These cuddly looking prairie dogs are ice-cold squirrel killers

John J. Mosesso

Keep your squirrel children away from this savage beast.

White-tailed prairie dogs are cuddly-looking vegetarians.

But as scientists are now learning, they're also vicious killers of herbivorous Wyoming ground squirrels.

The gruesome killings, which biologists describe in a study published the journal Proceedings of the Royal Society B (and we first saw at The Atlantic), are the first observed examples of herbivore-on-herbivore interspecific killing.

Ground squirrels pose no direct threat to the prairie dogs, but they do eat the same prairie grasses.

Offing a competitor for food is much more common amongst carnivores, whose daily feeding habits already involve hunting. But seeing a species that lives on prairie plants murdering its vegetarian neighbors is something new.

Vegetation is hard to come by in early spring - much of it is still buried in snow when the prairie dogs emerge from hibernation - and nursing prairie dogs need the extra calories to produce milk for their young. So any competition for those grasses may mean the difference between life and death.

In the study, 79% of the prairie dog attacks on ground squirrels were committed by lactating females. And 96% of the attacks were committed against juvenile ground squirrels.

JTchagbele / Wikimedia (CC BY-SA 3.0)

A Wyoming ground squirrel.

And these attacks were brutal. According to the study, "the prairie dog repeatedly bit the ground squirrel in the head, neck or thorax over a period of 1-3 minutes until death, and then abandoned the carcass and resumed foraging on nearby vegetation."

So prairie dogs are not only vicious, they're ice-cold: After they kill, they go back to chowing down grass.

Does this strategy actually work? Is killing off their competition actually worth it for prairie dog mothers?

The study's authors think so.

Their six years of spring observation revealed something fascinating: Prairie dog mothers who killed ground squirrels ended up having larger litters with better survival rates, even though a penchant for killing also shortened the mother's own lifespan.

The study even found that ground squirrel-killing was a better predictor for reproductive success than longevity - the extra food and subsequent offspring health that came with squirrel killing made up for the shortened lifespan of a violent prairie dog mother.

So while your human mother may have sacrificed a lot for you, she probably wasn't quite at the killing-the-neighbors-and-leaving-them-for-the-vultures level.