The parasite gives wolves what it takes to be pack leaders

A lone wolf pup in Yellowstone National Park.

Some wolves in Yellowstone National Park in Wyoming share territory with cougars — and can become infected with their parasites.credit: mtnmichelle/Getty

Wolves infected with a common parasite are more likely to lead a pack than uninfected animals, according to an analysis of more than 200 wolves in North America.1. Affected animals are also more likely to leave their home enclosures and strike on their own.

parasite toxoplasmaIt makes its hosts bold—a mechanism that increases their survival. for sexual reproduction, T. Gundi It must reach the cat’s body, usually when its host is being eaten by one. This becomes more likely if the parasite changes the behavior of the host, making it reckless. Research results are mixed, but in rodents, infection is generally associated with decreased fear of cats and increased exploratory behavior. Physical and behavioral changes are also found in people: testosterone and dopamine production increases, and risk increases.

Warm-blooded mammals can catch the parasite by eating an infected animal or ingesting forms of it T. Gundi Throwing in the feces of infected cats. After a period of acute infection, semi-inert cysts form in the muscle and brain tissue, and persist for the rest of the host’s life. Up to a third of people may become chronically infected.

unique data set

T. Gundi It is known to infect wildlife, but few studies have examined its behavioral effects. In one case, injured hyenas in Kenya became more likely to be eaten by lions2. Connor Meyer and Kira Cassidy, wildlife ecologists at the University of Montana in Missoula, pondered a rare opportunity to link infection to wild wolf behavior: data on gray wolves (the gray wolf) has been intensively grown in Yellowstone National Park, Wyoming, for nearly 27 years. Some wolves in Yellowstone live near cougars and sometimes steal prey from them (Concolor puma), which are known to carry the parasite. Wolves can become infected by eating cats — or their feces.

The team looked at 256 blood samples from 229 wolves, which were carefully monitored throughout their lives, recording their life histories and social status. Meyer and Cassidy found that injured wolves were 11 times more likely than uninjured ones to leave their birth families to start a new pack, and 46 times more likely to become pack leaders—often the only wolves in the pack to breed.

“We got this score with our mouths open staring at each other,” says Meyer. “This is a lot bigger than we thought it was going to be.” The work was published today in Communication biology.

Dan McNulty, a wolf biologist at Utah State University in Logan, says the study “provides compelling evidence of the profound impact pathogens can have on the environment and behavior of wild animal populations.” He adds that it illustrates the enormous value of the long-term study of wolves and other wildlife in Yellowstone National Park.

Ecosystem effects

In the future, the team hopes to look at whether infection might increase the likelihood of wolves reproducing successfully — and what the implications would be for low or higher infection rates across ecosystems. Wolves populations with high rates of T. Gundi The infection may spread more quickly across the landscape as individual wolves make the choice to disperse. Aggressive and risky pack leaders can influence how entire packs behave – potentially increasing their chances of encountering cougars and exposing more members to infection.

For Meyer, the moral of the story is that parasites can play a major role in ecosystems. “Parasites may have a much larger role than anyone generally ascribes,” he says.

Wolves have been known to kill cougars, however, so even bold and risky wolves infected with the parasite are unlikely to end up as a cougar’s lunch, Meyer says. It is speculated that in the past, injured wolves were more likely to be preyed upon by American lions (Panthera atrox), huge feline predators weighing about 200 kilograms, which roamed North America until they became extinct more than 11,000 years ago.

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