Diagram of the results of the demographic and behavioral analysis. Shown at the top are three sample packs with different cougar overlap categories and their corresponding predicted probabilities of T. gondii infection (seronegative in black; seropositive in red) based on the best-fit demographic model. Wolves filled with red indicate the expected percentage of infected wolves out of 100%. Cougar density ≥1.8/100km2 is represented by hatching. The cougar density of less than 1.8/100 km2 corresponds to the entire area outside the hatching. At the bottom are the predicted probabilities with 95% confidence intervals (gray lines) based on best-fitting behavioral models, of two risky behaviors: dispersing and becoming pack leader for seronegative and seropositive wolves at 24 .9 months tracked (the average number of months wolves in this study were tracked). 1 credit
A team of researchers from the Yellowstone Wolf Project at the Yellowstone Center for Resources in Yellowstone National Park, Wyoming, found that wolves in the park that are infected with Toxoplasma gondii, a common parasite, are much more likely to become leaders of their pack. In their study, reported in the journal Communications Biologythe group analyzed data from studies of wolves in the park over a 26-year period.
T. gondii is an obligate parasite that infects protozoa in the cells of infected animals. These infections are known as toxoplasmosis and occur in almost all warm-blooded animals, including humans. Previous research has shown that in most cases the symptoms are few, but some evidence suggests they may lead to an increase in erratic or aggressive behaviors.
In this new effort, the researchers wondered what kind of impact T. gondii infections might have on wild wolves. To find out, they conducted an in-depth study of wolves living in Yellowstone National Park.
The work involved studying data from blood samples taken from more than 200 wolves living in the park during the years 1995-2020, while looking for evidence of infection. The researchers also looked at notes taken by research observers to learn more about any behavioral changes that might have been evident in the wolves.
The researchers found that infected young wolves tended to leave their pack earlier than uninfected ones. Infected males were 50% more likely to leave their pack as early as six months after birth. Males normally remain for up to 21 months. And infected females were 25% more likely to leave their pack at 30 months, rather than 48 months.
The researchers also found that infected males were more than 46 times more likely to become pack leaders than uninfected males. The researchers also found that infection rates were higher in wolves that mingled with cougars. The researchers suggest the behavioral differences were likely due to the parasite’s impact on the wolves’ brains, making them bolder and less likely to back down when challenged by others.
More information:
Connor J. Meyer et al, Parasite infection increases risk taking in a carnivore intermediate social host, Communications Biology (2022). DOI: 10.1038/s42003-022-04122-0
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Quote: Wolves infected with a common parasite may be much more likely to become pack leaders (2022, November 25) Retrieved November 26, 2022 from https://phys.org/news/2022-11-wolves-infected-common -parasite-leaders.html
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