In a biology study published in Proceedings of the Royal Society B in March 2016, researchers revealed prairie dogs are cold-blooded killers. Over a six-year period, 47 white-tailed prairie dogs in western Colorado’s Arapaho National Wildlife Refuge murdered more than 100 ground squirrels. Classified as herbivores, the prairie dogs killed solely to reduce food competition and did not eat their prey.
Professor John Hoogland and a team of researchers at the University of Maryland Center for Environmental Science documented the slayings and compared the offspring survival rates of non-killer to killer prairie dogs. The results showed those who killed raised more successful pups than those who didn’t.
TU Professor of Biology Charles Brown, a coauthor of the paper, performed the statistical analysis of the raw field data. Brown studied under the advisement of Hoogland as a doctoral student at Princeton University more than 30 years ago.
“Killing ground squirrels had the biggest effect on prairie dog fitness of anything we measured,” Brown said. “The research showed the grass on which both prairie dogs and ground squirrels forage may be more limited than we thought, if prairie dogs are willing to kill over it and have increased reproductive success as a result.”
According to Brown, killing competitors of another species is unusual for herbivorous mammals. The killings have been reported only in white-tailed prairie dogs, which live in groups and often fight with members of its own species.
“They frequently fight with others nearby in the same colony,” he said. “They’ll steal from each other and try to seduce the females next door.”
The research revealed mean lifetime fitness was three times higher for serial killer prairie dogs than non-killers. Perhaps the biggest surprise, Brown said, was “actual longevity of life did not affect prairie dog fitness once we accounted for the killing of ground squirrels.”