ground squirrel

Unless you’re very familiar with plains-dwelling animals, you’d probably never peg the Richardson’s ground squirrel as a relative of the red squirrel or the grey squirrel. These mammals look much more like gophers or small prairie dogs. And they behave more like both: “ground squirrel” is an incredibly apt common name given how much of their lives these critters spend underground! (It’s a lot—see below.)

Ground squirrels vs. tree squirrels

The species was named after the Scottish naturalist Sir John Richardson. Looks-wise, they have larger bodies but much smaller tails than their tree squirrel relatives. (Tree squirrels need bushy tails to help with balance.) A ground squirrel’s skinny tail is almost constantly twitching, like a tiny whip—it’s one reason why they’re nicknamed “flickertails.” Their ears, meanwhile, are so flat that they appear mashed into either side of the head.

When do they hibernate?

The Richardson’s ground squirrel spends up to eight months hibernating. Adults emerge from their dens—in Canada, dug into open meadows and plains in the prairie provinces—between February and March. They return underground by mid-June at the latest. Juvenile squirrels spend a little less time in hibernation—between five and seven months. But even when the squirrels are not hibernating, they’re still only aboveground for eight to 10 hours of the day. An individual Richardson’s ground squirrel spends a mere 15 per cent of its existence on the surface. (Imagine living 85 per cent of your life in the basement.)

Ground squirrel dens provide digs for other prairie dwellers

Richardson’s ground squirrel burrows play an important role in the lives of other denning creatures. Mice, voles, burrowing owls, badgers—they enlarge the holes to suit their bigger bodies—plus salamanders and invertebrates repurpose empty dens. Even bumblebees nest in ground squirrel homes.

When do ground squirrels reproduce?

Squirrels mate soon after they emerge from hibernation in early spring. Females all give birth around the same time, so the population explodes all at once. But it can crash just as quickly: mortality is especially high with this species, thanks to prairie predators such as hawks, falcons, eagles, weasels, and rattlesnakes. About 50 to 70 per cent of babies don’t live long enough to reproduce (at about a year old). Despite this, it’s common to spot both adults and babies in Manitoba, Saskatchewan, and Alberta—at least, it’s more common to spot them than it is to spot other grassland mammals. They’re bold, and will happily approach people, looking for handouts. Cheeky!

Every year as the temperature drops, hibernating animals, fattened from a summer spent gorging on food, prepare to hunker down for the winter. When they wake up in the spring, they’re healthy and strong despite months of inactivity. So how do they do it?

This was the question that Matthew Regan, an assistant professor of biology at the University of Montreal, and his colleagues set out to answer in a new study recently published in Science. Hibernation has long intrigued scientists, he explains. There was speculation that something in the gut helped some hibernators preserve muscle. Regan and his colleagues tested this hypothesis on 13-lined ground squirrels in Wisconsin and found that bacteria play a key role in helping them stay strong while they hibernate.

These ground squirrels are an “extreme example of hibernation,” Regan says. They are inactive for six months, during which time their metabolism is reduced by 99 per cent. When they wake up in mid-April, the squirrels “start eating furiously” and double their weight by the fall, he says.

Like humans, ground squirrels have many different kinds of bacteria in their gut, and one group of microbes is doing them an important service. While the squirrels hibernate, urea, the main component in urine, is transported to their intestines where microbes break it down, releasing nitrogen, Regan explains. Nitrogen is essential for making protein, and this process allows the squirrels to preserve and build muscle through the winter.

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There is already interest in how this process could help humans prevent muscle-wasting—whether they’re patients on bed rest or astronauts in zero-gravity environments. Regan has received funding from the Canadian Space Agency to study the possible applications for space travel. However, the human gut microbiome is complex and delicate, and disruptions could have negative impacts, he says. So, careful research must be done before applying this mechanism in space.

For now, this process is best left to the squirrels. While it may be tempting to leave food out to help the little hibernators fatten up, Regan says it’s safer to “let them do what they’re evolved to do.”

Quiz: how much do you know about hibernation?