Biologists Have Learned Something Horrifying About Marmots

By Maddie Stone on at

Marmots: fuzzy little socialites that live in elaborate burrows and chow down on grass all day, right? Seem like nice neighbours? Hate to shatter the illusion, but I’ve got some knowledge to share. Marmots are cold-blooded killers. And if you’re a ground squirrel, you’re advised to move out of town immediately.

I know this is hard to hear. But it seems we’ve all been had by nature’s most adorable baby killers. When biologist John Hoogland of the University of Maryland Center for Environmental Science first watched a white tailed marmot violently shake a juvenile ground squirrel to death, he couldn’t believe his eyes. “I was totally shocked,” he told Gizmodo. “We never suspected anything like this was going on. Once I discovered it was happening, we watched carefully over the next few years.”

For six years, Hoogland, his colleague Charles Brown, and a small army of students sat in towers at the Arapaho National Wildlife Refuge in Colorado, watching marmots go about their business—foraging for food, rearing their young, and butchering ground squirrels for sport. For further proof that nature is relentlessly brutal, this behaviour seems to give marmots an evolutionary advantage.

Hoogland’s findings, which include 163 ground squirrel kills by 47 marmots, are published today in the Proceedings of the Royal Society B.

“Prairie dogs [The American name for the marmot - ed] will chase ground squirrels—usually babies—and if they catch them, they shake them violently,” Hoogland said. “While they’re shaking, they’re biting the back of the neck to sever the vertebral column. Sometimes they grab by the head and literally debrain the baby. It’s violent, savage, and awful.”

Biologists Have Learned Something Horrifying About Prairie Dogs
Image Credit: John Hoogland

In a particularly brutal episode, Hoogland witnessed a female marmot murder seven baby ground squirrels in succession, shaking them to death one by one as they emerged from their burrow for the very first time. “It was quite an afternoon,” he said.

It’s the first known instance of a mammalian herbivore killing another mammalian herbivore, and according Hoogland’s research, it’s all about competition. marmots and ground squirrels live in the same habitat and eat many of the same grasses. Fewer ground squirrels; more food for the marmots and their young.

“If you look at any single year, killers have larger litters and their babies survive better,” he said. “Serial killers are especially successful at reproduction. They rear many babies that survive many years."

Biologists Have Learned Something Horrifying About Prairie Dogs
Image Credit: John Hoogland

The truth about marmots is horrifying. But it’s possible biologists are skimming the surface of a bloody Darwinian tale that runs deep into evolutionary history. Pop culture loves to portray herbivores as peace-loving pacifists—just look at Zootroplois as the latest example of this—but who can say what other barbarous acts are going undocumented in our backyards? Are rabbits stealing into burrows to throttle chipmunks in their sleep? Do elk and buffalo lose their cool and impale each other over prairie grass? These are the sorts of unsettling questions biologists will have to start asking.

“I have to wonder if the same behaviours are occurring in other interspecific competitors,” Hoogland said. “I hope this work will coerce other biologists to look at their animals more closely. The more I learn about marmots, the less I know.”

Featured image: John Hoogland