Which mammal is most likely to be murdered by its own kind? It’s certainly not humans—not even close. Nor is it a top predator like the grey wolf or lion, although those at least are #11 and #9 in the league table of murdery mammals. No, according to a study led by José María Gómez from the University of Granada, the top spot goes to… the meerkat. These endearing black-masked creatures might be famous for their cooperative ways, but they kill each other at a rate that makes man’s inhumanity to man look meek. Almost one in five meerkats, mostly youngsters, lose their lives at the paws and jaws of their peers.
Gómez’s study is the first thorough survey of violence in the mammal world, collating data on more than a thousand species. It clearly shows that we humans are not alone in our capacity to kill each other. Our closest relatives, the chimpanzees, have been known to wage brutal war, but even apparently peaceful creatures take each other’s lives. When ranked according to their rates of lethal violence, ground squirrels, wild horses, gazelle, and deer all feature in the top 50. So do long-tailed chinchillas, which kill each other more frequently than tigers and bears do.
The point of this macabre census was to understand the origins of our own behavior. Gómez typically studies plants and insects, but he realized that the techniques he uses to study their evolution can be used to study our own. In particular, he noted that closely related species tend to show similar levels of lethal interpersonal violence. He could use those similarities to predict how violent any given mammal should be, and whether it meets, exceeds, or defies those expectations.