by Dan Schneider and Peter Pautler
Fight or flight
As a prey species, squirrels must be constantly vigilant. Leaping from tree to tree is one escape technique for tree squirrels, an ability most evident in flying squirrels. Relative to their body size flying squirrels have the longest legs of all our squirrels, allowing them to stretch out a skin membrane called a patagium and sail like a kite from tree to tree. For every metre of drop, a flying squirrel can glide forwards three metres. In one study, flying squirrels were observed sailing as far as 45 metres before touching down.
By mid-spring, ground squirrels – specifically woodchucks and Franklin’s ground squirrels – have emerged from their winter-long hibernation. These squirrel species will have spent the cold months inside elaborate burrows unlike tree squirrels (red, grey and fox) and flying squirrels (northern and southern) which nest, but do not hibernate, in tree cavities. Chipmunks, unable to store enough body fat to survive the winter, hibernate for intervals from a few hours to several days, waking up frequently to raid their stores of seeds, berries and nuts.
Squirrels are highly opportunistic creatures, feeding on buds, new shoots and early flowing sap in spring, insects in summer and seeds and nuts in autumn. Woodchucks, like other marmots, are grazers and eat mostly low-growing herbaceous plants. Less well known is that squirrels are also carnivorous, consuming birds’ eggs and nestlings – Franklin’s ground squirrels will even prey on duck nests.
The squirrel family (Sciuridae) is part of the rodent order (Rodentia), which makes up nearly 40 percent of all mammals. Like their rodent relatives, squirrels have gnawed, nibbled and chiseled their way to survival with impressively sharp incisors that grow constantly. The hard enamel on the front of the tooth wears down slowly. The softer tissue on the back of the tooth wears down more quickly, creating a perpetually sharp, chiseled edge. A gap between incisors and molars, called a diastema, allows squirrels to draw their furry cheeks inward so that chips don’t slip down their throats as they chew insistently with their incisors on nuts, seeds and other foods.
To learn more
Squirrels (The Animal Answer Guide). Richard W. Thorington Jr. and Katie Ferell. Baltimore: Johns Hopkins University Press, 2006.
Squirrels of Canada. S.E. Woods Jr. Ottawa: National Museums of Canada, 1980.
Hinterland Who’s Who, www.hww.ca
Its big bushy tail helps a tree squirrel keep its balance and allows flying squirrels to change direction while airborne. These arboreal squirrels have sharp, curved claws and hind feet that can rotate 180 degrees while descending a tree. A ground squirrel’s claws are strong and straight, excellent for digging burrows.
Preyed on by a host of predators, from hawks and owls to foxes, weasels and snakes, a squirrel’s lifespan is short – in the city, cars and cats are the dominant threats. One study showed that only 25 percent of grey squirrels lived past one year of age; their average lifespan is a mere five months.
Franklin’s ground squirrel is listed as vulnerable nationally due to habitat loss, and, until recently, southern flying squirrels were designated an Ontario species of special concern due to forest fragmentation and the consequent reduction in the number of tree cavities. Recent studies have shown the southern flying squirrel to be more widespread than previously thought, and the species was delisted in 2006. But most squirrel species are thriving. Farms provide habitat and food for some, such as woodchucks. Other species are attracted to coniferous plantations, bird feeders filled with seeds and fruit, and compost piles. While squirrels are not always welcome guests at bird feeders, they present a perfect opportunity to observe the agility and persistence of these creatures.
The largest of the squirrels in Ontario and third largest in Canada, woodchucks (also called groundhogs) range in size from 50 to 65 cm and weigh 2 to 6 kg. A familiar sight in fields, pastures, open woods and clearings, woodchucks have a grizzled appearance with brownish fur, blunt muzzles, short legs and stubby black tails. Woodchucks hibernate in dens up to 2 m deep during the winter but may inhabit much shallower dens in meadows close to food sources in the summer. A platform of excavated soil rims the primary entrance and one or more bolt-holes are hidden nearby. Woodchucks feed on grasses, leaves, seeds and berries, sometimes supplemented by bark, insects, birds’ eggs and carrion, and reach their maximum weight in time for hibernation.
Eastern Grey Squirrel
Some grey squirrels are grey overall with faint brown highlights on the head and back and silvery highlights on the tail. Others are entirely black and are often mistaken for a separate species. Including its large bushy tail, the eastern grey squirrel is 43 to 50 cm long and weighs 400 to 700 g – about as much as a one-month-old kitten. A common sight in deciduous forests that contain plenty of nut-bearing trees, as well as in urban neighbourhoods with mature trees, eastern grey squirrels range north into southern Ontario and westward into southern Manitoba. This species uses tree cavities (especially abandoned woodpecker nest holes) and large oval-shaped nests of leaves and twigs called dreys, constructed high up in treetops. Although they mostly feed on nuts, grey squirrels will also consume buds, flowers, leaves, fruit, berries, maple keys, insects and birds’ eggs. Grey squirrels bury nuts randomly throughout their home range to eat throughout the winter, which is why, in part, nut trees are plentiful in southern Ontario’s forests.
Red squirrels have a reddish cast over the back and tail and shades of olive brown on the sides, head, rump and legs. A black stripe runs along their sides. This species is on the small side, 27 to 36 cm in length and weighing between 140 and 250 g. Red squirrels inhabit coniferous and mixed forests and are found throughout Ontario. They favour tree cavities for dens, but will build leaf and twig dreys close to the trunk of a tree or dig burrows near stumps, logs and rocks. Heaps of discarded scales and the cores left over from cones are evidence of this squirrel’s presence. Red squirrels also eat buds, flowers, berries, mushrooms, insects, birds’ eggs, mice and even chipmunks.
Ontario’s only population of fox squirrels is found on Pelee Island, at the west end of Lake Erie, where this species was first introduced to Canada in 1893. The largest of our tree squirrels, fox squirrels range in length from 45 to 70 cm and can weigh 500 to 1050 g – about twice the size of a rat. Similar to eastern grey squirrels in colour, fox squirrels are beige-grey above with russet-coloured ears, cheeks and feet. Fox squirrels are most commonly found in stands of oak and hickory trees adjacent to open country and farms. They inhabit tree cavities, abandoned woodpecker nest holes and nests made of twigs and leaves (dreys). Fox squirrels feed on buds, flowers, seeds, berries, nuts, grubs, insects, caterpillars and birds’ eggs.
Dan Schneider and Peter Pautler are resource interpreters with the Grand River Conservation Authority.