Index of Species Information

WILDLIFE SPECIES:  Sciurus niger

Introductory

WILDLIFE SPECIES: Sciurus niger
AUTHORSHIP AND CITATION : Tesky, Julie L. 1993. Sciurus niger. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].
ABBREVIATION : SCNI COMMON NAMES : eastern fox squirrel stump-eared squirrel cat squirrel TAXONOMY : The currently recognized scientific name for the eastern fox squirrel is Sciurus niger L. Ten subspecies are recognized: four eastern, four mid-western, and two isolated subspecies [5,23]. Eastern fox squirrels are very large (2.4 to 3.2 pounds [900-1200 g]); gray, agouti, or black; and often have black markings on the head and white nose, ears, and paws [23]. Eastern fox squirrel subspecies are listed below: S. niger ssp. cinerea (Delmarva fox squirrel) S. niger ssp. niger S. niger ssp. shermani (Sherman's fox squirrel) S. niger ssp. bachmani Mid-western fox squirrels are smaller (1.6 to 2.4 pounds [600-900 g]) and reddish. Subspecies are as follows [23]: S. niger ssp. rufiventer S. niger ssp. vulpinus S. niger ssp. ludovicianus S. niger ssp. limitis A third group is composed of two small, variably colored, and isolated subspecies: S. n. ssp. avicennia Howell (Big Cypress fox squirrel) and S. n. ssp. ubauratus [23,24]. While eastern and mid-western subspecies are now widely separated in the Atlantic States, considerable gene flow is possible in the Gulf Region [23]. Where appropriate, the Delmarva fox squirrel will be highlighted in this report. ORDER : Rodentia CLASS : Mammal FEDERAL LEGAL STATUS : The Delmarva fox squirrel is Endangered [21]. OTHER STATUS : Information on state- and province-level protection status of animals in the United States and Canada is available at NatureServe, although recent changes in status may not be included.

