New research hints at how climate change is affecting some squirrels

Ground squirrels might remind you of prairie dogs. They live communally, in burrows, and have some pretty impressive social practices. As with a lot of squirrels, related females live together in groups. But males also stay part of the colony longer than other species.

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“They significantly delay leaving the house, but they don’t mate with the family group,” Waterman said. “They stay home and take care of the kids. It’s kind of weird.”

And when males disperse and join all-male groups, they get along. They are not aggressive with each other.

Waterman is primarily concerned with squirrel behavior: what squirrels do and why they do it. As part of her research, she has collected data about the squirrels’ morphology—size, weight, etc.—and about the environment in which they live. This is interested Postdoctoral researcher named Mia Warringtonwho came aboard two years ago.

“Mia is amazing with data,” Waterman said. I asked, have you ever looked at the temperature at the site and the size of the object? “

They didn’t, so Warrington took the numbers and crunched them. It found that over the past two decades, the maximum temperature at the study site in South Africa had risen by more than 2 degrees Celsius. During that time, the squirrels’ spine length became smaller and the relative size of their feet became larger.

“This is exactly what you would expect if the animals were trying to dissipate heat,” Waterman said.

Biologists have long known that a smaller body and larger feet help animals tolerate higher temperatures, the kind of temperatures that are rising across the planet.

Meanwhile, more than 9,000 miles away lives another species of squirrel Waterman studies: Richardson’s ground squirrel. These squirrels, found in western Canada and the northern United States, are not as social as their southern African cousins, and they hibernate.

“The hibernating types are really cool,” Waterman said. “It really is the time of their lives to miss the worst time of the year. I wish you were a hibernating type in some ways. You miss winter and only wake up when it’s nice.”

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But Richardson’s ground squirrels may also reveal how climate change is affecting animal biology.

Male Richardson’s ground squirrels emerge from their hibernation in front of the females, driven by a hitherto unknown internal clock. In their time above ground, males fight with each other to establish territories. After two or three weeks, the females emerge, driven by the high temperature. After a few days, the females are ready to mate and the copulation competition begins.

But something strange happened in 2012. That winter, temperatures rose rapidly, causing females to emerge from their burrows earlier than usual. The males haven’t been out on their own for a long time and when Waterman tested their sperm – she really looked at everything – she found… nothing.

“They were shooting blanks,” she said.

The male squirrels looked normal — their testicles were nice and big — but the indoor plumbing wasn’t online yet. The male squirrels didn’t have the only time they needed for it all to spill out.

Eventually, the sexes synced up and lots of babies were produced, but the effects were amazing.

“The females were able to have normal-sized litters — breeding with more than one male — but think about it: If this were going to happen on a regular basis, that kind of temperature would probably lead to extremes in climate that might,” Waterman said. “It makes the change more common, you reduce genetic heterogeneity. There is not much variation because half of the males are not able to reproduce successfully.”

Changes in climate can affect things in Africa, too — and it’s not just the size of a ground squirrel’s feet.

“These squirrels are ecosystem engineers,” Waterman said. “Burding mammals, especially social burrowing mammals, have a really big impact on grassland communities.”

Ground squirrel burrows affect other small mammals in the ecosystem. And they affect plants that grow there, including some plants that antelopes eat.

when affected [squirrels’] “Their morphology and physiology, that can also influence their sociology,” Waterman said.

The research by Waterman and Warrington appeared in the Journal of Mammalogy.

the University of Manitoba studies reflect two sides of the climate change coin: The numbers of ground squirrels were affected more gradually, with subsequent generations of animals having larger feet and shorter spines. Richardson’s ground squirrels experienced a quick shock: a rise in temperature that had the potential to throw off reproduction.

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tomorrow: Squirrel week continues.