg/ha/week; (4) diphacinone (0.005 percent), 50 kg/ha/week;
and (5) no toxicant (reference), 50 kg/ha/week.

At 12 WAT, a water sample was taken from each treated plot immediately
after bait application. A second water sample was taken 24 h later.
Water samples were frozen until analyzed for residues. At harvest,
plant and soil samples were removed from each of the treated plots.
The soil samples were dried, homogenized, and packaged. Plant samples
from each plot were split: half were dried, homogenized, and pack-
aged; grains from the remaining half were harvested, winnowed, hulled,
polished, and packaged. All samples were then sent to the Denver
Wildlife Research Center for residue analyses. These analyses are
underway (see page 85) and final results will be reported upon comple-
tion of these tests and statistical analysis of the data.

Preliminary trial of an electric rat barrier in a farmer's ricefield

The concept of using a nonlethal electric barrier to repel rats from
ricefields has been under study by DWRC staff for several years (see
previous annual reports). Most of this work has been done in the
laboratory or semifield situations and results of these earlier inves-
tigations have been encouraging. The purpose of this study was to
evaluate the electric barrier under actual field conditions.

A 0.12-ha plot containing high-yielding rice plants (IR-26) 3-4 weeks
from harvest, and with a potential for heavy rat damage, was selected
near Lumban, Laguna. A barrier was installed by placing stakes at 1-m
intervals along the inside, top of dikes surrounding the plot, and
stretching a plastic fishnet (5 mm mesh) from ground level to about
0.5 m above the ground from stake to stake around the plot. At the
base of the barrier, the netting was curled under for several centi-
meters, and topped with soil and cut weeds. At the top, the netting
was curled outward and loose, so that rats attempting to climb the
fence would fall back to the ground. A series of three electrodes
(35-gauge wire) were arranged along the top of the dike, outside and
parallel to the fence. The outermost wire was 5 cm above ground, the
innermost about 2.5 cm. The electrodes were affixed to small wooden
spikes driven into the dike, and insulated with plastic or varnish.
The barrier was electrified with a Gallagher Model E 12 fence charger
set at a medium pulse rate. The outermost and innermost electrodes
were energized and the center electrode was grounded. The barrier
operated continuously until harvest (approximately 3 weeks).

Tracking tiles and traps were placed uniformly around the fence, ten
outside and ten inside, during the first 3 days of operation. A
similar procedure was followed on an unfenced reference plot about 90
m away. Damage appraisals (percent damage on 100 randomly selected
rice plants) were conducted in both plots during the first 2 days of
operation and again at harvest. In addition, damage appraisals were
conducted at harvest on three fields surrounding and separated by 30
m from both the treated and reference plots.

The barrier held a 5-kV or better charge during most of the 3-week
study. The first battery, a new 12 V d.c. car battery, was defective
and was replaced after 8 days. The used replacement battery was
recharged once during the remaining 2 weeks.

Statistical analysis of the data revealed that the barrier was effec-
tive in reducing rat damage. Damage in the plot bounded by the
barrier averaged 1.9 percent and damage in the fields surrounding the
test plot averaged 8.6 percent. The reference plot suffered 18.8 per-
cent damage while the three fields surrounding it had an average of
11.9 percent damage.


Several staff members continued their pursuit of advanced degrees.
One completed the requirements for the Ph. D. degree and another has
completed the required course work, passed the comprehensive examina-
tion, and is currently finishing the thesis work. Four of six
Master's candidates completed requirements for their degrees.

Several Center staff held appointments with the University of the
Philippines at Los Bafos, acting as graduate advisors and teaching
courses in vertebrate pest management and/or related fields. Labora-
tory and classroom facilities, and equipment at the NCPC were utilized
for instruction and individual research projects.

Five staff members served as resource speakers at the "Short Course on
Integrated Pest Control for Irrigated Rice in South and Southeast
Asia" which was held in Manila, Maligaya, and U. P. at Los Baios, from
October 16 through November 18, 1978.


The red-billed weaver, or quelea (Quelea quelea), is found in some 25
African countries and is a serious pest of cereal grain crops such as
sorghum, wheat, millet, and rice. In the Sudan, quelea occupy some
90 percent of the country's grain production areas. DWRC investiga-
tions during late 1977 (see 1977 report) gave credence to the widely
held belief that quelea are the most destructive birds in the world.
In addition to quelea, there are other bird and rodent damage problems
in Sudan and other nations of Africa that are of significant economic

The agreement which established this vertebrate pest research program
in Sudan is scheduled to extend through 1981, with emphasis on quelea
depredation research. Future plans envision an extension of the pro-
gram beyond 1981, an additional biologist, and program expansion to
include applied research into other vertebrate pest problems, espe-
cially rodents.

The basic objectives of this project are to: (1) increase the avail-
able human food supply by reducing damage to field crops caused by
noxious birds and rodents; (2) develop integrated control programs
within Sudan in areas suffering losses from grain-eating birds and
rodents; (3) appraise the nature and magnitude of quelea bird and
rodent losses in Sudan; (4) develop indigenous capabilities to evalu-
ate and deal with vertebrate pest problems; (5) institutionalize
in-country research and control programs; and (6) coordinate activ-
ities with other international organizations to maximize results.

Many African countries affected by quelea have operational control
teams actively combating crop depredation problems by indirect means
(i.e., quelea population suppression). Considerable progress has
been made by these teams in better understanding some aspects of the
basic biology of quelea in relation to roost and nest site control.
However, large-scale campaigns to reduce the numbers of quelea have
provided only temporary or local relief from bird depredations. This
strategy, while often killing millions of birds each year, is costly
and potentially hazardous.

The DWRC will continue its policy of monitoring and evaluating all
efforts at control and methods development, including indirect con-
trol. Basically, our work on the quelea problem in Sudan will be
confined to direct crop protection research. Emphasis will be given
to development of economical and appropriate control methods which are
suited to use on small or traditional farms. Research spinoff bene-
fits for large or "modern" farm schemes, as have occurred after our
project work in the United States, Latin America, and the Philippines,
can be anticipated.

Indirect (population suppression) control efforts

We examined reports of several of the quelea population reduction
efforts carried out in Sudan during 1978. The largest kill at nesting
sites was made by the German Technical Assistance (GTZ) team near
Sennar and south of Kosti. Their estimated kill at five sites
amounted to about 160 million quelea.

The Plant Protection Department (PPD) station at Gedaref reported the
spraying of 29 nest and roost sites in 1978, two sites by a PPD Piper
Pawnee and the remainder by Polish Antinov planes. The results, using
fenthion or Thimul as control agents, were judged by PPD to be more
than satisfactory.

Helicopters were used in population reduction operations for the first
time in 1977. The results were enthusiastically termed by PPD person-
nel as the greatest success in 15 years of spray campaigns. Losses to
the extensive millet crop produced in the Nyala area were claimed to
have been reduced by 80-90 percent for the first time in years. PPD
helicopters spent about 150 h spraying nests or roosts of quelea
located in and around thousands of feddans (1 feddan = 0.415 ha) of
millet croplands. The cost of flying time was estimated at about
$280/h (helicopter owned by PPD and flown by PPD pilots). Fenthion
was the avicide used. No information on spraying by helicopter during
1978 was available.

