Gray Squirrel(Sciurus carolinensis Ord)
From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp.
Description: The gray squirrel’s appearance differs seasonally. The yellowish brown summer coat becomes thicker and gray in winter, the pelage of some individuals strikingly silver-gray. Underparts and eye-rings are buffy brown to white, usually lighter in winter. The backs of the ears, tan to cinnamon in color, have white tips in the winter and bold, conspicuous white spots at their bases and adjacent parts of the head. The bushy, 18-25 cm (7-10 in) tail, which is about half the total length of this 48-51 cm (18-20 in) rodent, is made up of long, wavy hairs, each banded alternately with brown and black at the base and broadly tipped with white. Seasonal color variation is a function of fading and molting. Additional individual color variation results in brown, black, silvery-gray color phases. Albinos are more frequent than in many rodents. Adults weigh 454-681 g (1-1.5 lb).
Range and Habitat: The deciduous forests of the eastern half of North America provide optimum habitat for the gray squirrel, but the range includes portions of the mixed forest in southern Canada. This species in the Adirondacks reaches its greatest abundance along the Champlain Valley, and the eastern and southeastern areas of the Park, e.g., along the western shore of Lake George, areas that have a greater abundance of oaks. To varying extents, the gray squirrel resides in the old-growth hardwoods, and mixed hardwood-coniferous forests of the Adirondacks at elevations up to 915 m (3000 ft), ranging in abundance from rare to common, the latter often occurring in towns, cities, parks, and more importantly, near residential bird feeding stations. Some populations, like that at Blue Mountain Lake, would probably not exist without the presence of bird feeding stations.
Merriam commented on the rarity of the gray squirrel in the Adirondack interior, rare enough to report individual observations by hunters and guides. He attributed their sightings to the irregular immigrations of this species. Before the large scale destruction of the eastern deciduous forests, gray squirrels were famous for their mass immigrations which may have been caused by population pressure following large most crops and/or failure of the mast crop. These immigrations are well documented, and Merriam’s recounting of the 1749 invasion of Pennsylvania by gray squirrels, which led to bounties being paid for 640,000 squirrels, indicates the magnitude of both populations and the extent of the immigrations. Perhaps the gray squirrel was absent as a resident in the central Adirondacks during Merriam’s time, but by the mid-1930’s no less than 6 sightings were made by Chief Ranger Oja in Huntington Wildlife Forest just west of Newcomb, although in neither locations are they common. Possibly, logging of the Adirondacks has led to range extensions.
Home for a gray squirrel may be a leafy nest, a dome-shaped mass of twigs and leaves with an inner chamber of shredded bark and leaves, or a tree cavity which it seems to prefer.
Food and Feeding Behavior: The principle foods are seeds and nuts with acorns, beechnuts, butternuts, and hickory nuts providing the mainstay of the autumn and winter diet. Beech and nuts, because of their relative abundance in parts of the Adirondacks, make the greater contribution. The smaller seeds of maples, ashes and basswood are of lesser importance. The buds, flowers, and inner bark of all these species, and others, contribute to the late winter and spring diet. Gray squirrels feed extensively on fungi, berries, and fruits during the summer, especially the fruit of the black cherry. In the south, this species requires 1.5 g (2 pounds) of food each week. The energy requirements of Adirondack populations probably exceed this amount.
In autumn, gray squirrels clip nuts from the canopy, and scatter hoard them in the ground, relying on their keen sense of smell to retrieve them in winter when they may have to dig through a foot or more of snow. Overlooked nuts sprout, some regenerating forests. Tree cavities may function as hiding places. Too, which may explain the survival of gray squirrels residing in the Adirondacks where deep snow is normal.
Activity and Movement: Gray squirrels stay in their dens or nests for several days at a time during periods of severe winter cold, eventually visiting stores of nuts at midday. Other than these brief periods, this diurnal species is most active in the 2-3 hours after dawn and preceding dusk, with the remainder of the day spent basking on a limb or resting in the nest. Heavy cloud cover and courtship may extend activity throughout the day.
Gray squirrels are arboreal acrobats, climbing, running and leaping about trees, their sharp claws gaining a purchase on slippery bark, long tails balancing and breaking leaps, long slender bodies twisting and turning around pencil-thin branches. When alarmed, they freeze, flattening their tails and bodies to a trunk or limb on the side opposite an intruder, inching around to stay hidden.
They are equally agile on the ground, walking, hopping, bounding, and running, their tails flowing behind them, attaining speeds of 10-15 mph by combining running with leaping. Although not aquatic in any sense, this species swims well, readily entering water, and swimming distances up to several miles. Merriam observed gray squirrels swimming across lakes of the Fulton Chain.Reproduction: Gray squirrel courtship is similar to the red squirrel’s, with 1-10 or more males engaging in “mating chases” of a female in estrous, the dominant male usually but not always mating with the female. Two breeding periods occur within a population, one in late winter, and another in mid-summer, with litters born in March-April and July-August. Adult females two years of age or older may bear one or two litters per year; yearling females just once.
After a gestation period of 40-44 days, the female bears her litter of 1 to 9 (average 2 or 3) in a den or leafy nest. The hairless, blind neonates weigh about 14-15 g (0.5 oz); their eyes open at 28-35 days, and they have a full coat of fur when they begin to leave the nest or tree cavity 42-49 days after birth. Not until they are 56-70 days old does the female wean her young. At this time, they begin to disperse. Young of the late summer litters may remain with the female during the winter. Sexual maturation takes place during the following spring or summer. Mean life expectancy for a gray squirrel at birth is 1-2 years; the average life span of an adult is closer to 6 years. Records for maximum life span are 12 years in the wild and 20 years in captivity.
Predators: The typical predators of small to medium-sized mammals prey upon gray squirrels.
- Social system - Hierarchies define the relationships among gray squirrels living in close proximity. Older, larger adult males dominate smaller males. Females are subordinate to males except when litters are present. At this time, females defend small territories around their dens or nests. Home ranges of both sexes overlap, the males being larger. Home range size depends on food availability, but is usually 0.4-2.4 ha (1-6 acre). Adults are promiscuous and do not form pair bonds. Female-young associations which may persist into winter are the only social groupings.
- Communication - Gray squirrels rely extensively on vocal signals, and produce many kinds of vocalizations. Before and after mating, females give “kuks,” “quas,” and “moans.” Young squirrels “shrill-cry” when disturbed. Alarmed adult gray squirrels “buzz,” and use slow “kuks,” low “moans,” and high-intensity, repetitive “quaas.” Foot-stamping and tail-waiving may accompany these. Visual signals include posturing and motor patterns of which tail-position, movement, and shape are always important components. Anal glands provide clues to sexual status and perhaps other information as well.
Additional ReferencesBarkalow, F.S. and M. Shorten. 1973. The world of the gray squirrel. J.B. Lippencott Co., Philadelphia. 160pp.
Barkalow, F.S. and R.F. Soots, Jr. 1975. Life span and reproductive longevity of the gray squirrel, Sciurus c. carolinensis. Journal of mammalogy, 56:522-24.
Horwich, R.H. 1972. The ontogeny of social behavior in the gray squirrel (Sciurus carolinensis). Verlag Paul Pary, Berlin, Hamburg. 103pp.
Johnson, C.E. 1937. Part I. Preliminary reconnaissance of the land vertebrates of the Archer and Anna Huntington Wildlife Forest Station. Roosevelt Wildlife Bulletin, (4):552-672.
Uhlig, H.G. 1956. The gray squirrel in West Virginia. Bulletin No. 3. Charleston, West Virginia Conservation Commission.