Title Page
 Table of Contents
 Population ecology
 Conspecific attraction
 Future of fox squirrels in...
 Summary and conclusions
 Biographical sketch

Title: Distribution and population ecology of the fox squirrel in Florida /
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00097374/00001
 Material Information
Title: Distribution and population ecology of the fox squirrel in Florida /
Physical Description: vi, 139 leaves : ill. ; 29 cm.
Language: English
Creator: Wooding, John Bruce
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1997
Copyright Date: 1997
Subject: Fox squirrel -- Ecology -- Florida   ( lcsh )
Fox squirrel -- Habitat -- Florida   ( lcsh )
Fox squirrel -- Geographical distribution -- Florida   ( lcsh )
Wildlife Ecology and Conservation thesis, Ph.D   ( lcsh )
Dissertations, Academic -- Wildlife Ecology and Conservation -- UF   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
Thesis: Thesis (Ph.D.)--University of Florida, 1997.
Bibliography: Includes bibliographical references (leaves 132-138).
Additional Physical Form: Also available on World Wide Web
General Note: Typescript.
General Note: Vita.
Statement of Responsibility: by John Bruce Wooding.
 Record Information
Bibliographic ID: UF00097374
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 002325395
oclc - 39476554
notis - ALS8954


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Table of Contents
    Title Page
        Page i
        Page i-a
        Page ii
        Page iii
    Table of Contents
        Page iv
        Page v
        Page vi
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
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        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
    Population ecology
        Page 34
        Page 35
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        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
    Conspecific attraction
        Page 107
        Page 108
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
        Page 114
        Page 115
    Future of fox squirrels in Florida
        Page 116
        Page 117
        Page 118
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        Page 125
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    Summary and conclusions
        Page 127
        Page 128
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    Biographical sketch
        Page 139
        Page 140
        Page 141
Full Text








3 1262 08552 4584


I conducted the field work on this project while employed as

a wildlife biologist with the Florida Game and Fresh Water Fish

Commission. The work was fully funded by the Commission, and I

appreciate the Agency's permission to use their data for this


Many people who work for the Commission assisted with the

project. Special thanks go to Tom Logan, Brad Gruver, Jim Brady,

Paul Moler, and Tim Breault. Help with the field work was

provided by many people, including Mark Cantrell, Dee Hungerford,

Don Coyner, Bill Frankenberger, Brett Kempker, Patricia McNeill,

and Vic Doig. Jeff Hamblen helped with mapping and graphics, and

Steve Linda assisted with the statistical analysis.

A portion of the field work was conducted on property

managed by the Florida Department of Environmental Protection.

Jim Stevenson of that agency was particularly facilitative.

Field work on the Fort White study area was conducted on

privately owned property. The landowners graciously allowed me

access and permission to study the fox squirrels living on their

farms. Special thanks go to Billy Cason, Tom Fowler, and the

Gray Shadow Ranch.

My graduate committee at the University of Florida has been

demanding. I have prospered from their demands, and I appreciate

their commitment to quality. Steve Humphrey has been helpful

during all aspects of the process.

I also thank the administrative staff at the University.

This includes Cathy Ritchie, Shannon Stull, Mindy Edwards, and

Cynthia Sain. I also thank the fine people working in the

Graduate School. On the numerous occasions when I've done

something incorrectly (one must follow the rules without

exception, no matter how trivial one believes them to be), they

have helped me straighten out the mess--and they have always done

it with a smile (sometimes with a strained smile, but a smile


On the home front, my family has been cheering me on

throughout the project. From the bottom of my heart, I thank




ACKNOWLEDGEMENTS ............................................ ii

A BSTRA CT ................... ................................ v


1 INTRODUCTION ...... ........ ............................. 1

Background Information on Fox Squirrels ................ 2

2 DISTRIBUTION ...... ........ ............................. 7

Methods ..................................... ... ....... 8
Results and Discussion................................ .. 9

3 POPULATION ECOLOGY..................................... 34

Study Areas ............................................. 35
Me thods ................................................ 38
Results and Discussion ................................. 44
Concluding Discussion.................................. 85

4 REINTRODUCTION..... ......... ........................... 98

Methods ...... ........................................ 99
Results and Discussion ................................. 100

5 CONSPECIFIC ATTRACTION... ............................... 107

6 FUTURE OF FOX SQUIRRELS................................ 116

7 SUMMARY AND CONCLUSION ................................. 127

LITERATURE CITED................................................. 132

BIOGRAPHICAL SKETCH......................................... 139

Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy



John Bruce Wooding

August 1997

Chairman: Stephen R. Humphrey
Major Department: Wildlife Ecology and Conservation

Fox squirrel (Sciurus niger) distribution, movements,

demographics, and management were investigated in Florida from

1989 to 1995. Fox squirrels were determined to be widespread in

Florida, occurring in 65 of the state's 67 counties. There were

no reported occurrences for Dade and Broward counties. The

distribution, however, was patchy due to habitat loss. The

largest expanses of fox squirrel habitat were found on public

lands in northern Florida.

Fox squirrel movements and demographics were studied on two

areas in northern Florida. Forty-four fox squirrels were

monitored during the study. The density of fox squirrels on one

study area was 7.4 fox squirrels/km2; the density on the second

area was 11.7 fox squirrels/km2. Male home ranges overlapped

extensively with those of females and other males, but there was

little overlap in home ranges of adult females. Eight of 15 fox

squirrels collared as subadults dispersed. Two older fox

squirrels also dispersed. Dispersal distances ranged from 1.0 to

7.2 km. The annual mortality rate for the radio collared animals

was estimated at 27-30%. Litter size ranged from 1-3.

Populations had two breeding seasons per year, but the litter

frequency of radio-collared females was 1.07 litters per year.

Six radio-collared fox squirrels were translocated in 1995

to establish a breeding population in a state park. The radio

signal was lost on one squirrel while it was still on the park,

but the other 5 animals left the park following their release,

indicating that the habitat on the park was unacceptable to fox

squirrels. Dispersing squirrels settled where neighboring

populations occurred, showing that local sources of fox squirrels

were available that could naturally colonize the park. Further

relocation of fox squirrels to the area was unwarranted under the

current conditions.


Five hundred years ago, Florida was a wilderness.

Today, it is a world famous center of urban and agricultural

development. Florida's human population reached 14 million in

1995, and the population is expected to increase to 20 million by

2020 (Floyd et al. 1996). Many species of wild animals that were

adapted to the Florida wilderness have declined in abundance due

to the state's development (Cox et al. 1994). The fox squirrel

(Sciurus niger) is one of those species.

This dissertation contains the results of an observational

study on the fox squirrel in Florida. The intention of the work

was to gather basic information on distribution and biology that

could be applied to conserve the species. This was not a study

of the theoretical or mathematical aspects of wildlife ecology.

My goals for the dissertation were to present a tightly written

report that contained the data I collected. Chapter 1 contains

an overview on fox squirrels and it is offered as background

information for the chapters that follow. The next three

chapters contain the data collected in the study. Chapter 2

contains information on fox squirrel distribution in Florida,

Chapter 3 contains information on the population ecology of fox

squirrels in northeastern Florida as determined using radio

telemetry methods, and Chapter 4 contains the results of an

effort to restock fox squirrels into a state preserve.


My intentions were to keep the discussion to a bare minimum,

something which I appreciate in technical reports written by

others. However, dissertations are an academic exercise. I

hence expanded the scope and included two discussion chapters.

Chapter 5 contains a discussion on conspecific attraction and the

influence this behavior has on patterns of animal distribution

and conservation of populations in fragmented habitat. Chapter 6

contains a discussion on the future of fox squirrels in Florida.

Background Information on Fox Squirrels

The remainder of this chapter presents a review of fox

squirrel life history and status and an overview of prior

research conducted on the species. This information is offered

as background for the chapters that follow.

Fox squirrels occur in most of the eastern and central

portions of the United States (Koprowski 1994), and their range

extends into south-central Canada. Fox squirrels have been

introduced into California, Oregon, and Washington (Flyger and

Gates 1982).

Fox squirrels are large tree squirrels (Silva and Downing

1995). Body mass can exceed 1.3 kg (Flyger and Gates 1982).

Pelage colors range from a grizzled gray tinged with orange in

the midwestern United States to black, silver, or khaki in the

southeastern United States. Fox squirrels in the southeastern

Coastal Plain usually have white ears and muzzles. Individuals

can be a mix of colors. I have seen fox squirrels in Florida

with black faces, white ears and muzzles, black shoulders and

front legs, chestnut brown backs, tan flanks, and burnt orange

tails. All are not this colorful, but the most colorful are

striking animals.


Fox squirrels are one of the world's 28 species of tree

squirrels (Wilson and Reeder 1993). The genus Sciurus occurs

throughout Europe, northern Asia, and North and South America

(Nowak 1991). One species occurs in Japan (Wilson and Reeder


Hall (1981) recognized 10 subspecies of fox squirrel. Four

of these occur in Florida: S.n. avicennia (Big Cypress fox

squirrel), S.n. bachmani (Bachman's fox squirrel), S.n. shermani

(Sherman's fox squirrel), and S.n. niger (Southeastern fox

squirrel). The taxonomy of fox squirrels in the southeast was

recently reviewed by Turner and Laerm (1993). They concluded

that S.n. bachmani was not distinct enough to warrant recognition

as a separate subspecies. In their opinion, S.n. bachmani, was

only a clinal variation of S.n. niger. S.n. shermani and S.n.

avicennia, however, were considered distinct subspecies.

The three subspecies that Turner and Laerm (1993) recognized

for Florida (S.n. avicennia, S.n. shermani, and S.n. niger)

differed primarily in body size: S.n. avicennia was the smallest,

S.n. niger was intermediate in size, and S.n. shermani was the

largest. Pelage patterns were used by Moore (1956) to help

distinguish the different subspecies in Florida, but Turner and

Laerm (1993) found that pelage was too subjective and varied for

use as an indicator of taxonomy.

Legal Status in Florida

The Big Cypress fox squirrel is the only subspecies endemic

to Florida (Turner and Laerm 1993). It occurs only in the extreme

southwestern portion of the state and is listed by the Florida

Game and Fresh Water Fish Commission (GFC) as a threatened

species. Sherman's fox squirrel occurs throughout the peninsula

and panhandle west to Okaloosa County. It also occurs in central

and southern Georgia. It is considered a species of special

concern by the Florida GFC. The southeastern fox squirrel only

occurs in Florida in the western panhandle, but its range outside

of Florida extends over much of Alabama, northern Georgia, South

Carolina, and North Carolina (Turner and Laerm 1993). It is not


Fox squirrels were formerly game animals in Florida, and

legally hunted statewide. The season was closed in stages,

beginning first in south Florida within the range of the Big

Cypress fox squirrel. The season closed there in 1972. Next,

the season was closed on all wildlife management areas in 1991.

Fox squirrels were then legal game only on privately owned land

in central and northern Florida. The season there ended in 1995.

The final closure ended all legal hunting of fox squirrels in


Previous Studies

Fox squirrel research specific to Florida was begun in the

1950s by Moore (1956, 1957), who focused his attention on

distribution, taxonomy, and life history. Status surveys were

conducted in the 1970s by Brady (1977) and Williams and Humphrey

(1979). In the late 1980s, Kantola and Humphrey (1990)

investigated habitat use of radio-collared fox squirrels in

northern Florida. A study of urban fox squirrels in southwestern

Florida was completed in the early 1990s by Jodice and Humphrey


There have been several studies of fox squirrels in other

southeastern states. In Maryland, Taylor (1973), Lustig and

Flyger (1975), Dueser et al. (1988), and Larson (1990) examined

the status and habitat requirements of the Federally endangered

Delmarva fox squirrel (S.n. cinereus). In North Carolina, Weigl

et al. (1989) conducted an 8-year study on fox squirrel

population biology and habitat requirements. In South Carolina,

Wood and Davis (1981) and Wood (1985a,b) investigated status and

human perceptions of fox squirrels, and Edwards (1986) studied

habitat selection by radio-collared fox squirrels. In Georgia,

Hilliard (1979) also conducted a study of fox squirrels using

radio-telemetry techniques. A similar study was completed in

southern Alabama by Powers (1993).