Large-scale operations such as these began in the Sudan in 1946 and
by 1953 in other African countries. Yet, in spite of these efforts
and the annual destruction of millions of quelea at roosts and nesting
colonies for the past 30 years, the quelea population is currently
maintaining itself at a very high and viable level. One noticeable
reason for the continued presence of quelea in Sudan is that popula-
tion control measures are annually directed at not more than 100 or
150 roost and nesting sites out of an estimated 1,000 or more such
sites in the country. If such control methods are to be truly effec-
tive in reducing quelea populations to the point that crop damage is
no longer significant, well over 900 of the estimated 1,000 roosting
or nesting sites would have to be treated. The cost of such an effort
would be astronomical.

These factors are evidence that population suppression (at least as it
is currently practiced) is not the answer to the quelea problem.

Some economic aspects

Published data on crop losses to birds in Africa are scarce. Staff of
the quelea research project are continually attempting to compile
damage assessment statistics in order to provide a proper foundation


The name weaver bird, commonly applied to members of the family Ploceidae, is derived from the
elaborately woven nests that they construct. These are nests of the red-billed weaver (Quelea
quelea), one of the most numerous and destructive birds in the world.

for implementation of direct crop protection control programs. We have
collected damage assessment information for the period 1965 to 1978
from literature, personal contacts, and field studies in Sudan, Kenya,
and Tanzania. These are summarized below.

H. Schmutterer (Pests of Crops in Northeast and Central Africa) calcu-
lated that annual sorghum losses to red-billed quelea in Sudan amounted
to a monetary loss of LS 200,000 (Sudanese pounds) ($500,000).

Sadig Beshir, Head, Bird and Rodent Section, PPD, placed the estimate
of annual losses of cereal crops to quelea in Sudan at 30 percent in

A 15-percent average annual loss on 3,000 feddans of sorghum in Umm
Seinat, Kassala Province, was estimated by farmer Hassan Hamid. In
1976/77, a year of heavy quelea damage to sorghum, only 9,000 sacks of
sorghum were harvested, instead of the usual rate of 15,000 sacks per
year. This is a 40-percent loss valued at LS 75,000 ($187,500) for
that year. (Calculation at LS 12.50 ($31.25) per sack.)

In 1975, at Abyei, South Kordofan Province, quelea were reported to
have devastated the sorghum crop to such an extent that sorghum had to
be brought into the region from neighboring areas. A conservative
estimate of this loss can be approximated from a figure of 14,000 sacks
of sorghum, the amount a local trader stated merchants brought to Bahr
el-Ghazal Province in 1977 as their marketable surplus. The value of
the crop lost at Abyei in 1975 would have been over $436,000. It is
reported that quelea and "pigeons" (doves?) continue their depredations
in this area, yet no population reduction measures at Abyei have been
reported by PPD for past years.

Before the helicopter spray campaign of 1977 in the Nyala area, in
southern Dafur, annual losses of millet production to quelea were esti-
mated between 30 to 75 percent.

In October 1976, PPD biologists collected data on sorghum losses at the
State Seed Propagation Farm at Jebel Sim Sim, Kassala Province. The
total production area was 12,000 feddans of various sorghum varieties.
One 150-feddan area was completely destroyed by quelea; 200 additional
feddans were slightly damaged. The 150 feddans had been expected to
yield 600 sacks of sorghum, providing an income of LS 7,500 ($18,750).
Quelea traveled from a breeding colony approximately 1 km from the
seed propagation farm.

In October 1977, PPD and DWRC personnel conducted their first damage
assessment study on approximately 100 feddans of premium Daber variety
sorghum near El Hawata, Kassala Province, 5 km southeast of a quelea

nesting colony estimated to consist of over 1.5 million adult
breeders. Nest trees contained an average of 250-300 nests each in an
area of 40 to 50 feddans. Foraging flights of quelea at the study
area averaged more than 3,000 birds/minute from nest colony to fields
and return. Officers of the Mechanized Farming Corporation (M.F.C.)
had reported about 110,000 feddans of six varieties of sorghum were
raised in the El Hawata area. The most important variety to farmers,
and the variety with the highest annual depredation by quelea, was the
small-seeded white "Daber" variety.

The results of this study were reported in the 1977 annual report but
are repeated here to illustrate the extent and severity of damage that
can be caused by quelea.

1. Six study blocks were randomly selected and divided into 10 plots,
each with 25 Daber heads, for a total of 1,500 heads.

2. Three of the six blocks were for reference and three for aerial
treatment with methiocarb and an adhesive. These were sprayed on
October 15, but the aerial spray was ineffective in preventing losses
due to partially inoperative spray equipment, spray coming out under
high pressure, and excessive heat and high winds. All of these fac-
tors combined to prevent the attainment of residue levels necessary
to deter the birds. Consequently, the study ultimately became more
significant as an exercise in damage assessment than for spray

3. Damage assessment readings on October 16, 1 day after spraying,
showed a 6.3- to 10-percent loss in Blocks 1-4 and 4.5 percent for
Blocks 5 and 6. Blocks 5 and 6 were just coming out of the tassel/
flower stage; the heads had not matured to the more vulnerable milk
stage of Blocks 1-4.

4. A second reading on October 23 showed an increase in damage as

Block 1 73.16%
Block 2 78.31%
Block 3 73.94%
Block 4 72.67%
Block 5 51.40%
Block 6 32.58%

By November 15, losses were more than 95-98 percent in all six blocks.
We concluded that at least five sacks of sorghum could have been
produced per feddan. The resultant loss was valued at approximately

Quelea damage small-grain crops and adversely affect the agricultural economies of some twenty
nations in Africa. The extent of damage they can cause is graphically illustrated in this
photograph; the center stalk of millet is undamaged but the other two have been completely
stripped of seed.

LS 6,250 ($15,625). Similar losses for many of the remaining farms
of the 110,000 feddans would have amounted to a considerable monetary

In 1964, the Food and Agricultural Organization (FAO) of the United
Nations calculated that there was an $8.5 million annual loss due to
quelea damage in small grains in Africa. A more up-to-date descrip-
tion of bird pest depredation was presented in a paper entitled "World
Bird Damage Problems" at the Eighth Vertebrate Pest Conference in
California. Table 4 is a reproduction of that segment of the report
which pertains to bird pest damage in Africa. Some of the outstanding
economic losses of African grain crops to the red-billed quelea and
other species are:

$0.7 million loss to cereal crops in Kenya in 1952;

$2.8 million lost in one province in Nigeria in one year;

100,000 to 200,000 tons of cereal lost annually in Senegal;

a $150/0.4 ha loss in Somalia;

in South Africa quelea are implicated as the most notorious bird
damage problem to cereal--a $1.5 million loss in sorghum alone.

