Parasite makes wolves likely to become pack leaders Sciences

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

“We really underestimated some of the findings of this parasite. The findings probably represent the tip of the iceberg in terms of the importance of the parasite for dynamics,” says Eben Gering, a biologist at Nova Southeastern University who was not involved in the work. of terrestrial ecosystems.

T. GundiIt is a single-celled parasite that only reproduces in domesticated cats and other cats. Infected cats excrete spore-filled eggs in their feces, which can live on plants or in soil or water. It can also persist in undercooked cattle or game meat. When a host—including humans—consumes the egg, the spores are released and spread to the brain and muscles, forming new cysts. Worldwide, one in four people is infected. Normally, the immune system keeps the parasite in check, but it can cause spontaneous abortions and other serious problems during pregnancy.

It has long been known that rodents are infected toxoplasma They lose their fear of predators. The sacs in the brain somehow increase dopamine and testosterone, which promotes boldness and risk-taking and increases the chance of cats eating the host. “These parasites use some general mind control or personality control that helps them complete their life cycle,” says Jaap de Roode, a biologist at Emory University who was not involved in the new study. “And that has all kinds of interesting consequences that we may not have thought of before.”

The consequences are not limited to rodents. In 2016, researchers in Gabon found that toxoplasmaInfected captive chimpanzees lost their aversion to tiger urine. And last year, another team described how toxoplasmaInfected hyena cubs in Kenya get closer to lions, making them more likely to be killed.

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

Meyer and Cassidy have spent more than 26 years researching gray wolves in the park, including toxoplasma Test results from blood samples collected in different park areas. They also examined data on cougars, which toxoplasma can multiply. Coyotes that ranged in areas with lots of cougars were more likely to be infected toxoplasma, they found. It’s possible, the authors say, that these wolves picked up their infestations from the cougars, perhaps by pricking or eating the excrement of the big cats.

By combining infection data with previous field observations, they also discovered that infected wolves were more likely to become pack leaders, the team reported today in Communication biology. Affected wolves were also more likely to leave their pack at a younger age and seek out new territories or other groups, just as injured ferrets became more eager to explore. “There may be a few cases where wolves or their pack become really successful because they push these boundaries and are more accepting of risk,” says Cassidy.

This study is one of very few studies examining toxoplasma in the wild. “We know that infection can change the behavior of animals, but it’s very difficult to document this in wildlife populations,” says Megan Craft, a wildlife disease ecologist at the University of Minnesota. “What’s great about this study is that it takes advantage of a great long-term study to be able to unpack these subtle effects of infection and behavior.”

As with rodents, coyotes’ boldness comes with risk, too. Coyotes that roam widely may be more likely to be hit by a car or leave park boundaries and be shot by hunters. “Scattering is one of the most dangerous things a wolf can do,” says Meyer. It is also possible for the leader of an infected group to transmit the parasite when mating, as it does in dogs, which could endanger the pregnancy. Overall, Cassidy suspects, the risks of infection may outweigh the long-term benefits. “Wolves live on a knife edge to begin with,” Cassidy says.

Since wolves are one of the park’s main species, this parasite “could really have very important impacts on ecosystems,” says de Roode. “They can control food webs; they can control the flow of energy within ecosystems.”

In their paper, the researchers speculated that the leaders of infected packs could affect even uninfected wolves. Pack members may imitate their leader’s boldness or curiosity about the cougar’s scents, striking more coyotes. “This is a great idea, and I find it very likely,” Gering says.

In the end, wolves seem to be a dead-end host to toxoplasmaHowever, they are unlikely to pass the parasite back to cougars. However, Meyer questions whether the parasite’s effect on wolves means that 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 who may have preyed on these infected—and encouraged—monsters.

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