Research on fox squirrels in the midwestern United States

has been more extensive than that completed in the southeast.

The first midwestern studies were completed in the 1940s (Allen

1943, Baumgartner 1943, Brown and Yeager 1945). These first

studies focused on life history, habitat requirements, and

management of fox squirrels as a small game species. More recent

studies of midwestern fox squirrels have built on the earlier

work. These include studies of behavior (Benson 1980, Koprowski

1993), food habits (Korschgen 1981, Nixon et al. 1968), ageing

techniques (McCloskey 1977), and habitat management (Nixon and

Hansen 1987).

There have been several general reviews of fox squirrel

research and biology. Flyger and Gates (1982) and Koprowski

(1994) reviewed the literature on fox squirrels for the species

entire range. Weigl et al. (1989) and Loeb and Moncrief (1993)

focused their literature review on fox squirrels in the

southeastern United States. Kantola (1992) and Humphrey (1992)

reviewed the biology and status of fox squirrels in Florida. A

review of the biology of all species of tree squirrels was

completed by Gurnell (1987).


Two previous surveys assessed the distribution of fox

squirrels in Florida. Brady (1977) used a mail survey of

wildlife experts to determine the state-wide distribution of fox

squirrels. He found that the species occurred throughout the

state but the distribution was patchy. He identified several

areas where there were large concentrations of habitat and where

fox squirrels were considered common, but overall, the species

was uncommon as a consequence of habitat loss. The second survey

was restricted to southern Florida, within the range of the Big

Cypress fox squirrel (Williams and Humphrey 1979). They

determined through personal interviews that fox squirrels were

present but rare in Lee, Hendry, Collier, and northern Monroe


In 1989, I attempted to update the statewide survey

completed by Brady (1977). To accomplish this, 437

questionnaires were mailed to field personnel employed by the

Florida Game and Fresh Water Fish Commission. Respondents were

provided a blank map of Florida on letter sized paper. The map

showed county borders and respondents were asked to mark specific

locations where populations of fox squirrels occurred. Of the

437 surveys mailed, 183 were returned. Upon review of the

surveys, it was decided the information mapped was not precise

enough to assess the current distribution. This was in part a

fault of the small scale map mailed with the survey. It was also

perhaps due to unclear instructions.

After going back to the drawing board, considering that time

and manpower were limited, it was decided that personal

interviews would be used to determine distribution and status.

The information gathered from the interviews is presented in this


First, a GFC field employee who would serve as a local

expert was identified for each of Florida's 67 counties. These

people were selected by contacting regional supervisors and

others in the Agency who knew which person was the best contact

for each county. Criteria used in the selection included the

person's time in the county and their level of knowledge. The

selected employees included wildlife officers, wildlife

biologists, and wildlife technicians.

These people were interviewed in person in the county of

interest. The interviews were conducted while looking at a

Department of Transportation county map. Each respondent was

asked to share their knowledge of fox squirrel distribution and

abundance in the county. Counties were examined by quarters

(northeast, northwest, etc.) to keep the respondent focused. The

distribution information was marked on the map as the interview


After the distribution data was mapped, the respondent was

asked to drive the interviewer to specific locations in the

county where fox squirrels occurred. The on-site visits allowed

the interviewer to observe first-hand the characteristics of the

habitat occupied. The intent was to make general observations on

the habitat such as dominant plant species, vegetation structure,

and land uses. Land-owners and managers encountered during the

field trips were asked general questions about fox squirrels.

A county survey was normally completed in one day. However,

if the respondent was unfamiliar with portions of the county,

they were asked for the names and phone numbers of people who

knew the area in more detail. These other people were contacted

by telephone and asked to share their knowledge of fox squirrel

distribution and abundance in the portion of the county in

question. The information they provided was added to the county

maps used in the field.

A crude estimate of habitat quantity for the larger

populations was made using the section grid on the county maps.

These estimates were used to assign the populations to one of

three size categories: small (<1,000 ha); medium (1,000-4,000

ha); or large (4,000 ha). These estimates were only ball park

approximations based on the information mapped, and they are

presented with that caution in mind.

Results and Discussion


Fox squirrels were widely distributed in Florida, but the

distribution was patchy. Similar conclusions were reached by

.Brady (1977) and Williams and Humphrey (1979).

Fox squirrels were reported to occur in 65 of Florida's 67

counties (Table 1). There were no squirrels reported for Dade

and Broward counties, although there was a possibility they

occurred in the extreme western portion of both counties. They

were reported to occur there in the earlier Florida surveys

(Brady 1977, Williams and Humphrey 1979), and while the habitat

still existed when the current survey was conducted, none of the

people interviewed had seen fox squirrels in either county.

Other than the difference noted above, there were no

indications from the data that there had been major changes in

fox squirrel distribution in the years between the surveys. As

will be discussed later, there have been changes in the quantity

of fox squirrel habitat in Florida in recent years, and from that

it seems reasonable to conclude that fox squirrels have declined

in abundance, but the survey data did not detect those changes.

Largest Populations

The largest populations identified in the surveys are listed

by county in Table 1. Several of the populations occurred in

habitat that crossed county lines. If the habitat was under the

control of one agency or landowner, it was counted as one fox

squirrel population for the discussions that follow. As an

example, the fox squirrels living in Apalachicola National Forest

were considered one population, although the forest lies in three


There were 59 large fox squirrel populations in Florida.

Eight of the 59 populations occurred in areas were the quantity

of habitat was estimated to exceed 4,000 ha. These were the

largest populations in the state. Two of the largest areas were

military bases (Eglin and Camp Blanding), two were National

Forests (Apalachicola and Ocala), and two were State Forests

(Blackwater and Withlacoochee). The habitat on these areas

consisted primarily of longleaf pine (Pinus palustris) sandhill,

except that on Apalachicola a large portion of the habitat was

longleaf flatwoods. The forests on these areas were generally

managed for timber production, and the understory vegetation was

controlled by prescribed fire. Camp Blanding, which appeared to

have the poorest quality habitat of the six major areas on public

land, contained vast areas of cut-over sandhills that were

dominated by turkey oak (Quercus laevis) thickets. The thickets

were believed a consequence of over-logging of pines and fire

suppression. My impressions were that most of the habitat on

Blanding was marginal as a result of the management. However,

Blanding is now under a different management approach, and the

habitat for fox squirrels should improve.

The two other large populations in Florida occurred on

private land. One of these occurred on the quail (Colinus

vircinianus) plantations that dominate the landscape in northern

Leon and northern Jefferson Counties. The habitat on the

plantations consisted of mature stands of longleaf, loblolly (P.

taeda), and shortleaf pine (P. echinata), interspersed with corn

(Zea mays) fields and food plots of various legumes planted for

quail. My impressions were that the habitat was the richest in

the state in terms of food abundance, partially due to quail

management activities, but also due to the natural fertility of

the clay soils. These soils contrast with the nutrient poor

sands that characterize most of Florida's upland soils.

The second large area of privately owned habitat occurred in

Osceola, Indian River, and Brevard counties, east of Kenansville

and west of the St. Johns River. The area contained a series of

neighboring ranches which managed their properties for cattle and

wildlife. The habitat on the ranches consisted of xeric

flatwoods with mature pines, scattered live oak (Q.

virginian)/cabbage palm (Sabal palmetto) hammocks, and forested

creek strands. Several of the ranches maintained feeding

stations for wildlife, and I was told that fox squirrels were

often seen at the feeders. My impressions were that this area

contained one of the densest populations of fox squirrels in the


In addition to the eight large populations, there were 32

populations that were classified as medium-size (1,000 4,000 ha

of habitat). Twenty one of these populations were on land

privately owned. Sixteen of these occurred on ranches managed

for cattle production. The habitat on the ranches consisted

primarily of live oak/cabbage palm hammocks, patches of xeric

longleaf and slash pine (P. elliotti) flatwoods, longleaf

sandhill, and forested fencerows and strips of hardwoods along

creeks and drainages. The understory on the ranches was kept low

by a combination of grazing, prescribed fire, and mowing.

However, in south Florida, in spite of these activities, much of

the understory vegetation consisted of dense stands of saw-

palmetto (Serenoa repens).

Of the other five medium-sized populations on private land,

two occurred on land managed for timber, two occurred on quail

plantations, and one occurred in a slowly developing residential

area located in sandhill.

Eleven of the 32 medium-sized populations in the state

occurred on publicly owned property. Seven of these were on

state lands managed for a variety of purposes. Four were managed

as wildlife management areas (Cecil Webb, Joe Budd, Apalachee,

and Three Lakes), one as a state park (Wekiva and surrounding

state lands), one as a state forest (Jennings), and one as a

nature reserve and research center (K. Ordway). The habitat on

the areas varied from primarily longleaf sandhills for the five

areas in northern Florida to xeric flatwoods and live oak

hammocks for the two areas in southern Florida. The understory

vegetation was managed by prescribed fire, and in addition, by

cattle grazing on the two areas in southern Florida.

The other four medium populations on public lands occurred

on Federally owned property. Two of these were military bases

(Cecil Field and Avon Park), one was a national forest (Osceola),

and one was a national wildlife refuge (St Marks, Panacea Unit).

The habitat on these areas was primarily xeric, longleaf

flatwoods. The habitat on Avon Park consisted of native longleaf

flatwoods and planted slash pine plantations.

There were 19 smaller concentrations of fox squirrels

identified in the state. The habitat base for each of these

populations was estimated at <1,000 ha. Thirteen of these were

on private land, and six on public land. Of the 13 on private

land, nine were on cattle ranches, two on timber land, two on a

quail plantation, and one on a cluster of urban golf courses.

Four of the six small populations on public lands were found

on state parks (Goldhead Branch, Hillsborough River, White Belt,

and Suwannee River), one occurred on a state forest (Cary), and

one occurred on property used for research (University of

Florida, Welatka). The habitat on the areas was primarily

longleaf sandhills and xeric longleaf flatwoods. The

understories were managed primarily using prescribed fire.

In addition to the major concentrations mentioned above and

listed in Table 1, smaller populations were scattered across the

state. The smaller populations were surviving in fragmented

strips and patches of habitat distributed in wooded fencerows,

grazed woodlots, pecan (Carva illinoensis) groves, golf courses,

and on the fringes of low density residential areas. The ground

cover was managed with cattle grazing or mowing. These

scattered, diffuse populations were particularly prevalent on the

small farms in northern Florida. In fact, 10 of the 14 counties

with fox squirrels but without a notable population occurred in

northern Florida (Table 1).

Habitat Features

The vegetative structure of the forests occupied by fox

squirrels in the state was consistent, and easily recognizable.

The habitat was generally park-like in appearance. The forests

had a grassy or otherwise low groundcover, a relatively open

understory, and an overstory of large pines and oaks. The pines

were usually longleaf, or in south Florida, slash pine, but there

were a few sites in northern Florida were the pines were either

loblolly, shortleaf, or sand pine (P. clausa).

Many wildlife professionals contacted during the surveys had

.the impression that fox squirrels were restricted to longleaf

pine sandhills. This turned out to be a too narrow a view,

because fox squirrels were found in a variety of plant

communities in addition to sandhills, including xeric flatwoods,


grazed woodlots, hardwood fencerows and golf courses dominated by

introduced plants.