Reports for 1978 from Kenya and Tanzania indicated the following.
Heavy quelea depredation occurred to government and privately owned
wheat farms on the western slopes of Mt. Kilimanjaro in Tanzania. One
privately owned farm, annually harvesting about 15,000 sacks of wheat,
suffered an 86-percent loss in 1978, and nearby government farms
suffered 80- to 90-percent losses. In the Ngorongoro Crater wheat-
growing area, quelea destroyed an estimated 50-60 percent of the crop.

In Kenya, wheat, rice, sorghum, and millet annually receive heavy
depredations from quelea. At Narok, in western Kenya, quelea were
responsible for 65- to 85-percent losses of wheat in 1978. Nanyuki
experienced losses ranging from 60-75 percent, with local losses often
exceeding 75 percent.

Many of the reports of annual depredations by quelea in Kenya and
Tanzania, with subsequent estimated percentage losses, will be
rechecked in 1979-1981 with the Ministries of Agriculture in the two
countries and the FAO Grain-eating Bird Pest Project personnel.

Table 4. Examples of reported economic losses to agriculture in Africa. (Adapted from De
J. W. 1978. World Bird Damage Problems. Proc. Vertebr. Pest Conf. 8:9-24.)

Location Crops Major Species Remarks


Emerging and
ripening Rice and
Wheat, Millet,

Rice, Wheat,
Millet, Corn,

Millet, Rice,

Coconut, Oil Palm

Wheat, Rice,
Millet, Sorghum


Laughing Dove, Cape Turtle

Red-billed Quelea, Golden
Sparrow, Tree Duck, Crowned
Crane, Ruff, "Weavers",

Red-billed Quelea, Golden
Sparrow, "Weavers",

Red-billed Quelea, Golden
Sparrow, "Weavers"


Red-billed Quelea, "Doves",
"Weavers", "Starlings"

"Weavers", "Mannikins"

Field and storage losses

30-40% defoliation damage at
experiment station

In 1952, $0.7 million loss;
100,000 bags

Wheat, Barley,
Millet, Sorghum

Rice, Sorghum


Red-billed Quelea,
"Weavers", "Parrots"

Irrigated rice schemes have
annual damage












Maur itani a






South Africa




Date Palm


Wheat, Rice,


Rice, Wheat,
Millet, Sorghum,
Corn, Palms

Millet, Rice

Rice, Sorghum,
other grains


Rice, Millet,


Red-billed Quelea,


Red Fody

House Sparrow, Spanish

European Starling, Thrush

Red-billed Quelea, Golden
Sparrow, "Starlings",
"Doves", "Weavers"

Red-billed Quelea,
"Weavers", "Waterfowl"

Red-billed Quelea, Golden
Sparrow, Ruff, "Weavers",
"Starlings", "Doves"

Red-billed Quelea

Red-billed Quelea, Golden
Sparrow, Red Bishop,

Red-billed Quelea

1.2 million tons lost annually

Wheat loss most severe;
$4.0 million loss

$2.8 million/year loss in one

100,000-200,000 tons of grains

Most notorious example of a bird
damage problem; $1.4 million
loss of sorghum in 1953

$150/acre; great pests of rice

200,000 Sudanese pounds


Wheat, Olives

Wheat, Rice,
Millet, Sorghum

Red-billed Quelea, "Doves",
Black-breasted Lark,
"Bishops", "Waterfowl"

Spanish Sparrow, European

Red-billed Quelea, Chestnut
Weaver, "Weavers", "Doves"

Includes waterfowl damage to
emerging rice

Starling damage to olives
--15,000 metric tons



Tanzani a

Basis for estimates of cereal grain losses to quelea in Africa

Crook and Ward (The Problems of Birds as Pests) estimate the continen-
tal population of quelea to be between 109 and 1011 individuals and
suggest that 90-100 percent of the quelea diet is comprised of the
seeds of wild grasses. Laboratory studies indicate the average food
consumption of quelea approximates 3 g/day. If we use the lower esti-
mate of 109 individuals and assume that 10 percent of the food con-
sumption of the entire bird population during a 30-day period each
year, when mature grains are present, accounts for total damage, the
total amount of grain consumed by this population is 90,000 metric
tons per year. Conservatively assuming a field value to small farmers
of $100 per metric ton, the value of this loss amounts to $9 million.
If we use the estimate of 1011 for the quelea population and make the
same assumptions, the result is a calculated annual loss of $900
million. Statements of losses as "more than $100 million per year"
are based on a midpoint population estimate and a recognition of the
conservative figures used in these assumptions.

Summmary of major bird damage problems in the Sudan

A summary of the major bird damage problems in the Sudan is given in
Table 5.

Table 5. Summary of major bird damage problems in the Sudan. (Prepared by Biologist Babiker Ali, PPD.)

damage Crops Crop phenology Preferred Major
Province areas affected Sowing Milk stage Harvest stage speciesa Remarks

Kassala Hawata


Sim Sim Millet

Um Senat Sesame

Late Jul Late Sep/Oct

Late Jul Late Sep/Oct

Late Jul Sep







Megrih Mtns.

Quelea Sorghum grown through-
out Province. Millet
Doves grown limited scale
--Hawata. Sesame
Ploceids grown in southern
region. Sowing dates
dependent on rains.
Damage occurs in all

Sennar Sorghum
District Millet







Late Jul Late Oct
Late Jul Late Oct

Late Sep

Late May Jul

Late May Jul













Irrigated sorghum at
Agr. Research Corp.
Millet grown on
limited scale. Damage
occurs in all stages.

Damage occurs in all

Damage occurs in all

Damage occurs in all

Blue Nile








Ed Damer Wheat
Vicia fulva

Late Nov

All year

Late Nov
Late Nov

Palm dates Feb






and fruit


and fruit
and fruit



Damage occurs in all
stages on sorghum and

Damage occurs in all
stages on sorghum and

a Doves are becoming a more serious pest.



Repellent testing: efficacy of methiocarb for protecting sorghum from
house sparrow damage

Prior work by DWRC staff indicates that chemical repellents and
frightening agents offer a promising strategy for reducing quelea
damage to African grain crops. Methiocarb is one of these chemicals.
It is widely used as a bird repellent in the U. S. and has been
registered for several crop applications. In laboratory tests, quelea
were found to be six times more sensitive to methiocarb than red-
winged blackbirds.

Cage tests conducted in Sudan during 1977 (see 1977 Annual Report)
showed that good protection could be achieved by applying methiocarb
to sorghum with a hand sprayer. Additional testing is necessary but
fieldwork in Sudan is hindered by factors such as weather, logistics,
and seasonal movements of the quelea population. To overcome some of
these hindrances, interim field testing will be done in the U. S.
These trials were initiated in July, at the Texas A&M Agricultural
Experiment Station, Weslaco, Texas. A variety of sorghum (TX 623),
which is comparable to the Daber variety common in Sudan, was heavily
damaged in 1976 by house sparrows (same family as quelea).

The bird damage situation at Weslaco was believed to be similar enough
to Sudan situations that information of importance to future field
testing in Sudan could be obtained relatively easily. The most impor-
tant data sought were: (1) the optimum concentration of methiocarb to
apply to the sorghum heads, and (2) the optimum concentration of adhe-
sive to use in combination with the repellent.