WILDLIFE DISTRIBUTION AND OCCURRENCE

WILDLIFE SPECIES: Sciurus niger
GENERAL DISTRIBUTION : Eastern fox squirrels occur along the Atlantic and Gulf coastal plains from the Delmarva Peninsula in Maryland south to central Florida and west to the Mississippi River floodplain [23]. Delmarva fox squirrels occur in only four Eastern Shore counties in Maryland and one location in Accomac County, Virginia. This subspecies was formerly found in southeastern Pennsylvania, Delaware, New Jersey, and probably the Virginia portion of the Delmarva Peninsula [2]. S. n. ssp. avicennia occurs in southern Florida; S. n. ssp. subauratus occurs on the Mississippi River floodplain [23]. The range of mid-western fox squirrels extends from the valleys of south-central Pennsylvania south through the Appalachian Mountains and the uplands of the Gulf States and west to the prairies and more recently to the front range of the Rocky Mountains [23]. Mid-western fox squirrels have also extended their range into northern Michigan and westward to North Dakota, eastern Colorado, and Texas. In northern Mexico, fox squirrels occur in the states of Coahuila, Nuevo Leon, and Tamaulipas [16]. Eastern fox squirrels have been introduced into many portions of the West. Introduced populations exist in California, Oregon, Washington, Idaho, and Montana [1,5,12,16]. ECOSYSTEMS : FRES10 White-red-jack pine FRES12 Longleaf-slash pine FRES13 Loblolly-shortleaf pine FRES14 Oak-pine FRES15 Oak-hickory FRES16 Oak-gum-cypress FRES17 Elm-ash-cottonwood FRES18 Maple-beech-birch FRES19 Aspen-birch FRES28 Western hardwoods FRES41 Wet grasslands STATES :
AL AR CA CO CT DE FL GA ID IL
IN IA KS KY LA MD MI MN MS MO
MT NE NJ NM NC ND OH OK OR PA
SC SD TN TX VA WA WI ON MEXICO
BLM PHYSIOGRAPHIC REGIONS : 1 Northern Pacific Border 2 Cascade Mountains 3 Southern Pacific Border 4 Sierra Mountains 5 Columbia Plateau 8 Northern Rocky Mountains 11 Southern Rocky Mountains 13 Rocky Mountain Piedmont 14 Great Plains 16 Upper Missouri Basin and Broken Lands KUCHLER PLANT ASSOCIATIONS : K025 Alder - ash forest K026 Oregon oakwoods K030 California oakwoods K080 Marl - everglades K090 Live oak - sea oats K091 Cypress savanna K092 Everglades K098 Northern floodplain forest K099 Maple - basswood forest K100 Oak - hickory forest K101 Elm - ash forest K102 Beech - maple forest K103 Mixed mesophytic forest K104 Appalachian oak forest K105 Mangrove K106 Northern hardwoods K108 Northern hardwoods - spruce forest K110 Northeastern oak - pine forest K111 Oak - hickory - pine forest K112 Southern mixed forest K113 Southern floodplain forest K115 Sand pine scrub K116 Subtropical pine forest SAF COVER TYPES : 14 Northern pin oak 16 Aspen 17 Pin cherry 18 Paper birch 19 Gray birch - red maple 20 White pine - northern red oak - red maple 24 Hemlock - yellow birch 25 Sugar maple - beech - yellow birch 26 Sugar maple - basswood 27 Sugar maple 28 Black cherry - maple 39 Black ash - American elm - red maple 40 Post oak - blackjack oak 42 Bur oak 43 Bear oak 44 Chestnut oak 51 White pine - chestnut oak 52 White oak - black oak - northern red oak 53 White oak 55 Northern red oak 59 Yellow-poplar - white oak - northern red oak 60 Beech - sugar maple 61 River birch - sycamore 62 Silver maple - American elm 65 Pin oak - sweetgum 71 Longleaf pine - scrub oak 70 Longleaf pine 76 Shortleaf pine - oak 78 Virginia pine - oak 80 Loblolly pine - shortleaf pine 81 Loblolly pine 82 Loblolly pine - hardwood 85 Slash pine - hardwood 87 Sweet gum - yellow-poplar 88 Willow oak - water oak - diamondleaf oak 89 Live oak 91 Swamp chestnut oak - cherrybark oak 92 Sweetgum - willow oak 93 Sugarberry - American elm - green ash 94 Sycamore - sweetgum - American elm 95 Black willow 96 Overcup oak - water hickory 100 Pondcypress 101 Baldcypress 105 Tropical hardwoods 108 Red maple 109 Hawthorn 110 Black oak 203 Balsam poplar 217 Aspen 221 Red alder 222 Black cottonwood - willow 233 Oregon white oak 235 Cottonwood - willow 236 Bur oak 241 Western live oak 246 California black oak 249 Canyon live oak 250 Blue oak - Digger pine 252 Paper birch 255 California coast live oak SRM (RANGELAND) COVER TYPES : NO-ENTRY PLANT COMMUNITIES : Eastern fox squirrels inhabit a variety of open hardwood, hardwood-pine, and swamp communities depending on geographic location. The Delmarva fox squirrel in Maryland prefers mature stands of hardwoods such as oaks (Quercus spp.), hickories (Carya spp.), walnuts (Juglans spp.), and beech (Fagus spp.) that are interspersed with mature loblolly pine (Pinus taeda). Delmarva fox squirrels are also found in deciduous swamps close to pine woodlands [2,5,9]. In southern Florida, fox squirrels occupy pine hammocks and range into mangrove (Rhizophora spp.) and cypress (Cupressus spp.) stands. In coastal regions of northern Florida, Georgia, and the Carolinas, eastern fox squirrels are most often found in longleaf pine (Pinus palustris)/turkey oak (Quercus laevis) habitats [5]. In Alabama, eastern fox squirrels occur along watercourses, on the shores of bayous and in deep bald cypress (Taxodium distichum) swamps, and in upland dry pine stands [5]. In eastern Texas, eastern fox squirrels inhabit oak-hickory ridges. Farther west, they occupy both timbered river bottoms and oak ridges. In the central portions of Oklahoma and Iowa, easter4n fox squirrels are most abundant in the transition belt between prairie and oak woodland. Here, eastern fox squirrels also occupy upland hardwood forests, dense timber along streams and rivers, and open pecan (Carya pecan) orchards [5]. Primary eastern fox squirrel habitat in Wisconsin is oak-hickory woodlots with oak, swamp hardwoods, and mixed upland hardwoods [5].

