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ZoologyA parasite helps wolves become pack leaders
Infected animals become more daring and dominate their congeners, often becoming the only ones to reproduce.
By modifying the behavior of its intermediate hosts, here the wolf, the parasite has a better chance of spreading.
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Parasites may well play a more important role in ecosystems than previously imagined. This is suggested by a new study conducted over 26 years on more than 200 wolves in Yellowstone Park, in the United States. Researchers have found that wolves infected with a certain parasite become pack leaders more easily.
This parasite is the Toxoplasma gondii (T. gondii), capable of infecting any warm-blooded species, including humans, and responsible in particular for toxoplasmosis. It is transmitted in several ways. Either via intermediate hosts, when they are devoured by predators or their excrement infects them. Either the parasite reproduces sexually, but only in its definitive hosts, which are felids.
Rodents are more easily eaten
Several studies have already shown behavioral changes in intermediate hosts, as recalled by “Nature“. Rodents infected with T. gondii see their fear of cats decrease and their exploratory behavior increase. Result: they are eaten more by cats, who are in turn infected and where, this time, the parasite can reproduce. This has also been seen in hyenas. Infected babies become bolder and individuals of all ages are more likely to fall prey to lions. In chimpanzees too, infected subjects take more risks and end up more in the mouths of big cats.
The advantage of conducting such a study in the wolves of Yellowstone is that they represent an intermediate host and rub shoulders with cougars, which are a definitive host. The results showed that infected wolves were 11 times more likely to leave their biological families to found a new pack and were 46 times more likely to become pack leaders.
“Furthermore, our results suggest that wolves contract T. gondii directly from cougars or from their excreted oocysts, and not through an intermediate host, the researchers write in their study. It also demonstrates “how community-level interactions can affect individual behavior and could potentially extend to group-level decision-making, population biology, and community ecology.”
Harder wolves, tending to expand their territory, this obviously also has consequences for its relationship with humans. As for the spread of the virus, it finds several advantages in these behaviors: by the increased reproduction of infected wolves, by their greater dispersion and by their greater mortality (and therefore the fact that their corpses can be devoured by cougars).
The infected human would become more sexually attractive
A study on the same parasite, but carried out on humans, suggests that there too, it modifies its behavior. An infected man or woman would be considered more attractive and healthier by their peers and would therefore have more sexual partners. The parasite can thus more easily be transmitted.