The gray wolves may be experiencing changes in behavior due to the Toxoplasma gondii parasite, which can influence animal behavior. This single-celled parasite is known to cause the disease toxoplasmosis and can infect a significant portion of the human population. While typically mild, it can be dangerous for those who are young or have a weakened immune system.
The Toxoplasma parasite can only reproduce in the intestines of cats, but it can infect any warm-blooded animal and is known for altering the behavior of its hosts, particularly making rodents act recklessly around house cats.
Parasitic Worm Manipulating Wolves' Brain
In a recent study published in Communications Biology, researchers analyzed behavioral data and blood samples from wolves in Yellowstone National Park over 26 years, starting from the time when the wolves were reintroduced to the park in 1995. They also examined the distribution of cougars in the park and analyzed blood samples from the big cats, which are known to be hosts for the Toxoplasma parasite.
The results indicated that wolves living in areas where cougars were present were more likely to be infected with Toxoplasma compared to wolves without feline neighbors. Additionally, wolves that tested positive for the parasite were more likely to leave their pack and become pack leaders compared tpo uninfected wolves. These findings align with the known effects of Toxoplasma on animal behavior and the previous observation that it can make rodents less fearful around predators.
An animal can become infected with Toxoplasma by consuming an infected animal or by coming into contact with the egg-like cysts of the parasite, which are found in cat feces. If the parasite infects a host that is not a cat, it can reside in different parts of the body, including the brain, for an extended period. Toxoplasma needs to end up in a cat's intestine to reproduce, and it has evolved ways to make this happen, such as causing infected rodents to be more active and less afraid of predators, such as house cats.
This behavior increases the likelihood of the rodent coming into contact with a cat, allowing the Toxoplasma parasite to reach its preferred environment. Infected mice and rats may also lose their fear of cat urine and even become attracted to the scent. Previously, researchers have studied the effects of Toxoplasma infection in controlled laboratory settings, but more recently they have begun to investigate its impact in the wild. One study found that chimpanzees infected with Toxoplasma were attracted to the urine of leopards, their natural predators.
Grey wolves in Yellowstone National Park take in the snowy scenery.
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Infecting Other Species
Another study showed that infected spotted hyena cubs were more likely to approach and be killed by lions. These findings suggest that the behavioral changes caused by Toxoplasma infection, which have been observed in rodents and confirmed in wild animals, may also influence group dynamics and behaviors that have ecological consequences in highly social animals like hyenas and wolves. These effects of Toxoplasma infection on animal behavior are an area of ongoing research.
There is proof to suggest that people with toxoplasmosis may be more prone to taking risks, such as driving dangerously, which can lead to fatal traffic accidents. However, not all of the effects of Toxoplasma infection are negative. In a study of college students and business professionals, those infected with the parasite were more likely to study business or start their businesses. In countries with higher rates of Toxoplasma infection, people were also less likely to be fearful of failure when considering new entrepreneurial endeavors. It is not fully understood how Toxoplasma, which is a distant relative of malaria, causes these changes in mammal behavior.
On the other hand, there is some evidence that Toxoplasma may affect neurotransmitters, such as dopamine, or hormones, such as testosterone, to alter behavior. It is also possible that the parasite causes low-grade inflammation, which can impact behavior. The exact mechanism by which Toxoplasma influences animal behavior is not yet fully understood. However, it is becoming clear that parasites, especially Toxoplasma, have a significant and often underappreciated role in the lives of animals. Scientists estimate that around 40% of animal species are parasites, and they may constitute a majority of undiscovered species.
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