BIOLOGICAL DATA AND HABITAT REQUIREMENTS

WILDLIFE SPECIES: Sciurus niger
TIMING OF MAJOR LIFE HISTORY EVENTS : Breeding season - Female eastern fox squirrels come into estrus in mid-December or early January and again in June. Eastern fox squirrels normally produce two litters a year [3,5]. However, yearling females may produce only one litter, and poor food conditions may prevent some adult females from breeding [5]. Breeding age - Females become sexually mature at 10 to 11 months of age. They usually produce their first litter when they are 1 year old [5]. Gestation/litter size - The gestation period of eastern fox squirrels is 44 to 45 days. Earliest litters appear in late January; most births occur in mid-March and July [5]. The average litter size is three, but litter size can vary according to season and food conditions [5]. Development of young - Tree squirrels develop slowly compared to other rodents. Eyes open when eastern fox squirrels are 4 to 5 weeks old, and ears open at 6 weeks. Eastern fox squirrels are weaned between 8 and 10 weeks but may not be self-supporting until 12 weeks [5,16]. Juveniles usually disperse in September or October, but they may den together or with their mother the first winter [3,22]. Longevity - Eastern fox squirrels generally live up to 6 years in the wild but have survived 13 years in captivity [5,16]. PREFERRED HABITAT : Eastern fox squirrels are most abundant in open forest stands with little understory vegetation; they are not found in stands with dense undergrowth. Ideal habitat is small stands of large trees interspersed with agricultural land [1,9]. The size and spacing of pines and oaks are among the important features of eastern fox squirrel habitat. The actual species of pines and oaks themselves may not always be a major consideration in defining eastern fox squirrel habitat [23]. Eastern fox squirrels are often observed foraging on the ground several hundred meters from the nearest woodlot. Eastern fox squirrels also commonly occupy forest edge habitat [6]. In general, the woodland habitats occupied by the Delmarva fox squirrel are similar to those occupied by other subspecies of eastern fox squirrels [6]. The Delmarva fox squirrel habitat consists primarily of relatively small stands of mature mixed hardwoods and pines that have relatively closed canopies, open understories, and a high proportion of forest edge. Occupied areas include both groves of trees along streams and bays and small woodlots near agricultural fields. In some areas, particularly in southern Dorchester County, Maryland, occupied habitat includes areas dominated by mature loblolly pine located adjacent to marshes and tidal streams. Nest - Eastern fox squirrels have two types of shelters: leaf nests and tree dens. They may have two tree cavity homes or a tree cavity and a leaf nest. Tree dens are preferred over leaf nests during the winter and for raising young. When den trees are scarce, leaf nests are used year-round [3,16]. Leaf nests are built during the summer months in forks of deciduous trees about 30 feet (9 m) above the ground. Eastern fox squirrels use natural cavities and crotches (forked branches of a tree) as tree dens [3]. Den trees in Ohio had an average d.b.h. of 21.2 inches (53 cm) and were an average of 58.6 yards (52.7 m) from the nearest woodland border. Eighty-eight percent of den trees in eastern Texas had an average d.b.h. of 12 inches (30 cm) or more [1]. Dens are usually 6 inches (15.2 cm) wide and 14 to 16 (35-41 cm) inches deep. Den openings are generally circular and about 2.9 to 3.7 inches (7.3-9.4 cm). Eastern fox squirrels may make their own den in a hollow tree by cutting through the interior; however, they generally use natural cavities or cavities created by northern flickers (Colaptes auratus) or redheaded woodpeckers (Melanerpes erythrocephalus). Crow nests have also been used by eastern fox squirrels [16]. COVER REQUIREMENTS : Eastern fox squirrels use leaf nests or tree cavities for shelter and litter rearing [1]. Forest stands dominated by mature to over mature trees provide cavities and a sufficient number of sites for leaf nests to meet the cover requirements. Overstory trees with an average d.b.h. of 15 inches (38.1 cm) or more generally provide adequate cover and reproductive habitat. Optimum tree canopy closure for eastern fox squirrels is from 20 to 60 percent. Optimum conditions understory closure occur when the shrub-crown closure is 30 percent or less [1]. FOOD HABITS : Food habits of eastern fox squirrels depend largely on geographic location [5]. In general, eastern fox squirrel foods include mast, tree buds, insects, tubers, bulbs, roots, bird eggs, seeds of pines and spring-fruiting trees, and fungi. Agricultural crops such as corn, soybeans, oats, wheat, and fruit are also eaten [1,5,16,23]. Mast eaten by eastern fox squirrels commonly includes turkey oak, southern red oak (Q. falcata), blackjack oak (Q. marilandica), bluejack oak (Q. incana), post oak (Q. stellata), and live oak (Q. virginiana) [23]. In Illinois, eastern fox squirrels rely heavily on hickories from late August through September. Pecans, black walnuts (Juglans nigra), osage orange (Maclura pomifera) fruits, and corn are also important fall foods. In early spring, elm buds and seeds are the most important food. In May and