(Photo: Eric Kilby/CC BY-SA 2.0)

Prairie dogs are considered cute by many North Americans, even Teddy Roosevelt, who once called them “the most noisy and inquisitive animals imaginable.”

It turns out they’re also stone-cold killers.

Prairie dogs—actually a species of rodent—are seen across the West, from Texas to Montana, building dense underground warrens that they emerge from to eat grass, seeds, fruit, and sometimes insects.

What they do not eat is meat, yet prairie dogs frequently murder other animals for reasons other than sustenance, researchers reported Wednesday.

Their victims? Typically squirrels, who die in violent and bloody fashion.

“I describe the behavior in eight words: catch them, shake them, kill them, leave them,” John Hoogland, a professor at the University of Maryland, tells Discovery News. Hoogland and a co-author published their prairie dog findings in Proceedings of the Royal Society B.

The study found that most of the prairie dog killers were female, and female prairie dogs were also more likely to become serial killers.

Why the brutality? To keep in shape, but also, possibly, to root out the competition.

“It’s not that certain nasty females only do this,” Hoogland tells Discovery News, adding that the animals were likely not dogged by a guilty conscience. “In fact, the female serial killers will often dispatch their victims and then go on to graze peacefully or play with their babies, as though nothing had just happened.”