The habitat characteristics observed in this survey are

well documented, both for Florida (Moore 1957, Brady 1977,

Williams and Humphrey 1979, Kantola and Humphrey 1990) and for

other regions of North America (Flyger and Gates 1982, Dueser et

al. 1988, Koprowski 1994). Fox squirrel habitat in the

midwestern United States was described as a wooded savanna (Nixon

et al. 1984), a description that applies to Florida habitat as

well. The plant species differ between regions, but the

structure of the forest remains consistent. Dueser et al.

(1988), for example, found that vegetation structure could be

used to accurately predict if Delmarva fox squirrels woul-d be

found in a particular forest patch.

Habitat Trends

Fox squirrels remain widely distributed in Florida, but the

distribution is patchy, and the species is locally rare in most

of the state because of a lack of habitat. This situation was

not always the case, because Florida once contained vast

quantities of fox squirrel habitat in the form of great, open

pine forests. In fact, open pine forests, dominated by longleaf

pine, were until recently the major forest type in the state

(Kautz 1993).

This began to change in the late 1800's when industrial

logging companies moved their operations from the upper

midwestern states to the southern pine forests. Certainly there

had been logging, turpentining, and land clearing earlier than

this, but the scale was minor in comparison to the changes that

followed the arrival of the logging companies (Williams 1989).

By 1916, some were lamenting the loss of the longleaf forests

(Young and Mustian 1989). By 1936, although greatly depleted,

longleaf forests still covered 3.09 million ha of Florida (Kautz

1993). Over the next 50 years, the coverage of longleaf fell by

88%; in 1987, only 0.38 million ha remained.

The great longleaf forests were replaced by a variety of

other land uses, such as orange groves, shopping centers,

pulpwood plantations, and cattle pastures. There are a few large

longleaf forests protected on public lands, but most of the

remaining forest patches are scattered in and around other land

uses. Fox squirrels still occupy these patches, but they

represent remnant populations, stranded by habitat loss. The

situation is analogous to a lake drying that leaves fish stranded

in pools and puddles scattered over the lake bottom.

The forest changes that have occurred in Florida in the past

100 years, for fox squirrels at least, have made a common species

rare. Fox squirrels are rare mainly because their habitat is

rare, and it is rare because people have made it so.

Similar trends in fox squirrel habitat have occurred in

other southeastern states. Fox squirrels are rare throughout the

region as a result (Weigl et al. 1989). The Delmarva fox

squirrel has been particularly hard hit by habitat loss and it is

currently listed as federally endangered. In contrast to the

situation in the southeast, fox squirrels in the midwest have

benefited from habitat changes associated with human settlement.

Humans have created savannah habitat in the midwest, and fox


squirrels have responded with range expansions and population

increases (Flyger and Gates 1982).

The fox squirrels' future in Florida depends on the

availability of their habitat, which will be influenced by a

number of factors. There are several possible scenarios. These

alternative futures are discussed in a later chapter of this


Table 2-1. Distribution of fox squirrels in Florida by county. Habitat quantities estimated for
notable populations: S<1,000 ha; M=1,000-4,000 ha; L>4,000 ha. Abbreviations used: National
Forest (N.F.), State Forest (S.F.), State Park (S.P.), Wildlife Management Area (WMA), National
Wildlife Refuge (NWR), Air Force Base (A.F.B.)

Notable Populations

County (Quantity of Comments


Watermelon Pond

area (S)

Osceola N.F. (M)



Most remaining habitat scattered on farms in grazed woods.

A few fox squirrels present in uplands on Lochloosa WMA.

Only reports from Osceola N.F.; occur in patches of xeric

flatwoods in Forest and in mowed flatwoods at Olustee


A few fox squirrels reported to occur in Pine Log S.F. and

around town of Fountain in pecan groves.

A few fox squirrels scattered on farms along New River and

around Santa Fe Lake in grazed woodlots and pecan






Table 2-1--continued






Notable Populations

(Quantity of


Cattle ranches in

SW corner of county




Cecil Webb WMA.

(M), Babcock Ranch



Occur on ranches in pine/oak hammocks scattered in

pastures. Locally common. Also a few fox squirrels

scattered in flatwoods on Farmton WMA.

No fox squirrels reported.

A few fox squirrels scattered in northern half of county

in patches of cut-over sandhill. No reports of squirrels

in southern half of county.

Fox squirrels restricted to scattered patches of xeric

flatwoods and pine/oak hammocks on ranches.

Table 2-1--continued





Notable Populations

(Quantity of


Withlacoochee S.F.

(L), Rook Ranch

(M), Hollings Ranch


Camp Blanding (L),

Gold Head Branch

S.P. (S), Jennings

S.F. (M)

Naples golf courses



Fox squirrels common in southeastern part of county. A

few fox squirrels occur in scattered patches of sandhill

elsewhere in county.

Habitat marginal but widespread on Camp Blanding and

Goldhead. Fox squirrels occur elsewhere in sandhill

patches in pastures.

Common on some golf courses. A few squirrels scattered in

xeric flatwoods in Golden Gate Estates, Collier Seminole

S.P., Everglades City, Immokalee Ranch, and Big Cypress


Table 2-1--continued

Notable Populations

(Quantity of


Ft. White area on

Cason Farm (S)


Small, scattered pockets of fox squirrels; most habitat on

farms in grazed woods and fencerows.

No fox squirrels reported

Carlton Ranch (M)

Mature stand of

slash pine--3 miles

SW of Old Town (S)

DeeDot Ranch (M),

Cecil Field Navy

Base (M)

Bulk of habitat on Carlton Ranch. A few squirrels reported

for Brighthour Ranch.

Fox squirrels only reported for northeastern part of

county; very rare even there. A few squirrels reported

around Guaranto Springs in grazed woods.

Bulk of habitat in county on DeeDot and Cecil Field.

Common in suitable habitat on DeeDot.








Table 2-1--continued







Notable Populations

(Quantity of


La Floresta

Perdido, former WMA


Ranches bordering

Cresent Lake (M)

St. James Island


Joe Budd WMA (M)



Fox squirrels restricted to northwestern part of county.

Locally common in longleaf stands managed for pole timber.

Most habitat on Cresent Lake ranches in pine/oak hammocks

in pastures. A few fox squirrels in pulpwood plantations

in remnant patches of xeric flatwoods.

Only report for county from a natural longleaf stand

surrounded by planted sand pine.

Common on Joe Budd. A few fox squirrels elsewhere in

county; restricted to grazed woods and fencerows.

A few squirrels reported around Ginnie Springs, Pleasant

Grove Church, and along S.R. 26 on the east and west side

of Waccasassa Flats. Found in grazed woods and fencerows.


Table 2-1--continued






Notable Populations

(Quantity of


Lykes Ranch (M)


Champion Quail

Plantation (M)

Carlton Ranch (M)


Only present in county on Lykes property in pine/oak

hammocks in pasture. Rare on the property.

A few squirrels reported on St.Joe seed tree orchard, on

M&K Ranch near Downes Island, on along S.R. 71 south of

White City.

Only reported from western half of county. Other than

quail plantation, a few reported to occur along S.R. 51 on

the Suwannee River.

Bulk of habitat on Carlton Ranch in hammocks and xeric

flatwoods in pastures. A few squirrels reported to occur

south of Wauchula along the Peace River and on the Smoke


Table 2-1--continued






Notable Populations

(Quantity of


Alico, Hilliard,

and Duda Ranches


Withlacoochee S.F.


Avon Park A.F.B.

(M), K-D Ranch (M)

Hillsborough River

S.P. (S)


Most habitat in northwestern corner of county on ranches.

A few squirrels reported for Big Cypress Indian


Fox squirrels common on Withlacoochee S.F. Restricted

elsewhere to remnant patches of sandhill forests found in

subdivisions and golf courses.

Fox squirrels common on K-D Ranch in southeastern corner

of county. A few squirrels reported for Avon Park A.F.B.,

on farms surrounding Highlands Hammock S.P., and along

Fisheating Creek.

A fox squirrels on and around Hillsborough River S.P. and

on ranches in southern part of county.

Table 2-1--continued

Notable Populations

(Quantity of




Indian River





Ranches west of St.

Johns River marsh


Apalachee WMA (M)

Quail plantations



Squirrels few and scattered in pecan groves and grazed


Common in patches of grazed woods on ranches. No

squirrels reported east of St.Johns River.

Common on Apalachee. A few squirrels reported to occur on

Florida Caverns S.P. and in scattered locations along the

Apalachicola and Chipola Rivers.

Common on the numerous quail plantations scattered in

northern half of county. None reported for southern half

of county.

A few squirrels reported to occur in grazed woods on farms

along Suwannee River.


Table 2-1--continued


Notable Populations

(Quantity of


Ocala N.F. (L),

State lands in

Wekiva River basin


Alico Ranch (M)

Quail plantations

(L), Apalachicola

N.F. (L)

Williston Highlands



Bulk of habitat in Ocala N.F. and on state lands bordering

Wekiva River. A few squirrels reported to occur around

Astatula, Hancock Lake, and Klinger Airport.

Most habitat on Alico Ranch. Also reported on golf

courses and ranchettes built on western edge of Alico.

Fox squirrels common in northern half of county on

plantations. Widely scattered in Apalachicola in patches

of sandhill and xeric flatwoods.

Scattered pockets of squirrels on farms around Chiefland

and in remnant longleaf stands in Williston area.





Table 2-1--continued

Notable Populations

(Quantity of


Apalachicola N.F.



Taylor (S), Jim

Walters (S), and

Drosey Ranches (S)


Ocala N.F. (L)

Bulk of habitat and fox squirrels occur on Ocala N.F. in

longleaf islands. Fox squirrels abundant on Marion Oaks

Golf Course. A few squirrels on horse ranches.


Bulk of habitat for county in Apalachicola N.F. in

vicinity of Camel Pond. Occur in patches of sandhill and

xeric flatwoods.

Squirrels rare. Bulk of habitat along Suwannee River near

1-10 rest area and along Withlacoochee River near Hickory

Grove Church.

Bulk of habitat on ranches. Occurred in scattered

locations in patches of grazed woods in pastures.





Table 2-1--continued

Notable Populations

(Quantity of









White Oak

Plantation (S),

Cary S.F. (S)

Eglin A.F.B. (L),

Blackwater River

S.F. (L)

Williamson Cattle

Co. (M)


A few squirrels in grazed woods on ranches west of 1-95.

Reported on White Belt and Bluefield Ranchs.

Only reported from Loop Road. Reportedly seen in slash

pines bordering road.

Most habitat along St.Marys River in patches of mature

pines. Populations few and scattered.

This is the largest habitat block in the state.

A few squirrels scattered on ranches in grazed woods.


Table 2-1--continued




Palm Beach

Notable Populations

(Quantity of


Leo Faurot Ranch

(M), Wekiva Springs

S.P. (S)

Ranches around

Kenansville (L),

Three Lakes WMA (M)

White Belt Ranch

(S) (this property

is state owned)


Other than Wekiva Springs S.P., most habitat scattered on

ranches in eastern part of county. Common on Leo Faurot

ranch located in southeastern portion of county.

Fox squirrels widespread in county.

Kenansville area.

Common on ranches in

Reportedly only occur in county in grazed woods on White

Belt Ranch.

Ranches (M)

Bulk of habitat and squirrels in central portion of county

on ranches. Also reported to occur in vicinity of Big

Fish Lake.


Table 2-1--continued



Notable Populations

(Quantity of



Avon Park A.F.B.


K. Ordway Preserve

(M), Fla. Rock

property (M), Univ.

Fla.--Welaka Unit


McCormick Ranch (S)

Peacock Ranch (S)

Bulk of habitat scattered in northwestern corner of county

in grazed woods.

Habitat limited to a few pine stands along Bluefield Road

and on Peacock Ranch.

Reported to occur but very rare. Habitat on golf courses

and grazed woods in remaining pastures.

A few squirrels on Avon Park A.F.B. Also occur on ranches

along Kissimmee River.

Habitat scattered across county in remnant stands of

longleaf sandhill. Locally common.






Table 2-1--continued

Notable Populations

(Quantity of



Santa Rosa



Eglin A.F.B.(L),

Blackwater River

S.F.(L), T.R.

Miller Timber

Co. (M)


Ranches around

Geneva(M), Lower

Wekiva River S.P.


Habitat abundant in eastern half of county. Fox squirrels

common. No habitat or fox squirrels reported for western

half of county.

Fox squirrels few and widely scattered on ranches and in

new subdivisions along 1-75.

Other than the small population on Lower Wekiva, most

habitat on ranches along the St. Johns River. Common on

some ranches.


Table 2-1--continued

Notable Populations

(Quantity of


Ranches in NW

corner of county


Chinquapen quail


Suwannee River S.P.


Circle S Ranch (S)


A few squirrels on small ranches around Bushnell, but most

habitat and squirrels in northwest corner of county on

large ranches west of 1-75 and north of S.R. 44.

Small pockets of squirrels widely scattered; most found in

pecan groves and grazed woods on small farms.

A few squirrels in remnant patches of sandhill between

Perry and the Gulf.

Squirrels widely scattered in grazed woods; other than

Circle S Ranch, most habitat on farms along New River and

Olustee Creek.






Table 2-1--continued






Notable Populations

(Quantity of


Ranchs and camps

around Lake Dias(M)

St.Marks NWR

(Panacea Unit) (M),



Eglin A.F.B. (L)


Bulk of habitat around Lake Dias. A few squirrels

scattered in Tomoka WMA in xeric flatwoods.

Bulk of habitat in scattered patches of xeric flatwoods in

Apalachicola and on St. Marks.

Most habitat in county on Eglin A.F.B. Elsewhere found in

pecan groves and grazed woods on small farms.

Habitat on small: farms in pecan groves and grazed woods.



Radio telemetry has become a standard tool for

investigations of wildlife movements and demographics. It has

been used in Florida on two previous studies of fox squirrels.

In the first study, radio transmitters were attached to six fox

squirrels on a sandhill study area in northeastern Florida

(Kantola and Humphrey 1990). In the second study, five fox

squirrels in Collier County were radio-collared and relocated

from golf courses to the Big Cypress National Preserve (Jodice

1993). Both studies have provided valuable insight into fox

squirrel biology in Florida, but both were hampered by small

samples of radio-collared animals. Because of the limited data

that were available on fox squirrel population ecology in

Florida, the current study was initiated.

The study attempted to answer several questions on fox

squirrel population ecology, including: 1. What are the home

range sizes and how are the home ranges spatially distributed? 2.

What are the mortality rates of radio-collared animals, and what

are the important mortality factors? 3. What is the average

litter size, litter frequency, and when is the breeding season?

4. What is the density of fox squirrels on the study areas? 5.

What are the characteristics of subadult dispersal? and 6. How

does the population ecology of fox squirrels in northern Florida

compare to that observed for fox squirrels in other regions in

North America?


The first phase of the study was conducted on Goldhead

Branch State Park and surrounding private property, Clay County.

Field work was conducted there from January 1990 to March 1991.

The 6.9 km2 area was about 80% forested (Figure 3-1); 80% of the

forest cover was longleaf pine/turkey oak) sandhill, 18% hardwood

hammock (primarily oaks), and 2% sand pine scrub. The non-

forested portions of the study area were open water, marsh, or

uplands developed for public use or park maintenance. Hunting

was prohibited on the Park, but the surrounding land was hunted.

Fox squirrels were difficult to trap on Goldhead, and

because of this, the study was moved to a second area in 1991.

The second study area was in southern Columbia County, about 3 km

north of the town of Fort White. Field work was conducted from

January 1991 to June 1994. The primary study area of 2.3 km2

(Figure 3-2) was a patchwork of upland hardwoods (49.3 ha),

pastures and row crops (144.0 ha), and clearcuts (34.3 ha).

There were three residences on the study area (2.8 ha). The

clearcuts were the result of a 1989 logging of planted slash


The wooded portions of the Fort White area occurred as

fencerows, two closed-canopy hammocks (each about 10 ha in size),

and a wooded but open-canopied pasture (Figure 3-2). Tree

species were predominantly laurel oak (Q. hemisphaerica) and live

oak. Black cherries (Prunus serotina) and dogwoods (Cornus

florida) were common in the fencerows and hammocks. Longleaf

pines were scattered over the area, but they were a minor

component of the forest cover. Cattle grazed most of the study


Study Area

1 k m
1 km

Figure 3-1. Goldhead study area, Clay County, Florida.

Ft. White Study Area

Land Cover


Figure 3-2. Fort White study area, Columbia County, Florida.


area, and their activity kept the hammocks and fencerows clean of

undergrowth. There were four fields planted in peanuts or corn.

State Road 47, a moderately traveled 2-lane highway, formed the

western border of the primary study area. The landowners on the

study area allowed gray squirrel (S. carolinensis) hunting, but

they protected fox squirrels. This had been their practice

before the study began and continued during the study.


Capture Procedures

Adult and subadult fox squirrels were captured in live

traps. Two were caught in wooden traps (61 cm long) modeled

after the design of Ludwig and Davis (1975). All other trapped

fox squirrels were caught in wire traps (Tomahawk brand, Models

103, 104, and 105). Raw, dried peanuts in the hull were settled

on as the bait of choice, but only after using a variety of

baits, including dried corn (shelled and on the cob); fresh,

grocery store mushrooms; peanut butter and raisin mix, suspended

in the trap in a cheese cloth sack; and scented lures, including

anise and artificially flavored extracts of strawberry, banana,

and walnut.

Traps were checked in the morning and again in the evening.

Traps were left open overnight prior to 1993, but after that they

were tripped in the evening and reset the following morning.

This eliminated the capture of nontarget, nocturnal species such

as raccoons (Procyon lotor), opossums (Didelphis virginiana), and

striped skunks (Mephitis mephitis). It also eliminated the

possibility of a fox squirrel spending the night in a trap.

Prior to handling, trapped fox squirrels were calmed by

covering the trap with a jacket or towel. Next, a mesh nylon

sack with a drawstring was placed over the door end of the trap.

The drawstring was tightened and the door was opened with the bag

in place. The jacket was then removed, and the squirrel was

flushed into the bag for handling.

Animals requiring extensive handling were tranquilized with

an injection in the hip of 100mg/cc ketamine hydrochloride. As a

rule of thumb, all adult-sized squirrels (weight >950grams) were

drugged with a dosage of 0.3 cc/squirrel. This dosage was

reduced to 0.25cc/ adult squirrel in the later portions of the

study. Lighter squirrels were normally given less drug, but it

was found that 0.2 cc was a minimum dose for handling squirrels

>800 g. The reaction of the squirrels to the tranquilizer was

variable: some squirrels succumbed and were limp within 2 minutes

of injection, but others never went fully under -- they continued

to move and crawl but made no attempt to bite and were safely

handled. Animals tranquilized in the afternoon were routinely

held overnight in traps placed in a storage shed to allow them to

fully recover from the drugs before their release. They were

released at the capture site the next morning.

Recaptured animals that were only physically examined were

processed in the mesh bag without using tranquilizers. These

squirrels made no attempt to bite, but some kicked without

warning with razor-clawed hind feet.

Fox squirrels were weighed to the nearest 25g with a spring

scale. Body weights of adult animals were compared by sex using

a nested ANOVA.

Subadults and adults were tagged in each ear with a monel

tag (National Band and Tag Co., Size #1). Squirrels >700grams

were radio collared. The transmitters used were either Telonics

M080 or Holohil MI-2M. Fox squirrels on Goldhead were also

marked by toe clipping one digit, but toe clipping was not used

at Fort White. Nestlings from 2 litters handled on Fort White

were marked on their leg pelage with a leather dye, and nestlings

from a third litter were tagged in one ear with an adult eartag.

Estimates of Age and Sexual Maturity

Age estimates were assigned to fox squirrels based on

criteria presented by Moore (1957) and Flyger and Gates (1982).

Nestling fox squirrels with hair on their backs were considered

at least 10 days old, and nestlings with open eyes were

considered at least 4-5 weeks (Flyger and Gates 1982). The age

of males caught in traps was assessed by body size, testes

descent, and the amount of hair on the scrotum. Males with

undescended testes and heavily furred scrotums were considered <8

months old. Males <900g with testes .3.5cm and mostly furred

scrotums were aged as 8 months old; the testes on these squirrels

were assumed to have just descended. Males >900g with scrotal

testes and sparsely furred, black scrotums were considered

monthss old. Female fox squirrels <900g were considered <5

months old.

The age in months for squirrels <9 months old was estimated

by backdating from the date of capture to the appropriate winter

or summer birthing periods. Animals thought born in the summer

birthing period were assigned an August 1 birthday; winter born

animals were assigned a January 1 birthdate.

Sexual maturity of males was assessed by testes size and

scrotal characteristics. Males with undescended testes and

furred scrotums were considered sexually immature. Males with

large, swollen testes (>3.5 cm long) and black, mainly furless

scrotums were considered sexually mature. Sexual maturity of

females was assessed by nipple characteristics (McCloskey 1977).

Females with nipples <1 mm long that looked like they had never

been suckled were considered sexually immature. Females with

nipples >3mm were considered sexually mature and thought to have



Radio-collared fox squirrels on Goldhead were located as

time permitted using triangulation procedures from fixed

stations. Data were recorded by station number and azimuth. Fox

squirrels on the Fort White area were normally located 2-3

times/week. All locations there were plotted in the field on

aerial photographs (scale, lcm=48m), and the data were recorded

as Universal Transmercator Grid (UTM) coordinates. Squirrels

were located using standard triangulation procedures or by

walking or driving to the tree where the squirrel was located. A

fixed-wing airplane was used to search for squirrels that could

not be found from the ground. The Fort White study area was

open, and visibility for seeing fox squirrels on the ground was

.normally unimpeded. Locations on the Fort White study area were

extremely accurate because of the visibility and the attempts to

pinpoint most locations to the nearest tree or clump of trees.

Attempts were made on both study areas in the initial months of

field work to locate animals more than once daily to obtain daily


activity data. This was discontinued on Goldhead because of time

constraints and on Fort White because of the influence that

observers had on squirrel movements.

Home range sizes were estimated by the harmonic mean and

convex polygon methods using the computer program TELEM. Pre-

dispersal (natal) and post-dispersal (adult) home ranges were

calculated for fox squirrels that dispersed from the study area.

Transition locations between home ranges were discarded from the

analysis. Home range sizes of adult males and adult females were

compared using the Mann-Witney test (p<0.01).

Habitat Use Versus Availability

Habitat use was determined by assigning each location to one

of the major cover types. The four habitat types used for the

analysis on the Goldhead study area were sandhill, hardwood,

scrub, and barren land (or non-forested land). The habitat types

used on the Fort White area were hardwood, planted pine, wooded

pasture, and field (includes pastures, rowcrops, and clearcuts).

