Sherman's Fox Squirrel at White Oak Plantation

Description of White Oak Plantation

White Oak Plantation is a privately owned, funded and operated nature and conservation center in Northeast Florida. Five Hundred acres of the plantation are dedicated to White Oak Conservation Center where 60 threatened animal species are preserved. Many of these exotic Species at White Oak Conservation Center are associated with the Species Survival Plans coordinated by the American Zoo and Aquarium Association. Using the knowledge gained by studies on these animals, Species Survival Plans are formulated and refined to aid in the preservation of these unusual species.

Another 6500 acres of pine forest, wetlands and riparian habitat comprise the balance of White Oak Plantation. White Oak Plantation straddles the St. Marys River so part of the wooded area is found in Southeastern Georgia. Habitat for Sherman's Fox Squirrel (Sciurus niger shermani) occurs in these wooded areas of White Oak Plantation.

Acknowledgments

We gratefully acknowledge the support of White Oak Plantation during this project. White Oak Plantation provided the opportunity for us to work on Sherman's fox squirrel in a natural setting. They provided assistance in determining our initial sampling locations, provided a laboratory where we could work, and especially lunch on those really long days of field work. A special thanks goes to Pat Rider, of White Oak Plantation, who gave generously of his time and knowledge of the plantation to facilitate this exciting project.

We especially wish to thank Mr. John Lukas, Director of White Oak Plantation, who extended the invitation to Dr. Ken Hoover to conduct research at White Oak Plantation. We know that only through his generous support was this project possible.

We also acknowledge the ongoing support of Jacksonville University and the Department of Biology and Marine Science for providing the vehicles and sampling equipment needed for this project.

Current Status

Although the total population of Sherman's Fox Squirrel (Sciurus niger shermani) is not known exactly, research suggests that their numbers are declining due to a rapid decrease in their primary habitat (Weigl et al. 1989). As a result, the state of Florida has listed the fox squirrel as a "Species of Special Concern" (Logan 1997) while the U.S. Fish and Wildlife Service completes its evaluation determining whether or not the species should be listed under the Endangered Species Act.

In Florida, impacts of widespread development projects, hunting, and the establishment of pine monocultures (tree farms) have resulted in the loss or conversion of mature, fire-maintained pine-turkey oak sandhills and flatwoods, the fox squirrel's primary habitat. However, the fox squirrel thrives in isolated populations throughout Central and Northern Florida into Southeastern Georgia.

The modification of the fox squirrel's primary habitat has resulted in decreased availability of the primary food sources upon which the species thrives (pine seeds, acorns). Pine plantations consist primarily of young trees which produce few seeds. Protection of these forests from the wildfires allows understory vegetation, such as gallberry (Ilex glabra), to thrive. Dense understory inhibits movement of the squirrels and competes with the tree species that provide acorns and seeds for the fox squirrel's diet. Previous research supports the need for habitat management by inducing controlled burns within pine sandhill communities to restore the fragmented populations of fox squirrel throughout Central and Northern Florida and Southeast Georgia (Weigl et al. 1989).

Unlike the fox squirrel, the eastern gray squirrel (Sciurus carolinensis) appears to thrive in urban areas and habitats altered by human activity. Previous research indicates that the success of the gray squirrel may be affiliated with its habitat preference of hardwood hammocks (Edwards et al. 1998, Edwards and Guynn 1995). The fox squirrel, however, prefers slash pine-turkey oak associations of sandhill communities. Previous studies have also shown that the fox squirrel nests in fewer tree species than the gray squirrel. While hardwood hammocks provide a variety of oak trees for gray squirrel nesting and feeding, tall mature pines allow the fox squirrel to build their nests up higher in the trees, a distinguishing feature between the two species. This statistic may help explain why the fox squirrel population has decreased and become fragmented, while the gray squirrel species has managed to survive in areas impacted by human development.

Natural History

Sherman's Fox Squirrel inhabits longleaf pine (Pinus palustris) and turkey oak (Quercus laevis) associations in sandhill habitat, and flatwood forest. It is known to feed on mature pine seeds during the summer months and turkey oak acorns when they are available for the rest of the year. Turkey oak mast production is unreliable and therefore is not a constant food source for wildlife species including fox squirrels. Sherman's fox squirrel is an opportunistic feeder on a wide variety of mast and is known to increase its daily range to feed on mast from neighboring hardwood communities such as live oak in years of reduced mast production (especially turkey oak) in its habitat (Kantola 1986). It is also known to feed in granaries and fields in agricultural areas (Sheperd and Swihart 1995) and to raid bird feeders when they are available. Sherman's fox squirrel may find a more reliable supply of food in ecotones of longleaf pine-turkey oak community with live oak (Quercus virginiana) or other hardwood forest where food is available from a greater number of tree species (Kantola and Humphrey 1990).

