A strange parasite massively improves a wolf’s chances of leading the pack

There’s a parasite at work among gray wolf packs in America’s Yellowstone National Park, and surprisingly, the animals it infects are much more likely to lead their pack than wolves that have deflected the infection. The guilty? Toxoplasma gondii – the parasite responsible for toxoplasmosis, a disease we can catch from contaminated feces and undercooked meat.

T. gondii is a strange parasite that has been associated with risk-taking behaviors in human hosts as well as animals. Research has linked infection with the parasite to certain political views, and even suggested that it can make you more attractive to others. Now, a study has found that it could have unexpected benefits for ambitious wolves, too.

The research looked at gray wolves (Canis lupuss) living in Yellowstone, Wyoming, to see if or how contamination with T. gondii affects the behavior of the wolf. Armed with 26 years of data and blood samples from 229 wolves, they were able to look for correlations between geography, behavior and infection status.

Yellowstone is also home to cougars (Puma concolor) known to carry the parasite, and sure enough, wolves living in close proximity to pumas were more likely to become infected. Interestingly, the analyzes also showed that infection with the T. gondii parasite made the wolves much bolder.

toxoplasmosis wolves

Three sample packets with different cougar classes are overlaid and the corresponding predicted probabilities of T. gondii infection (negative in black, positive in red). Image Source: Kira Cassidy

Infected wolves were 11 times more likely to leave the group than uninfected individuals. While dispersal is a natural part of wolf life, it is a dangerous behavior because there is safety in numbers when moving with the pack.

Infected wolves were also more likely to become pack alphas. Each group is led by a pair of alphas and wolves infected with T. gondii they are more than 46 times more likely to end up leading the pack in this way.

As to why this association might exist, it is possible that parasitism leading to risk-taking behaviors allows T. gondii to reach its ultimate goal: to spread as far and wide as possible.

“Due to the social hierarchy within a wolf pack, we hypothesize that the behavioral effects of toxoplasmosis may create a feedback loop that increases spatial overlap and disease transmission between wolves and cougars,” the study authors write.

“These findings demonstrate that parasites have important implications for intermediate hosts, beyond acute infections, through behavioral effects. Particularly in a social species, these effects can transcend individuals and affect groups, populations, and even ecosystem processes.”

Now, excuse us while we go think about his idea a bit T. gondii leading us like Arquillian.

The study was published in Communications Biology.

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