Habitat selection of non-dispersing squirrels was examined with

Friedman's method (Alldredge and Ratti 1986). The difference

between proportion used and proportion available for each habitat

type was computed for each animal. These differences were ranked

for each animal (lowest to highest), and the ranks were used to

compute Friedman's test statistic (habitat types were considered

as "treatments" and animals as "blocks"). If Friedman's test was

significant, then a signed rank test was used to determine

differences among use versus availability for each of the habitat


Mortality Rates

Annual mortality rates were calculated with the computer

program MICROMORT (Heisey and Fuller 1985). The daily survival

rate was assumed constant for the study period. A z-statistic

was used to compare mortality rates for males and females and for

residents and dispersers. In addition to the confirmed deaths

of radio-collared squirrels, radio contact was lost with other

squirrels for unknown reasons. It was assumed these squirrels

died. Two mortality rates were calculated: one used only the

confirmed deaths; the second used the number of confirmed deaths

plus the number of assumed deaths.


Female fox squirrels have the potential for producing two

litters/year, one in winter and one in summer (Flyger and Gates

1982). The frequency of litters from radio-collared females for

each potential reproductive period in 1991, 1992, and 1993 was

assessed using movement data, capture data, sightings of

subadults, sightings of females that appeared to be nursing, and

nest checks in 1992 and 1993.

Food Habits

Anecdotal data on food habits also were collected on the

Fort White study area. Whenever fox squirrels were seen eating,

attempts were made to identify the foods. The food habits data

are presented by season using the following seasons: winter

(January February), spring (March-May), summer (June-August),

and fall (September-December).


Capture Success

Six adult fox squirrels (3 male:3 female) and one nestling

(male) were captured on Goldhead. Five of the six adults were

caught in traps (2,877 trap days, or 1 capture/575 trap days);

one adult female and her nestling were caught in a nest box built

by Park personnel for kestrels (Falco sparverius). Five of the

six adults on Goldhead were radio collared. The adult not

collared was caught at the end of the study during attempts to

catch the radio-collared squirrels for collar removal.

Forty-four fox squirrels (27 male:17 female) were captured a

total of 120 times in 3,486 trap-days on the Fort White study

area (1 capture/29.1 trap days). Thirty-nine of the squirrels

were radio-collared. One fox squirrel died after handling. Four

squirrels caught in traps were not collared, either because they

were too small (n=2) or because they were captured at the end of

the study (n=2) during attempts to catch radio-collared squirrels

for collar removal. Thirteen fox squirrel nestlings were also

handled; 11 of these were sexed (4 male:7 female) and eight were

marked with either dye or eartags.

Body Weights

Weights were taken on five adult fox squirrels (2 male:3

female) on Goldhead. The average weight of males was 1,055 grams

(SE 55); the average weight of females was 1,075 grams (SE 80).

The weights were not compared statistically because of the small-


Weights were taken on 30 adult fox squirrels (22 males:8

females) on Fort White. The average weight of males was 999


grams (SE 10); the average weight of females was 1,120 grams (SE

14). Females were significantly heavier than males (p=0.0003).

Wood (1988) and Larson (1990) also reported that adult females

were heavier on average than adult males, although Wood (1988)

stated the differences in his data were not significant. Other

studies have found no significant differences in the weights of

males and females (Flyger and Gates 1982, Weigl et al. 1989).

Home Range Sizes

The minimum convex polygon home ranges on Goldhead ranged

from 19.4 to 95.8 ha (Table 3-1). The average home range size

for the two males (83.0 ha; SE 9.1) was over twice the mean size

for the three females (35.6; SE 9.6).

The average convex polygon home range size on Fort White for

17 adult males (79.5 ha; SE 8.3) was significantly larger

(p<0.01) than the average home range size for 12 females (33.0

ha; SE 4.9) (Tables 3-2 to 3-4). The natal home ranges of eight

subadults averaged 6.35 ha (SE 1.76). Five animals monitored on

the Fort White area did not clearly fit into the category of

adult or subadult. The home ranges for these animals appears in

Table 3-5.

Home ranges for both study areas also were calculated using

the harmonic mean method. Based on the time I spent in the field

tracking the squirrels, my opinion is that the 80% harmonic mean

estimate represented the area where the squirrels were usually

found. The average home range sizes using 80% of the locations

were as follows: Goldhead -- adult males (n=2) 29.5 ha; adult

females (n=3) 22.1 ha; Fort White -- adult males (n=17) 35.7 ha

(SE 4.7); adult females (n=12) 12.8 ha (SE 2.4); subadults (n=7)

Table 3-1. Home range sizes (ha) of adult fox squirrels on the
Goldhead study area by the harmonic mean (HM) and minimum convex
polygon (MCP) methods.

Sex/# Monitoring Period # 65% 80% 95% MCP

Locations ha ha ha ha

M390 01/25/90 02/12/91 134 24.1 33.0 74.7 70.3

M340 02/01/90 03/05/91 100 11.3 26.0 96.9 95.8

F300 02/09/90 08/03/90 67 6.0 9.4 25.4 19.4

F430 02/06/90 05/20/90 59 13.1 23.4 33.8 28.9

F410 02/02/90 03/05/91 104 20.5 33.7 56.6 58.4

Table 3-2. Home range sizes (ha) of subadult fox squirrels on the

Fort White study area by the harmonic mean (HM)
convex polygon (MCP) methods.

and minimum


Sex/# Monitoring Period




F069 11/05/92 -


F630 11/04/92 -


F870 11/07/92 -


M129 10/03/91 -


M130 02/04/91 -


M150 02/05/91 -






ha ha











11.9 22.9


M170 02/01/91












Table 3-3. Home range sizes
on the Fort White study area
minimum convex polygon (MCP)


(ha) of adult female fox squirrels

by the harmonic mean (HM)




Sex/# Monitoring Period

F010 01/15/91

F069a 04/07/93

F070b 04/21/93

F099b 03/17/92

F100 03/18/91

F120 02/04/91

F140a 06/16/91

F260 01/18/91

F270 01/21/91

F429 02/03/93

F630a 03/11/93


F870a 04/30/93


- 12/07/92

- 08/11/93

- 01/28/94

- 04/29/94

- 01/28/94

- 06/25/92

- 09/22/92

- 06/23/94

- 04/29/94

- 04/16/94

- 04/29/93

- 11/07/93

- 10/03/93















- 11/19/93 13



ha ha



























4.2 8.7
































14.9 8.9

a Post dispersal home ranges. F069 remained on the primary study
area after dispersal, but the other three females (F140, F630,
and F870) left the area.
b F070 and F099 attained sexual maturity during the monitoring

Table 3-4. Home range sizes (ha) of adult male
the Fort White study area by the harmonic mean
convex polygon (MCP) method.


Sex/# Monitoring Period


fox squirrels on
(HM) and minimum





ha ha ha

M049 11/05/92


24.4 38.8 165.5 96.3


M090 02/05/91


39.4 72.4 183.3 134.4


M119 01/29/93


13.8 28.7 78.2 75.7


M128a 02/03/93


M130a 05/01/91



13.7 166.7 76.7

10.0 21.6 37.5 44.5


M150a 03/19/91

14.3 34.8 76.8 60.5


M159 03/17/92




53.7 38.7


M210 06/06/91


62.3 132.8 125.4


M239 01/29/93 -

16.2 39.0 100.2 71.5


M240 12/31/91



29.0 78.3 115.7


Table 3-4--continued

Sex/# Monitoring Period

M259 04/20/93 -


M300 11/07/91 -


M308 09/07/93 -


M368 12/31/91 -


M430 01/03/92 -


M540 01/06/93 -


M690 03/18/92 -


a Post-dispersal home ranges.













20.1 43.3 91.4 75.3

30.8 51.8 167.7 101.3




12.4 30.1 22.8

14.8 30.5 37.1

17.4 31.0 86.0 67.6

16.0 38.5 126.7 75.3


37.3 67.2 178.8 132.3

Table 3-5. Harmonic mean (HM) and minimum convex polygon (MCP)
home range sizes (ha) of fox squirrels captured as subadults
whose sexual maturity during the period of monitoring was
unknown, but suspected to be that of a subadult (the possible
exception is M188, who may have been sexually mature during the
period shown below).


65% 80%

Sex/# Monitoring Period



ha ha ha

F370 11/07/91 08/19/92a

F869 03/03/93 12/07/93

M128 02/03/93 10/12/93b

M160 02/04/91 09/18/91

M188 12/16/93 04/01/94

7.0 8.6

6.5 9.7



12.6 11.2

13.7 12.6

23.7 37.2 46.0 39.9

2.0 3.8






a F370 slipped her radio collar one month after capture and was
last located with telemetry methods on 12/07/91. She was sighted
3 times subsequently, with the last confirmed sighting on
b Unlike the other fox squirrels in the table, M128 dispersed
from the primary study area; his post-dispersal home range
appears in Table 4.

Table 3-6. Comparison of fox squirrel home ranges in the
southeastern Coastal Plain (minimum convex polygon method). Data
from this study are for adult squirrels only. The other studies
did not report the ages or sexual maturity of the squirrels they

Home Range Size (ha)


This study





Fort White


83.0 (n=2)

79.5 (n=17)


35.6 (n=3)

33.0 (n=12)

Kantola (1986)


40.0 (n=4)

20.6 (n=2)

Putnam County

Powers (1993)



38.0 (n=14)

11.6 (n=9)

Edwards (1986)

National Forest

South Carolina

31.6 (n=9)

19.3 (n=4)


Weigl et al.


North Carolina

Coastal Plain

26.6 (n=8)

17.2 (n=14)

4.7 ha (SE 1.4). Two other harmonic mean estimates of home range

size were calculated (65% and 95%). These estimates are

presented in the home range tables as a reference for those who

may find the information of value.

The home range sizes determined in this study were compared

to those determined in other studies conducted in the

southeastern United States (Table 3-6). Home ranges of males in

all studies were larger than those of females.

The home ranges of both sexes on Goldhead and Fort White

were almost double the size of those found in other studies.

There are several possible explanations for these differences.

One may be due to differences in food abundance between areas.

As an example, fox squirrels on Goldhead may have had large home

ranges because of low food abundance in comparison to the other

study areas in the southeast. Fox squirrels on Goldhead also

occurred at relatively low densities (Table 3-12), and low food

abundance would explain both the low densities and large home

ranges. The large home ranges on the Fort White study area were

believed a result of habitat distribution. The forested habitat

was distributed in fencerows and hammocks scattered in fields and

pastures. The pattern may account for the large home range sizes

there relative to other areas where the habitat was more

continuous. Other differences in home range sizes between study

areas may be due to differences in sample sizes of radio-collared

animals and the duration of telemetry monitoring.

Spatial Relationship of Home Ranges

The spatial relationships of the home ranges of adult fox

squirrels are illustrated in Figures 3-3 to 3-11. I tried a

number of ways to depict the characteristics I observed in the

field, and the method used here was the best I found. The

figures contain the complete set of locations for each of the

home ranges that are illustrated. The vertical spikes on the

graphs represent sites with frequent locations. These normally

represent locations of preferred nests. The graphics may at

first glance look too "busy" to interpret, but in my opinion,

they are worth taking the time to "read".

The home ranges for the three adult females tracked on

Goldhead displayed minimal overlap (Figure 3-3). This pattern

also observed for adult females on the Fort White study area

(Figures 3-4 to 3-7).

Two males were radio-tracked on Goldhead, and although there

was no overlap between them, there were too few data to evaluate

the spatial arrangement of adult males on the Goldhead area

(Figure 3-8). Although adult males were generally solitary,

their home ranges on Fort White overlapped extensively with those

of adult females and other adult males (Figures 3-9 to 3-11).

The natal home ranges of subadults monitored on the Fort White

area were within their mother's home ranges.

