PREDATORY BEHAVIOR OF LARGEMOUTH BASS ON
SOFT AND SPINY-RAYED FORAGE SPECIES







By

Daniel C. Hatton
















A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY







UNIVERSITY OF FLORIDA

1977















ACKNOWLEDGEMENTS

Gratitude is expressed to Dr. Merle E. Meyer for his

advice and support throughout the course of this study and

my graduate career. Thanks are also extended to Drs.

Donald A. Dewsbury, Robert L. Isaacson, Edward F. Malagodi,

and Thomas H. Patton for their critical reading of the manu-

script and for sharing their knowledge with me.

A special thanks is due Gray Bass of the Fisheries

Division of the Florida Game and Fish Commission and to

Robert Stetler, Douglas Colle and Roger Rottian of the White

Amur Research Team at the University of Florida for their

invaluable aid in the collection of subjects used in this

study and for their thoughtful and provocative comments on

the design of the study.

A debt of gratitude is owed to Richard Kearley, Peter

Spyke, Lisa Stalnaker, Rebecca Bellamy and John Heins for

their help in various aspects of the study.

Appreciation is extended to Virginia Walker for her

considerate attention in typing the manuscript. Finally,

a special "thank you" to my wife, Nikki, for so many things,

but mostly for her support, encouragement, and endurance

throughout.

















TABLE OF CONTENTS


Page


ACKNOWLEDGEMENTS . . . . . . . . . .

LIST OF TABLES . . . . . . . . . . .

ABSTRACT . . . . . . . . . . . .

GENERAL INTRODUCTION , , , . . . . . .

EXPERIMENT I . . . . . . . . . . .

EXPERIMENT II . . . . . . . . . . .

EXPERIMENT III . . . . . . . . . . .

INCIDENTAL OBSERVATIONS . . . . . . . .

GENERAL DISCUSSION . . . . . . . . . .

APPENDIX I . . . . . . . . . . .

REFERENCES . . . . . . . . . . . .

BIOGRAPHICAL SKETCH . . . . . . . . .


ii

iv

vi

1

4

39


52

58

71

74
















LIST OF TABLES

Table Page

1. Conditional probabilities for predator's
behavior . . . . . . . . . 11

2. Predator behavior conditional upon prey
behavior . . . . . . . . . . 17

3. Conditional probabilities for prey behavior
contingent upon immediately preceding predator
behavior . . . . . . . . . . 19

4. Attempted captures/successful captures. ... .22

5. Number of responses by each prey in each of the
swimming categories and number of captures
during each category . . . . . ... 25

6. Number of yawns occurring before and after
capture . . . . . . . . .. ... . 28

7. Number of gill flares, yawns and headshakes
following captures . . . . . . . 30

8. Mean sequence length for prey smaller and
larger than 0.59 times the gape width of the
predator's mouth . . . . . . . .. 32

9. Number of attempted captures and the position of
the prey in the mouth following capture for blue-
gill above and below 0.59 times the gape width of
the predator's mouth . . . . . . .. 34

10. Number of attempted captures and the position of
the prey in the mouth following capture for bass
above and below 0.59 times the gape width of the
predator's mouth. . . . . . . . ... 36

11. Number of attempted captures and the position of
the prey in the mouth following capture for
shiners above and below 0.59 times the gape width
of the predator's mouth . . . . . . 37

12. Behavior that occurred after capture of spined
and de-spined bluegill . . . . . .. 41









LIST OF TABLES (continued)

Table Page

13. Size selection for grass carp. The number
represents the number of fish selected by
the predator in that size class . . . .. .46

14. Size selection for bluegill. The number
represents the number of fish selected by
the predator in that size class . . . .. 47















Abstract of Dissertation Presented to the Graduate
Council of tie University of Florida in Partial Fulfillment
of the Requirements for the Degree of Doctor of Pnilosophy



PREDATORY BEHAVIOR OF LARGEMOUTH BASS ON
SOFT AND SPINY-RAYED FORAGE SPECIES

By

Daniel C. Hatton

March, 1977

Chairman: Merle E. Meyer
Major Department: Psychology

The predatory behavior of captive largemouth bass,

Micropterus salmoides, was observed on two species of spiny-

rayed fish, bluegill, Lepomis macrochirus, and largemouth

bass, and two species of soft-rayed fish, golden shiners,

Notomigonous crysoleucus, and grass carp, Ctenopharyngodon

idella, in three experiments. In the first experiment, the

behavior of the bass and the swimming of the prey were

categorized and the frequency and order of occurrence of

the behavioral components were recorded. Differences were

found in the susceptibility of the different species to

predation and in the manner in which the predator interacted

with the prey.

Susceptibility to predation was found to be consistent-

ly related to movement of the prey in the vicinity of the

predator. Inhibition of movement decreased risk, while








movement, particularly rapid movement, resulted in a sub-

stantial increase in risk. Bluegill, which appeared to as-

sume species-typical postures when motionless in the pres-

ence of a predator, were the least susceptible to predation

as measured by the average sequence lenght per test trial

and capture success. Grass carp had the highest risk to

predation.

The presence of spiny fin rays appeared to increase the

difficulty that the predator encountered in swallowing the

prey. Wnile there were no obviously different handling or

capture techniques employed by the predator to capture

spiny-rayed prey, it was noted that the majority of captures

of such prey resulted in the prey being taken into the mouth

tailfirst. The majority of captures of soft-rayed fish re-

sulted in the prey being taken into the mouth headfirst.

The difference in the position of the prey in the mouth of

the predator appeared to be due more to the behavior of the

prey than the behavior of the predator.

In the second experiment the bass were presented with

despined bluegill. Recordings were taken on the frequency

of yawns, gill flares, and headshakes that occurred after

capture. Collectively, these behaviors were taken as indi-

cations that the predator was experiencing difficulty in

swallowing the prey. There were significantly fewer gill

flares, yawns and headshakes following capture of de-

spined prey than after capture of spined bluegill. The

difficulty the bass experienced with the despined bluegill

vii









was significantly greater than the difficulty experienced

with soft-rayed prey.

The third experiment examined the question of size

selection of prey by the bass. The bass were presented

with consecutive size classes of bluegill and grass carp in

separate tests. The size of the first prey captured by the

bass in each test was recorded. There was no evidence of

size selection for either species of prey.


viii















GENERAL INTRODUCTION


Predation can have substantial impact upon both the

number and kinds of species comprising a community (Lewis,

1967; Slobotkin, 1968). Despite numerous investigations of

the impact of predation, little work has been completed

upon the actual behaviors involved in prey capture (Chiszer

and Windell, 1973), especially for piscivorous fish. Con-

sidering the diversity of potential prey species available

to most piscivorous fish, the behavioral interaction between

predator and prey may be critical in determining the diet.

In the absence of behavioral data on the predator-

prey interaction it is not possible to specify all of the

factors that contribute to the vulnerability of a prey.

Nevertheless, data from predator impact investigations in-

dicate that there may be a limited number of variables that

may account for a major portion of the variance. Lewis

(1967) contends that selectivity in the predator's diet

can be accounted for by variation in the vulnerability of

the prey to predation.

For predators that swallow their prey intact, as do

most piscivorous fish, the size of the prey relative to the

size of the predator is a prime determinant of which prey

are available to the predator (Lawrence, 1957). Size, how-









ever, is not a unitary variable. The size of a fish varies

along four important parameters: length, depth, width and

weight. The upper size limit of prey available to the preda-

tor will be set by some physical dimension of the predator,

in most cases the narrowest structure leading to the esopha-

gus (Lawrence, 1957). Consequently, depth of body may be-

come a limiting factor before either length or width in

many prey species. Weight, considered independently of

other size dimensions, would not, of itself, be a physically

limiting parameter but it may play a substantial role in

the economic behavior of the predator insofar as weight can

be considered an index to the caloric content or energy

value of the prey.

An additional morphological feature of the prey that

may contribute to differential selection by the predator

is the spiny fin rays located in the dorsal, anal, and

pelvic fins of many species of fish. Numerous species of

fish have evolved specialized spines as a possible means of

defence by providing aversive mechanical stimulation to the

mouth of the predator that attempts to capture it (Marshall,

1966). Hoogland, Morris and Tinbergen (1957) demonstrated

the utility of the specialized spines of the three-spined

stickleback in defense against pike predation. Although it

is not clear that defense was the selective pressure for

the development of spiny fin rays, they certainly may

function in that capacity given the rigidity and sharpness

of the spines found in many species (Beyerle and Williams,

1968).









For visually oriented predators, movement can be a

potent stimulus in the detection of prey (Walls, 1942;

Marler and Hamilton, 1966). Consequently, the movement

pattern of the prey in the vicinity of the predator may in-

fluence the prey's vulnerability. For the most part, move-

ment will be the result of normal locomotion, although

feeding, aggressive behaviors, and other such behavior

patterns may involve very conspicuous motor patterns. In-

hibition of movement in the presence of a predator may

serve to lower the incidence of predation. Although vary-

ing with the predator and the situation, successful ex-

ploitation of a source of cover or utilizing cryptic colora-

tion often depends upon the inhibition of movement. More-

over, inhibition of movement in the absence of cover or an

appropriate background for effective use of cryptic colora-

tion may also reduce the likelihood of predation, itself.

In addition to these rather general factors, there

are numerous variables that probably have substantial im-

pact on predation. Included would be such variables as

reaction distance of the prey to the predator (Dill, 1974),

grouping patterns (Thomas, 1974), and schooling, of both

predator and the prey (Major, 1976).