Three caged test plots were established and treated as follows: (1)
reference (no treatment), (2) hand-sprayed methiocarb at 3 Ib/acre,
and (3) hand-sprayed methiocarb:adhesive at 3:1 Ib/acre. House spar-
rows were introduced into each caged test plot along with alternate
food and water.

After 120 bird days of exposure, damage to the untreated (reference)
plot was about 27 percent. Damage to the methiocarb:adhesive-treated
plot was about 18 percent and the methiocarb-treated plot was evi-
dently not damaged. The apparent relative effectiveness of each
treatment was confirmed by direct observation of bird activity. Birds
in the untreated test cage began to feed on sorghum heads immediately
and did not disturb the alternate food available to them. In con-
trast, birds in the methiocarb (no adhesive) cage spent little time on
the sorghum heads and consumed or spilled much of their alternate
food. Some feeding on heads was observed in the methiocarb:adhesive

These results indicate that the acrylic resin, Rhoplex AC-33, when
used at one part adhesive solids to three parts methiocarb solids,
probably interferes with or masks the repellent properties of methio-
carb. They also suggest that adhesives should probably be omitted
from spray treatments in very dry climates, such as in Sudan, where
rains seldom fall during the season when sorghum heads are maturing.
If adhesives are needed, ratios of less than one part adhesive to
three parts methiocarb should be used. A 1:10 ratio is proposed for
further trials.

Field trials: Upper Nile, Blue Nile, Kordofan, and Kassala Provinces

Several field trials and cage studies were conducted to further evalu-
ate the effectiveness of repellents as a means of reducing quelea
damage to sorghum. The results of these studies are summarized here.

1. The effective level of methiocarb for protection of dura (sorghum)
against quelea is less than 0.5 kg/feddan when sprays are directed at
the heads only. A plant population of 10,000 plants/feddan was
assumed for this calculation. This is probably near optimum effec-
tiveness as 'the residue level at this concentration was computed to be
about 65 parts per million (ppm). Each 60-g head was treated with
5 cm3 of a 0.09-percent methiocarb suspension with about 90 percent
retention of spray.

2. Methiocarb applied to dura heads at levels computed to be about
200 ppm (a 0.27-percent spray) was lethal to about one-fourth of caged
quelea and nearly one-half of caged masked weavers, clearly indicating
that lower levels would adequately protect dura. A 1-percent level on
flowering dura was highly lethal to fasted red bishops which were
taking an average of about five seeds, again indicating that much
lower levels would give effective repellency.

3. A 1-percent Avitrol spray on dura heads is lethal to quelea taking
one to three seeds from heads just beyond the flowering stage.
Slightly higher levels may be needed for late-dough-stage sorghum
where only the germ may be taken. A ratio of 10 heads/feddan
(1:1,000) is apparently too low for effective protection, unless
flock response is obtained and large numbers of quelea are involved.

4. In mist-netting birds for enclosure experiments, it was soon
discovered that quelea, masked weavers, and red bishops could be
taken in substantial numbers. From 25 to 100 birds were taken per
net hour from populations not exceeding 2,000 birds.

Blue Nile Integrated Agriculture Development Project

The Blue Nile Integrated Agriculture Development Project located
south of Damazin is a new agricultural development scheme. Since
quelea depredation is one of two major deterrents to sorghum produc-
tion, the project director requested input from this project relative
to actual or potential quelea problems in the area. Accordingly, a
survey was made of the project area. Data on quelea control and past
nesting in this area were collected from the Sennar Plant Protection

Damage estimates obtained from local farmers in the immediate project
area were approximately 5 percent. On this basis, the design team
decided not to include funding for quelea control research, at least
for the present time. It was pointed out that past history has shown
that agricultural schemes, both large and small, located in prime
quelea habitat, have suffered heavy depredation of agricultural
crops, especially sorghum, wheat, and millet. The Blue Nile project
is in prime quelea habitat, and little or no indirect control has
been available for this area in the past. The potential for severe
quelea problems is present and may materialize as development of the
scheme progresses.

Rodent problems in Sudan

The agricultural rodent situation in Sudan was the subject of a dis-
cussion in early 1978 with Dr. Salah Omer, Agricultural Zoology
Department, University of Khartoum at Shambat; Dr. Michael Fall,
Biologist, DWRC; and Mr. Hassan Farog, Vertebrate Pest Specialist,
Agricultural Research Corporation (ARC). It was concluded that two
rodent species, Arvicanthis niloticus and Mastomys natalensis, cause
significant damage to a variety of agricultural crops, including
cotton, sorghum, wheat, groundnuts, and vegetables.

Dr. Omer cited data on damage losses in Sudan as follows:

total loss of sorghum in some parts of Central Sudan during a
heavy rat outbreak in 1961/62;

sixty to eighty percent damage to wheat in 1961/62;

up to 70 percent loss of wheat crop (approximately 500,000
feddans) during a rat outbreak in 1975/76;

thirty percent loss of groundnuts during this same outbreak in


Quelea are captured in mist nets for use in laboratory studies at our
African field station and at the Denver Wildlife Research Center.

Dr. L. Brader, FAO/UNDP, Plant Protection Service (1976), reported
rat damage losses of cotton in 1962 at between 50 and 200 kg per
0.4 ha in an area of 30,000 feddans.

A viable rodent research program should include: (1) damage assess-
ment training; (2) species identification; (3) testing of chemical and
bait acceptance; and (4) timing of experimentation during the year.
The need for a second DWRC biologist to handle rodent research and
development of controls was discussed.

Personnel and training

During early 1978, Mr. Sadig Beshir, Ornithologist and Head of the
Bird and Rodent Section, PPD, took an assignment with FAO in
Pakistan. His vacancy was filled in May by Mr. Abdel Zarrough,
Entomologist and Head of PPD station at Gedaref, Kassala Province.
Shortly thereafter, Mr. Babiker Ali, Vertebrate Pest Biologist,
returned with an M.S. degree from Bowling Green State University to
join the Bird and Rodent Section at Khartoum.

Messrs. Mohamed Hamza and Saeed Mohamed Suliman continue their
training as USAID participants in Master's programs at Bowling Green
State University. They will undertake thesis problems at the Denver
Wildlife Research Center under the direction of DWRC staff members.
We anticipate their return to the PPD, Bird and Rodent Section, by
January 1980.

Academic, laboratory, and field training are an integral part of the
quelea project. This training over the next several years will pro-
vide a nucleus of personnel to handle future research, training, and
extension activities in the area of vertebrate damage research and

Cooperation with international and national organizations

USAID/DWRC were invited by UNDP/FAO to participate with five East
African countries in its grain-eating bird project from 1978 to 1981
by demonstrating research and control methodology and technology for
direct crop protection programs. This project is discussed in more
detail under the program development section of this report.