Fox squirrels are known to construct leaf nests in many tree species including turkey oak, longleaf pine, live oak, laurel oak (Quercus hemisphaerica), slash pine (Pinus elliottii) and to utilize tree cavities in turkey oak snags especially in the northern parts of its range during inclement weather (Weigl et al. 1989). Several squirrels are known to inhabit a single leaf nest at one time (Koprowski 1996). Although they are known to move from leaf nest to leaf nest, and to seek out suitable habitat and food (Jodice 1993 and Bendel and Therres 1994) the

density of leaf nests in a habitat should allow calculation of density of squirrels if a correction factor can be generated.

Tree cavities are known to be of lesser importance to fox squirrels in Florida than they are in the more northerly parts of their distribution (Moore 1957, Kantola 1986). Nests on our study site were constructed of pine needles, sticks, grasses, palmetto frond fibers, and bark stripped from cypress trees as observed by Jodice (1990).

Sherman's fox squirrel is known to host a variety of ectoparasites (Coyner et al. 1996) in Florida as do other fox squirrels (Mennelli et al. 1993). This requires that special care and handling techniques should be employed during any direct contact with these animals.

Statement of the Problem

The fox squirrel is a declining species in the Southeastern United States and Sherman's Fox Squirrel (Sciurus niger shermani) is listed as a Species of Special Concern by the Florida Game and Freshwater Fish Commission (Logan 1997). Sherman's Fox Squirrel favors mature pine-hardwood associations with an open understory. This habitat type was historically maintained by frequent naturally occuring fires that burned throughout the Southeastern United States. Natural fires have been discouraged for decades and much of the habitat that once favored the fox squirrel has been allowed to proceed beyond the fire-maintained mature pine-hardwood association to a seral stage dominated by hardwood species which favor the gray squirrel (Sciurus carolinensis). Additional habitat is being replaced by urbanization and agriculture throughout the Southeastern U. S.

As habitat for Sherman's Fox Squirrel is increasingly eliminated or altered by an ever-expanding human population in Northern Florida, proper habitat management for the remaining populations will become increasingly important. Habitat management to favor the fox squirrel in Northern Florida will include prescribed burning on a regular schedule to favor mature pine forests with an open under story.

Determination of precise habitat parameters preferred by the fox squirrel has received little attention. This study was designed to elucidate habitat parameters which favor Sherman's Fox Squirrel at White Oak Plantation in Northeast Florida.

Results

Data analysis included application of a Single-Factor Parametric Analysis of Variance (ANOVA) test. We determined significance at the 99% confidence level (Cox, 1996) and a P-value less than 0.05.

The results of the ANOVA for the Gilman Road sample area (Area A) were: Critical F = 0.01 for 1,26 DF = 8.096. These data showed that increased distance from the feeding station contributed significantly to decreased squirrel nest density (F = 115.2746, P = 4.73E-11). Increased DBH, nest height, and tree height positively influenced the density of the nests (Table 1). The results of ANOVA for the Hadley road sample area were: Critical F = 0.01 for 1,42 DF = 7.5625. These data also showed that increased distance from the feeding station contributed significantly to decreased nest density ( F = 39.59877, P = 1.51E-7). Increased nest height, tree height, and DBH also positively influenced the density of squirrel nests in this sample area (Table 2).

Density vs. Distance from feeding station for Gilman Rd. Two transects were sampled immediately West of the feeding station (Area A). Additional transects should be sampled to complete this analysis. No correlation between density and proximity to the feeding station was shown because all samples were close to the feeding station and all samples contained several nests.

Density vs. Distance from feeding station for Hadley Rd. Twelve transects were sampled; transects 1-6 were on the west side and transects 7-12 were on the east side of Hadley Rd. A feeding station was located between transects 5

and 6. The data show a strong positive correlation between proximity to the feeding station and squirrel nest density (Figure 1).

Single Factor ANOVA Results. F-value exceeding critical F indicates the factor contributes to squirrel nest density. Low P-values indicate increased confidence in rejecting the null hypothesis.

Table 1: Gilman Road

Critical F (0.01) for l, 42 DF F P ^-value

Table 2: Hadley Road

Critical F (0.01) for l, 26 DF F P ^- value

Figure 1: Density vs. Distance for Hadley Rd. Sampling Area