The experiments described below have as their major

emphasis a description of the predatory interaction of

largemouth bass on various prey that differ in terms of

body configuration, the presence or absence of spiny fin

rays, and movement patterns.















EXPERIMENT I

Bluegill sunfish, Lepomis macrochirus, golden shiners,

Notomigonous crysoleucus, largemouth bass, Micropterus

salmoides floridanus, and grass carp, Ctenopharyngodon

idella, were selected as prey species for largemouth bass

on the basis of body configuration and availability. All

of the species, except the grass carp, commonly occur in

the diet of the largemouth bass (Chew, 1974). The grass

carp is not indigenous to areas inhabited by the bass, but

is has been introduced in some areas and does occur in the

diet when available (D. Colle, personal communication).

Both bluegill and largemouth bass are spiny-rayed

fish, with the bluegill being relatively shorter, more later-

ally compressed and possessing greater body depth per unit

length than the largemouth bass (see Figure 1). Shiners

and grass carp, by contrast, are both soft-rayed species.

The depth of body per unit length of the grass carp is less

than that of the shiner, which is similar to the largemouth

in that regard. Aside from the morphological differences

among the prey species, it was expected from prior ob-

servation, that the fish would differ considerably in their

behavior patterns.
Methods

Subjects
Eight largemouth bass, obtained by electroshocking

4






Side View


Golden Shiner, Notomigonous crysoleucus


Front View

0


0


Bluegill sunfish, Leponis racrocnirus


Largei.Louta Bass, Micropterus salmoides


Grass Carp, Cteno.naryngoaon idella
Figure 1. Body configurations of prey species.


0









in Newnan's Lake, Alachua County, Florida, were used as

predators. Seven bass were initially used as predators

in the study, however, following completion of testing on

shiners and bluegill, four of the bass died, presumably as

a result of disease introduced into the tank via the prey.

Four additional bass were placed with the remaining three

but only one survived the reorganization of the dominance

hierarchy. Consequently, four bass were used in the de-

scriptive portion for bass and grass carp. The bass

ranged in size from 160 to 328 mm. These fish were main-

tained in a 2.4 x 1.2 x .9M plywood and fibreglass tank

which was partitioned at its middle by fibreglass screening.

Water in the tank was maintained at a level of approximately

.6 M in depth. The water was filtered and aerated by pump-

ing water from one end of the tank by means of a Taco model

110 pump and discharging it through a charcoal and floss

filter at the opposite end. Temperature in the tank was

maintained at room temperature, 210C + 2'C.

Bluegill, golden shiner, largemouth bass fingerlings

and grass carp were utilized as prey species. The bluegill

were collected as needed by seining in local lakes and

ponds near Gainesville, Alachua County, Florida. The gold-

en shiners were obtained from a local commercial supplier,

while the largemouth bass fingerlings were obtained from the

Welaka Natural Fish Hatchery, Welaka, Florida. Dr. Jerome









Shireman of the University of Florida contributed the grass

carp for the study. The prey were maintained in a 3.05 x

.46 M circular plastic wading pool and were treated with a

formalin dip at 5,000 parts to 1 as well as a commercial

solution of methylene blue, malachite green and acriflavin

after the dip and before being introduced into the testing

tank with the predator.

Procedure

Testing was conducted in one-half of the tank used to

house the bass. Ten minutes prior to testing, one predator

was introduced through a sliding door in the partition sep-

arating the two halves of the tank. A test consisted of a

single presentation of a prey to an individual predator.

The predator was allowed ten minutes in which to consume

the prey. If the prey was still alive after the ten-minute

period, it was removed and replaced with a different fish

of the same species. The predator was allowed to eat 1 -

2% of its body weight per day in prey.

Each predator was presented with 20 prey of a variety

of sizes from one species before introductions of prey from

another species was initiated. The order of presentation

was golden shiners, bluegill, bass and grass carp.

Prior to introduction into the testing tank each prey

was weighed and measured for length and depth of body. Ob-

servations began immediately upon the introduction of the

prey fish and were terminated after 10 minutes or after the

prey was swallowed. In order to reduce distractions caused

by the observer, the fish were viewed through a one-way glass









during testing. All data were recorded on a tape recorder

and later transcribed to data cards for computer analysis.

Selected behaviors of both the predator and the prey

were recorded. For the prey, swimming behavior was record-

ed and was broken into four distinguishable classifications:

1) Motionless fish may be moving pectorals and

riffling tail, but no movement through the water.

2) Pectoral swimming based upon the movement of the

pectoral fins.

3) Normal whole body undulations during swimming.

4) Escape same as 3 but much more rapid.

For predators the frequency and order of occurrence of

the following behaviors were recorded:

1) Orientation head pointed directly at the prey.

2) Approach movement toward a motionless or pectoral-

ly swimming prey.

3) Stop cessation of movement toward or away from

the prey while remaining oriented.

4) Turn away predator turns body away from prey.

5) Chase rapid swimming toward a prey that is mov-

i ing away.

6) Follow predator maintaining a constant distance

between itself and a moving prey.

7) Backpedal pectoral swimming backwards.

8) Lunge mouth open, gills flared, rapid thrust of

body toward the prey.

9) Yawn mouth open, gills flared, no movement of

the body.









10) Rejection prey taken into the mouth and then

expelled.

11) Miss predator lunges at prey and misses.

12) Headfirst capture prey taken into the mouth

headfirst.

13) Tailfirst capture prey taken into the mouth

tailfirst.

14) Sideways capture prey taken into the mouth

sideways.

15) Headshaking rapid side to side movement of the

head, occurred after the prey was in the mouth.

16) Gill flares gills open, mouth not open. Oc-

curred after the prey was in the mouth.

17) Intercept predator swims along a path that in-

tercepts that of the swimming prey.


Results and Discussion

Description of the Predatory Interaction for all Prey

Only those behaviors that occurred while the predator

was oriented toward the prey were recorded. Accordingly,

all behavioral sequences recorded for the predator began

with an initial orientation. For the prey, recording be-

gan with the behavior that it displayed immediately prior

to orientation by the bass. The statistics presented in

this section represent average conditional probabilities

computed from the data for all of the fish employed in the

study. Each probability presented was calculated as a per-









centage of the frequency of all behaviors following im-

mediately upon a given conditioned behavior (Chiszer and

Windell, 1973).

All trials began with the introduction of the prey

into the testing tank. Following introduction of the prey,

the behavioral sequence proceeded rapidly, often ending in

the prey being captured within approximately 30 seconds or

less. Eighty-one percent of all prey introduced were eaten

within the ten-minute test trial. In many trials prey were

captured more than once due to rejections and subsequent

recaptures. The behavioral sequences employed by the pred-

ator will be discussed in more detail below.

Upon introduction into the testing tank the prey typic-

ally responded by swimming at normal or escape speeds (p =

.70). In the absence of any movement by the bass toward

the prey, beyond orientation, the swimming of the prey us-

ually terminated within a few seconds of introduction by

the prey becoming motionless in the tank (p = .68).

Orientation by the bass normally occurred immediately

upon introduction of the prey into the tank (p = .81). An

orientation was followed by either an approach, chase, in-

tercept, lunge, follow, turnaway or yawn, depending upon the

behavior of the prey and its proximity to the bass (see

Table 1). If the prey was motionless or swimming pectorally

subsequent to orientation there was a high probability that

the bass would approach (p = .61). Approaches took either

of two forms, the most frequent being slow, pectoral swim-














TABLE 1

Conditional probabilities for predator's behavior. Probabilities
are for behaviors immediately following another behavior by the
predator. S = Shiner, BL = Bluegill, B = Bass, C = Carp.

Behaviors

Orient Approach Stop Chase Intercept
Behavior S BL B C S BL B C S BL B C S BL B C S BL B C

Orient 64 69 54 40 13 13 31 22 04 01 01 01


Approach

Stop

Chase

Intercept

Lunge

Miss 07

Backpedal

Follow

Turnaway 70 70 67 86

Yawn

Headfirst

Tailfirst

Sideways

Gill Flare

Headshake

Reject

In Mouth


09


71 77 60 48


56 43 44 48


08 02 05

06


02 04

04 01 25


50 97 33

01

15


07 04















TABLE 1 (Extended)


Lunge Miss Backpedal Follow Turnaway Yawn
S BL B C S BL B C S BL B C S BL B C S BL B C S BL B C

05 02 04 03 02 09 04 02 -


06 11 22

01 17

44 48 14

05 08 12


01 02 06 04

16 22 24 08


02 -

02 -

02 -


14 04

07 -


04 03


33 57 68 36


07 06 11


2 06 07

- 02 33


19

46


- 05 18


- 22 02 02

19 67 01

- 16 15


0


- 03 -


- 04 33 04 - 14 08 43 36


- 80


10 53 35 1001

100*35 08 -


- 13 07 04


11 03


--














TABLE 1 (Continued)






Headfirst Tailfirst Sideways No Further Gill Flare
S BL B C S BL B C S BL B C S BL B C S BL B C


10 05 03 19 32 50 78 04 01 -

52 78 92 79 05 - 07 05 -

43 14 02 18 17 26 21 45 08 10 05


30 30 33 14


07 24 67 -









- 26 33 -



08 27 13 01















TABLE 1 (Extended)


lieadshake Reject
SBL B C S BL B C


Swim out In mouth Swallow
S BL B C C BL B C S BL B C


04 33


23 13 33

02 06 -


- 12 08 -

08 06 -

09 28 05 -

33 -


92 94 100100

92 94 100100

91 72 95 100

03 - 100


10 02 -


- 06 -


80 45 65 -

100 28 59 100



90 31 66 85


02 29 14 10









ming toward the prey interspersed with numerous stops. The

other form of approach was rapid whole body swimming toward

the prey.

Prey which continued swimming either normally or at es-

cape speeds following orientation increased the probability

that the bass would either chase (p = .16), intercept (p =

.11), follow (p = .02) or lunge (p = .02) at it. Chases oc-

curred most frequently (p = .80) to prey swimming at es-

cape speeds away from the bass. Most intercepts, on the

other hand, occurred while the prey was swimming normally

(p = .75). Following pursuant to orientation was directed

exclusively toward normally swimming prey.

Lunges which followed upon orientation occurred when

the prey swam into the immediate vicinity of the bass.

Similarly, most yawns following orientation were toward

prey in close proximity to the bass. Turn aways were not con-

sistently related to the behavior of prey immediately fol-

lowing orientation.

While an approach was the most frequently observed

behavior following an orientation, a stop was the most fre-

quently observed behavior following an approach (p = .64).

Most of the stops occurred during the pectoral approach se-

quence. Typically, in the pectoral approach sequence, the

bass would swim a portion of the distance between itself

and the prey, stop, and then again resume its approach. As

many as a dozen such approach-stop sequences may occur be-

fore the bass came to rest within a few cm of the prey.

Aside from the stop, the most frequently observed be-









havior following an approach was a lunge (p = .14). Lunges

in this context, were directed toward motionless prey after

the bass had approached to within 10 cm of the prey or clos-

er. The lunge itself was characterized by a rapid thrust of

the body toward the prey while the mouth was opened, which

created a strong water current into the mouth (Nyberg,

1971).

Yawns followed approaches 8% of the time. Yawns were

directed at the prey from an average distance of approxi-

mately 5 cm, and involved the bass opening its mouth and

creating a local water disturbance that was directed away

from the bass. No gross body movements were observed dur-

ing the yawn except the opening of the mouth. The probabil-

ity that the prey would respond to a yawn was .73 (see

Table 2). Most of those responses were escape swimming

away from the bass (p = .75). This can be contrasted to

the .3+ probability of responding to an approach.

The most frequently occurring behavior following an

approach was a stop. Likewise, the most frequent response

following a stop was an approach (p = .48). This outcome

is primarily due to the approach-stop sequences employed

by the bass. A further outcome of this process is that many

of the behaviors observed following a stop were part of the

approach-stop sequence, as well. This is particularly true

of yawns (p .05) and lunges (p = .04) which tended to oc-

cur when the bass stopped within 10 cm of the prey follow-

ing an approach and is also true of backpedals (p = .18)








17












o
H-H


.oW o m < N co0
O 0 IC o Cr o
4,
ZU a (z N (N N (N -l -H H
O a) 4 Co C 0 0 0 C0 0 0 C
4U P4 r3





*U
r( U P4 c ID m Co w.
Ir o 0 0 0C)





O0 0 m -W n
-Hl N zr C N CO
m H nlZI m N r o Uo aC N~



o II 01

SCo m H C H o o
41 (a ,--4 11
O> 0 ,. (a




(N 0 4 u

S0* 0
pl 00 o N c oo

H( O C) H r U n vo U) M oo
C P, H U) C) C) C C H ) C 0
0.11 0q U m o C H Co Co
N Z 0 0 0 H
-(40 a C) o m o H
Sio o H N
0
OH)
CO H W H U) r (N C) C)
OH ( C) a (N C) C) 0 H (N
>0 Z m N H O N o Um) N W
.0 U a o a m a N o a
(UN 0 m w Co m ( 0 0 AH
OH m- U H H o 0 C

( 0

O 0) H ) C)
>) 0 Q0 (a 04 N 4 o
S0 C) a) (m 0 r

> Zo* d o o o o o
(H 4- (U (U f U.0

S 0 0 0p (U O 0 I- ( U(
H O 4 0 W H 4J r 0 C H
n3 -P m) 4 0 r. H j EC .- i gU









which were interspersed into the approach sequence. A

bass may approach, stop, then backpedal and stop, and then

again approach. This type of sequence was common.

Turning away from the prey occurred with appreciable

frequency (p = .23) following a stop, but was much more fre-

quent following a backpedal (p = .41). In fact, turning

away occurred at almost the same frequency as that with

which a stop followed a backpedal. Turning away and stop-

ping accounted for 90% of the responses following a back-

pedal.

Chases, intercepts and follows could occur only when

the prey was moving. As mentioned previously, chases oc-

curred with the greatest frequency whenever the prey was

moving at escape speeds (see Table 3). Thus, chases oc-

curred most frequently following behaviors by the predator

that increased the probability of the prey making escape

maneuvers. In this regard, initial introduction of the prey

along with lunges, yawns and rapid approaches were the set-

ting conditions for the majority of the escape responses by

the prey.

The most frequent responses following a chase were

lunges (p = .37) and tailfirst overswims (p = .45). These

represent the two basic ways that a bass captures its prey.

In the overswim, the bass simply swims over and engulfs the

prey (Nyberg, 1971). Lunges, which were described above,

occurred whenever the prey deviated from its swim path as

the predator was about to overtake it. Most lunges occur-
























o

r^.
N


C oi


- 0 0 D o


000


01

- 4 -

Oro
00
0>i













4J (0

,- I -,1


0 0 *4

0 4 II
--4 W


















0

0 -4 -H I
4o
00 0
4- B









-. aC II







.-1
0o a ,
O H
-H i 0

S'0








H 0.1
0


OH
do
*H m


4o

r
o (4


LO 0




m <




-O 0o
Lo n


-1 4-)
o '4 0
4-) ( 0 )
0c a 0 m ) t) 0

a4 4-' d 0 o 0 0 -.i
O w 0 0 0 N6 H -4 S


N f


aI


Ln r-





0 m



01r-
N ID
o o








'4 14-



(N



Co CN
0 M









ring in this context resulted in the predator missing the

prey.

In the majority of cases intercepts were directed

toward prey which were swimming normally. Here again the

overswim mode of capture was the most successful, with the

prey being taken head on and it was also the most frequent

outcome of an intercept (p = .75). As with chases, lunges

occurred whenever the prey veered away from the predator

immediately before contact.

The majority of follows were of normally swimming prey

(p .57), and were usually terminated by the predator stop-

ping (p = .50). Following could be accomplished by the

predator swimming pectorally, normally, at chase speed or by

backpedalling. The defining characteristic was a constant

position between the predator and the prey. The high inci-

dence of stopping pursuant to a follow was due to the ten-

dency of the prey to become motionless when followed (p = .71).

Similarly, chases were terminated first by the prey stopping

and then the predator stopping (p = .66)(provided that the

prey was not captured by the bass beforehand).

There were several responses that commonly followed

captures. Gill flares, head shakes and yawns prior to

swallowing or rejecting the prey occurred frequently. These

responses will be discussed in more detail below.

Prey Species Differences

There were a number of differences in the behavioral

interactions observed among the different species of prey









and the predator. One measure of these differences is in

the average number of behaviors engaged in prior to the

termination of a test. The mean values for sequence length

were 26.1 for the bluegill, 17.2 for shiners, 12.1 for the

bass and 9.3 for grass carp. The analysis of variance for k

independent groups (Freund, 1967) showed a significant dif-

ference among the groups (F=10.43, df=3,429, p < .05).

Duncan's multiple comparison procedure revealed that there

were significantly more behaviors employed in the bluegill-

bass interaction than to the remaining species (k=6.52, p<

.05). The number of behaviors in the shiner-bass inter-

action was significantly greater than the carp-bass inter-

action (k=6.86, p <.05) but not significantly different

than the bass-bass interaction. The bass and carp did not

differ significantly from one another in sequence length

per test trial.

Mode of Capture

All captures occurred as a consequence of a chase,

lunge or intercept. Table 4 lists the relative frequency

of occurrence of each of the different modes of capture for

each species along with the outcome of the attempts. Ex-

cept for shiners, intercepts were the most efficient means

of capturing prey whereas chases were the more frequent

method attempted. For shiners, the lunge was both the most

efficient and more frequently occurring method of capture.

Ninety-five percent of the captures subsequent to in-

tercept resulted in the prey being taken into the mouth

headfirst whereas 85% of the captures following a chase



















Cl C 0 0 Hl
000
fa 0 00 0
UE-l CM H


r-l

t m H M




01 -r4






NO"
a) U) U) 0 0 0



4 a)



0 H 1,



Svl II o
Ha H




0,*H Hl




u m 0-
3- -HI










aa a,iiol
04I N a) m

aa)


4 .


o 4- CE- l C) L0
?! l Hv 1n (m














H H
a 00











0 C(N H
SII H -
a,

4- a)E-4 0 n o0
4 cfl H CM









ended with the prey in the mouth tailfirst. There are no

significant differences among the species in this respect.

Lunges resulted in tailfirst captures most often in all

species but shiners where the majority of lunges resulted

in headfirst captures. This result appears to be due to

significantly more lunges (p < .05) made to shiners swim-

ming pectorally or normally than to the other species where

most of the lunges were made to prey moving at escape speed.

Efficiency

In part, the sequence length reflects the efficiency

of the predator in capturing the prey. A more accurate in-

dication of the efficiency of capture is given by the ratio

of captures to attempted captures presented in Table 4.