June, mulberries (Morus spp.) are heavily utilized. By early summer, corn in the milk stage becomes a primary food [5]. During the winter in Kansas, osage orange is a staple item supplemented with seeds of the Kentucky coffee tree (Gymnocladus dioicus) and honey locust (Gleditsia triacanthus), corn, wheat, eastern cottonwood (Populus deltoides var. deltoides) bark, ash seeds, and eastern redcedar (Juniperus virginianus) berries. In the spring, eastern fox squirrels feed primarily on buds of elm, maple, and oaks but also on newly sprouting leaves and insect larvae [5]. Eastern fox squirrels in Ohio prefer hickory nuts, acorns, corn, and black walnuts. The squirrels are absent where two or more of these mast trees are missing. Eastern fox squirrels also eat buckeyes, seeds and buds of maple and elm, hazelnuts (Corylus spp.), blackberries (Rubus spp.), and tree bark. In March, they feed mainly on buds and seeds of elm, maple, and willow. In Ohio, eastern fox squirrels have the following order of food preference: white oak (Quercus alba) acorns, black oak (Q. velutina) acorns, red oak (Q. rubra) acorns, walnuts, and corn [5]. In eastern Texas, eastern fox squirrels prefer the acorns of bluejack oak, southern red oak (Q. falcata), and overcup oak (Q. lyrata). The least preferred foods are acorns of swamp chestnut oak (Q. michauxii) and overcup oak. In California, eastern fox squirrels feed on English walnuts (J. regia), oranges, avocados, strawberries, and tomatoes. In midwinter, they feed on eucalyptus seeds [5]. In Michigan, eastern fox squirrels feed on a variety of foods throughout the year. Spring foods are mainly tree buds and flowers, insects, bird eggs, and seeds of red maple (Acer rubrum), silver maple (A. saccharinum), and elms. Summer foods include a variety of berries, plum and cherry pits, fruits of basswood (Tilia americana), fruits of box elder (Acer negundo), black oak acorns, hickory nuts, seeds of sugar (A. saccharum) and black maple (A. nigrum), grains, insects, and unripe corn. Fall foods consist mainly of acorns, hickory nuts, beechnuts, walnuts, butternuts (J. cinerea), and hazelnuts. Caches of acorns and hickory nuts are heavily used in winter [5]. PREDATORS : Relatively few natural predators can regularly capture adult eastern fox squirrels. Of these predators, most only take eastern fox squirrels opportunistically [23]. Eastern fox squirrel predators include: bobcats (Felis rufus), foxes (Vulpes spp. and Urocyon spp.), red-tailed hawks (Buteo jamaicensis), red-shouldered hawks (Buteo lineatus), great-horned owls (Bubo virginianus), barred owls (Strix varia), and dogs (Canidae) [3,5,23]. Nestlings and young eastern fox squirrels are particularly vulnerable to climbing predators such as raccoons (Procyon lotor), opossums (Didelphis virginiana), rat snakes (Elaphe obsoleta), and pine snakes (Pituophis melanoleucus) [23]. In those states where eastern fox squirrels are not protected, they are considered a game animal [5,23]. Eastern fox squirrels are hunted more for trophy than for food [23]. Overharvest by hunting has been reported from small woodlots and public shooting areas in Ohio, Michigan, and Indiana [5]. MANAGEMENT CONSIDERATIONS : The range of eastern fox squirrels in the the eastern states has been greatly reduced in the past 100 years [5]. Habitat reduction is one cause. The Coastal Plain of North Carolina and other southern states is undergoing rapid deforestation and forest modification due to accelerated residential and agricultural development, and intensive management techniques in commercial forests [23]. Another major cause of eastern fox squirrel population decline is mange mite (Cnemidoptes sp.) along with severe winter weather [5]. One of the primary reasons for the decline of the endangered Delmarva fox squirrel is timber harvest. As large trees are removed so are much of the areas that provide the Delmarva fox squirrel with an open understory habitat. With loss of habitat, this subspecies is forced to compete with gray squirrels (Sciurus carolinensis) for food and nesting resources. Logging practices that include harvesting all the big hardwoods and replacing them with stands of pure loblolly pine are also detrimental to Delmarva fox squirrels, since stands of pure species do not provide good fox squirrel habitat [19]. In addition, the effects of timber harvest prohibit eastern fox squirrel habitat from developing. At the point where trees become of a salable size, they are not large enough to provide sufficient food and den sites for squirrel utilization [19]. Habitat can be improved for eastern fox squirrels by selective cutting to encourage nut-bearing trees and other food species; planting corn and soybeans; leaving overmature and large-crowned trees; and opening up the forest understory by burning or light grazing [5]. Maintenance of wooded fencerows and breaking up forests into small, 5- to 10-acre (2-4 ha) woodlots of irregular shapes also would promote eastern fox squirrel populations [5]. In cut-over areas where all den trees have been removed, den boxes can be used to supplement natural den trees. Den boxes are very useful on prairies and young woodlots where there is a shortage of natural cavities [20]. Use of artificial den boxes is an important part of the recovery plan for the Delmarva eastern fox squirrel [9].

