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The parasite makes wolves more likely to become pack leaders | Science

The parasite makes wolves more likely to become pack leaders | Science

Toxoplasma gondii sometimes called a “mind control” parasite: it can infect the brains of animals and corrupt their behavior in ways that may kill the host but help ensure the parasite’s spread. But now, researchers have discovered that infected wolves can actually benefit from those mind-altering tricks. A Toxoplasma the infection, they found, makes wolves bolder and more likely to become pack leaders or disperse to other habitats, giving them more opportunities to breed.

“We really underestimated some of the consequences that this parasite has,” says Eben Gehring, a biologist at Nova Southeastern University who was not involved in the work. “The findings likely represent the tip of the iceberg regarding the importance of parasites to the dynamics of wild ecosystems.”

T. gondii, a single-celled parasite, reproduces only in domestic cats and other cats. Infected cats shed spore-filled oocysts in their feces, which can survive on plants or in soil or water. They can also survive in undercooked meat from livestock or game. When a host – including humans – eats the oocyst, the spores are released and spread to the brain and muscles, forming new cysts. Worldwide, approximately one in four people is infected. Usually the immune system keeps the parasite under control, but it can cause miscarriage and other serious problems during pregnancy.

Rodents have long been known to be infected Toxoplasma they lose their fear of predators. The cysts in the brain somehow increase dopamine and testosterone, increasing boldness and risk-taking and increasing the chance that cats will eat their host. “These parasites use some generic mind control or personality control that helps them fulfill their life cycle,” says Jaap de Roode, a biologist at Emory University who was not involved in the new research. “And that has all kinds of interesting consequences that we might not have thought of before.”

The consequences are not limited to rodents. Researchers in Gabon discovered this in 2016 Toxoplasma-infected captive chimpanzees lost their aversion to leopard urine. And last year, another team described how Toxoplasma– infected hyena cubs in Kenya venture closer to the lions, making them more likely to be killed.

When researchers learned a few years ago that some wolves in Yellowstone National Park were infected Toxoplasma, Connor Meyer, Ph.D. student at the University of Montana, teamed up with park biologist Kira Cassidy to see if the parasite also changes wolf behavior.

Meyer and Cassidy studied 26 years of research on gray wolves in the park, incl Toxoplasma test results from blood samples collected in various areas of the park. They also examined data on cougars, in which Toxoplasma can be reproduced. Wolves that have moved in areas with a lot of cougars are more likely to be infected Toxoplasma, they found. It’s likely, the authors say, that these wolves picked up their infections from cougars, possibly by scavenging around or eating the chat of big cats.

By combining infection data and earlier observations in the field, they also discovered that they were infected wolves were much more likely to become pack leadersreports the team today at Communications Biology. Infected wolves are also more likely to leave their pack at a younger age and seek new territory or other packs, just as infected rodents become more exploratory. “There may be a few cases where wolves or even their pack become really successful because they push those boundaries and become more risk-averse,” Cassidy says.

The study is one of the few that examines Toxoplasma in the wild. “We know that infection can change animal behavior, but it’s very difficult to document that in wildlife populations,” says Meggan Craft, a wildlife disease ecologist at the University of Minnesota. “What’s cool about this study is that it uses a fantastic long-term study to be able to tease apart these subtle influences of infection and behavior.”

As with rodents, boldness in wolves also carries risk. Wide-roaming wolves are more likely to be hit by a car or leave park boundaries and stay shot by hunters. “Scattering is one of the most dangerous things a wolf can do,” says Meyer. It is also possible that an infected pack leader can transmit the parasite during mating, as can occur in dogs, potentially jeopardizing pregnancy. Overall, Cassidy suspects the risks of infection probably outweigh the long-term benefits. “Wolves live on a knife’s edge to begin with,” says Cassidy.

Because wolves are one of the key species of the park, this parasite “can really have a very important impact on ecosystems,” says de Roode. “They can control food webs; they can control the flow of energy within the ecosystem.”

Infected pack leaders can even influence uninfected wolves, the researchers speculate in their paper. Pack members may imitate their leader’s boldness or curiosity about the cougar’s scent, leading to more wolves being infected. “This is a brilliant idea and I think it’s very plausible,” Goering says.

In the end, wolves seem to be a dead-end host Toxoplasma, however, because they are unlikely to transmit the parasite back to cougars. Still, Meyer wonders if the parasite’s effect on wolves means the animals played a role in the infection cycle at some point in the distant past. During the last ice age, he notes, large lions roamed North America that may have hunted these infected — and emboldened — beasts.



#parasite #wolves #pack #leaders #Science

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