The highest efficiency was achieved in the carp-bass

interaction where the success rate for attempted captures was

67%. Z-tests of proportion (Fruend, 1967) showed this

value to be significantly different from the values obtained

for the other species (p < .05). The 49% success rate for

the shiner-bass interaction differs from both the bass-bass

and bass-bluegill interactions (p <.05), while the bass-

bass and bass-bluegill interactions did not differ (p > .05).



All values for Z-tests in this and subsequent sections
are presented in Appendix 1.









Movement

The capture success data are somewhat surprising in

view of the data on sequence length, particularly in regard

to the bass, bluegill and shiner data. One reason for the

disparity between the sequence lengths and capture success

is the risk incurred by the prey as a function of movement.

Table 5 presents the number of responses made by each spe-

cies in each movement category and the number of captures

that occurred while the prey was engaged in that behavior.

As can be seen from Table 5, most of the captures oc-

curred while the prey were moving normally or at escape speed.

For grass carp, 93% of the captures occurred while the fish

was swimming normally or escaping with 47% of such responses

by the carp resulting in capture. At the same time, 63% of

the responses made by the carp were in the normal or escape

category. These values are very similar to the values ob-

tained for bass fingerlings where 97% of the captures oc-

curred during normal or escape swimming while 62% of such

responses resulted in capture. Sixty percent of the respon-

ses made by the bass were in the normal and escape swimming

categories. The values for the carp and the bass did not

differ significantly from one another with regard to fre-

quency of normal and escape swimming (p > .05) but did

differ in risk with bass having a significantly higher risk

while swimming at normal and escape speeds (p <.05).

Bluegills made the smallest number of normal and escape

responses for a 40% ratio and had the lowest capture ratio























0)
OZ
0 1

4J
a m

t,- U



ul
tp 0
Sin
.H a)










E a
-ri 0















- II
o o
0
u ,

0) 0a



0 0


04 II
d 4u





OH


Ea a

0 0
0) 04




01)



O) U










A I
00C
0 (


Ln Ln
N rH

N CN
N



r-l

(n N
to m



H
o 0








^ r






>-i
W N










r-I







NN



aO N

Nr m
m CT^
- i Ln










> o o
r-d
N L
N m


OO N



lA l



n a,

g, c
a 0









for the responses (p = .23). Shiners made significantly

more normal and escape responses (p = .56) with a signifi-

cantly higher risk to the fish (p < .05).

Motionless

All of the species had a relatively low risk while

motionless or swimming pectorally as can be seen from Table

5. Shiners had the highest risk while motionless (p = .13)

which was significantly higher than all other prey (p <.05)

except grass carp (p > .05). The other species did not

differ significantly from one another (p > .05). There

were differences in the positions in the tank that the prey

typically assumed when motionless that may have contributed

to the differential risk while motionless.

Bluegill tended to become motionless at the sides and

in the corners of the tank with the side of the fish pressed

closely against the wall. Often the fish would be oriented

perpendicular to the normal swimming position with either

the head or the tail in the up position. At other times

they would rest against a surface with the body tilted 90

from the vertical axis with the dorsal or ventral surface

against the wall.

Shiners also tended to become motionless near the sides

and in the corners of the tank, but the posture of the fish

was normal in the sense that the body was in the normal

swimming posture. Bass fingerlings usually were motionless

on the bottom of the tank irrespective of position relative

to the sides of the tank. Carp did not appear to become









motionless in any one position in the tank any more than

any other position.

Both the carp and the bass were significantly more

responsive to approaches by the predator when motionless

than either bluegill or shiners (p < .05) but did not dif-

fer between themselves (p > .05). Shiners were signifi-

cantly less responsive than bluegill (p < .05). As a con-

sequence of the responsiveness of the bass and carp to the

approach of the predator, the predator did not often ap-

proach close enough to these species to lunge at them

while they were motionless. While shiners were the least

responsive to approaches by the predator when motionless,

significantly more lunges were directed toward the shiners

when motionless than to bluegills with a greater success

ratio (p = .88 vs p = .66, p <.05).

Yawns

Yawning occurred in three contexts. Bass were ob-

served to yawn in the absence of prey, when the bass was

within 10 cm and oriented to the prey, and after the prey

had been taken into the mouth. Yawning in the absence of

a prey was not recorded. The frequency of occurrence of

yawns in the other situations are presented in Table 6.

There were significantly more yawns (p < .05) direct-

ed at bluegill and shiners before capture than at carp or

bass, the majority of which were directed at motionless and

pectorally swimming prey. The outcome of this type of yawn

was usually movement by the prey at normal or escape speed






28












TABLE 6

Number of yawns occurring before and after capture.


Prey Species

Shiner Blueaill


Bass Caro


Before capture 64 98 10 2

After capture 2 46 13 4







29

(p = .61). It appeared that this behavior served to induce

movement by the prey which, in turn, increased the risk to

the prey.

Difficulty

Yawning that occurred after the prey was in the preda-

tor's mouth was often in conjunction with headshaking and

gillflaring. Collectively these behaviors were taken as in-

dications that the predator was experiencing difficulty in

swallowing prey. The frequency of occurrence of these be-

haviors are presented in Table 7.

Any or all of these responses could occur following

any given capture and each of the behaviors could be re-

peated more than once following a capture. Significantly

more of the responses were shown for the two spiny-rayed

species than to the soft-rayed species (P <.05) which did

not differ from one another (p > .05).

Rejections

Rejections were often associated with the responses

that indicated difficulty in swallowing but not always.

There were 15 rejections of shiners, 24 of bluegill, 3 of

bass and no carp rejections. All of the rejections of

shiners occurred in the absence of any of the responses

indicating difficulty in swallowing. Seventy-three percent

of the rejections of bluegill followed tailfirst captures

as did all of the rejections of bass. Only 27% of the

shiner rejections followed a tailfirst capture. There were

significantly more rejections of bluegill than of the re-




















TABLE 7

Number of gill flares, yawns and headshakes
following captures.


Prey Species

Behavior Shiners Bluegill Bass Carp

Gill Flare 8 42 17 1

Yawn 2 46 13 4

Headshake 1 35 12 7

Capture 127 107 70 81









maining species (p < .05) which did not differ among them-

selves (p> .05).

Size Differences

Werner (1974) has suggested tnat the optimal prey size

for a piscivorous predator is 0.59 times the gape width of

the predator's mouth to body depth, based on handling time

from capture to swallowing. Since Werner established this

figure with bluegill and green sunfish as predators on in-

animate prey, its generality to the present situation is

debatable. Nevertheless, it does provide a point of de-

parture for examining the effect of body depth on the be-

havior of the bass. Accordingly, the data were sorted into

two groups for each species based on whether or not the

body depth exceeded 0.59 times the gape width of the preda-

tor involved. The data were then analyzed in the same

manner as employed in the previous section.

The results were that only seven of the 80 grass carp

presented to the bass exceeded the 0.59 cutoff. In contrast,

109 of the 132 bluegill presented were greater than 0.59

the gape width. The figures for shiners and bass showed

similar trends in group size with 40 of the 140 shiners

greater than 0.59 and 14 of the 80 bass greater than 0.59.

Due to the disparity among the group sizes, an analysis of

variance was not performed on the sequence lengths. The

mean sequence lengths are presented in Table 8.

With the exception of the data on carp, the means for

the groups exceeding 0.59 were consistently greater than the

group means for the smaller fish. The relative ordering of






32








TABLE 8

Mean sequence length for prey smaller and larger than
0.59 times the gape width of the predator's
mouth.


Prey species
Gape width
of bass Shiner Bluegill Bass Carp

Below 0.59 12.03 18.5 9.55 9.6


Above 0.59 28.23 29.0 24.42 6.3









the means among the species is the same as observed in the

previous section.

Bluegill

While the mean sequence lengths for the two groups

of bluegill indicated a greater efficiency on the part of

the predator in capturing the smaller fish, there were no

significant differences in the capture/success data for the

two groups (p > .05). These data are presented in Table 9.

There were, however, a significantly greater number of

attempted captures of smaller fish (p < .05). For the most

part, the differences in sequence length between the two

groups appeared to be due to a greater number of behaviors

directed toward the larger prey. Most of the additional

behaviors appeared to be attempts on the part of the preda-

tor to place itself in a position to capture the prey.

Specifically, there were significantly more approaches,

stops, follows and yawns before capture for the larger fish

(p < .05). There were more large prey taken headfirst and

significantly fewer large prey taken tailfirst (p < .05).

Although there were significantly more yawns following

captures of large prey (p < .05), there were no differen-

ces between the two groups among the other behaviors, indi-

cating difficulty in swallowing (p > .05).

Bass

The data for bass fingerlings show that the capture/

success ratio was significantly higher for the small fish

than for the larger fish (p < .05); while attempted captures
















TABLE 9

Number of attempted captures and the position of the
prey in the mouth following capture for bluegill
above and below 0.59 times the gape width of the
predator's mouth.




Attempt Head Tail Side
Intercept 16 12 0 2


Above 0.59 Lunge

Chase


Intercept

Below 0.59 Lunge

Chase


88 13 19 2


5 23 1


4 1 0

2 7 1

1 9 0






35

were similar for both groups (p > .05). These data are

presented in Table 10.

There was no difference between the swimming behavior

of the two groups (p > .05) and only during escape swim-

ming did the small fish incur a higher risk than the large-

er fish (p <.05). Yawning occurred more frequently before

captures in the larger group than in the smaller group as

did the number of approach-stop sequences (p <.05). The

predators seemed to have some of the same problems with

larger bass fingerlings that they experienced with large

bluegill. While the greater number of misses of larger

prey may be accounted for by the fact that a larger fish is

a stronger swimmer and therefore is more capable of eluging

the predator, the approach-stop sequence and yawning

suggest that the predator engages in more behaviors pre-

paratory to an attempted capture. Yawning after capture

was similar in both groups as were gill flaring and rejec-

tions (p > .05) but more headshaking was evident after

capturing larger fish (p < .05).