There was one exception observed regarding the separate home

ranges of adult females. In this case, a subadult that did not

disperse attained sexual maturity while within the range of the

female believed to be her mother. The spatial arrangement of

home ranges and the behavior behind the patterns is discussed in

the end of this chapter.


0 F300 0 F410 0 F430

O -

1 km

Figure 3-3. Spatial relationship of three adult female fox squirrels radio-tracked on the
Goldhead study area.

K/ -


c F1Q00 O' F260


Figure 3-4. Spatial relationship of two adult female fox squirrels radio-tracked on the
Fort White study area.



SF099 [] F270





Figure 3-5. Spatial relationship of two adult female fox squirrels radio-tracked on the
Fort White study area.
\\ _- ^^\ ^ A ^^_-

\ ---\- \ \ ,_-----^'^
\ _----- \ ^ -- ^----- ________________________________
\.^- ~^^^'^500

Fiur 35.Sptil eatonhi o to dutfeal fx qurrl rai-trake onth
Fort White- stuy rea y


0 FO10 0 F120


Figure 3-6. Spatial relationship of two adult female fox squirrels radio-tracked on the
Fort White study area.

V F010

A F099

0 F100 0 F120

-' F260

E F270

0 F429


Figure 3-7. Spatial relationship of seven adult female fox squirrels radio-tracked on the Fort
White study area.


V F300 O M340 0


0 F410 0 F430


s~- -\ --

- S

1 km

Figure 3-8. Spatial relationship of three adult female fox squirrels and two adult male fox
squirrels radio-tracked on the Goldhead study area.





^. -


A M090 v


0 F120



Figure 3-9. Spatial relationship of two adult female fox squirrels and one adult male fox
squirrel radio-tracked on the Fort White study area.







0 F100 0 M210 O F270 O M368

j0---4- <,"----
S - -
S -- S

Figure 3-10. Spatial relationship of two adult female fox squirrels and two adult male fox
squirrels radio-tracked on the Fort White study area.



2 M049 O M259 > M430


0- -'


[- > [> __[- 0

-" 500m

Figure 3-11. Spatial relationship of three adult male fox squirrels radio-tracked on the Fort
White study area.

Habitat Use Versus Availability

Fox squirrels on the Goldhead area were located most

frequently in sandhill (Figure 3-12). The second most commonly

used habitat was hardwoods. There was no significant difference

in habitat use versus availability (p=0.145).

On Fort White, fox squirrels were located most often in the

hardwood fencerows and hammocks (Figure 3-13). Friedman's test

indicated that habitat use on the study area was not in

proportion with availability (p=0.001). When the four habitat

types on the study area were examined individually using the

signed rank test, it was found that wooded pasture was used in

proportion to its availability (p=0.795), however, the other

three habitat types were not used in proportion to their*

availability (p=0.0001 for each of the three types). Hardwood

fencerows and hammocks were used in greater proportion than their

availability, while planted pines and fields were used in smaller

proportion than their availability.


Ten fox squirrels dispersed during the study (Table 3-7).

Seven dispersed between the estimated ages of 7-9 months old, and

one dispersed at an estimated age of 14 months. The other two

dispersers were also believed to be subadults at the time of

dispersal, but their exact ages were unknown. Two of the ten

squirrels that dispersed left their natal home ranges in October,

and the other eight dispersed between late February and mid-June

(Table 3-7).

The distances between natal and adult home ranges varied

from 1.0km to 7.2km. The average dispersal distance was 3.7 km





o 0.4-




c P c P c P c

Barren land Hardwoods Sandhill Sandpine

Figure 3-12. Habitat available versus habitat used by fox
squirrels radio-tracked on the Goldhead study area.

C 2 c S C

(D a

Wooded pasture

Figure 3-13.

Habitat available versus habitat used by fox
squirrels radio-tracked on the Fort White study



Planted pine

for males and 3.3 km for females. Two females moved from their

first adult home range to a second adult home range. The

distances between the two adult home ranges were 5.4km for F630

and 2.0km for F870. The second adult home ranges were 3.1 km

(F630) and 3.6 km (F870) from the natal home ranges.

Two of the ten squirrels that dispersed were killed or their

radio signals were lost during dispersal. Seven of the eight

that seemed to have completed their dispersal movements during

the monitoring period settled in areas that contained other fox

squirrels, based on subsequent sightings of fox squirrels in

their adult home ranges. No other fox squirrels were sighted in

the adult home range of one of the eight squirrels, but the post-

dispersal monitoring period for this squirrel was brief because

he was killed by a bobcat (Lynx rufus) about one month after


Fox squirrels dispersing from the Fort White study area had

a limited choice of habitats within the distances they dispersed.

Basically, they could choose agrarian land, either in row crops

or pastures, with scattered hardwood hammocks and fencerows, or

they could choose planted slash pine plantations. Seven of the

eight chose habitat that was primarily agrarian and, thus,

similar in composition and structure to the habitat in their

natal home ranges. The one exception occurred with a female fox

squirrel that dispersed to a 15-20 year old slash pine


Several of the radio-collared subadult fox squirrels did not

disperse. Five females captured as subadults were monitored for

Table 3-7. Summary

Sex/# Date of



F140 04/23/91

F630 11/04/92

F870 11/07/92

F069 11/05/92

M130 02/04/91

M170 02/01/91

M150 02/05/91

M129 01/03/92

M630 10/01/92

of subadult fox squirrel dispersal, Fort White study area: January 1991-June

Estimated Age at First

Capture (Months)


3 months

3 months

3 months

6 months

>9 months

8 months

5 months

8 months

Last Known

Date in Natal

Home Range










First Known

Date in

Adult Home












Age at



7 months

7 months

7 months

9 months





9 months

8 months













Table 3-7--continued.

Sex/# Date of Estimated Age at First Last Known First Known Estimated Dispersal

First Capture (Months) Date in Natal Date in Age at Distance

Capture Home Range Adult Home Dispersal (km)


M128 02/03/93 6 months 10/12/93 10/29/93 14 months 2.4

a F140's small nipples suggested she was a sexually immature, and therefore a subadult when
Her exact age at the time of capture was not known.
b F630 remained in this area from 03/11/93 to 04/29/93. She then traveled 5.4km to her second
post-dispersal home range. She remained there from 06/01/93 to 01/17/94, at which time the
battery in her transmitter failed. The second post-dispersal home range was 3.1 km from her natal
home range.
c F870 remained in this area from 04/30/93 to 10/03/93. She then moved 2km to her second post-
dispersal home range. She occupied this second area from 10/17/93 to at least 11/19/93. She was
killed by a vehicle sometime in the week after her last location. The second post-dispersal home
range was 3.6 km from her natal home range.
d M170 was last located 06/18/91, after which the signal was lost. An aerial search was conducted
06/27/91, without success, and it was concluded the transmitter had failed.
e M630's carcass was found 10/20/92, the day after he was located in the new area. It is unknown
how far he would have gone had he survived.

>300 days; three of the five dispersed. Nine males captured as

subadults were monitored for >133 days; five of the nine


Young fox squirrels of both sexes dispersed. Koprowski

(1996) also observed that both sexes of fox squirrels dispersed.

These observations are unusual in that the normal pattern in

mammals is for males only to disperse (Greenwood 1980). The fact

that female fox squirrels dispersed may be related to the

intolerance that adult females have towards other females.


There were two sources of recruitment into the adult segment

of the Fort White population. The first were animals born on the

study area. As previously noted, six of the 14 radio-collared

subadults did not disperse. Recruitment was documented for three

of the six. One of these was a female, and the other two were

males. Both males participated in breeding activities as they

grew older. Sexual maturation of the female was assessed by

nipple characteristics observed through binoculars. As she

matured, her nipples enlarged and darkened. This was taken as

evidence that she reached sexual maturity on the study area.

The other three non-dispersing squirrels either died or were lost

from radio contact before they reached sexual maturity.

The second source of recruits were animals that immigrated

to the study area. I did not have proof of immigration, but, in

two instances, I suspected that "new squirrels" were recent

immigrants to the study area. In both instances the squirrels

were males which suddenly appeared. Both squirrels had descended

testes when they arrived on the study area, and both were

captured soon after being first sighted. They remained in the

capture area during the period they were monitored (six months

for one squirrel and nine months for the other).


One of the five squirrels monitored on Goldhead died during

the study. The squirrel, an adult female, was believed killed

by a raptor based on the condition of the carcass. When the body

was found, the skin of the legs was turned inside out. The sign

was indicative of raptor feeding (B. Millsap, GFC, personal


Nineteen fox squirrel deaths were documented on Fort White

(16 squirrels were radio-collared and three were unmarked). Nine

deaths were due to predation, one death was due to unknown

causes, and nine deaths were due to human-related factors (six to

vehicles, one to a steel trap set by the landowner for coyotes,

one to drowning in a metal drum, and one to capture stress). A

total of 16 of the 39 animals radio-collared died during the

study (Table 3-8).

Two instances of nest predation were observed at Fort White.

During the winter of 1991-92, the leaf nests of two radio-

collared females were found destroyed. Both females were thought

to have had young when the nests were destroyed. Large buteo

hawks have been observed attacking squirrels that were hiding in

leaf nests (B. Millsap, M. Cantrell, GFC, personal

communication). Based on these observations, and the fact that

red-tailed hawks (Buteo jamaicensis) were the only large hawk

seen on the study area, I suspect that the nests were destroyed

by a red-tailed hawk that was digging after the nestling


squirrels. Nest loss of this type was seen only twice, and, if a

red-tail was responsible, it may have been a transient bird that

had learned the technique of hunting squirrels in their nests.

Although red-tailed hawks were year-round residents on the

Fort White area and suspected of destroying these two nests,

their impact on radio-collared squirrels was less than I

expected. I had been anticipated that they would be a

significant predator of the fox squirrel. They are known to prey

on fox squirrels in Florida (B. Millsap) and they were commonly

seen hunting on the area. In addition, the habitat was open,

providing good hunting conditions for the hawk, both species were

active at similar times, and furthermore, the squirrels were

often seen foraging or traveling across open pastures where they

seemed extremely vulnerable. However, only three fox squirrel

deaths could be attributed to raptors (all believed due to red-

tailed hawks, the only large raptors seen on the study area).

The minimal impact of red-tailed hawks to fox squirrels on

the Fort White area may be due to two factors. One may be that

they normally select smaller prey than fox squirrels, and the

second may be that fox squirrels have excellent defenses against

hawk attacks. Regarding the latter, fox squirrels crossing open

pastures ran with a loping, stop-and-go pattern of travel. They

sat up on their haunches when they stopped and scanned the area

for a fewseconds before loping off again. Fox squirrels foraging

on the ground behaved similarly in that they stopped frequently,

sat on their haunches, and looked around. The squirrels often

flicked their tails above their backs when running and foraging,

a behavior which might attract the attack to the tail rather than

to the body. These behaviors, in addition to the squirrel's

large body size, may have reduced their vulnerability to red-

tailed hawk predation.

Other predators that were seen on the study area included

bobcats, coyotes, domestic dogs (Canis familiaris), gray foxes

(Urocyon cinereoargenteus), and diamondback rattlesnakes

(Crotalus adamanteus). Owls were not seen or heard on the study


Bobcats were thought responsible for three deaths of radio-

collared squirrels and canids for three deaths (Table 3-8). Two

of the squirrels that canids killed were found buried. When the

carcasses were found, they were intact, and it looked like the

uneaten bodies had been cached. The size of the bite marks on

the dead squirrels suggested the predator was either a small

domestic dog or coyote.

Mammalian predators seemed to be rare on the primary study

area based on sightings and tracks, yet they killed twice as many

radio-collared animals as the more common red-tail hawks. This

suggests that fox squirrels may be more vulnerable to predation

by bobcats and canids than to predation by red-tailed hawks.

