Squirrels

Racing across the grass or chattering from the safety of a tree, squirrels are a familiar feature in many of our neighbourhoods. But how much do we really know about these small, furry creatures?

Introducing the Family

Squirrels are rodents and members of the Sciuridae family. There are 23 species in Canada, including tree squirrels, ground squirrels, and flying squirrels.

Tree squirrels include red squirrels, gray squirrels, and fox squirrels. They are “highly specialized for arboreal life: they typically have larger eyes and ears than their ground-dwelling relatives, as well as longer, bushier tails to better balance in the treetops. Unlike ground squirrels and chipmunks, tree squirrels have no cheek pouches for storing and carrying food, and they don’t have any stripes on their backs.” [1]

Ground squirrels include chipmunks, prairie dogs, and marmots. They are often heavier and larger than tree squirrels and, although their height varies, can all stand upright on their hind feet. While tree squirrels are usually found in forested areas, ground squirrels inhabit fields, grasslands, and rocky outcrops.

Flying squirrels are the paragliders of the squirrel family. They can’t fly but excel at gliding from one tree to another: “Enabling the squirrels to ‘fly’ are glide membranes – cape-like furred skin that extends from their wrists to their ankles, down the length of the body. Before a glide, a squirrel identifies a target and maneuvers into the launch position, a head-down, tail-up orientation in the tree. Then, using its strong hind legs, the squirrel propels itself into the air, all four limbs extended. Once airborne, it resembles a flying paper towel and can glide for up to 160 ft (49 m).” [1] Unlike other squirrels, flying squirrels are active at night rather than in the daytime.

Food & Caches

“While the caches of most other squirrels germinate if left for too long, Eastern Gray Squirrels determinedly nip off the germinating end of the nuts before burying them.” [1]

A 35-year study of individual red squirrels in Kluane, southwest Yukon, found they feed extensively on the white spruce cone seeds. The white spruce is a masting species, so some years there are lots of cones but many less in other years. In a bumper cone year, squirrels can store up to 20,000 cones that can last them for 3-4 years. Somehow the squirrels know when it will be a bumper year and increase reproduction in the spring before the cones are even available.

Thirteen-lined ground squirrels eat grasshoppers as well as grasses and seeds, so “although these ground squirrels may cause some damage to a farmer’s seedling crops, they more than make up for it by eating great numbers of harmful insects” [1].

Unlike thirteen-lined ground squirrels, red-tailed chipmunks don’t hibernate. Before winter arrives, they transfer any food remaining in their caches to their winter den where they wake up frequently to eat [1].

Home Sweet Home

“Like most tree squirrels, they [red squirrels] live in any of three types of nests: old woodpecker holes, refurbished corvid nests or ground nests that are dug under stumps or inside their middens.” [1]

Red-tailed chipmunks nest either in a tree or on the ground. A tree nest is located 6-18 metres off the ground and looks like a shaggy ball of grass and leaves. Ground nests, found in stumps, under logs, or in burrows, are lined with dry grass and leaves.

Thirteen-lined ground squirrels curl up into tight balls and spend about 7 months in their solitary nest chambers.

When excavating their burrows, hoary marmots usually place their sleeping chamber below a large boulder to protect themselves from being dug up by a hungry bear.

Chirps & Chatter

“Chipmunks chirp – a ‘chip chip chip’ sound – in response to terrestrial predators. They cluck more slowly for aerial predators, making a sound that Seton, the early twentieth-century naturalist, compared to horse hooves hitting pavement. Low-frequency clucking sounds carry far and wide and can even launch a chorus of chipmunks across the forest.” [2]

Clucks are a useful way to warn other chipmunks of danger. However, if they’re really scared, yellow-pine chipmunks are silent and run for cover.

Richardson’s ground squirrels are also known as ‘flickertails’ as their shrill whistle is accompanied by a flick of the tail.

Sociability

“Daily life for Hoary Marmots involves eating two meals, dodging predators, sunbathing, hugging, nuzzling and wrestling.” [1]

Hoary marmots are gregarious and live in large colonies. The large family groups provide good protection as one marmot is always on the lookout for predators.

Tree squirrels lead solitary lives. Each one maintains its own territory and supply of food. The Kluane study found that red squirrel mothers sometimes relinquish their territory to one of their pups before moving to a new area. When a squirrel dies, the neighbours quickly arrive to steal from their cache of cones. The cache will be passed on to the squirrel that takes over the territory.

Urban Squirrels

Squirrels have adapted well to towns and cities. There is an abundance of food and an absence of many of their traditional predators, although cars, cats, and dogs pose a significant risk. They’re also affected by the urban environment. Researchers found squirrels in central London had worse lung damage than squirrels living further from the centre with less air pollution from heavy traffic. 12% of Montreal’s squirrels are black with black squirrels appearing more frequently in northern areas where it’s cooler. Black coats keep them warmer as they absorb more heat.

Squirrels take advantage of all available food sources, including bird feeders, although some people get annoyed and use multiple methods to deter them. Nancy Castaldo, in her book Squirrel: How a Backyard Forager Shapes Our World, says, “I’m always curious why they don’t like the squirrels. Aren’t you feeding wildlife because you want to see them? Why is it you only want to see birds, rather than birds and squirrels together?” She feels it reflects our conditional love of wildlife, “I will love you and accept you if you stay out of my owl nest boxes and don’t eat my birdseed or dig up my flower bulbs and make a mess. I will love you if you don’t behave like a wild animal.” [3]

At Risk

“By using a scatter hoarding method of burying single nuts in lots of locations, squirrels provide one of the only ways nuts get far enough from the parent tree’s shade to have a successful germination.” [3]

Squirrels may be abundant in our towns and cities, but 80% of the world’s squirrel population is threatened. And threats to squirrels represent a threat to our forests and grasslands.

Squirrels contribute to forest health in many ways. Forgotten caches of nuts grow into new trees. Chipmunks spread mycorrhizal fungi and moss. Old squirrel nests become homes for bumblebees. Litter moths take up residence in the leaves lining nests, and their caterpillars then break down the leaves to create a rich compost.

Ground squirrel tunnels provide a home for other wildlife and aerate the soil. Following the eruption of Mount St. Helen’s, pocket gophers were air-dropped into the ash-covered area to see if they could jump-start recovery. “The gophers’ digging behavior was a powerful ecological tool, enhancing soil structure and microbial activity. Six years later, the researchers recorded forty thousand plants flourishing in the spot. In contrast, the surrounding area was still very barren.” [3]

Further Information

1. Squirrels of North America, Tamara Eder [Lone Pine Publishing]

2. Wildscape: Trilling Chipmunks, Beckoning Blooms, Salty Butterflies, and Other Sensory Wonders, Nancy Lawson [Princeton Architectural Press]

3. Squirrel: How a Backyard Forager Shapes our World, Nancy F. Castaldo [Princeton University Press]

Kluane Red Squirrel Project [Kluane Red Squirrel Project]

The wild world of urban squirrels [The Minnesota Daily]

Black squirrels are helping Montreal scientists understand a city’s role in animal evolution [CBC]

Squirrels live longer in leafier parts of London, air pollution study shows [The Guardian]

Squirrels, Nature Companion, A Comprehensive Nature App for Canada’s Four Western Provinces [EcoFriendly West]

Photo credit: https://www.flickr.com/photos/apmckinlay/53911650395

EcoFriendly West informs and encourages initiatives that support Western Canada’s natural environment through its online publication and the Nature Companion website/app. Like us on Facebook, follow us on BlueSky, X, and Mastodon, or subscribe by email.