Shiner

The data for shiners were very similar to those for

bass. There was a significant difference in the capture/

success ratio between the two groups (p < .05), with more

of the smaller prey being captured per attempt than the

larger prey (see Table 11). Although there were no dif-

ferences in the number of attempted captures between the

two groups (p > .05), there were significantly more chases















TABLE 10

Number of attempted captures and the position of
the prey in the mouth following capture for bass
above and below 0.59 times the gape width of the
predator's mouth.


Attempt Head Tail Side
Intercept 5 3 0 0

Above 0.59 Lunge 21 0 1 0

Chase 43 0 9 0



Intercept 10 9 1 0

Below 0.59 Lunge 45 1 12 0


Chase


60 0 34 0
















TABLE 11

Number of attempted captures and the position of
the prey in the mouth following capture for shin-
ers above and below 0.59 times the gape width of
the predator's mouth.



Attempt Head Tail Side


Intercept

Above 0.59 Lunge

Chase



Below 0.59 Intercept

Lunge


Chase


0 1


48 11 3 3


56 2


7 3


15 10 0 1

79 39 17 2

44 8 12 1









and fewer lunges directed toward the larger prey (p < .05).

There were differences in the swimming behavior of

the prey with the larger prey becoming motionless more often

than the smaller prey (p < .05), while the smaller prey en-

gaged in more normal swimming (p < .05). In all swimming

modes, the smaller prey had a higher risk of predation than

the larger prey (p < .05).

As with the larger bass fingerlings, the differences

between the two groups of shiners appeared to be due to the

ability of the larger fish to elude the predator. However,

there were no significant differences in the numbers of

approach-stop sequences although there were significantly

more yawns before capture for the larger group (p < .05).

Carp

There were essentially no differences in the data for

the two groups of grass carp.















EXPERIMENT II

The descriptive data from Experiment I suggest that

the predators experienced more difficulty in swallowing

spiny-rayed prey than with soft-rayed species. This was

indicated by the greater number of yawns, gill flares, and

headshakes following captures of spiny-rayed prey. To test

the hypothesis that the spines themselves were the source

of the difficulty, the predators were presented with blue-

gill which had had the spines removed from the dorsal, anal,

and pelvic fins.

Methods
Subjects

The predators were the same as those used in the

previous study. Four additional bass, housed and tested

in individual 68-liter aquaria, were added to the study.

These bass were obtained in the same manner as the bass

for Experiment I and were maintained in the laboratory for

three months prior to testing. The bluegill were collected

and maintained as in Experiment I.

Procedure

The procedure was similar to that used in Experiment I,

except that the spiny portions of the fin rays were removed

with surgical scissors after the prey had been weighed and

measured. Swimming behavior did not appear to be substan-









tially affected by the removal of the spines.

The control data were those on intact bluegill from

Experiment I. Since the intact fish had not been trauma-

tized, only mode of capture, position of the prey in the

mouth as well as yawns, gill flares, headshakes and rejec-

tions following capture were recorded for the despined

prey. Recordings were made as in Experiment I.

Results and Discussion

There were significantly fewer gill flares, yawns,

and headshakes following the capture of despined bluegill

than after the capture of spined bluegill (p < .05). There

were also significant differences in the mode of capture,

intercepts, lunges, and chases, employed by the predator

for the two groups of fish (p < .05). However, mode of

capture did not appear to have a significant effect upon

the difficulty the predator encountered in swallowing the

prey (see Table 12) although there were significantly more

rejections of spined bluegill that were taken into the

mouth tailfirst than those taken headfirst (p < .05).

More of the attempted captures of despined bluegill

were intercepts and lunges (p < .05), while there were few-

er chases (p < .05). As a consequence, more of the de-

spined bluegill were taken into the mouth tailfirst (p <.05).

The distribution of yawns, gill flares and headshakes as a

function of the position of the prey in the predator's

mouth showed that significantly more headshaking (p < .05)

occurred after a tailfirst captures than after head-on cap-















TABLE 12

Behavior that occurred after capture of spined
and de-spined bluegill.

Behavior
Gill Head-
Flare Yawn shakes Reject Capture

Headfirst 22 18 7 1 37

Spined Tailfirst 20 28 28 14 59

Total 42 46 35 15 96



Headfirst 8 5 2 7 48

De-spined Tailfirst 7 4 11 4 34

Total 15 9 13 11 82









tures in both spined and de-spined fish. In the spined

group, significantly more gill flares occurred after head-

first captures than after tailfirst (p <.05) captures,

with yawns being more evenly distributed between head and

tailfirst captures (p > .05). The de-spined group showed

no differences for position in the mouth and yawns or gill

flares (p > .05).

Presumably these behaviors are related to the posi-

tioning of the prey in the mouth preparatory to swallowing

and it may well be that each of the behaviors is uniquely

related to this function. However, in the majority of

cases, since the prey could not be viewed by the observer,

the function or result of each of these behaviors could not

be differentiated. Nevertheless, it remains the case that

there existed differences related to both the position of

the prey in the mouth and the behavior of the predator

following capture.

On the few occasions in which the prey could be ob-

served in the mouth of the predator it appeared to the

observer that more headshaking occurred when the prey was

obviously stuck in the mouth. According to Lawrence

(1957), who took X-rays of the position of the prey in the

mouth prior to swallowing, the prey is turned 900 to the

vertical axis before swallowing. On the few occasions that

the prey was observed to be positioned in the mouth on the

vertical axis and the mouth was propped open, headshaking

was employed by the predator to dislodge it.
















EXPERIiENT III

Size selection of prey by a predator has received

considerable theoretical treatment in the literature

(Ivlev, 1961; Schoener, 1969; Werner, 1974) with most

authors agreeing that there is an optimal size of prey for

a given sized predator. There have been two investigations

of size selection by largemouth bass; both obtained equivo-

cal results. Tarrant (1960) found a positive correlation

between prey size and predator size using green sunfish as

prey, while Wright (1970) reported no evidence of size

selection of gizzard shad. It should be noted that,

amongst other differences, Tarrant employed spiny-rayed

prey and that Wright worked with soft-rayed prey.

The data from Experiment I indicate that the predator

experiences greater difficulty in capturing larger prey

than smaller as evidenced by longer sequence lengths and a

greater number of unsuccessful capture attempts. The fol-

lowing study was designed to examine whether or not large-

mouth bass would demonstrate selection for size of prey

within a single prey species when both soft and spiny-rayed

prey were available.

Methods
Subjects

The predators were the same as those used in Experi-

ment II. Bluegill and grass carp were utilized as prey
43









species. All fish were housed and maintained as in the

previous studies. Between the testing of grass carp and

bluegill, one predator died and one began to refuse to eat

bluegill, despite four weeks of deprivation.

Procedure

Four different sized prey were presented simultaneous-

ly to the predators each day. For the grass carp, the size

classes varied by 10 mm with four consecutive size classes

being presented simultaneously. Smaller size class inter-

vals (5 mm) were employed for the bluegill, due to the

smaller range of sizes available before the mouth width of

the smaller predators was exceeded by the body depth of the

prey. The carp ranged in size from 30 to 110 mm in stand-

ard length (SL) as measured from the tip of the snout to

the end of the vertebral column. Two presentations of each

of the possible combinations of four consecutive size class-

es were made for each predator. All of the carp were pre-

sented before presentations of bluegill began. The same

format of presentation was followed for bluegill in the size

range from 30 to 75 mm SL.

This method of presentation was employed, rather than

having prey continuously available to the bass, because

three of the bass in the 68-liter aquaria consistently

killed all of the fish with them in the tanks, regardless

of the number. The killing was accomplished by continual

harassment of the prey in the form of chasing, ramming,

and by taking them into the mouth and rejecting at an aver-









age rate of one attack every 30 seconds until all of the

fish were dead. One of the bass engaged in this behavior

with such vigor that it went ventral up with apparent ex-

haustion and had to be removed to allow for recovery.

The size of the first fish captured by the bass was

recorded whereupon the remainder of the prey were removed

from the testing area. This was done to maintain the bass

at a sufficient level of deprivation to allow for daily

testing.

Results and Discussion

A Chi Square test for goodness of fit was performed on

the data (Freund, 1967). There was no evidence of size

selection by any of the predators for either of the prey

species (p > .05 values are reported in Appendix 1).

There was a significant effect for size of prey on each

presentation (p < .05) with selection being away from the

smaller of the four fish presented, regardless of the size

of the smallest fish. There was no effect for the remain-

ing three positions in the presentations. The selection

data are presented in Tables 13 and 14, and it appeared that

proximity of the prey to the predator and the behavior of

the prey determined which prey were selected. However, the

three-dimensional nature of relative position between preda-

tor and prey made it difficult to establish in all cases

which fish was closest to the predator. Rarely did the

predator pass one fish to take another unless the fish

passed was motionless. Once the predator initiated an
















TABLE 13

Size selection for grass carp. The number
represents the number of fish selected by
the predator in that size class.