Several factors may have reduced the fox squirrel's vulnerability

to mammalian predators and thus kept the mortality within

sustainable limits. One was that contact was reduced by activity

periods with minimal overlap, in that the fox squirrels were

diurnal whereas the mammalian predators were generally nocturnal.

A second factor was that fox squirrels seemed to minimize the

time spent foraging or traveling in open areas more than 20m from

trees where they were vulnerable to being chased and caught;

normally they tended to stay close to the safety of the trees. A

third factor that may minimize mammalian predation is that fox

squirrels seemed to prefer habitats with low ground cover. There

may be two advantages to the low groundcover: first, it was

easier to traverse to escape a pursuer and second, in low ground

cover, the squirrel's vision was unimpeded by vegetation, making

escape from approaching predators more probable. An

unsustainable vulnerability to mammalian predation may be a

primary reason why fox squirrels do not inhabit forests with a

dense understory.

Mortality Rates

Annual mortality rates were calculated for the

radio-collared fox squirrels on Fort White (Table 3-9). There

were 10 confirmed male deaths and five confirmed female deaths

(the one death due to capture stress was excluded from the

calculations). In addition to the confirmed deaths, radio

contact was lost on three other males. The possibility that they

died is reflected in the bracketed values presented in Table 3-9.

The annual mortality rate for all radio-collared squirrels

was about 30% (Table 3-9). Similar mortality rates were observed

by Nixon et al. (1986) for an unexploited fox squirrel population

in Illinois.

Mortality rates of resident and dispersing squirrels were

compared by sex, with the expectation that dispersing squirrels

would suffer higher mortality rates than resident animals.

Although the average mortality rates were higher for squirrels

that dispersed (Table 3-9), the differences were not significant

(p>0.05). A comparison also was made between the mortality rates

Table 3-8. Summary of fox squirrel mortality, Fort White study

area: January 1991

-June 1994.


















Last Date



















Cause of Death




















Predation, red-tailed hawk

Predation, bobcat


Predation, canid

Predation, canid

Predation, raptor



Drowned in a barrel

Predation, suspect canid

Predation, raptor

Predation, bobcat

Predation, suspect bobcat

Capture stress



Table 3-9. Annual mortality rate of fox squirrels radio monitored on the Fort White study area,
1991-94. Rates calculated by the methods of Heisey and Fuller (1985). Contact was lost with
three radio collared males, one for unknown reasons, and the other two because they lost their
collars, perhaps after death. These three males represent the assumed deaths in the table below.

Confirmed Deaths

(Assumed Deaths)

Mortality Rate -

Confirmed Deaths

(Confirmed + Assumed

95% CI -Confirmed Deaths

(Confirmed + Assumed Deaths)





All Males




All Females

All Squirrels







7 (2)

3 (1)

10 (3)

0.29 (0.36)

0.53 (0.63)

0.34 (0.42)

0.09 -

0.00 -

0.15 -




0.00 -

0.00 -

0.03 -

0.45 (0.14 0.52)

0.80 (0.02 0.86)

0.49 (0.21 0.57)




0.15 0.38 (0.19 0.43)




17,178 15 (3)

0.27 (0.32)

of males and females, with the expectation that the wider ranging

males would suffer higher mortality rates than the more sedentary

females. Males did suffer higher mortality rates (Table 3-9),

but the differences were not statistically significant (p>0.05).


Information on reproduction on Goldhead was restricted to

the capture of a nestling male fox squirrel. At the time of its

capture on 2 February, 1990, it weighed 100 grams, its dorsal

surface was furred, and its eyes were closed. The squirrel was

estimated to be about 3 weeks old based onthese characteristics.

By back-dating and assuming a 45-day gestation period (Flyger and

Gates 1982), the squirrel would have been conceived in the last

week of November 1989 and born in the second week of January


Five litters were found on the Fort White area (Table 3-10).

All were in leaf nests in oaks. There were 2-3 young/litter. By

back-dating, three of the litters were conceived in the period 31

May 4 August and the other two litters in the period 15

December 2 February.

The summer breeding season on Fort White began as early as

17 April, based on observations of an adult male chasing an adult

female on that date, and extended until 4 August, based on the

back dating of one litter. The winter breeding began as early as

12 October, based on observations of an adult male pursuing an

adult female on that date, and extended until 2 February, the

estimated date of conception for one of the litters handled.

Radio-collared males on Fort White expanded their home

ranges during the breeding seasons, when some were located about

Table 3-10.



26 Feb 92

10 Apr 91



squirrel litters found in nests

Young Sex Weight(g)

on the Fort



28 days

21 days


White study



29 Jan 92

20 Mar 91


Estimated Date of


15 Dec 91

2 Feb 91

5 Aug 92

19 Aug 93

9 Oct 92







21 days

21 days

21 days

15 July 92

29 July 93

18 Sept 92

31 May 92

14 June 93

4 Aug 92

Table 3-11. Litter frequency for female fox squirrels monitored
on the Fort White study area. A "Y" indicates there was evidence
that a litter was born during the breeding season. A "N"
indicates there was no evidence a litter was born.




Animal #




Winter Summer Winter Summer Winter Summer






4Y:1N 1Y:3N 4Y:1N

Total 3Y:2N

2Y:3N 1Y:3N


1.0 km outside of their normal home ranges. Females remained in

their normal home ranges during the breeding season. This is the

normal fox squirrel breeding pattern (Koprowski 1994). Seven

radio-collared males were observed on one occasion clustered

within 50m of a radio-collared female. All of the males were 0.5

to 1 km outside of their normal home ranges.

The frequency of litters for adult females on Fort White

appears in Table 3-11. Sufficient data were available to

evaluate the productivity of these females for 28 reproductive

periods. Litters were produced in 15 of the 28 potential

reproductive periods. The females averaged about one

litter/year. Nine of the 15 litters were born in the summer

period and six in the winter period.

Scent Marks

Fox squirrels often were seen climbing trees with their

noses to the trunk or limb, apparently sniffing the bark as they

traveled. They also were seen rubbing their faces on the bark, a

method fox squirrels use to scent mark (Benson 1980).

Adult male fox squirrels were seen on three occasions

rubbing their faces on trees in spots where the outer bark had

been chewed away. Two of the squirrels first bit at the spot

before they rubbed their faces on the tree. In one instance, the

squirrel pressed his abdomen to the mark point after he had

.rubbed his face on it. The points were on the trunk but

immediately under an overhanging branch or knot and sheltered

from rain. One of the marked trees was a southern red oak (Q.

falcata). This tree had at least four different spots marked.

The spots ranged in size from about 5 by 15 cm to 10 by 30 cm.

All were under the lower most branches on the tree and clearly

visible from the ground. The highest mark seen was about 10m

above the ground. The other two trees where males were seen

marking were pecans. Additional marks were seen on laurel oaks

and live oaks. No effort was made to systematically survey the

study area for mark trees, however, mark trees were observed

scattered across the study area. Similar marking behavior and

mark points have been observed in other studies; both gray

squirrels and fox squirrels have been observed exhibiting this

behavior (Taylor 1968, 1976; Koprowski 1993).


Ten fox squirrels were sighted on the Goldhead study area

during two months of intensive field work in January and-

February, 1990. A 95 ha portion of the study area was trapped

more intensely than any other, and, within this area, seven

adult-sized fox squirrels were sighted. Five of the seven were

captured and radio collared. The collared squirrels restricted

most of their activity to the 95-ha area, and it is assumed the 2

uncollared fox squirrels did also. The minimum fox squirrel

density for this 95-ha area is therefore 7.4 fox squirrels/km2.

This was the best quality fox squirrel habitat in the study area,

and based on sightings and trapping results, it contained the

highest density of fox squirrels.

The primary Fort White study area was 2.3 km2; 27 fox

squirrels lived on the area in April-May 1993: 20 were radio

collared (11 adult males, 5 adult females, 1 subadult male, 3

subadult females); two were ear-tagged only (both subadult

females); and five were unmarked (age and sex unknown). The

unmarked squirrels were assumed residents. The density was

therefore 11.7 fox squirrels/km2.

Fox squirrels on Fort White restricted most of their

activity to the wooded portions of the study area, an area of

49.3 ha. This was their primary habitat. Their density in the

wooded areas was or 54.8 fox squirrels/km2.

Estimates of fox squirrel density from this and other

studies appear in Table 3-12. Density estimates for the

southeastern Coastal Plain range from 5 39 fox squirrels/km2.

This compares to an estimated density for a study area in

Illinois of 153-314 fox squirrel/km2. The striking difference in

densities between the southeast and midwest is believed due to

habitat quality. Even the best fox squirrel habitat in the

Coastal Plain is of marginal quality compared to the habitat in

the midwest.


Anecdotal observations were made on food habits of fox

squirrels on the Fort White area. They are reported only because

there is little information on the food habits of fox squirrels

in the southeast. The following items were eaten by fox

squirrels on the Fort White area (the season the items were eaten

follows the item): acorns (WI,SP,SU,FA); newly emergent

herbaceous growth (WI,SP); hardwood buds (WI,SP); oak flowers

(SP); mushrooms (WI,SP,SU,FA); mistletoe (Phoradendron serotinum)

berries (WI); field corn (FA); pecans (WI,SU,FA); jelly fungi

(Auricularia sp.) (WI); peanuts (WI,SU,FA); black cherries (SU);

lichens (SU,WI); longleaf and slash pine seeds (SU,FA); magnolia

(Magnolia grandiflora) fruit (SU); and oak galls (FA). Though

Table 3-12. Density estimates for fox squirrels.


Weigl et al.


This study

Humphrey et

al. 1985

This study

Kantola 1986

Tappe et al.


Moore 1957

Larson 1990

Nixon et al.


Benson 1980


North Carolina




Putnam County


Fort White


Putnam County



Putnam County




Nest Count







Nest Count
















153 314

Illinois Sightings


not observed, fox squirrels also may have eaten wild grapes

(Vitus sp.) and blackberries; both fruits were common on the area

in the summer. Evidence of squirrels eating pear seeds was

found, but the sign could have been that of gray squirrels.

Fox squirrels were seen caching food items on 10 occasions.

Food caching was also observed in Florida by Moore (1957) and

Jodice (1990). The items cached on the Fort White study area

were pecans, acorns, peanuts, and, in one instance, an immature

puff ball (Order Lycoperdales). On one occasion I observed a fox

squirrel moving a pecan and an acorn that had been cached

previously. The items were reburied about 7m from where they

were previously cached.

It is common knowledge that squirrels cache food items, and

it was only mentioned here because of speculation that

southeastern fox squirrels do not cache foods (Loeb and Moncrief

1993). Fox squirrels in Florida cache foods, but perhaps less

frequently than fox squirrels in other areas. The infrequency of

the behavior may have caused other researchers in the southeast

to miss it, thus leading to the statements made by Loeb and

Moncrief (1993).

Fox squirrels supplemented their diet with peanuts and corn.

The importance of these crops varied by year and by squirrel.

Peanuts, for example, were planted on a 2-4 year rotation. They

grew as volunteers in the off-years, but they were only abundant

in the years when planted. Fox squirrels ate the crops available

within their home range, but there were no observed instances of

fox squirrels traveling outside of their normal home range to

exploit crops.


