The gray wolf almost went extinct some decades ago. But they were reintroduced in Yellowstone National Park in 1995 and scientists have been monitoring them ever since.
Pack behavior is observed via trail cameras and plane flyovers, and about a quarter of the wolves wear radio tracking collars and undergo blood tests. Wolves are pack animals, living in family groups led by a matriarch and her mate. Some wolves stay with their pack their whole lives, helping hunt and raise pups like aunts and uncles as they mature, but others split off to find a mate of their own and start their own packs giving rise to the expression, “lone wolf”.
Scientist have wondered why some wolves simply break off from the pack. They conclude generally that there are lots of factors that go into these types of behavior, such as quirks of personality and family relationships established as pups, but new scientific findings revealed a surprising influence on wolf-pack dynamics: a mind-controlling parasite that makes a gray wolf engage in riskier behavior.
Researchers found that gray wolves in Yellowstone National Park that are infected with a parasite known as Toxoplasma gondii were more likely to leave the group of wolves they were born into or become a pack leader.
The startling revelations could change scientists’ understanding of wolf-pack dynamics and improve conservation efforts for an apex predator that plays a major role in the health of its mountain ecosystem.
The parasites enter the intermediate host’s brain and muscle tissue and change its behavior. The mechanism isn’t yet clear to researchers, but the phenomenon is most well known in rodents: Mice infected with T. gondii seem to lose their inherent fear of cats and no longer avoid the scent of cat urine, studies have shown. These daredevil mice make an easy meal for a cat, and in eating them, the newly infected feline unwittingly sets the process in motion once again. And now, a recent study in the journal Communications Biology has shown the first evidence of T. gondii’s effect on gray wolves.
A wolf puts itself in danger when it leaves its family and goes off to join or form a new pack, so the researchers looked back on a quarter century’s worth of records of wolf dispersal and pack leadership, linked with blood test results from all the wolves in the study.
The study team found something startling: “A wolf that is positive for toxo is 11 times more likely to disperse than a wolf that’s negative,” said wildlife biologist Kira Cassidy, a research associate at the Yellowstone Wolf Project and co-lead author of the study. “And then becoming a pack leader was even more of an impact: A wolf that was positive was 46 times more likely to become a pack leader than a wolf that was negative.”
Given the behavioral patterns associated with T. gondii in other animals, the researchers suspect that toxo is responsible for these trends. “We assume that there might be some sort of link between boldness caused from toxo and being more willing to leave your home range and go to another wolf’s territory and possibly be killed,” Meyer said—a thought-provoking conclusion that might apply to human behavior as well.