A mind-altering parasite could make wolves bolder

A mind-altering parasite could make wolves bolder

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The mind-altering effects of a well-known parasite may extend to more species than we thought. In new research this month, Yellowstone scientists argue that Toxoplasma gondii infection may influence the behavior of gray wolves in the area. This seems to increase their chances of risky behaviors, such as leaving their pack or becoming pack leaders.

Toxoplasma gondii is a unicellular protozoan parasite. To complete its complex life cycle and reproduce, it must eventually infect members of the feline family. In order to accomplish this, T. gondii is believed to alter the behavior of infected rodents, a common intermediate host. T. gondii-infected rodents become less suspicious of cat urine and less fearful of predators in general, which then makes them more likely to be eaten by a cat.

However T. gondii would probably prefer to be inside rodents or birds that cats like to nibble on, their resistant cysts regularly infect all sorts of warm-blooded species. These infections seem to rarely cause acute illness, but the cysts themselves often survive in the body for life. And over the years, some studies have shown that this infection could have subtle behavioral or neurological effects in non-rodent animals. Most of this research has focused on humans, with studies discovery that infected humans might have a higher risk of schizophrenia, for example. But wildlife researchers at Yellowstone National Park wanted to know what factors might affect the prevalence of T. gondii infection in their wolves, and whether this infection may have significant consequences for them as well.

Image for article titled Mind-altering parasite could make wolves bolder

The team analyzed more than 25 years of data on the park’s gray wolf populations, which included blood tests that could screen for antibodies against T. gondii. They also looked at data on the park’s cougars, as they suspected that wolves living closer to these cats would have a higher risk of infection.

As expected, cougars were regularly exposed to T. gondii (about 50% of the sample tested positive). And when wolves lived in areas that overlapped cougar populations, they more often had T. gondii antibodies — infections likely obtained through direct contact with cat feces or cysts in the environment, the researchers said. These infected wolves were then more likely to display risky behaviors than uninfected wolves, such as dispersing (leaving their pack and traveling far elsewhere) or becoming the breeding leaders within their pack. Interestingly, this influence can then create a kind of feedback loop, the researchers speculate, since bolder infected wolves might be more likely to lead their packs into cougar territory, allowing the parasites to infect more wolves.

“This study is a rare demonstration of a parasitic infection influencing the behavior of a population of wild mammals,” the authors wrote in their paper. published this month in Communications Biology. “These two life-history behaviors represent some of the most important decisions a wolf can make in its lifetime and can have dramatic impacts on gray wolf body condition, distribution, and vital rates.”

Findings, however intriguing, should ideally be confirmed by further studies before they are presumed to be true (even in humans there is a ongoing debate on how much T. gondii the infection really affects us). And we don’t know exactly how T. gondii could affect the wolf’s behavior, although the authors hypothesize that the infection could increase testosterone levels. But this is only the latest research that suggests that T. gondii is not only able to play puppeteer with rodents. A study from last year, the authors note, found that infected hyenas were bolder and more likely to be eaten by lions than uninfected hyenas. So, if nothing else, more research is needed to understand and unravel the many ways in which T. gondii and similar organisms can influence the world around them.

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

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