Prairie dogs are 'serial killers' that snuff out the competition

Prairie dog
CC BY 2.0 skitterphoto

First we learn they talk about us, now we find they kill competing animals in a way not seen in other mammals; next, world domination?

Honestly, a planet ruled by prairie dogs might not be such a bad thing – at the very least it would be quite cute. I still think bacteria are in the front running for overlord status, but prairie dogs are proving to be remarkably crafty creatures.

A few years ago it was discovered that prairie dogs actually have one of the most sophisticated forms of vocal communication in the natural world, “really not so unlike our own,” wrote TreeHugger back in 2013:

According to Dr. Con Slobodchikoff … the chirps these animals use as 'alert calls' are actually word-like packages of information to share with the rest of the colony. Amazingly, these unique sounds were found to both identify specific threats by species, such as hawks and coyotes, and to point out descriptive information about their appearance. And, when they're talking about humans, that might not always be flattering.

"For example, a human alarm call not only contains information about the intruder being a human, but also contains information about the size, shape (thin or fat), and color of clothes the human is wearing," says Dr. Slobodchikoff.

OK, so they talk about us – that’s pretty amazing (and who can blame them?).

But meanwhile, out in the rough-and-tumble American West, things have gone even further. As it turns out, white-tailed prairie dogs have moved beyond idle gossip and gone into sinister mode. As Michael Greshko writes for National Geographic, according to a new study, “These social rodents, native to Colorado, Wyoming, Utah, and Montana, ruthlessly bite and thrash Wyoming ground squirrels to death, leaving their bloody bodies to rot.”

(Wyoming ground squirrel, pictured below. Run, little squirrel, run!)

Wyoming ground squirrelUSFWS Mountain-Prairie/flickr/CC BY 2.0

Greshko characterizes the adorable butchers as “serial killers.” And likely that’s because this is the first time that a herbivorous mammal has been seen killing competitors without eating them, he writes, “suggesting that a plant-based diet doesn’t preclude mammals from having a taste for bloodsport.”

But as it turns out it’s likely more about ensuring the longevity of the species than it is about the thrill of blood and guts. The researchers of the study found that the offspring of the killer prairie dogs lived longer, healthier lives, and probably because their folks iced the competition.

“In my 43 years of research, this is perhaps the most provocative, puzzling, and far-reaching discovery I’ve ever made,” says study co-author John Hoogland of the University of Maryland Center of Environmental Sciences. “The results are just staggering.”

Hoogland is a very dedicated authority on the creatures and tirelessly studied those from Colorado’s Arapaho National Wildlife Refuge from 2003 to 2012.

“For four months every year, we live like prairie dogs,” says Hoogland, a National Geographic grantee. “We get to the colony early in the morning before the prairie dogs wake up, we sit in towers all day watching what they do, and we stay until the last prairie dog submerges, just around sunset.”

Prairie dogUSFWS Mountain-Prairie/flickr/CC BY 2.0

In 2007 Hoogland first noticed a white-tailed prairie dog tossing around a young rodent. Greshko writes:

Initially, he suspected that it was killing another prairie dog’s pup, which is not surprising: Infanticide is common in other prairie dog species, though it has never been observed in white-tailed prairie dogs.

But once Hoogland examined the prairie dog’s victim up close, he realized that it was in fact a Wyoming ground squirrel, a species that eats the same grass and prickly pears as prairie dogs.

An lo and behold, over the next five years the researchers identified 47 killer prairie dogs – both male and female, and always adults. And in comparing survival rates of the killers’ kids, they found that killers' offspring had better survival odds than those of non-killers – and to everyone’s surprise, a prairie dog’s taste for killing was the only thing that predicted its offspring’s success.

“The condition of the female, her longevity – the factors that normally influence [success] – none of them apply to this case,” says study co-author Charles Brown of the University of Tulsa.

“It seems to me is that there are major, major benefits to killing these ground squirrels.”

It wouldn’t be the first time that competing for resources has led to aggression, but to kill without eating the victims is unique. The researchers note that the weight of the evidence points to the benefitting-the-kids motivation, but more research will have to be conducted to rule out the possibility that the killing spree isn't just from aggression brought on by limited resources.

"Regardless," writes Greshko, "the results suggest that for herbivores of all stripes – including white-tailed prairie dogs and ground squirrels – competition won't just bring hardship. For many, there will be blood."

Tags: Animals

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