Since the USAID/DWRC quelea project is established with the Government
of Sudan's Plant Protection Department and is fully committed to
vertebrate pest problems in Sudan, all such collaborative activities
outside of the Sudan will be coordinated with PPD. East African
activities will involve temporary duty assignments for the resident
DWRC representative in Sudan and a DWRC biologist on an ad hoc basis;
all costs of the assignments, excluding salaries of the biologist,
will be borne by FAO.


Each field program maintained under this project is currently staffed
by one resident U.S. technician. The undertaking of a major research
project at an overseas field station is a sizable task for one or two
persons. But a unique feature of the DWRC international programs is
the backup research capability available to assist the resident field
personnel. The Section of Supporting Sciences, along with other
sections of the DWRC, provide this backup research and support for the
field units. Specialists in several scientific disciplines and modern
scientific instrumentation and facilities provide the capability for
investigation into many facets of a vertebrate pest problem. It would
be difficult, if not impossible, and certainly illogical to attempt to
duplicate this staff and physical capability at the overseas field
stations. DWRC research activities pertinent to, or in support of
this project are summarized in the following reports.

Toxicity of 1,3-difluoro-2-propanol (DFP)

The active ingredient of gliftor, a rodenticide widely used in the
Soviet Union, is 1,3-difluoro-2-propanol (DFP). Detailed studies on
the pharmacology of DFP have not been published but judging from its
structure it would appear to be metabolized to fluoroacetic acid (FA).
Unlike FA, however, DFP has a wide range of toxicity which is prob-
ably dependent upon whether animals can metabolize DFP to FA. The
data reported herein is part of the toxicity profile we are obtaining
for gliftor. Two groups of ground squirrels (Spermophilus richard-
soni; three males and five females per group) were individually caged
and prebaited for one night with untreated rolled oats. The next
night the animals had a choice between treated and untreated bait.
One group received 1 percent gliftor, the other 2 percent. Consump-
tion of treated bait was substantially less with the 2-percent con-
centration and mortality was also less than with the 1-percent bait
(Table 6). These data indicate that gliftor may be unpalatable at
the 2-percent level.

Table 6. Consumption and mortality with gliftor baits when offered to
ground squirrels in a free-choice test for one night.

tration Mean bait consumed g (range) Gliftor consumed (mg/kg)
(%) Treated Untreated Mean (range) Mortality

1 3.7 (2.1-6.9) 6.9 (1.1-16.6) 137.2 (80-231) 8/8

2 0.7 (0.01-2.3) 4.1 (0.6-9.2) 30.1 (0.3-84) 5/8

Laboratory bioassays of diphacinone baits

Six batches of a pelletized commercial diphacinone bait were subjected
to an accelerated shelf-life test for 30 days at 500 C and then bio-
assayed in a two-choice, 15-day feeding study. For a product to be
considered satisfactory in this type of test, the average mortality
and treated food consumption for each bait should be 90 and 33 per-
cent, respectively. Results for albino rats are given in Table 7.
These data show that the baits remained highly toxic but that palata-
bility may have been altered by the shelf-life test. Table 8 gives
the results of tests with albino mice. Interestingly, the average
consumption of treated bait was greater for the mice than the rats,
but mice mortality was slightly less. The results of these bioassays
indicate that these baits would be effective in a field control pro-
gram, especially if there was marginal availability of alternate

Table 7. Toxicity and consumption of 0.005-percent diphacinone baits
with albino rats.

Batch Bait consumption (g) % Treated Average
No. Sex Mortality Treated Untreated bait consumed %

66 M


66A M


66B M


67 M


67A M


67B M






































Table 8. Toxicity and consumption of 0.005-percent diphacinone baits
with albino mice.

Batch Bait consumption (g) % Treated Average
No. Sex Mortality Treated Untreated bait consumed %

66 M


66A M


66B M


67 M


67A M


67B M






































Results with a loose grain bait that had undergone an accelerated
aging test (30 days, 500 C) are given in Table 9. These data are
similar to results in Tables 7 and 8 and suggest that the aging proc-
ess does not chemically alter the potency of diphacinone but that
palatability of the bait, particularly to rats, is changed.

Table 9. Toxicity and consumption of 0.005-percent diphacinone grain
bait with albino rats and mice.

Bait consumption (g) % Treated Average
Species Sex Mortality Treated Untreated bait consumed %

Rats M 10/10 204 844 19
F 10/10 154 713 18

Mice M 10/10 46 52 47
F 9/10 58 73 44

Acute oral toxicity of CAT (DRC-2698; N-(3-chloro-4-methylphenyl)
acetamide) to male albino rats

CAT is being developed as a bird toxicant and a great deal of biolog-
ical data must be generated to meet regulatory agency registration
requirements. One area in which sufficient data are lacking is the
acute oral toxicity of CAT to rats. There are conflicting reports on
this topic in the literature. Two studies report the LD50 to be
greater than 3,000 mg/kg, whereas another reports an LD50 of 376
(243-510) mg/kg with 95-percent confidence limits. Using standard
laboratory techniques and procedures, we found the LD50 to be 760
(673-859) mg/kg. This LD50, with corn oil as the carrier, is biologi-
cally comparable to the LD50 of 376 in which carboxymethyl cellulose
was used as the carrier. No symptoms of intoxication were reported in
those studies where dosages of 3,000 mg/kg or greater were used, but
toxic symptoms (prostration, labored breathing) were observed in each
of the two studies that resulted in a calculated LD50. Factors such
as genetic strain, sex, body weight, fasting period, and vehicle used
for dosing were compared among the four studies. There appears to be
no plausible explanation to account for this extreme variation in the
reported toxicity of CAT to rats.

Markers for toxic grease formulations

Experiments are underway to find an adequate marking agent to use in
evaluating the delivery of acute toxicants to rats via grease formula-
tions. These markers are needed to gain information on the percentage
of rats that come in contact with toxic grease under field conditions.
Preliminary tests have been conducted in the laboratory with three
markers: rhodamine B, tetracycline, and calcuflour. Each was pre-
pared at a concentration of 10 percent in a multipurpose ultra-lube
grease. About 500 mg of each was applied to the mid-line abdominal
surface of each of three individually caged ricefield rats (R. r.
mindanensis). Rhodamine B was the better marker under these condi-
tions. Seven days after application it could still be readily seen on
the tail, feet, lips, and abdominal fur without the aid of fluorescent
light. Additional laboratory tests with closed rat colonies are
planned and, if these are successful, a rhodamine B-grease formulation
will be field tested.

Evaluation of adhesives for foliar application of methiocarb

The avian repellent methiocarb (4-methylthio-3,5,-xylyl N-methylcarba-
mate) has shown promise in field and laboratory tests as a potential
agent for reducing quelea (Quelea quelea) damage to African grain
crops. The efficacy and economic benefits associated with the use of
methiocarb or other chemical repellents could be enhanced if the
effective duration of the applications could be prolonged. This is
especially true where treated crops may be exposed to rainfall. The
incorporation of foliar adhesives may prolong the duration of repel-
lent applications. Hence, this study was designed to evaluate differ-
ent adhesives for such use. The first phase of the study involved
treatment of sorghum with different concentrations of methiocarb and
different adhesives. These were subsequently exposed to different
levels of simulated rainfall (see 1977 report). We had hoped to com-
plete residue analyses and bioassay tests in time for inclusion in
this report. However, results of the chemical tests, to date, have
been inconsistent. We suspect that the problem is associated with
the simulated rain system. For this reason, the initial phase of the
study will be repeated with a different system of simulated rainfall.

