Parasites 'brainwash' young hyenas, urging them to come close to predators

Young hyenas infected with the parasite Toxoplasma gondii close the gap with lions, putting them at greater risk than their healthy counterparts.

Young hyenas are the lion's favorite food, so they often stay close to their parents to avoid surrendering their lives to predators. With animals infected with the parasite Toxoplasma gondii, this mentality is reversed.

According to data collected over decades in Kenya's Masai Mara National Reserve, young hyenas infected with Toxoplasma gondii are closer to lions and four times more likely to die than their healthy counterparts. strong.

Toxoplasma gondii makes young hyenas more "aggressive". (Photo: Science News)

"I was surprised to see the huge difference in 'closeness' between lions and their infected and uninfected cubs," said Kay Holekamp, ​​a behavioral ecologist at Michigan State University and a co-author of the study published in the journal Nature Communications, said.

Toxoplasma is a single-celled parasite that infects at least a third of the world's population. It is famous for its ability to manipulate hosts, such as mice, to act recklessly around cats. But this is the first time scientists have documented such an effect in large wild mammals.

"This parasite not only affects domestic cats and rats, but also has the potential to spread very widely," said scientist Kay Holekamp. Holekamp's expertise is backed up by 33 years of hyena research.

Cat playing with hyena

Toxoplasma parasites can be transmitted to many animals at the lower levels of the food chain, including rodents, birds, etc. They are transmitted to these species through meat or feces contaminated with Toxoplasma. However, Toxoplasma can only reproduce in the cat intestine. So how can the parasites get in contact with as much of a cat's intestines as possible?

Toxoplasma gondii.

Taking millions of years of evolution, the distant relative of the malaria parasite Plasmodium has acquired a surprising mechanism of transmission: rodents infected with Toxoplasma will be attracted to the smell of cat urine, drawing them close to the baby. hungry cat.

Because the parasite can reproduce in the intestines of lions, and hyenas are one of many species that carry Toxoplasma in humans, researchers Kay Holekamp and Zach Laubach wanted to find out if Toxoplasma could manipulate hyenas. are not.

The team of scientists associated with the decades-old Mara Hyena Tracking Project has recorded data on the specific location of individual hyenas, including their distance of contact with other hyenas. other animals in the reserve. In addition, the project also records the number, age, sex and blood samples of young hyenas - this is the data that allows the research team to identify individuals infected with Toxoplasma, the parasite species will follow the animal. owner for life.

Their study found that up to a third of hyena cubs are infected with Toxoplasma, about 71% of juveniles and 80% of adults carry the human parasite.

A hyena over one year old knows that she should not get close to a lion.

Young hyenas that are not infected with the parasite will stay about 100 meters away from lions, but the average distance between hyena cubs with Toxoplasma antibodies and lions is 40 meters. When hyenas are a year old, they are wise enough to know that they should not go near those large cats.

One of the limitations of this study, according to the two report authors, is that it is unclear whether young hyenas are afraid of other predators and dared to approach the danger. The team is still looking for more data to answer the question.

Research to change opinion

Stefanie Johnson, a University of Colorado scientist who has spent years tracking the Toxoplasma parasite, appreciates the new study. 'It confirms that the Toxoplasma parasite has a strong influence on the behavior of mammals', possibly including humans.

Most people infected with Toxoplasma only have a mild fever and recover quickly, but the parasite can seriously affect the fetus, so pregnant women should not come into close contact with cat feces. And yet, there are studies that offer controversial evidence that people with Toxoplasma are more careless driving or more willing to take business risks; Research has shown that people infected with parasites have a reduced ability to perceive fear.

Researcher Johnson believes that these behavioral changes are an indication that Toxoplasma parasites, affecting their hosts, may be able to manipulate high-level mammals in ways that are still unknown.

'This is a parasite most of us consider to be temperate, especially when it comes to infecting people,' Ms. Stefanie Johnson said. 'But when you look at the effects, Toxoplasma can have a big impact on human behavior, even manipulating at the level of social behavior'.