Size class of grass carp
30mm 40mm 50mm 60mm 70mm 80mm 90mm 100mm 110mm

1 1 2 1 4 2 2

2 1 1 5 2 2 1

3 2 3 2 3 1 1

4 1 2 3 4 1 1

5 1 4 1 2 2 2

Bass 6 1 3 4 1 2 1

7 1 2 1 2 3 1 1 1

8 1 2 2 2 3 1 1

9 1 1 3 2 2 2 1

10 1 1 3 2 2 1
















TABLE 14

Size selection for bluegill. The number
represents the number of fish selected by
the predator in that size class.


Size class of bluegill
30mm 35mm 40mm 45mm 50mmn 55mm 60mm 65mm 70mm 75mm

1 1 1 2 2 2 2 1

2 3 3 2 2 2 2

3 1 1 2 4 1 3 2

4 1 2 2 1 1 5 1 1

5 1 2 1 1 3 4 1 1

Bass 6 3 3 2 2 1 3

7 1 2 2 2 1 2 2 1 1

8 1 2 2 2 2 3 1 1






48

attack on one prey rarely did it deviate to other prey even

when the attack resulted in an extended chase sequence.
















INCIDENTAL OBSERVATIONS

A number of observations were made during the course

of these studies that were not systematically recorded, yet

were none the less interesting and informative.

Regurgitations of swallowed prey were very common if

the bass were disturbed, as often happened when the remain-

ing prey were removed during tests for size selection. The

fish was expelled by a series of stomach contractions and

yawns. Regurgitations of partially digested fish were al-

so common if the fish was guite large. This became appar-

ent when tests were made to determine whether the largest

size of grass carp available to the predator was a function

of length or depth of body. The length of a grass carp may

approach 60% of the length of the predator before depth of

body becomes a limiting factor. In contrast, a bluegill,

30 percent of the length of the bass may exceed the gape

width in body depth.

In most cases, it was necessary to deprive the bass

for a minimum of three days before they would accept grass

carp between 45 and 60% of the body length of the bass.

Usually in such cases, the tail and a portion of the caudal

peduncle protruded from the mouth of the bass for up to

two hours. Typically, such fish were found partially di-

gested and regurgitated on the bottom of the tank the









following day.

Bluegill that had been chased or lunged at repeatedly

by the predator and were motionless on the sides of the

tank, often with their heads oriented upward, downward, or

horizontally, could be picked up out of the water in the

observer's hand. It was also noted that such fish, with

their heads oriented upward, would occasionally begin to

roll backward with the ventral up. The fish usually re-

gained its original posture before it had rolled completely

over.

Occasionally a fish apparently would be tonically im-

mobile when introduced into the tank. That is, except for

the gills, the fish would be completely immobile, with the

pectoral fins directed outward from the body. The fish

spontaneously began swimming after a variable length of time

if not disturbed by the predator. The predator's response

to the fish was the same as that to any motionless fish with

the occasional exception that occurred if the predator ap-

proached and yawned at the prey. If the prey did not re-

spond to the yawn the predator turned away. However, in

most cases the immobile fish responded with escape swim-

ming.

With very large prey, such as bluegill near the lim-

its of the bass' mouth, the predator expended considerable

effort apparently attempting to position itself in front of

the prey. In chases, the predator would swim up alongside

of the prey, or past the prey, forcing the prey to turn.






51

There were very few attempted captures of very large prey

that would result in the prey being taken into the mouth

tail first.
















GENERAL DISCUSSION

In this study, differences in the susceptibility of

the different species to predation by largemouth bass have

been demonstrated. Further, the manner in which the preda-

tor interacts with the prey varies across species. Risk to

the prey was found to be consistently related to movement

of the prey in the vicinity of the predator. Inhibition of

movement decreased risk, while movement, particularly rapid

movement, resulted in a substantial increase in risk. To

some extent, the movement of the prey was induced by the

behavior of the predator, especially yawning behavior.

Those prey which did not respond to the behavior of the

predator enjoyed a lower risk to predation.

The field literature on the feeding behavior of large-

mouth bass indicates movement to be a significant variable.

(McClane, 1955; Kramer and Smith, 1960; Chew, 1974). Moehn

(1959), examined the hypothesis that the high incidence of

empty stomachs observed in field-collected largemouth bass

is due to the low vulnerability of the forage species. He

found that rotenone poison, lightly applied to the surface

of a small lake, reduced the incidence of empty stomachs

significantly and increased the number of items per stomach.

The bass appeared to be gorging themselves on the dying

fish. Rotenone, while ultimately asphyxiating the fish,

causes very erratic swimming by the fish. Since the
52









smaller fish are affected before the larger fish, the

erratic swimming behavior of the small fish is generally

regarded as the stimulus condition eliciting a feeding

frenzy (Zweiacker and Summerfelt, 1973; Moehn, 1959;

Lewis et al., 1974) in the bass. The implication from

this research is that the forage fish have low vulnerabili-

ty to bass predation under normal conditions. In all prob-

ability, the low vulnerability of the prey species is re-

lated to both movement patterns on the part of the prey and

the utilization of cover.

The propensity of the bass to capture fish that were

moving could be due to several factors. First, motionless

prey are less conspicuous in their environment than are

moving prey. Several times the bass apparently ignored

motionless prey but immediately responded to the same fish

when it moved. It should be added here that many of the

orientations to motionless prey, in this study, were to

prey to which the predator had previously oriented when

introduced, thus the predator might have known their loca-

tion.

Second, the apparent tendency to take moving prey may

simply have been the result of the prey responding with

movement to an approaching predator. A third possibility

is that the predator actively induced movement on the part

of the prey. Yawning was very effective in this respect.

Yawning was usually directed at motionless prey close to

the sides of the tank, with the notable exception of the









behavior toward immobile prey. The yawning behavior of the

bass probably counteracts, to some extent, the utilization

of cover by the forage species. Obviously, a predator can-

not lunge at a prey if the prey is near cover that will

physically obstruct the lunge. Yawning could cause the

prey to move away from the cover, thus affording the bass

an opportunity to capture the prey.

A final possibility is that the bass responds to

sudden and rapid movement in its vicinity with orientation

and rapid approach. If it is going to enjoy success, a

predator, such as bass, that preys upon highly mobile prey,

should respond to sudden movements in its environment with

approach. Hesitation may permit the escape of the prey.

It was noted during the course of the study that prey swim-

ming at escape speed almost always precipitated a chase by

the bass whether or not the bass had been oriented toward

the prey when the swimming was initiated and regardless of

whether or not the bass had just turned away from the prey.

This kind of responsiveness to sudden movement by the bass

may be the basis for the reflexive feeding reported for

piscivorous predators (Hobson, 1968; Lewis et al., 1974).

In any event, it is probable that the high risk to moving

prey is a result of a combination of all of these factors,

although further research could do much to clarify the

issue.

Lewis (Lewis, Gunning, Lyles and Bridges, 1961; Lewis,

Anthony, and Helms, 1964; Lewis, 1967; Lewis, Heidinger,







55

Kirk, Chapman, and Johnson, 1974) contends that bluegill have

very low vulnerability to largemouth bass predation relative

to other species of prey. The data obtained in this study

also indicate that bluegill have a lower risk to bass pre-

dation.

The relatively low risk of the bluegill, as measured

by sequence length and capture/success ratios, appears to be

primarily due to the movement pattern of the bluegill, in-

cluding responsiveness to the predator and utilization of

cover; but is probably also due to the relative depth of

body and the presence of spiny-rays. The presence of

spines in the fin ray of both bluegill and bass finger-

lings increased the difficulty that the predator encoun-

tered in swallowing these species. While there were no

obviously different handling or capture techniques employed

by the bass to capture spiny-rayed prey, it is interesting

to note that most of the spiny-rayed captures resulted in

the prey being taken into the mouth tailfirst. Since mode

of capture determines the position of the fish in the mouth,

and mode of capture is an interactive effect of the behavior

of both the predator and the prey, it may be that the spiny-

rayed prey were maintaining a position, relative to the

predator which dictated a tailfirst capture, and which, in

turn, resulted in significantly more rejections of the prey,

and hence, more opportunities for the prey to escape.

The relationship between depth of body and weight sug-

gest that the bluegill is not an optimal configuration for








predation by largemouth bass. Lawrence's (1960) data indi-

cate that at the limit of gape width for bass in the 12 inch

class, acceptable bluegill weight a third of what a bass

would weigh and slightly more than half of what a golden

shiner would weigh. Although he did not include grass carp

in his equations, the relationship in weight at maximum depth

for the two species is with the bluegill being the lighter

of the two species. Coupled with the difficulty the bass en-

counters in capturing and swallowing bluegill, the weight

considerations suggest the bass should utilize an alternative

source of prey, if available.

Equation for body depth, above and below 0.59, the

gape width of the predator, resulted in more uniformity in

sequence length for the larger prey across all species ex-

cept the grass carp. Moreover, it revealed a positive

relationship between sequence length and body depth for all

species, again excepting grass carp. The disparity in se-

quence length between large and small prey appeared to be

due, primarily, to a greater number of unsuccessful attempt-

ed captures of larger prey along with a greater number of

behaviors designed to place the predator in a position to

capture the prey.

Doubtless there is a point at which the difficulty en-

countered by the bass in capturing larger prey exceeds the

additional energy value provided by the larger prey. However,

observations of the bass when presented with multiple prey







57

suggests the possibility that the bass may be basically op-

portunistic across the range of prey sizes that it is

capable of swallowing. If such is the case, prey size in

the diet may be determined by the conspicuousness of the

prey, with smaller prey being less conspicuous, than larger

prey at equivalent distances from the predator, while more

of the larger prey would escape attempted captures by the

bass.