FIRE EFFECTS AND USE

WILDLIFE SPECIES: Sciurus niger
DIRECT FIRE EFFECTS ON ANIMALS : Eastern fox squirrels would probably not be able to escape fast-moving fires [15]. However, they could probably easily escape low-severity ground fires. Kirkpatrick and Mosby [11] found no evidence that prescribed burning caused significant direct mortality among eastern fox squirrels. Wildfires could destroy leaf nests, nest trees, and eastern fox squirrel nestlings. However, cavities used for denning and leaf nests are usually above the impact zone of prescribed fires [11]. HABITAT RELATED FIRE EFFECTS : Fire often has a positive effect on eastern fox squirrel habitat. Fire maintains the pine-oak habitat preferred by eastern fox squirrels and has a direct effect on eastern fox squirrel foods. Under presettlement conditions longleaf pine savannas (preferred eastern fox squirrel habitat) may have burned at average intervals of 3 to 5 years, usually between April and October. The open stands produced by fire result in better pine cone and mast production. Pines and oaks growing in the open receive more light, maintain more branches at lower levels, and produce heavier crops of cones and nuts [23]. Additionally, nutrient availability and the enhanced vigor of burned pine forest are associated with larger crops of fungi. which are also important eastern fox squirrel foods [23]. A lush, grassy understory maintained by fire is important as protective cover [15]. Fire has probably been a determining factor in the niche separation between gray and eastern fox squirrels on the Coastal Plain. Both exist in mixed pine-oak forests and feed heavily on acorns, but the more competitive gray squirrel dominates where the overlap of oak crowns allows tree-to-tree travel throughout the canopy. Eastern fox squirrels are more abundant where patches of oaks comprise less than 30 percent of pine-hardwood stands and do best in fire-type pine forests with scattered hardwood inclusions [15]. Fire could be a deciding factor in determining the availability of suitable habitat and resources for one or the other species [23]. Fire can also have a negative effect on eastern fox squirrel habitat. Low-intensity ground fire may destroy acorns in the forest duff [15]. FIRE USE : Prescribed fire can be used to maintain eastern fox squirrel habitat. Prescribed burning at 2- to 5-year intervals can be beneficial to eastern fox squirrels by maintaining an open understory and better foraging habitat [11]. According to Humphrey [24], ground fires are valuable in maintaining habitats of Big Cypress fox squirrels. In the habitat of this subspecies, future fire management plans call for an increase in prescribed burning to 50,000 acres a year. Pinelands are expected to be burned on a 5- to 7-year rotation [24].

REFERENCES

WILDLIFE SPECIES: Sciurus niger
REFERENCES : 1. Allen, A. W. 1982. Habitat suitability index models: fox squirrel. FWS/OBS-82/10.18. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. 11 p. [21083] 2. U.S. Department of the Interior, Fish and Wildlife Service. 1979. Restoration of Demarva fox squirrel planned. Endangered Species Technical Bulletin. 4(12): 6. [25176] 3. Banfield, A. W. F. 1974. The mammals of Canada. Toronto, ON: University of Toronto Press. 438 p. [21084] 4. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. [434] 5. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. [21085] 6. Dueser, Raymond D.; Dooley, James L., Jr.; Taylor, Gary J. 1988. Habitat structure, forest composition and landscape dimensions as components of habitat suitability for the Delmarva fox squirrel. In: Management of amphibians, reptiles, and small mammals in North America: Proceedings of the symposium; 1988 July 19-21; Flagstaff, AZ. Gen. Tech. Rep. RM-166. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 414-421. [21086] 7. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905] 8. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; [and others]. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998] 9. Gilley, Susan. 1982. The non-game update: the Delmarva fox squirrel; making a comeback?. Virginia Wildlife. 43(12): 24-25. [3463] 10. Kantola, Angela Torres; Humphrey, Stephen R. 1990. Habitat use by Sherman's fox squirrel (Sciurus niger shermani) in Florida. Journal of Mammalogy. 71(3): 411-419. [26449] 11. Kirkpatrick, Roy L.; Mosby, Henry S. 1981. Effect of prescribed burning on tree squirrels. In: Wood, Gene W., ed. Prescribed fire and wildlife in southern forests: Proceedings of a symposium; 1981 April 6-8; Myrtle Beach, SC. Georgetown, SC: Clemson University, Belle W. Baruch Forest Science Institute: 99-101. [14815] 12. Knapp, Stephen J.; Swenson, Jon E. 1986. New range records for the fox squirrel in the Yellowstone River drainage, Montana. Prairie Naturalist. 18(2): 128. [26450] 13. Kraus, Kent E.; Smith, Christopher C. 1987. Fox squirrel use of prairie habitats in relation to winter food supply and vegetation density. Prairie Naturalist. 19(2): 115-120. [150] 14. Kuchler, A. W. 1964. Manual to accompany the map of potential vegetation of the conterminous United States. Special Publication No. 36. New York: American Geographical Society. 77 p. [1384] 15. Landers, J. Larry. 1987. Prescribed burning for managing wildlife in southeastern pine forests. In: Dickson, James G.; Maughan, O. Eugene, eds. Managing southern forests for wildlife and fish: a proceedings; [Date of conference unknown]; [Location of conference unknown]. Gen. Tech. Rep. SO-65. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station: 19-27. [11562] 16. MacClintock, Dorcas. 1970. Squirrels of North America. New York: Litton Educational Publishing, Inc. 184 p. [21087] 17. Ofcarcik, R. P.; Burns, E. E.; Teer, J. G. 1973. Acceptance of selected acorns by captive fox squirrels. Southwestern Naturalist. 17(4): 349-355. [11365] 18. Smith, Christopher C.; Follmer, David. 1972. Food preferences of squirrels. Ecology. 53: 82-91. [2942] 19. Taylor, Gary J. 1974. Present status and habitat survey of the Delmarva fox squirrel (Sciurus niger cinereus) with a discussion of reasons for its decline. Proceedings, Southeastern Association Game & Fish Commissioners. 27: 278-289. [21088] 20. Terrill, Harold V.; Crawford, Bill T. 1946. Using den boxes to boost squirrel crop. Missouri Conservationist. 7: 4-5. [16740] 21. U.S. Department of the Interior, Fish and Wildlife Service. 2013. Endangered Species Program, [Online]. Available: http://www.fws.gov/endangered/. [86564] 22. Van Gelden, Richard George. 1982. Mammals of the National Parks. Baltimore, MD: Johns Hopkins University Press. 310 p. [20893] 23. Weigl, Peter D.; Steele, Michael A.; Sherman, Lori J.; Ha, James C. 1989. The ecology of the fox squirrel (Sciurus niger) in North Carolina: Implications for survival in the southeast. Bull. No. 24. Tallahassee, FL: Tall Timbers Research Station. 93 p. [18032] 24. Humphrey, Stephen R.; Jodice, Patrick G. R. 1992. Big Cypress fox squirrel: Sciurus niger avicennia. In: Humphrey, Stephen R., editor. Rare and endangered biota of Florida. Mammals: Volume 1. Naples, FL: Florida Game and Fresh Water Fish Commission: 224-233. [21060] 25. Wood, Don A., compiler. 1994. Official lists of endangered & potentially endangered fauna and flora in Florida. Tallahassee, FL: Florida Game and Fresh Water Fish Commission. 22 p. [24196]


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