Wolves with the famous mind-altering parasite have a strange thing happen to them

The parasite Toxoplasma gondii makes wolves 46 times more likely to become pack leaders, according to a study of 26 years’ worth of wolf behavior data and an analysis of the blood of 229 wolves.

The research shows that the effects of this parasite in the wild have been horribly understudied, and its role in ecosystems and animal behavior has been underestimated.

You probably know about this parasite if you have a cat. The tiny organism can only reproduce sexually in the bodies of cats, but it can infect and grow in almost any animal with a warm body temperature.

This includes people, in whom it can cause a parasitic disease called toxoplasmosis, which usually has no symptoms but can still be fatal.

If T. gondii doesn’t want to become an evolutionary dead end, it needs to find a way to get its offspring back into a cat once it’s in another host. And it has a weird way to increase its chances.

Animals like rats that have the parasite start to take more risks. In some cases, they become fatally attracted to the smell of cat urine and are therefore more likely to be killed by cats.

It means that bigger animals, like chimpanzees, are more likely to run into a bigger cat, like a leopard. Hyenas with T. gondii are also more likely to die from lion attacks.

Gray wolves (Canis lupus) in Yellowstone National Park aren’t really something that cats would want to eat. But sometimes their territory overlaps with that of cougars (Puma concolor), which are known to carry T. gondii, and both species eat the elk (Cervus canadensis), bison (Bison bison), and mule deer (Odocoileus hemionus) that live there.

It’s possible that wolves can also get infected. This could happen if they sometimes eat dead cougars or eat cougar poop.

Almost 27 years of data on the wolves and how they act gave scientists a rare chance to study how the parasite affects a wild intermediate host.

Researchers from the Yellowstone Wolf Project, led by biologists Connor Meyer and Kira Cassidy, also looked at blood samples from wolves and cougars to figure out how often they were infected with T. gondii.

They found that T. gondii was more likely to be found in wolves that shared a lot of territory with cougars.

But there was also a change in behavior, with people taking a lot more risks.

11 times as many infected wolves moved away from their pack and into new territory. Infected males were more likely to leave their pack in six months than uninfected males, who usually stayed with their pack for 21 months.

Infected females had a 25% chance of leaving their pack within 30 months, while uninfected females had a 50% chance of leaving their pack within 48 months.

Infected wolves also had a much higher chance of becoming pack leaders. T. gondii may cause testosterone levels to rise, which could make wolves more aggressive and dominant. These are qualities that would help a wolf become the leader of its pack.

There are a few important things that come from this. The pack leaders are the ones who have babies, and T. gondii can be passed from mother to child at birth. But it can also change how the pack works as a whole.

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

“If the lead wolves are infected with T. gondii and start acting differently, this could set off a chain reaction in which the behavior of one infected wolf affects the rest of the pack.”

If, for example, the pack leader follows the smell of cougar pee as they boldly move into new territory, they could be exposed to the parasite more, which would mean that more wolves would get T. gondii. This generates a sort of feedback loop of increased overlap and infection.

It’s strong evidence that small, little-studied agents can have a big effect on the way an ecosystem works.

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

It is important to include the effects of parasite infections in future wildlife research if we want to know how parasites affect individuals, groups, populations, and the way ecosystems work.