There did not appear to be a consistent relationship

between depth of body and difficulty in swallowing. This

finding is surprising since it would be expected that the

larger fish, by virtue of being nearer the physical capacity

of the predator, would result in greater difficulty in

swallowing. It would seem that there is some other factor,

beside the presence of spines and depth of body, responsible

for the difficulty experienced by bass in swallowing blue-

gill. This suspicion is reinforced by the fact that de-

spined bluegill caused as much difficulty as intact bass of

equivalent size.

Grass carp neither avoided nor escaped predation with

any degree of success. In observing this species it did not

appear that the grass carp modified their swimming behavior

in the presence of the predator, although they were respon-

sive to behaviors by the bass that were directed toward

them. The lack of inhibition of movement, the absence of

spiny-rays and the body configuration of the grass carp

combine to suggest that this species would be highly vul-

nerable to bass predation in the field.


































APPENDIX I

Statistical Summary Tables










TABLE 1-A

Z tests for efficiency of capture between species of prey.

Shiner Bluegill Bass Carp
Capture 126 102 70 70
Attempt 259 275 184 104


Shiner-Bluegill
Shiner-Bass
Shiner-Carp


Z=2.59,
Z=2.31, Bluegill-Bass Z=0.22,
Z=3.10 Bluegill-Carp Z=5.26


Bass-Carp Z=4.75

*Significant at the p = .05 level or greater.

TABLE 2-A

Z tests for proportion of captures to frequency of normal
and escape swimming between species of prey.

Shiner Bluegill Bass Carp
Capture 85 83 81 62
Normal/escape 264 345 130 131

Shiner-Bluegill Z=2.16 ,
Shiner-Bass Z=5.66, Bluegill-Bass Z=7.76,
Shiner-Carp Z=2.94 Bluegill-Carp Z=4.89

Bass-Carp Z=2.42

*Significant at the p = .05 level or greater.

TABLE 3-A

Z tests for the proportion of motionless and pectoral re-
sponses to all swimming responses between species of prey.

Shiner Bluegill Bass Carp
Motionless 235 507 85 79
Total Responses 499 852 215 208

Shiner-Bluegill Z=4.64
Shiner-Bass Z=1.75, Bluegill-Bass Z=5.26,
Shiner-Carp Z=2.50 Bluegill-Carp Z=6.05

Bass-Carp Z=0.64

*Significant at the p = .05 level or greater.









TABLE 4-A


proportion of captures to frequency
responses between
species.


of motionless


Shiner Bluegill Bass Carp

Capture 18 19 2 3
Motionless 140 323 76 55

Shiner-Bluegill Z=2.59,
Shiner-Bass Z=2.50 Bluegill-Bass Z=1.07
Shiner-Carp Z=1.90 Bluegill-Carp Z=0.57

Bass-Carp Z=0.59

*Significant at p = .05 level or greater.

TABLE 5-A

Z tests for proportion of responses by the prey to approaches
by the predator.

Shiner Bluegill Bass Carp

Responses 41 106 45 22
Approaches 349 469 81 46
--------------^---------------------*


Shiner-Bluegill
Shiner-Bass
Shiner-Carp


Z=4.07 ,
Z=10.23, Bluegill-Bass Z=6.42,
Z= 6.85 Bluegill-Carp Z=3.88


Bass-Carp Z=0.78

*Significant at p = .05 level or greater.

TABLE 6-A

Z tests for proportion of headfirst captures to tailfirst
and sideways captures following intercept.


Shiner Bluegill Bass


Carp


Headfirst 16 16 13 27
Total captures 18 19 15 38


Shiner-Bluegill
Shiner-Bass
Shiner-Carp


Z=0.42
Z=0.18 Bluegill-Bass Z=0.24
Z=1.50 Bluegill-Carp Z=1.07


Bass-Carp Z=1.23


Z-tests for









TABLE 7-A

Z tests for proportion of tailfirst captures to headfirst
and sideways captures following chase.

Shiner Bluegill Bass Carp

Tailfirst 19 32 43 28
Total captures 33 39 43 29


Shiner-Bluegill
Shiner-Bass
Shiner-Carp


Z=2.24
Z=4.72
Z=3.58


Bluegill-Bass Z=2.86*
Bluegill-Carp Z=1.89


Bass-Carp Z=1.40

*Significant at p = .05 level or greater.

TABLE 8-A

Z tests for proportion of headfirst captures to tailfirst
and sideways captures following a lunge.

Shiner Bluegill Bass Carp

Headfirst 50 15 1 1
Total Captures 75 44 14 15
----------------^-------------------


Shiner-Bluegill
Shiner-Bass
Shiner-Carp


Z = 3.67,
Z = 4.16,
Z = 2.90


Bluegill-Bass Z=1.97
Bluegill-Carp Z=0.50


Bass-Carp Z=1.43

*Significant at p = .05 level or greater.

TABLE 9-A

Z tests for proportion of yawns occurring before capture
to captures.

Shiner Bluegill Bass Carp

Yawns 64 98 10 2
Captures 127 107 70 81

*


Shiner-Bluegill
Shiner-Bass
Shiner-Carp


Z-6.83,
Z=5.00, Bluegill-Bass Z=10.41,
Z=7.27 Bluegill=Carp Z=12.19


Bass-Carp Z=2.73

*Significant at p = .05 level or greater.










TABLE-10A
Z tests for the combined proportion of
and yawns after capture to the

Shiners Bluegill

Difficulty 11 123
Captures 127 107


gill flares, headshakes,
number of captures.

Bass Carp

42 12
70 81


Shiner-Bluegill Z=16.56,
Shiner-Bass Z= 7.73 Bluegill-Bass Z=14.10,
Shiner-Carp Z= 1.36 Bluegill-Carp Z=15.38

Bass-Carp Z=5.77

*Significant at p = .05 level or greater.


TABLE-llA

Z tests for proportion of rejects to captures between species.

Shiners Bluegill Bass Carp

Rejects 15 24 3 1
Captures 127 107 70 81

Shiner-Bluegill Z=2.04
Shiner-Bass Z=1.90, Bluegill-Bass Z=3.27,
Sniner-Carp Z=2.89 Bluegill-Carp Z=4.12

Bass-Carp Z=1.07

*Significant at p = .05 level or greater.







63

TABLE 12-A
Z tests for differences between shiners above and below 0.59
the gape widta of tie predator
involved.

Above 0.59 Below 0.59 Z Value
Effic. Capture 36 80
ic. Attempt 121 138 4.51

Intercept Capture 7 11
Attempt 17 15 1.45
Capture 17 58
Lunge Attempt 48 79 4.27

ase Capture 12 21
ase Attempt 56 44 2.84

Gill Flare 3 5
Diff. Capture 36 91 0.64

f Yawn 2 0
S Capture 36 91

Headshake 0 1
Dif. Capture 36 91 -

Rejects 11 4
Rejects Capture 36 91 4.22


Risk Captures 1 17
MRk otionless 109 31 7.94

Risk Captures 17 36
Rik Normal 68 74 2.93

Risk Captures 9 15
Pectoral 54 41 2.25

Risk Captures 9 23
Escape 67 55 3.63

Response Motionless 109 31
Pattern Total response 298 201 4.89

Response Normal 68 74
Pattern Total response 298 201 3.50

Response Pectoral 54 41
Pattern Total response 298 201 0.56

Response Escape 67 55
Pattern Total response 298 201 1.39









TABLE 13-A

Z tests for differences between bluegill above and below 0.59
the gape width of tie predator involved.

Above 0.59 Below 0.59 Z Value
ffic. Capture 77 24
Attempt 215 60 0.57

Capture 14 5
InterceptAttempt 16 5 0.78

Capture 34 10
Lunge Attempt 88 28 0.32

Capture 29 10
Chase Attempt 111 27 1.15

Di Gill flare 32 10
Capture 77 36 1.43

Diff. Yawn/after 38 6
Capture 77 36 3.24

Dif. Headshake 28 7
Capture 77 36 1.82

Rejects Rejects 17 7
SCapture 77 36 0.37

Risk Captures 14 5
Motionless 281 42 1.79

Risk Captures 30 9
Normal 163 13 4.25

Risk Captures 5 0
Pectoral 162 22

Risk Captures 32 12
Escape 146 23 3.09

Mode of Intercept 16 5
capture Attempts 215 60 0.25

Mode of Lunge 88 28
capture Attempts 215 60 0.69

Mode of Chase 111 27
capture Attempts 215 60 0.82

Position Headfirst 30 6
in mouth Captures 77 24 1.24






65


TABLE -13A (continued)


Above 0.59 Below 0.59 Z Values

Position Tailfirst 42 17
in mouth Captures 77 24 1.98

Position Sideways 5 1
in mouth Captures 77 24 0.36

Predator Yawns/before 92 6
Position Captures 77 36 16.45

Predator Approach 420 38 *
position Total 2174 320 3.04

Predator Stop 417 32 *
position Total 2174 320 3.91

Predator Follow 72 3
position Total 2174 320 2.40









TABLE 14-A

Z tests for differences between bass above and below 0.59
the yape widta of the predator involved.

