Something strange happens to wolves infected with infamous mind-altering parasite: ScienceAlert

A study of 26 years of wolf behavioral data and blood analysis of 229 wolves showed that infection with the parasite Toxoplasma gondii makes wolves 46 times more likely to become pack leaders.

Research shows that the effects of this parasite in the wild have been woefully understudied – and its role in ecosystems and animal behavior has been underestimated.

If you have a cat, you have probably already heard of this parasite. This microscopic organism can only reproduce sexually in the bodies of felines, but it can infect and thrive in almost any warm-blooded animal.

This includes humans, where it can cause a usually asymptomatic (but potentially fatal) parasitic disease called toxoplasmosis.

Once in another host, individual T. gondii Parasites must find a way to bring their offspring back inside a cat if it doesn’t want to become an evolutionary dead end. And he has a slightly scary way of maximizing his chances.

Animals such as rats infected with the parasite begin to take more risks and in some cases become fatally attracted to the smell of feline urine and are therefore more likely to be killed by them.

For larger animals, like chimpanzees, this means an increased risk of encountering a larger cat, like a leopard. Hyenas infected with T. gondii they are also more likely to be killed by lions.

The gray wolves (Dog lupus) in Yellowstone National Park are not really prey for cats. But sometimes their territory overlaps with that of cougars (Puma concolor), known carriers of T. gondiiand both species feed on elk (Canadian Cervus), bison (bison bison), and mule deer (Odocoileus hemionus) which can also be found there.

It is possible that wolves also become infected, perhaps by occasionally eating dead cougars or ingesting cougar poop.

Data collected on wolves and their behavior over nearly 27 years provided a rare opportunity to study the parasite’s effects on an intermediate wild host.

The researchers, led by biologists Connor Meyer and Kira Cassidy of the Yellowstone Wolf Project, also examined blood samples from wolves and cougars to assess the rate of T. gondii infection.

They found that wolves whose territory overlapped with that of cougars were more likely to be infected with the virus. T. gondii.

But there was also a behavioral consequence, with considerably increased risk-taking.

Infected wolves were 11 times more likely to disperse from their pack to new territory. Infected males had a 50 percent chance of leaving their pack within six months, compared to a more typical 21 months for uninfected ones.

Similarly, infected females had a 25 percent chance of leaving their pack within 30 months, compared to 48 months for those who were not infected.

Infected wolves were also much more likely to become pack leaders. T. gondii can increase testosterone levels, which in turn could lead to increased aggression and dominance, which are traits that would help a wolf assert itself as a pack leader.

This has several important consequences. Pack leaders are those who reproduce, and T. gondii transmission can be congenital, passed from mother to offspring. But it can also affect the dynamics of the entire peloton.

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“Due to the group living structure of the gray wolf pack, pack leaders have a disproportionate influence over their comrades and over group decisions,” the researchers write in their paper.

“If the main wolves are infected with T. gondii and show changes in behavior…this can create a dynamic in which behavior, triggered by the parasite in one wolf, influences the rest of the wolves in the pack.

If, for example, the pack leader is looking for the smell of cougar pee as they boldly advance into new territories, they could face greater exposure to the parasite, therefore a higher rate of T. gondii infection throughout the wolf population. This generates a sort of feedback loop characterized by increased overlap and infection.

This is compelling evidence that tiny, understudied agents can have a dramatic influence on ecosystem dynamics.

“This study demonstrates how community-level interactions can affect individual behavior and could potentially extend to group-level decision-making, population biology, and community ecology,” the researchers write.

“Integrating the implications of parasitic infections into future wildlife research is essential to understanding the impacts of parasites on individuals, groups, populations and ecosystem processes.”

The research was published in Communication biology.

An earlier version of this article was published in November 2022.