Cute prairie dogs are serial killers savaging ground squirrels

2019-03-07 06:19:05

John Hoogland By Aisling Irwin Species: white-tailed prairie dog (Cynomys leucurus) Habitat: prairies of central US It was thought to be just a small, furry grass-nibbler, but the white-tailed prairie dog has another life – as a serial killer. The rabbit-sized herbivore’s relations with the ground squirrels that forage alongside it often explode into murderous attacks – with some prairie dogs biting squirrels to death on a regular basis. This is thought to be the first time that one mammalian herbivore has been seen routinely killing members of another herbivore species. What’s more, those who kill go on to lead more successful lives than those who don’t, so it may be an important behaviour shaping evolutionary “fitness”. John Hoogland, a biologist at the University of Maryland Center for Environmental Science, had been studying white-tailed prairie dogs for four years before he saw one kill a Wyoming ground squirrel (Urocitellus elegans). John Hoogland He then spent six years in the Arapaho National Wildlife Refuge in Colorado, along with Charles Brown of the University of Tulsa, Oklahoma – and watched the squirrel death toll soar to 163. “It boggles the imagination that something like that was going on under our noses and we didn’t notice,” says Hoogland. He describes the killings as “quick, subtle and unanticipated”. While some prairie dogs chased the squirrels, others stalked them, waited outside their burrows or even dug babies out of their holes. They bit them to death and then abandoned the carcass and resumed foraging on nearby vegetation. “The killer supreme killed seven babies from the same litter in one day,” says Hoogland. Over the years, about 47 prairie dogs killed squirrels, and 19 of them were serial slayers, including one female who dispatched nine squirrels over four years. John Hoogland Crucially, the pair have shown that serial killers went on to have more offspring than non-killers, and that their “fitness” levels – a measure of evolutionary advantage based on theirs and their offspring’s survival – were nearly three times higher than those of non-killers over their lifetime. If the killings are really improving their families’ chances of survival, then the discovery is of fundamental importance in understanding ecosystems, says Hoogland. “It begs the question of whether it’s going on in other species,” he says. Dieter Lukas, behavioural ecologist at the University of Cambridge, says that, from the squirrel’s point of view, a competitor species may turn out to be as much of a risk as a predator or as lack of food. “It’s really something surprising that people hadn’t been aware of,” he says. Journal reference: Proceedings of the Royal Society B: Biological Sciences, DOI: 10.1098/rspb.2016.0144   More on these topics: