Fox Squirrel Study

Fox SquirrelFox squirrel populations appear to be declining throughout the Southeast. In fact, three of the eight eastern subspecies are afforded some degree of protection due their rarity. The fox squirrel subspecies found at the Jones Ecological Research Center is generally considered to be the Sherman's fox squirrel, the largest tree squirrel in North America. Fox squirrels are an important species within Coastal Plain forests and may be an indicator of quality longleaf pine habitats.

Because little research had been conducted on fox squirrels in the southeastern United States, we initiated a study of the ecology of this species at the Jones Ecological Research Center. The investigation spanned a 2 year period and over 100 fox squirrels were monitored during the study.

Fox and Gray Squirrel Associations Within Minimally Disturbed Longleaf Pine Forests

Fox SquirrelResearch Team: Dr. L. Michael Conner (Associate Scientist), Dr. William K. Michener, Larry Landers

Fox squirrels (Sciurus niger) are an important species in longleaf pine (Pinus palustris) forests. We estimated fox squirrel density within 6 minimally disturbed longleaf pine stands, examined association between fox and gray squirrels (S. carolinensis), and measured habitat variables at fox and gray squirrel capture sites. Fox squirrel density estimates ranged from 12 –19 squirrels/km2 among study areas. Fox squirrel capture sites had higher pine basal area, higher total basal area, higher herbaceous groundcover and lower woody groundcover than other sites. Gray squirrel capture sites had higher hardwood, oak, and total basal areas; lower pine basal area, higher woody groundcover, and less herbaceous groundcover than other sites. A strong negative association between fox and gray squirrel capture sites appeared related to species-specific habitat preferences. Fox squirrel capture sites had higher pine and lower hardwood basal areas than gray squirrel capture sites. Groundcover was more dense at fox squirrel capture sites than at gray squirrel capture sites. Further, herbaceous groundcover, especially wiregrass (Aristida stricta), dominated fox squirrel capture sites, whereas woody groundcover dominated gray squirrel capture sites. Logistic regression models indicated that pine basal area and herbaceous groundcover were positively related to probability of fox squirrel capture, whereas fern groundcover was negatively related to probability of fox squirrel capture. Oak basal area and total basal area were positively related to probability of gray squirrel capture, whereas herbaceous groundcover was negatively related to probability of gray squirrel capture. Oak basal area, total basal area, and herbaceous groundcover best discriminated between fox and gray squirrel capture sites. Prescribed fire retards hardwood encroachment, increases herbaceous groundcover, and thus may be critical to maintaining fox squirrel habitat.

Additional Information:

Conner, L. M., J. L. Landers, and W. K. Michener. 1999. Fox and gray squirrel associations within minimally disturbed longleaf pine forests. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 53:364 ­– 374.

Funded by: The Joseph W. Jones Ecological Research Center

Home Range Sizes of Fox Squirrels in Southwest Georgia

Fox SquirrelResearch Team: Dr. L. Michael Conner (Associate Scientist) and Bruce Plowman (Lead Technician)

Home range size quantifies space needed by an animal in a given area and time. Because fox squirrel (Sciurus niger) home range estimates in the Southeast are rare, I radio-monitored fox squirrels to determine their seasonal and composite (i.e., total duration of monitoring) home range size in southwest Georgia between March 1998 and September 1999. There was no sex by season interaction (P = 0.11). Male seasonal and composite home ranges (35.8±4.4 ha and 37.0±3.6 ha, respectively) were larger (P < 0.001) than female home ranges (seasonal = 13.3±1.5 ha, composite = 21.0+6.3 ha). Seasonal home ranges were largest (34.3 ± 5.9 ha) during March – May of 1998 and smallest (5.9 ± 1.2 ha) during January – February of 1999. Southeastern fox squirrels require more space than midwestern fox squirrels, perhaps a result of patchily distributed and/or temporally variable food supplies. Food abundance and breeding behavior may explain seasonal variation in home range size.

Additional Information:

Conner, L. M. Home range sizes of fox squirrels in southwest Georgia. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 54:400-406.

Funded by: The Joseph W. Jones Ecological Research Center

Survival and Cause-specific Mortality of Adult Fox Squirrels in Southwestern Georgia

Fox SquirrelResearch Team: Dr. L. Michael Conner (Associate Scientist), Ivy Godbois (Research Technician) and Bruce Plowman (Lead Technician)

Survival estimates are important for understanding and managing wildlife populations. I used radiotelemetry to estimate survival and cause-specific mortality of a nonharvested fox squirrel (Sciurus niger) population in southwestern Georgia. Adult fox squirrels (n = 101) were monitored continuously from March 1998 to December 1999. I determined the cause of death to be predation in 7 cases, disease in 5 cases, and unknown in 12 cases. Sex and season-specific mortalities were independent of the cause of mortality; therefore I omitted cause of mortality from subsequent analyses. I did not detect differences in seasonal survival between males and females (P = 0.27) or among seasons (P = 0.52). When sexes were pooled, seasonal survival (±SE) ranged from 0.86 ± 0.07 to 0.92 ± 0.02. Annual survival of males (0.73 ± 0.07) and females (0.66 ± 0.07) was similar (P = 0.60). When sexes were pooled, annual survival was 0.69 ± 0.07. High fox squirrel survivorship, relative to gray squirrels (S. carolinensis), challenges the paradigm that similar strategies should be used to manage harvest of fox squirrels and gray squirrels.

Additional Information:

Conner, L. M. 2001. Survival and cause-specific mortality of adult fox squirrels in southwestern Georgia. Journal of Wildlife Management 65:200-204.

Funded by: The Joseph W. Jones Ecological Research Center

Habitat Associated With Daytime Refugia of Fox Squirrels in a Longleaf Pine

Research Team: Dr. L. Michael Conner (Associate Scientist), Ivy Godbois (Research Technician), and Micah Perkins (Research Technician III)

Fox squirrel (Sciurus niger) populations are declining in many areas of the eastern United States, and habitat loss may be partly responsible for these declines. We measured habitat variables at fox squirrel refuge sites and random sites and used an information theoretic approach to determine the influence of these variables on probability of a site being used for refuge. There was compelling evidence to support tree and stand level habitat variables as important predictors of refuge sites, but little evidence in support of understory variables. Fox squirrels were more likely to use hardwoods than pines (Pinus spp.) for refuge. Tree size (height and dbh) was positively associated with probability of use as was tree density around the refuge site. Percent debris groundcover, the only understory variable of importance, was positively related to probability of use as a refuge site, but the parameter estimate did not convincingly differ from zero. We conclude that large hardwoods within an open-canopy pine matrix are important as fox squirrel refuge sites.

Additional Information:

Conner, L. M., and I. A. Godbois. Habitat associated with daytime refugia of fox squirrels in a longleaf pine forest. American Midland Naturalist. In Press.

Funded by: The Joseph W. Jones Ecological Research Center