A related study was designed to better our understanding of the
relationship between the bird repellent methiocarb and selected
adhesives. An R50 value for the adhesive Rhoplex AC-33 was determined
for red-winged blackbirds. Using a level of 0.1 percent methiocarb
with varying levels of adhesive, the R50 level was 0.00999 percent,
with confidence levels of 0.00096 percent to 0.10361 percent. Next,
the R50 value for the adhesive was used to determine the R50 value for
methiocarb. The resultant R50 value was 0.094 percent, with

confidence levels of 0.0496 percent to 0.1780 percent. This indicates
that a 10:1 ratio of methiocarb to adhesives would be effective in
repelling blackbirds.

Evaluation of rodent glues

Toxic baits are the most common means of controlling rodents in crop
damage situations. However, there are instances in which an alterna-
tive, nontoxic method may be more desirable or necessary. For exam-
ple, in situations where abundant food is available, rodents may not
be attracted by baits. In other situations they may have ingested
sublethal doses, become bait-shy, and simply will not accept toxic

We are exploring several alternative, nontoxic methods of rodent con-
trol in field crops. One of these possible alternatives is rodent
glues, substances that are currently used in commensal rodent control.
The concept is simple; the glue, on a glue board or similar carrier,
is placed where rodents will walk on it. They become stuck, unable
to extricate themselves. They may then be removed and destroyed.
Several of these substances are available commercially and may have
application in certain field situations.

We tested three of these products in the laboratory. A test chamber,
approximately 240 cm X 25 cm X 25 cm was designed to hold about 4 cm
of water (to simulate a rice paddy) and a glue board. Five Philippine
rice rats were tested with each glue. In every instance, the test
animals were held fast (even though they were wet) and remained so
during the 2-h test period. While these results are favorable, they
are prelusive and further testing, both in the laboratory and under
field conditions, is necessary.

Automatic data-acquisition system for measuring the bait intake of
ricefield rats (R. r. mindanensis)

In the 1977 Annual Report, we discussed the initial results of a study
to analyze the minute-by-minute feeding patterns of ricefield rats.
Bait consumption was monitored using a single electronic balance
programed to automatically record food consumption on cassette tapes.
Essentially, results showed that: (1) rats feed on bait for only
limited portions (i.e., 35-90 min) of each 24-h period, and (2)
feeding patterns of rats presented with zinc phosphide or warfarin
baits are characterized by intermittent, 1- to 3-min samplings of
<0.1 g of bait, whereas, rats given nontoxic bait eat several 5- to
10-min "meals" (i.e., 0.5-1.5 g of bait) separated by 1- to 2-h non-
feeding intervals.

Despite the satisfactory results obtained with the original equipment,
major problems of data acquisition, reduction, and analysis plagued
this earlier study. Efficient handling of large volumes of data was
difficult, and use of a single-bait (no-choice) test limited inter-
pretation of these data.

Recently, we purchased an improved system for automatic, continuous
measurements of rodent feeding patterns. This system consists of:
(1) four 200-g electronic balances, (2) one Horizon II microprocessor,
Sone multiplexer-scanner, and (4) one teletypewriter. All data
acquisition is under the control of the microprocessor; the minute-by-
minute bait intake by rats from two choice cups is automatically
transferred and stored on permanent 75 mm X 75 mm X 1.6 mm magnetic

A series of studies are planned to assess the effects of different
rodenticides and rodenticide concentrations on bait intake patterns
of ricefield rats as well as other species. Automatic recording and
analysis of data will permit evaluation of changes in feeding behavior
induced by sublethal doses of toxic baits. This information will make
possible the development of improved bait formulations for both new
rodenticides as well as those currently in use.

Drug-induced taste aversion in ricefield rats (R. r. mindanensis):
factors affecting drug effectiveness and feasibility of use for
reducing crop damage

If a rat is exposed to sufficient levels of ionizing radiation or
given certain drugs within a short time after tasting a novel sub-
stance, subsequent intake of that substance is reduced. This effect
is termed "conditioned taste aversion" and it is currently being pro-
posed as a nonlethal method for control of agricultural damage by a
variety of vertebrate species (e.g., bear damage to apiaries, rat and
bird damage to grain or fruit crops, and coyote predation on sheep).

Despite repeated laboratory demonstrations of the conditioned taste
aversion effect, a number of factors can affect generalizations from
laboratory to field situations. Laboratory use of deprivation
regimens, intraperitoneal injection or gavage administration of drugs,
and controlled presentation of novel taste stimuli serve to optimize
the effect. Our current work is designed to: (1) clarify several
factors likely to influence field applications of drug-induced aver-
sion and (2) assess the feasibility of drug-induced taste aversion
for reducing crop damage by the ricefield rat (R. r. mindanensis). To

date, work has consisted of pilot tests to develop appropriate proce-
dures and an initial study to compare copper sulfate, cyclophos-
phamide, lithium chloride, and red squill as aversion-producing drugs.

The procedures developed for these tests involve placing rats on a
daily 22-h water deprivation schedule followed by a 2-h period in
which saccharin-flavored water is available. The preconditioning
phase lasts 14 days. On the treatment day, the rats are presented
with saccharin-flavored water which either contains an aversive drug
or precedes gavage or intraperitoneal injections of the drug.
Subsequently, each rat's saccharin preference is monitored for 28
successive days following the same procedure outlined for the pre-
conditioning phase, but during the 2-h nondeprivation period the
animals have a choice of water or water plus saccharin.

Results of these pilot tests indicate that: (1) ricefield rats will
orally ingest saccharin-flavored water containing lithium chloride,
(2) the mode of drug administration (free ingestion, gavage, or
intraperitoneal injection) affects taste aversion conditioning, and
(3) aversion effects lasting from 19 to 28 days can be produced.

In a study to select a drug that produces a high level of aversion,
42 male rats were randomly assigned to six different drug treatments
(n = 7/group). Gavage dosages of 125 mg/kg lithium chloride, 5 mg/kg
copper sulfate, 33 mg/kg cyclophosphamide, 35 mg/kg red squill, 125
mg/kg sodium chloride, or volumes of water equal to those of the
lithium doses were administered after the 2-h presentation of
saccharin. Results were marginal; lithium-treated rats showed an
aversion to saccharin for approximately 10 days.

