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Collier County

BIG CYPRESS FOX SQUIRREL (Sciurus niger avicennia)

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Big Cypress (mangrove) fox squirrel picture
Family: Sciuridae

Order: Rodentia

STATUS: Threatened

DESCRIPTION:
The Big Cypress fox squirrel is distinctly smaller than Sherman's fox squirrel (Sciurus niger shermani). The head plus body average 28 centimeters long versus 32 centimeters for the Sherman's fox squirrel. Like other subspecies of the fox squirrel it has a long, bushy, fox-like tail and it is highly variable in color, ranging from buff to black. The most frequent color phase of this subspecies is buff, with a buff underside and buff basal bands on the tail hairs, white toes, lips, nose, and eartips, a black crown, and an agouti back. Second in frequency is the black phase, all the coat is black except for white lips, nose, and eartips, white or blackish toes, and agouti feet. The least frequent color phase is tan, with a tan underside and tan basal bands of the tail hairs, white lips, nose, and eartips, white to tan limbs, and agouti cheeks, nape, back and sides.

HABITAT AND DISTRIBUTION:
This subspecies is endemic to southwestern Florida, but the species is widespread in eastern and central North America. It occurs in the Immokalee Rise, Big Cypress Swamp, and Devil's Garden area in Collier County. Some areas of this range have become vacated, while many other suitable areas are being altered or becoming isolated through development. The subspecies uses most types of forest occurring in its range. Only the dense interiors of mixed cypress-hardwood strands seem to be avoided, because these are occupied by dense populations of gray squirrels (Sciurus carolinensis). Big Cypress fox squirrels have been reported in cypress swamp, pine flatwood, tropical hammock, hardwood hammock, mangrove swamp, and suburban habitats including golf courses, and residential areas in native vegetation. Big Cypress fox squirrel densities appear to be quite low, and on this basis the subspecies can be considered inherently rare.

LIFE HISTORY AND ECOLOGY:
Platform nests in pines and hardwoods, and moss and stick nests in cypress, tops of cabbage palms, and large clumps of bromeliads have been observed. Cabbage palms and bromeliads seem especially important, because they allow fox squirrels to range over large areas without the need to construct nests on a daily basis. Fox squirrels often strip bark from cypress trees for incorporation into the nest. They are primarily solitary animals, coinhabiting a nest only during the mating season.

Mating chases and cheek rubbing are a large proportion of social interactions and are observed most frequently during the mating season (May to August). Vocalizing is common during this time, but takes place infrequently outside of mating season. Litters of 2 to 4 young are produced per year. Gestation period is approximately 45 days. The young are weaned at about 2 or 3 months. At one year of age females breed. Fox squirrels have been known to live 10 years or more.

Foraging is the most frequent activity. Slash pine seems to be a primary food source for Big Cypress fox squirrels. Individuals have been observed feeding on microstrobili (male cones) in winter, while seeds from magastrobili (female cones) form the bulk of the diet during the summer rainy season. Mega- and microstrobili from cypress are consumed in autumn and early winter, respectively. Cabbage palm fruits, bromeliad buds, and acorns also are important food items. Fox squirrels on golf courses have been observed eating all the above, plus, on a regular basis, queen palm fruits, fig fruits, and fungi. They are known to cache fruits and acorns when they are ground foraging. During wet seasons and when there is a lack of understory and closed canopy, fox squirrels may be observed traveling long distances in order to obtain sufficient food resources.

Inactive time varies seasonally, peaking in the humid summer months. Diurnal inactivity may last from a few minutes between foraging events to several hours during extreme weather. During warmer weather fox squirrels often lie draped over a branch or palm frond, with legs dangling on opposite sides. Animals resting this way often remain motionless even when disturbances are present. During cooler weather, fox squirrels sit-up on branches, covering their backs with their tails.

BASIS OF STATUS CLASSIFICATION:
Early reports considered habitat destruction to endanger the Big Cypress fox squirrel. While public acquisition of large parcels of land in the subspecies' range has reduced the majority of this threat, large-scale residential and commercial development of pine flatwoods west of Big Cypress National Preserve, conversion of forested wetlands to citrus north of Big Cypress National Preserve, and expansion of Interstate 75 (along with increased local traffic on State Road 29) still pose serious threats to habitat quality and quantity. This loss of habitat will make the distribution smaller and will further isolate remaining populations of squirrels. For instance, some of the populations at golf courses in Naples now are completely isolated from source and dispersal areas by urban growth that has claimed native habitats formerly connecting the golf courses.

Ground fires are valuable to the habitats of Big Cypress fox squirrels because they retard plant succession. Suppression of wild fires has been the historical norm in the Big Cypress Swamp. Consequently, many pinelands in the Big Cypress National Preserve currently have a dense understory of palmetto, which is considered an undesirable habitat for fox squirrels. Future fire management plans within the Preserve call for an increase in prescribed burning. In order to provide a more open understory and improved seed bed for slash pine seedlings, pinelands are expected to be burned on a 5 to 7 year rotation. Similarily, light grazing maintains the sparse ground cover favored by fox squirrels; it also probably contributes to the value of hardwood hammock habitat. Golf courses may represent an important residential habitat and may provide suitable resources, provided that it is maintained and it is protected from poaching and dogs.

Since 1990, the Big Cypress fox squirrel has been listed as threatened by the Florida Game and Fresh Water Fish Commission and it currently under review for possible listing by the U.S. Fish and Wildlife Service.

HABITAT GUIDELINES:
Preferred Big Cypress fox squirrel habitat consists of pine flatwood, cypress swamp, and mixed hardwood-pine forest, with low ground cover. Big Cypress fox squirrels have been known to utilize several habitat types for foraging, including golf courses, pastures with scattered trees and rural residential areas with wooded lots. The literature consistently suggests that large amounts of suitable habitat are necessary to maintain a viable population. One pair requires 25 acres of suitable habitat for foraging and at least 600 acres is necessary to maintain a viable population.

In determining whether any given area meets the minimum acreage necessary to maintain a viable population of Big Cypress fox squirrels, all contiguous, potentially utilized habitats both natural and ruderal, should be considered. Heavily used roads define the edge of any potential habitat.

RECOMMENDATIONS:
Existing lands dedicated to conservation should be consolidated and/or enlarged, including the planned acquisitions of Big Cypress National Preserve, Fakahatchee Strand State Preserve, South Golden Gate Estates, Belle Meade, and Corkscrew Regional Ecosystem Watershed additions. Strong protection from poaching should be provided. A study of habitat use and diet would help management agencies protect the populations under their care. The relationship of burning to habitat use by fox squirrel should be documented in the course of accelerated fire management of the Big Cypress National Preserve. Further study of the populations on golf courses and on adjacent undeveloped lands would help clarify fox squirrel use of available long-term habitat.

REFERENCES:
Humphrey, S.R. and P.G.R. Jodice. 1992. Big Cypress fox squirrel. Pp. 224-233. In S.R. Humphrey (ed.), Rare and Endangered Biota of Florida. Mammals. University Presses of Florida, Gainesville, FL.

Jodice, P.G.R. 1993. Movement patterns of translocated Big Cypress fox squirrels (Sciurus niger avicennia). Florida Scientist 56:1-6.

Jodice, P.G.R. and S.R. Humphrey. 1992. Activity and diet of an urban population of Big Cypress fox squirrel. Journal of Wildlife Management 56:685-692.

Williams, K.S. and S.R. Humphrey. 1979. Distribution and status of the endangered big cypress fox squirrel (Sciurus niger avicennia) in Florida. Florida Scientist 42:201-205.

Content updated Date March 4, 2005