Above 0.59 Below 0.59 Z Value
Lffic. Capture 13 57
ic. attempt 69 115 4.25

Intercept Capture 3 10
Intercept attempt 5 10 2.17

Capture 1 13
Lunge Attempt 21 45 2.23


Chase Capture 9 34
Chase Attempt 43 60 3.71

Gill Flare 2 15
Captures 15 68 0.79

Diff. Yawn/after 1 12
Captures 15 68 0.87

Di Headshake 0 12
Capture 15 68

Rejet Rejects 1 2
Rejects Captures 15 63 0.71


Risk Captures 0 2
fMotionless 19 57

Risk Captures 6 25
Normal 16 43 1.37

Risk Captures 0 0
Pectoral 4 5

Risk Captures 9 41
Escape 20 51 2.91

Predator Yawns/before 8 2
position Captures 15 68 5.38

Predator Approach 39 42
position Total 271 471 2.08

Predator Stop 45 12
position Total 271 471 7.00

Predator Follow 4 2
position Total 271 471 1.39







67

TABLE 14-A (continued)

Above 0.59 Below 0.59 Z Value
Mode of Intercept 5 10
capture Attempts 69 115 0.49

Mode of Lunge 21 45
capture Attempts 69 115 1.29

Mode of Chase 43 60
capture Attempts 69 115 1.39

Position headfirst 3 10
in mouth Captures 13 57 0.50

Position Tailfirst 10 47
in mouth captures 13 57 0.50

















Z tests for differences


Diff.

Diff.


Diff.


Rejects

Position
in mouth

Position
in mouth

Mode of
Capture

Mode of
Capture

Mode of
Capture


Gill Flares
Captures

Yawn/after
Captures

Headshakes
Captures

Rejects
Captures

Headfirst
Captures

Tailfirst.
Captures

Intercept
Attempt

Lunge
Attempt

Chase
Attempt


TABLE 15-A

s between spined

Spined
42
96

46
96

35
96

15
96

37
96

59
96

21
275

116
275

138
275


and de-spined

De-spined
15
82

9
82

13
82

11
82

48
82

34
82

21
82

50
82

21
82


bluegill.

Z Values

3.28


5.29


2.99


0.56


2.67


2.67


4.00


3.02
















TABLE 16-A

Z tests for differences in the proportion of gill
flares, headshakes, yawns, and rejections as a function of
position of the prey in the mouth of the predator for both
spined and de-spined bluegill.


Gill flare Yawn Headshake Reject
Head Tail Head Tail Head Tail Head Tail
Kesponses 22 20 18 28 7 28 1 14
Spined Capture 37 59 37 59 37 59 37 59

Z Value 2.40 0.19 2.80 2.73


Responses 8 7 5 4 2 11 7 4
De-spined Capture 48 34 48 34 48 34 48 34
Z Value 0.47- 0.23 3.41 0.40
















TABLE 17-A


Chi square tests of goodness of fit
data from grass carp and bluegill.


on size selection


Grass Carp


Fish number


Significance


2 Value


5.50
7.50
5.00
7.00
7.00
7.00
4.00
4.00
5.00
3.00



8.50
5.17
4.34
6.84

4.84
8.17

1.84
3.84


Bluegill















REFERENCES

Beyerle, G. B. and Williams, J. E. Some observations of
food selectivity by northern pike in aquaria.
Transactions of the American Fisheries Society, 1968,
97, 28-31.

Chew, R. L. Early life history of the Florida Largemouth
Bass. Fisheries Bulletin No. 7, Florida Game and Fish
Commission, Tallahassee, Florida, 1974.

Chiszer, D. and Windell, J. T. Predation by bluegill sun-
fish Lepomis macrochirus rafinesque, upon meal worm
larvae, Tenebrio molitar. Animal Behaviour, 1973, 21,
536-543.

Dill, L. M. The escape response of the Zebra danio,
Brachydanio rerio, I. The stimulus for escape.
Animal Behaviour, 1974, 22, 711-722.

Freund, J. E. Modern elementary statistics. Prentice Hall
Inc., Englewood Cliffs, New Jersey, 1967.

Hobson, E. S. Predatory behavior of some shore fishes in
the Gulf of California. U. S. Bureau of Sport Fish-
eries and Wildlife Research Report 73, 1-92, 1968.

Hoogland, R., Morris, D., and Tinbergen, N. The spines of
sticklebacks as a means of defense against predators.
Behaviour, 1957, 10, 201-235.

Ivlev, V. W. Experimental ecology of the feeding of fishes.
Yale University Press, New Haven, Connecticut, 1961.

Kramer, R. H. and Smith, L. L. Sexual maturity and fecundi-
ty of the largemouth bass, ricropterus salmoides, and
some related ecological factors. Transactions of the
American Fisheries Society, 1960, 89, 222-233.

Lawrence, J. M. Estimated sizes of various forage fishes
largemouth bass can swallow. Proceedings of South
Eastern Association of Game and Fish Commissions,
1957, 11, 219-225.

Lewis, W. M. Predation as a factor in fish populations.
In G. E. Hall (Ed.) Reservoir fishery resources,
Special Publication No. 8, American Fisheries Society,
Washington, D. C., 1967.









Lewis, W. IH., Gunning, G. E., Lyles, E., and Bridges, W. L.
Food choice of largemouth bass as a function of avail-
ability and vulnerability of food items. Transactions
of the American Fisheries Society, 1961, 90, 277-280.

Lewis, W. M., Anthony, M., and Helms, D. R. Selection of
animal forage to be used in the culture of channel
catfish. Proceedings of the 17th Annual Conference of
the South Eastern Association of Game and Fish Com-
missioners, 1963.

Lewis, W. M. and Helms, D. R. Vulnerability of forage or-
ganisms to largemouth bass. Transaction of the
American Fisheries Society, 1964, 93, 315-318.

Lewis, W. M., Heidinger, R., Kirk, W., Chapman, W., and
Johnson, D. Food intake of the largemouth bass.
Transactions of the American Fisheries Society, 1974,
2, 277-280.

McClane, W. M. Fishes of the St. Johns River system.
Doctoral Dissertation, University of Florida,
Gainesville, Florida, 1955.

Major, P. F. The behavioral ecology of predator-prey inter-
actions in schooling fish. Animal Behavior Society
Meetings, Boulder, Colorado, June, 1976.

Marler, P. and Hamilton, W. J. Mechanisms of animal behavior.
John Wiley and Sons Inc., New York, 1966.

Marshall, N. B. The life of fishes. The World Publishing
Co., New York, 1966.

Moehn, L. D. Demonstration of low vulnerability of forage
fishes to predator fishes. M. S. Thesis, Southern
Illinois University, Carbondale, Illinois, 1959.

Nyberg, D. W. Prey capture in the largemouth bass. American
Midland Naturalist, 1971, 86, 128-144.

Schoener, T. W. Models of optimal size for solitary preda-
tors. American Naturalist, 1969, 103, 277-313.

Slobotkin, L. B. How to be a predator. American Zoologist,
1968, 8, 43-51.

Tarrant, R. M., Jr. Choice between two sizes of forage fish
by largemouth bass under aquarium conditions. Pro-
gressive Fish Culturalist, 1960, 22, 83-84.

Thomas, G. The influences of encountering a food object on
subsequent searching behavior in Gasterosteus aculeatus.
Animal Behavior, 1974, 22, 941-952.







73

Walls, G. L. The vertebrate eye. Cranbrook Institute of
Science, Bloomfield Hills, Michigan, 1942.

Werner, E. E. The fish size, prey size, handling time re-
lation in several sunfishes and some implications.
Journal of the Fisheries Research Board of Canada,
1974, 31, 1531-1536.

Wright, L. D. Forage size preference of the largemouth bass.
Progressive Fish Culturalist, 1970, 32, 39-43.

Zweiacker, P. L. and Summerfelt, R. C. Seasonal variation
in food and diet periodicity in feeding of northern
largemouth bass, Micropterus salmoides lacepede, in an
Oklahoma reservoir. Proceedings of the South Eastern
Association of Game and Fish Commissioners, 1973, 27,
579-590. -















BIOGRAPHICAL SKETCHi

Daniel C. Hatton was born in Aberdeen, Washington on

March 4, 1944. In Hay, 1961 he was graduated from Moclips-

Aloha High Scnool in Moclips, Washington. In April, 1967

he joined the United States Air Force. After serving four

years in the Air Force, he enrolled at Grays harbor Community

College in aberdeen, Washington where he met and married the

former Nikki Chapin of Stevenson, Washington. In June of

1969 he received an associate of Arts degree from Grays

harbor College. The following September he enrolled at the

University of Washington in Seattle, Washington where he re-

ceived his Bachelor of Arts in Psychology in March of 1971.

In September of 1971 he began work as a graduate student at

Western Washington State College in Bellingham, Washington.

He was graduated with a Master of Science in Psychology from

Western Washington in August of 1972. He began work as a

graduate student at the University of Florida in September,

1972, and is presently a candidate for the degree of Doctor

of Philosophy at the University of Florida.









I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of Doctor of Philosophy.






Merle E. Meyer, Chairman
Professor of Psychology



I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of Doctor of Philosophy.






Donald A. Dewsbury
Professor of Psychology



I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of Doctor of Philosophy.






Robert L. Isaacson
Professor of Psycnology



I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, s cope and quality, as
a dissertation for the de ree of D o" of Phil opny.



ward F. lMalagodi
Associate Professor of Iychology










I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality, as
a dissertation for the degree of Doctor of Philosophy.






Tnomas H. Patton
Associate Curator of Natural Sciences
Florida State Museum



This dissertation was submitted to the Graduate Faculty of
the Department of Psychology in the College of Arts and
Sciences and to the Graduate Council, and was accepted as
partial fulfillment of the requirements for the degree of
Doctor of Philosophy.

March, 1977





Dean, Graduate School




































UNIVERSITY OF FLORIDA
3IIII 22l85ll 54mll 8111
3 1262 08554 7098