‘Mind Control’ Parasite Makes Wolves Effective Pack Leaders

‘Mind Control’ Parasite Makes Wolves Effective Pack Leaders


The parasite Toxoplasma gondii can change the behavior of infected wolves in ways that make them more likely to be pack leaders

North American Grey Wolf, canis lupus occidentalis, Adult running on Snow. Credit: Gerard Lacz/Alamy Stock Photo

Wolves infected with a common parasite are more likely than uninfected animals to lead a pack, according to an analysis of more than 200 North American wolves. Infected animals are more likely to leave their pack and go on their own.

The parasite, Toxoplasma goesndii makes its hosts fearsome–a mechanism that helps it survive. T.gondii must reach a cat’s body to reproduce sexually. This usually happens when the host is eaten. This is made more likely if the parasite alters a host’s behavior, making it foolish. Research results are mixed, but in rodents, infection generally correlates with decreased fear of cats and increased exploratory behaviour. People also show physical and behavioral changes: dopamine and testosterone production are higher, and there are more risks.

Warm blooded mammals can be infected by the parasite by eating infected animals or ingesting T.gondii shed from infected cats. Semi-dormant cysts can form in the brain and muscle after an acute infection and last for the rest of the host’s life. One-third of people might be chronically infected.

Unique data set

T. Gondii has been shown to infect wildlife. However, few studies have looked at its behavioural effects. One study found that infected hyenas from Kenya were more likely to be eaten and killed by lions after they had been infected. Connor Meyer and Kira Cassidy, wildlife ecologists at the University of Montana in Missoula, thought of a rare opportunity to link infection with behaviour in wild wolves: data on grey wolves (Canis lupus) collected intensively in Yellowstone National Park, Wyoming, over nearly 27 years. Some wolves in Yellowstone live near, and sometimes steal prey from, cougars (Puma concolor), which are known to carry the parasite. The parasite could be transmitted to wolves by eating cats or their faeces.

The team looked at 256 blood samples from 229 wolves, which had been carefully watched throughout their lives, and had their life histories and social status recorded. Meyer and Cassidy found that infected wolves were 11 times more likely than uninfected ones to leave their birth family to start a new pack, and 46 times more likely to become pack leaders–often the only wolves in the pack that breed.

” We got that result and just stared at each others open-mouthed,” Meyer said. “This is way bigger than we thought it would be.” The work is published today in Communications Biology.

Dan Macnulty is a wolf biologist from Utah State University in Logan. He says that the study “provides compelling proof of the profound impact that pathogens may have on the ecology, behaviour, and ecology of wild animal populations”. He says it shows the immense value of long-term studies of wolves and other wildlife in Yellowstone National Park.

Ecosystem effects

The team plans to investigate whether infection might make wolves more prone to reproducing successfully and what the ripple effects might be of low or high infection rates across ecosystems. High rates of T.gondii infection may lead to a greater spread of wolves in a given area as individual wolves decide to disperse. Aggressive and risk-taking leaders can influence how whole packs act, possibly increasing their chances of encountering Cougars and exposing more members.

Meyer believes that parasites can play a major role in ecosystems. Meyer says that parasites may play a greater role in ecosystems than most people give them credit for.

Wolves have a reputation for killing cougars. However, Meyer states that even brave, risk-taking wolves infected by the parasite are unlikely to be eaten by cats. He speculates that in the past, infected wolves could have been more likely to be preyed on by American lions (Panthera atrox), massive feline predators weighing around 200 kilograms, which prowled North America until they went extinct over 11,000 years ago.

This article is reproduced with permission and was first published on November 24 2022.


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