What compels some animals—maybe even humans—to become leaders of their pack? A new study suggests the answer could be surprisingly simple: a brain parasite. Researchers studying Yellowstone wolves discovered that those infected with a parasite called Toxoplasma gondii are more likely to become pack leaders or to roam from their native habitat, reports Science. T. gondii reproduces only in cats—though it can affect other animals, including humans—and it's possible the infected wolves picked it up while eating cougar scat.
The parasite has a unique characteristic: It makes infected hosts act fearlessly—which increases the host's odds of being killed and eaten, thus allowing the parasite to spread. (Previous research, for example, suggests that infected mice lose their fear of cats, with all the expected consequences.) The study in Communications Biology, then, suggests that infected wolves begin to act more boldly and become pack leaders as a result. Specifically, infected wolves were 46 times more likely than uninfected wolves to lead a pack, and 11 times more likely to venture out from their birth family and start a pack of their own, per Nature.
"We got that result and we just open-mouth stared at each other," says Connor Meyer, a wildlife ecologist at the University of Montana. "This is way bigger than we thought it would be." As NPR notes, the researchers aren't saying the parasite necessarily makes the infected wolves good leaders. "I think the quality of the leadership, once it reaches that position, is going to be one of the most interesting things to look at next," says study co-author Kira Cassidy, also of the University of Montana. (More wolves stories.)
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