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Southern Flying Squirrel (Glaucomys Volans)

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COSEWIC
Executive Summary
from the 1998 Status Report

Southern Flying Squirrel
Glaucomys volans

Atlantic (Nova Scotia) population
Great Lakes Plains population

Species Information

The southern flying squirrel is a small, arboreal squirrel with soft, greyish-brown fur on the back and sides and pure white belly hairs. They are distinguishable from northern flying squirrels (Glaucomys sabrinus) from live specimens in the hand or good photographs. There is no record of interbreeding between the species. There is little evidence of genetic structuring of populations of southern flying squirrels in Ontario. Genetic results from Nova Scotia suggest the isolated population in that province is diverging from central Canadian populations.

Distribution

G. volans occurs from Minnesota in the northwest, New England and Nova Scotia in the northeast and south to the Gulf of Mexico. Isolated populations occur in Nova Scotia, Mexico and Central America as far south as Honduras. In Canada, G. volans occurs in south and central Ontario, southwestern Québec and southern Nova Scotia. It is not known to occur in New Brunswick.

In Canada, the Great Lakes population ranges along the northern shore of Lakes Erie and Ontario eastward into southwestern Québec. Northward, the species is found throughout much of central Ontario. Recent work has extended the northern limit from a line roughly between Muskoka and Petawawa to Temagami and Killarney Provincial Park. However, the northern edge of the species’ range fluctuates year-to-year; the northern limit in 2004 was over 200 km further south than in 2003. Data from Québec are lacking, but there has been no systematic effort to search for this species. They are known from the Outaouais region and may occur throughout the Eastern Townships, but have not been located there. The Extent of Occurrence of the Great Lakes population is estimated at approximately 160 000 km2. The Atlantic Population occurs entirely within southern Nova Scotia between Kentville in the northeast and Tobeatic Wilderness Area in the southwest. The population’s Extent of Occurrence is estimated at 6500 km2.

Habitat

Suitable habitat requirements are primarily mast-bearing trees for food and tree cavities for nesting. Southern flying squirrels select older forest stands, but whether southern flying squirrels depend on old growth is a matter of debate. In the northern part of their range, southern flying squirrels utilize forests dominated by hardwood, mast-bearing trees with some conifer. The southern flying squirrel is a secondary cavity nester, utilizing holes excavated by woodpeckers, or resulting from broken limbs or disease in dead and live trees. There are several protected areas throughout their Canadian range.

Biology

G. volans are polyestrous and may reach sexual maturity after six months (though this is unusual). One annual litter is most common in Canada, occasionally two. Mean litter size is 2.75 in the US and 3.5 in Canada. Limited survival data for G. volans suggest survival to three years is rare. Generation time is estimated to approximate 1.5 years. Parturition occurs as early as late April and as late as August.

The diet of southern flying squirrels is varied. The food is hardwood tree mast, particularly hickory (Carya spp.), oak (Quercus spp.) and beech (Fagus grandifolia), though they also readily consume insects, eggs, nestlings and other foods when available. Predators of G. volans include domestic cats, owls, elaphid snakes and raccoons. Feral and domestic cats likely contributed to the extirpation of G. volans from Point Pelee National Park and may limit flying squirrels in rural areas.

Relatively little is known about the dispersal habits of southern flying squirrels. Adults are capable of covering large distances in short periods of time. Individuals have been recorded to move > 2 km in a night.

Population Sizes and Trends

There is no abundance estimate for either the Great Lakes or Atlantic population. Estimates of population size for southern flying squirrels are constrained by low capture rates and unequal capture of individuals. G. volans also exhibits wide annual variation, rendering any single point-in-time estimate unreliable. In both populations historical declines have likely occurred due to substantial habitat loss, particularly in southern Ontario. Whether populations have declined in recent years is unknown. Neither population has substantive opportunity for rescue from the United States. The Atlantic population is completely isolated, some 500 km by land from the nearest location in Maine. The only land border with the Great Lakes population is in northeast New York, Vermont and possibly New Hampshire. However, status of southern flying squirrels in these border areas is unknown. The Great Lakes and associated rivers effectively isolate Ontario from US populations; flying squirrels are poor swimmers.

Limiting Factors and Threats

Overwinter survival is likely dictated primarily by availability of stored food, while cold minimum winter temperatures may increase mortality. Other thresholds limiting southern flying squirrel populations are unknown, including minimum density of nesting cavities and woodlot size and connectivity.

Habitat loss is the major threat facing southern flying squirrels. Activities that reduce overall forest cover (e.g. conversion of forested land to urban development) or remove forest structure attributes within a stand (e.g. removal of nesting trees or harvesting of mature mast-producing hardwoods) are key threats to southern flying squirrel survival at both the individual and population levels. Habitat fragmentation can also be disruptive to southern flying squirrel ecology. G. volans will use ‘greenbelt’ corridors between larger habitat fragments, but population densities in Arkansas declined following forest harvesting, while populations in adjacent mature stands increased.

Mortality threats come from trapping and domestic cats. Southern flying squirrels are known to be killed in traps set for other species. Where their range overlaps with registered traplines, they may be at risk. Domestic cats are effective flying squirrel predators and pose a major predation risk to southern flying squirrels throughout their range.

Existing Protection

Nova Scotia lists G. volans as “yellow,” indicating “sensitive to human activities or natural events”. Ontario ranks the southern flying squirrel as “special concern”. Québec lists the species as “likely to become threatened or vulnerable”. NatureServe conservation rankings in adjacent states are all S5, except for Vermont (S4) and Maine (SU).