Pine trees were uncommon on the Fort White study area, and

although the squirrels ate the pine mast that was available, it

was a minor component of their diet. This contrasts to the

Goldhead study area and other areas in the Coastal Plain were

pine mast was a critical component of the summer and early fall

diet (Kantola 1986, Weigl et al. 1989). Fox squirrels on the

Fort White area successfully substituted other foods for pine


Concluding Discussion

In the past 10 years, our knowledge of fox squirrel

population ecology in northern Florida has increased

considerably, both with the study reported here and with the work

of Kantola and Humphrey (1990). Prior to these studies, our

knowledge of fox squirrel biology in northern Florida was based

primarily on a two year study conducted in the 1940s (Moore

1957). In some aspects, the new information has changed our

understanding of fox squirrels, whereas in other areas additional

study has only strengthened Moore's (1957) conclusions. I have

tried to summarize our knowledge of fox squirrel biology in

northern Florida in the discussion that follows. Sample sizes

remain small for many aspects of their biology, and our knowledge

remains limited. However, we know more than we did. When

necessary, I have compared and contrasted the Florida

observations to those made on fox squirrels in other parts of the

species's range in an attempt to clarify the discussion.


The only data on fox squirrel predation for northern Florida

were the observations reported earlier from the Fort White study


area. The important predators on the Fort White study area were

raptors, canids, and bobcats. This probably applies throughout

the state, but other predators, such as great horned owls (Bubo

virginianus), gray and red foxes (Vulpes vulpes), rattlesnakes,

and domestic dogs, may be locally important predators on fox

squirrels. Moore (1957) considered that bald eagles might be a

significant predator of fox squirrels. This seems unlikely.

Eagles are relatively uncommon, they tend to hunt around lakes or

scavenge along highways (Wood 1992), and because of these traits,

I doubt if they encounter fox squirrels often enough, or are

proficient enough at hunting them, to be an important predator.

Human predation on fox squirrels may have been significant

in the past, but interest in fox squirrel hunting in Florida has

been low in recent times (Wooding 1990). The lack of interest

was one of the factors which lead to the season closure on fox

squirrels in northern Florida. This took affect beginning with

the 1996-97 season. Fox squirrels were legal game on Fort White

study area during the time of the field work, but no one hunted


A number of fox squirrels on the Fort White study area were

killed by vehicles while crossing S.R. 47, a two-lane highway

that formed the western border of the study area. Roadkill

mortality was not observed on the Goldhead study area, and it was

not mentioned by Moore (1957) or Kantola and Humphrey (1990).

There may be areas in Florida where roadkill mortality is so

severe that it limits fox squirrels, such as in urban areas or

subdivisions with a high road density, but these conditions did

not exist on any of the northern Florida study areas.


The only data available on mortality rates for Florida were

obtained on the Fort White study area. The annual mortality rate

of radio collared squirrels was about 30%. The rate included

mortality by vehicles and predators. Similar rates were observed

by Hansen et al. (1986) for an unhunted fox squirrel population

in Illinois. Moore (1957) had speculated that predators would

only kill an occasional fox squirrel. The Fort White data

supported his suspicions. Weigl et al. (1989) believed that

coastal plain fox squirrels were too rare to become a major food

item, and as a result, no predator could afford to hunt

specifically for them.

Before concluding this section on mortality, I want to

comment on one of Moore's (1957) observations on fox squirrel

behavior. He reported several incidents in which fox squirrels

that were fleeing for their lives ran down gopher tortoise

(Gopherus polyphemus) burrows. Moore (1957) believed that the

behavior was common, but it was not observed by myself or Kantola

and Humphrey (1990). My interpretation of the events Moore

(1957) described were of desperate animals taking desperate

actions, and I believe if given a choice between a tree or a hole

in the ground, a fox squirrel will tree every time. While there

are a number of species that depend on gopher tortoise burrows

for their survival, the data suggest that fox squirrels are not

one of them.


Moore (1957) identified 2 breeding seasons per year for fox

squirrels, a pattern that is consistent throughout the species

range (Koprowski 1994). The first data for the state on litter

frequency was collected at Fort White. Several females produced

two litters per year, but the overall litter frequency was 1 per

year. Similar litter frequencies have been observed elsewhere

(Harnishfeger et al. 1978).

Knowledge of litter size in northern Florida is based on a

sample of 17 litters; 11 were examined by Moore (1957), and six

were examined in the current study). Litter size ranged from 1

to 4, with a mean of 2.3. Fox squirrels usually have 2-3 young

per litter throughout their range (Koprowski 1994).

Weigl et al. (1989) studied fox squirrel reproduction in

coastal North Carolina in habitat similar to that found in

northern Florida. He reported rather emphatically that the

winter breeding season was the major period of reproduction. His

data were based almost exclusively on examinations of nest boxes.

In Florida, data are available on the period of birth for 27

litters; 11 in Moore (1957) and 16 in this study. Fourteen of

the litters were born in the winter breeding season, and 13 in

the summer season. Only one of the Florida litters was found in

a nest box, and it was a winter litter. I believe that the

Florida data more accurately represent the breeding

characteristics of fox squirrels, and until further data show

otherwise, that the two breeding seasons are of equal importance.

I believe the North Carolina observations (Weigl et al. 1989)

were biased by their study methods. Fox squirrels use nest boxes

mainly during cold weather (Nixon et al. 1989), and I think the

summer litters were missed because they were not checking leaf


Nesting Habits

Much of Moore's (1957) field effort was spent in studying

fox squirrel nesting habits. Among other observations, Moore

(1957) concluded that leaf nests were used more often than were

tree cavities. This conclusion was also reached by Kantola and

Humphrey (1990). My observations are largely anecdotal, but they

support the other studies. I can only remember 4 occasions when

I located a radio collared fox squirrel in a tree cavity,

compared to hundreds of locations when the squirrels were in leaf


Edwards (1986) believed that litters born in tree cavities

were safer from predators than those born in leaf nests. This is

probably true, and even though nest predation was suspected at

Fort White, there are no indications that the availability of

cavities limits fox squirrels in Florida. Kantola and Humphrey

(1990) observed abundant cavities on their study area, yet they

observed little cavity use. Cavities may be needed at times in

northern areas as a thermal refuge, but Florida winters are mild

and it is unlikely that cavities are needed for warmth. The

conclusion of this is that cavities, or artificial cavities such

as nest boxes, are not a necessary component of fox squirrel

habitat in Florida.

Normally when we think of cavities for a tree squirrel, we

think of above ground cavities in standing trees. Moore (1957)

made a number of unusual observations on his study area, one of

which was of fox squirrels nesting in tree stumps. He found 5

such underground dens. I never saw this behavior, nor did

Kantola and Humphrey (1990), and nor have any other studies with

which I am familiar. It thus seems, based on the evidence, that

underground nesting is not a common event in fox squirrels. This

topic was mentioned because of a current debate underway among

management area biologists over the value of pine stumps for

wildlife in northern Florida. For fox squirrels at least, pine

stumps do not appear to be a limiting factor, and the removal of

the stumps for the turpentine they contain will not impact fox


Food Habits and Habitat Use

There have been no detailed studies of fox squirrel food

habits in northern Florida. However, certain conclusions can be

reached with the data that are available. One conclusion is that

acorns are probably a major component of the diet. Important oak

species include live oak, turkey oak, southern red oak, and

laurel oak. No research has been conducted in xeric flatwoods

habitat on fox squirrels, however, the runner oaks (Q. minima and

Q. pumila) may be an important source of acorns.

The importance of a particular species will vary with its

abundance and the quantity of seeds it produces. Moore (1957)

believed that turkey oak was a major producer of acorns, but

Umber (1975) demonstrated that turkey oak only occasionally

produces large quantities of mast. In an average year in

sandhill habitat, live oak may be more important than turkey oak

(Kantola and Humphrey 1990).

Pine mast is another important food for fox squirrels in

northern Florida. In certain habitat types, such as longleaf

sandhill, longleaf pine seeds are a primary summer food (Moore

1957, Kantola and Humphrey 1990). Fox squirrels will also eat

the seeds of other pines. I have seen them eat seeds from

loblolly, slash, and sand pine. My impressions are that fox

squirrels relish pine seeds, which are an energy rich source of

food (Weigl et al. 1989). However, if other foods are available,

fox squirrels can survive in northern Florida without pine mast.

Mast bearing pines were rare on the Fort White area, and although

fox squirrels ate the pine mast that was available, they

subsisted on other foods in the summer.

Under most conditions, oak and pine seeds appear to be the

staple foods of fox squirrels in northern Florida. Other foods

that may be seasonally or locally important include leaf buds,

oak flowers, row crops, pecans, and wild fruits, such as black


Fox squirrels also ate a mystery food on the Fort White

study area. I often saw fox squirrels eating items which they dug

from the ground. The foods were occasionally acorns, but on a

number of occasions, the foods were not acorns or other nuts. I

was never able to identify the food, but it was darkly pigmented

and appeared to be soft in texture because they ate it with

minimal chewing. My suspicions were that it was the fruiting

body of a subterranean fungi. Weigl et al. (1989) suggested that

fungi may be an important food item for fox squirrels in the

southeastern coastal plain.

Habitat Use and Quality

Fox squirrels in northern Florida are normally associated

with mature longleaf pine forests. As discussed in Chapter 2, my

impressions are that it is not the pines that draw the squirrels,

but it is the structure of the habitat. Fox squirrels are

especially adapted for life in wooded savannahs (Nixon et al.

1984, Weigl et al. 1989). The savannahs occupied by fox

squirrels in Florida are pine dominated, whereas those occupied

in the midwestern United States are hardwood dominated. The

longleaf savannah is the natural habitat of the fox squirrel in

Florida, and still the animal's predominate habitat. Fox

squirrels have adapted to man-made savannahs, such as those found

on the Fort White study area, demonstrating that it is not the

pines but the structure. Longleaf pine forests just happen to be

the most common forests in northern Florida with the required


Fox squirrel studies conducted in northern Florida have

revealed that fox squirrels here occur at low densities and

occupy the largest home ranges determined for the species. In

comparison to Florida, fox squirrel densities in the midwestern

United States were up to 90 times greater than those in Florida

(Table 3-12), and home ranges have been observed there that were

90% smaller than those in Florida (Adams 1976).

Difference in carrying capacity and reproductive potential

between the midwest and Florida can be clearly demonstrated by

comparing data collected on the Fort White study area to that

collected on a study area in Illinois (Hansen et al. 1986). If

we assume a litter frequency of 1/year, an average litter size of

2.5 for both study areas, and use the adult female density

estimates of 77/km2 for Illinois and 2.2/km2 for Fort White, the

annual production of offspring per km2 is 192 for Illinois and

5.5 for Florida.

Differences in fox squirrel abundance between Florida and

the midwest are believed a consequence of differences in the

abundance of hardwood seeds. Midwestern savannahs contain an

assortment of hardwood tree species that produce highly

digestible, energy rich seeds that are easily stored, or cached

for later use (Nixon et al. 1968, Korschgen 1981). The best

seeds in terms of energy and digestibility are hickories (Carva

sp.) and black walnuts (Juglans niger) (Smith and Follmer 1972,

Havera and Smith 1978).

Florida pine savannahs typically contain a low diversity of

mast producing species. Pine seeds are one of the richest foods

produced in the habitat (Weigl et al. 1989), but they are only

available for about 4 months of the year, and they are not

storable. Oaks are the primary hard mast producer in Florida fox

squirrel habitat. Acorns are lower in calories and less

digestible than hickories and walnuts (Havera and Smith 1979).

Acorns also have less storage potential than the other seeds,

which limits the period they are available as a food source.

Smith and Follmer (1972) have shown the nutritional value of

acorns decreases after germination. Acorns of the white oak

group, which includes live oak, tend to germinate soon after

falling, which makes them undesirable for storage. Acorns of the

red oak group, such as turkey oak, have delayed germination,

which would increase their value for caching. However, Florida's

winters are mild, which could lead to quicker germination of

these seeds, thus decreasing the length of time they are

available. These factors relating to seed storage may be the

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