Grey wolves infected with this parasite are more likely to become pack leaders, scientists say

Researchers studying gray wolf populations in Yellowstone National Park have discovered an interesting reason why some wolves tend to be pack leaders.

Gray wolves exposed to Toxoplasma gondii (the parasite that causes toxoplasmosis) are 46 times more likely to become pack leaders than uninfected wolves, according to a study released Thursday. communication biology.

The researchers analyzed behavioral and distributional data from 1995 to 2020, as well as blood samples from 229 anesthetized wolves, to examine the association between risk-taking behavior and infection with Toxoplasma gondii. . They identified an association between parasitic infections and high-risk behaviors in both men and women.

Findings showed that T. gondii-positive wolves were 11 times more likely than uninfected wolves to disperse from the pack and more than 46 times more likely to become pack leaders. Males were 50% more likely to leave the herd within six months if infected with the parasite, while she was 50% more likely to leave the herd during that period if unaffected, he jumped to 21 months for that period. . If a female becomes infected, she has a 25% chance of leaving the herd within 30 months, and if uninfected she extends to 48 months.

Infections with T. gondii often do not adversely affect fitness in healthy individuals, but can be fatal to young and immunosuppressed wolves, researchers say. According to Ph.D. Conor Meyer, it’s not yet known how the parasite affects things like survival. A student at the University of Montana, he is one of the authors of this study.

The findings are the first to show parasite infections affecting species decision-making and behavior, the researchers said.

Previous studies have identified a link between T. gondii infection and increased boldness in hyenas and increased testosterone production in rats, and the authors found that similar mechanisms were observed in parasite-positive wolves. We speculate that it may be causing dangerous behavior.

Wolves living in areas with high cougar population density were more likely to be infected with T. gondii than wolves not living near cougars, and wolves contracted the parasite as a result of direct contact with cougars and their environment. suggests that it is possible to , the researchers discovered. Cougars in Yellowstone National Park are known to host parasites.

The findings “tell the story of this entire ecosystem and how the species interact with each other,” said one of the authors, a nonprofit affiliated with Yellowstone National Park and the National Parks. Kira Cassidy, a researcher at the organization Yellowstone Forever, said.

Researchers believe that the infection could have a broader impact on wolf populations, as infected pack leaders may lead the pack into areas of high risk of overlapping with cougars, increasing the risk of uninfected wolves becoming infected further. assumed to give.

“So that’s probably the link between the parasite and the actual mechanism behind the infection,” Meyer said.

It’s only the second study of its kind to look at how toxoplasmosis infection affects predator species, and is “strong evidence of what long-term studies can solve.”

Cassidy added: “Taking an ecological approach to a research question can be very difficult in many places, but Yellowstone is a place where you can see all the species that were here hundreds of years ago. It’s one.”

Gray wolves were widely eradicated in the western United States in the 1940s, but populations have begun to recover in recent decades. some say it increases Wolves are harmful to humans because of their ability to travel long distances and spread disease. Wolves can also be an important factor in the decline of big game herds and the killing of livestock.

Earlier this month, a federal judge in Montana temporarily ruled Restrictions on hunting and catching wolves in close quarters Yellowstone and Glacier National Park.

However, wolves are usually wary of humans. In Yellowstone, they are “the most shy and cautious” of all large mammals, says Cassidy.

“If you see one, you’re incredibly lucky,” she said. “Overall, they’re not inherently dangerous to people.”