Due to the tenuous results obtained in this study, a second trial,
involving increased dosages of drugs, was conducted. Gavage dosages
for this study were: lithium chloride, 375 mg/kg; copper sulfate, 30
mg/kg; cyclophosphamide, 198 mg/kg; red squill, 210 mg/kg; sodium
chloride, 375 mg/kg; and volumes of water equal to the lithium dose.
Figure 1 is a graph of the mean daily aversion indices obtained. As
shown, the lithium chloride rats displayed the most prolonged
aversion to saccharin. Intermediate aversion was noted in rats
treated with cyclophosphamide and red squill; copper sulfate produced
practically no aversion to saccharin, a result similar to that for
sodium chloride and water. Together, these data confirm that lithium
chloride is an effective drug for further studies to evaluate the
concept of drug-induced aversion as a means of protecting field crops
from damage by rodents.

I- LCI --Cyclo ...R.Sq -- H20 -CuSO, -. NaCI

10 12 14


16 18 20 22 24


Figure 1. Mean aversion indices when preference tests were conducted for 28 days posttreatment
with four different drugs (lithium chloride, red squill, cyclophosphamide, copper
sulfate) or two control (reference) agents (water, sodium chloride).


0.8 *





26 28

Cotton rats (Sigmodon hispidus)
in many areas of Latin America.
tested for repellent activity by

cause widespread damage to young corn plants (and other crops)
In this laboratory experiment, selected chemical agents are
exposing topically treated plants to the rats.

Laboratory tests of the repellent activity of selected chemicals for
protecting corn from damage by cotton rats (Sigmodon hispidus)

In parts of Latin America, cotton rats (S. hispidus) often cause
extensive damage to young corn plants by direct cutting of the stalk
or digging the roots from the base of the plant. Damage is sometimes
so severe that fields must be replanted several times before adequate
corn stands can be raised. Our laboratory research on this problem
has been aimed toward development of repellent chemicals that will
alleviate rat damage to young plants. Four chemical formulations
were evaluated using topical (surface) treatments on growing corn
plants (<15 cm high). The only treatment that produced a consistent
decrease in damage was a 1-percent solution of red squill, a
commercial rodenticide. This effect is shown in Table 10, with
comparative results for R-55 (commercial rodent repellent) and
acetone extracted tannins from a bird-resistant variety of sorghum.

Numbers (mean SD) of corn plants
(n = 3) of cotton rats. Plants (n
day for 5 days during the baseline

damaged by small groups
= 10-15) offered each
and treatment sessions.

Baseline Treatment
No. plants No. plants
No. plants cut and No. plants cut and
Treatment cut eaten cut eaten

1% R-55 8.00.0 4.01.4 8.22.2 5.44.2

1% Red Squill 10.00.0 10.00.0 5.82.9 5.82.9

1% Tannin 10.57.8 5.53.5 7.64.8 4.62.1

5% Tannin 10.57.8 5.53.5 10.00.0 6.20.8

Additional tests with 5 percent red squill and an
rodenticide are in progress. Closed circuit videotaped
the treatment periods (4 p.m. 8 a.m. each night) should
refined analysis of the repellency effects.

sessions of
allow a more

Table 10.

Nonlethal electric barriers for control of ricefield rats

Previous laboratory and field data have shown that ricefield rats (R.
r. mindanensis) can be repelled with a prototype electric barrier--two
electrodes and two ground wires spaced 15 cm apart and fastened to a
35- to 45-cm poultry wire barrier. A major problem with this configu-
ration is the high cost of materials. In order to evaluate modified
designs, made with less expensive materials, two versions of the
prototype barrier were compared with three plastic net configurations
in an 240 cm X 60 cm X 120 cm laboratory observation chamber.

Infrared closed-circuit television was used to monitor the fence-
climbing behavior of individual ricefield rats (n = 15 per barrier
design). The test animals were fasted and subsequently exposed to a
small amount of whole rice on the opposite side of the barrier.

As shown in Table 11, the fewest crossings and the lowest percentage
of successful attempts occurred with the plastic net III design.
This configuration consisted of two grounded electrodes (10 and 30 cm
above ground) and three active electrodes (5, 15, and 35 cm above
ground level). These data indicate that less expensive and more
readily available materials can be used with essentially no loss in
efficacy as compared with wire barriers--at least under laboratory

Table 11. Performance of five nonlethal electric rodent barrier designs.

% Lower Upper %
No. No. Successful electrode electrode Attempts
Barrier design crossings attempts attempts shocks shocks shocked

Prototypea 2 47 4.3 37 5 89.4

prototype 3 45 6.7 30 15 100.0

Plastic net Ic 3 42 7.3 40 1 97.6

Plastic net IId 5 37 13.5 36 3 105.4*

Plastic net IIIe 1 32 3.1 28 1 110.4*

a Twenty-five millimeter chicken wire (35 cm high) with two ground and two
active electrodes spaced 15 cm apart at top.
b Same as above with lower ground wire excluded.

c Twenty-five millimeter plastic fish net with one ground wire and three
active electrodes spaced 30 cm apart.

d Three electrodes interspaced with three ground wires at a distance of 37
e Three electrodes 5 cm in front of net interspersed with two ground wires
spaced 5 cm apart vertically.

* Exceeded 100 percent when more than one shock was received by rats per each
attempt to cross.

Development of highly preferred baits for Quelea

Operational quelea control programs, involving spray applications of
parathion or fenthion on roosts and nest sites, have been in existence
for many years. Despite these widespread efforts, quelea populations
are only temporarily reduced and crop damage is generally not
affected. These marginal results are partially due to two related
problems: (1) the quelea popu action base is extremely large
(estimated to be between 109 and 10 1), and (2) quelea movement and
migration patterns are not always very predictable. More effective
reductional control of quelea might be achieved by distributing well-
accepted toxic bait at potential crop depredation sites.

The literature indicates that physical characteristics (taste, tex-
ture, size, etc.) of food items will influence acceptance by quelea.
In this experiment, two of these factors, particle size and texture,
were evaluated with small groups (n = 5 or 6) of caged quelea. The
birds were first adapted to feeding from automatic, two-choice pref-
erence testing devices. They were then exposed to different millet
particle sizes over 2- to 3-week periods. Actual preference data
were obtained during four 6-h test sessions using a weigh-back pro-
cedure. Percent preference scores were calculated by comparing the
amounts of whole and particulate millet consumed by each bird.

Results of the size preference tests are given in Table 12. Note
that all birds in the three groups preferred whole hulled millet to
ground particles. These laboratory data suggest that quelea prefer-
ence for small (0.1-0.3 mg) grass and weed seeds is probably deter-
mined by factors other than size per se (e.g., flavor, texture,

In a related study, bait particle or pellet texture was examined as a
variable that could affect bait acceptance. This test incorporated
four levels of pellet hardness, achieved by mixing different moisture
levels (16, 14, 10, and 8 percent) with bentonite and mixed grain
before pelleting. The higher moisture levels produced firmer pellets.
Three independent groups of quelea (n = 6) were exposed to the pellets
in the two-choice preference devices over a 3-week period. Data were
obtained during four 6-h test sessions using a weigh-back procedure.
Percent preference scores were then calculated for each level.

As shown in Table 13, the birds were indifferent (50 percent prefer-
ence) when the harder pellets were used, but preference decreased (X =
38.0 percent) when softer (<8 percent moisture) pellets were used.
The data indicate that quelea readily accept pelletized baits when
bentonite and 10-percent or higher moisture levels are used, but low-
moisture, soft pellets are not as well accepted.

A ricefield rat falls back after receiving a nonlethal shock from an
experimental electric barrier in a DWRC laboratory experiment. These
nonlethal electric barriers are one of many techniques being developed
to reduce rodent damage to agricultural crops (Photograph by James L.
Stanfield, National Geographic Society.)


Percent preference response (mean SD) of quelea for whole
hulled millet when different millet particle sizes were
used as alternate foods.

Bird No.














Millet particle size
0.6 mg
(16-20 mesh)
Bird No. X SD

236 95.33.9

270 97.33.3

234 96.84.9

224 96.34.6

255 96.32.7


Bird No.







Table 12.









Percent preference response (mean SD)
pellets formulated at various moisture
percent as the standard for comparison.

of quelea for
levels with 16

Pellet moisture level
14% 10% 8%
Bird No. X SD Bird No. SD Bird No. X SD

250 51.014.4 284 47.1 8.8 290 45.711.3

248 54.414.9 258 49.5 8.4 238 31.819.9

223 55.0 3.9 257 56.6 5.8 207 37.6 4.3

215 51.010.4 252 60.410.9 221 19.711.9

259 50.410.7 208 53.8 7.3 278 55.116.0

226 56.016.4 230 44.412.4 291 37.012.9

means 53.017.7 52.013.4 38.019.1

Future preference tests with quelea will include evaluations of color
and flavor as potential factors affecting bait acceptance. Baits
developed from this research could provide an improved method of
applying toxicants for control of quelea depredations in agricultural

Design modification trials of sublethal electric barriers

Engineering support was provided at the Los Ba'hos field station in the
Philippines for development of high-voltage electric barriers to pro-
tect ricefields from rodent damage. Fourteen electrode configurations
were evaluated in an effort to optimize the barrier design. A config-
uration that uses only three electrode wires was selected as best for
a planned full-scale field evaluation in a ricefield during 1979. Two
types of high-energy fence chargers, imported from New Zealand, were
used to drive these electric barriers. In addition, a 200-W wind-
powered electric generator was taken to Los Banos for testing as a
possible alternative energy source. Custom-designed electronic activ-
ity counters were developed to measure the number of rat encounters
with the barriers. One type of counter monitors rat activity along a

Table 13.


A male quelea (Quelea quelea) is tested for bait preference with selected particle sizes of
cracked millet seed. Tests such as this can provide information useful in the development of
highly accepted bait material.

deenergized barrier while the second counter is designed to record the
number of shocking pulses delivered by the fence charger. Thus, rat
activity can be measured prior to electrification of a fence for later
comparison with the number of shock pulses actually delivered.

Coulometric event counter problems corrected

Two years ago, specialized coulometric event counters were designed
and sent to the Philippine field station for use in measuring and
evaluating rodent activity during field baiting tests. However, a
puzzling, intermittent functional problem developed. The problem has
now been resolved and the units repaired. Apparently, the high rela-
tive humidity in the Philippines reacted with the encapsulating mate-
rial and interfered with the functioning of the apparatus.

Chemical analyses of Philippine ricefield samples for diphacinone and
warfarin residues

Analytical methods for diphacinone and warfarin, which were developed
at the DWRC, are being used to study possible accumulation of these
chemicals in various types of ricefield samples. The analyses are
being performed to determine whether residues might occur in rice
plants, rice grains, soil, and water samples following intensive
application of the chemicals (see page 36). Analyses of water samples
have been completed. Diphacinone was not found in any of these.
Warfarin was found at very low concentrations, ranging from 0.01 to
0.02 ppm, in some water samples from fields receiving the highest rate
of application. Analyses of the plant, grain, and soil samples will
be made after sensitivity and recovery standards have been established
for each type of material.

A potential new wildlife marking agent

Several aspects of vertebrate damage control investigations, as well
as other types of wildlife research, would benefit from improved
methods for marking animals and toxic baits. DWRC scientists have
been experimenting with a new and promising wildlife marking tech-
nique. The following report describes the agent and a series of
experiments designed to examine potential uses.

Small plastic particles called "microtaggants" were originally devel-
oped by the 3M Company to provide a means of identifying the type and
origin of explosives used in criminal activities. They have proper-
ties which make them suitable for use in bait formulations or as a
topical (surface) marking agent. Microtaggants are irregular flakes,
all of which will pass a 425-p screen. Colored layers in the parti-
cles form a code which can be read with a 30X or greater optical
magnifier. The number of layers used ranges from five to seven and

ten colors are available. The colors are numbered from 0 to 9 with
the color-number relationship based on the standard color code of the
electronics industry. When a purchase is made, a code is generated
and assigned exclusively to that buyer. The number of codes available
with different combinations and orders of colored layers is in the
millions. Two features that make recovery and/or detection of micro-
taggants easy are the incorporation of one or more fluorescent layers
and a ferromagnetic layer. Visual detection or magnetic recovery can
be made from a variety of materials. The manufacturer states that the
particles are chemically stable; the base material is an inert thermo-
set plastic that is unaffected by most solvents, acids, and bases.
The particles are also claimed to be thermally stable to 2000 C during
extended exposure and 3500 C for 30 seconds.

Bait-marking experiments: A number of tests were conducted to deter-
mine if microtaggants could be used to identify toxicants in baits,
rodenticides, or similar products in the digestive tracts of species
ingesting these materials. A 0.3-percent concentration of micro-
taggants was used in all bait tests.

Twelve Norway rats were used to test the acceptance of bait containing
microtaggants. The rats ate significantly (p = 0.03) more rolled oat
bait with microtaggants than without. In a toxic bait test, two
groups of white rats (n = 30/group) showed no significant difference
(p = 0.33) in mortality after being offered a 2-percent zinc phosphide
bait with microtaggants (22 of 30 died) or without them (26 of 30
died). To determine if microtaggants remained intact in the digestive
tract and fecal matter, the following species were tested on the
specified toxic bait: (a) six Norway rats and six white-footed deer
mice, 2-percent zinc phosphide on rolled oats; (b) five Richardson's
ground squirrels, 0.075-percent 1080 on oat groats; (c) two coyotes,
0.5 or 1 mg/kg 1080 on meat; (d) six red-winged blackbirds, 3-percent
Avitrol on cracked corn; (e) six starlings, 1-percent Starlicide
pellets. All species died within the expected time range for each
toxicant and all species, except three of the starlings, were well
marked in the digestive tract with intact particles that showed no
signs of degradation. Microtaggant detection was made under ultra-
violet light by dissection and gross observation of the digestive
tract, or by recovering microtaggants with a magnetic stirring rod
from a water suspension of fecal matter.

We also examined the potential of using microtaggants for determina-
tion of secondary hazards. Five Richardson's ground squirrels were
poisoned with 1080 bait containing the marker and subsequently fed to
a coyote. The coyote succumbed after 48 h. At least ten micro-
taggants were found in the digestive tract of the coyote, and fecal
samples collected before death were all well marked.