Leaders, are they born or made? In the case of wolves in Yellowstone National Park (United States), the answer could lie in a tiny parasite, Toxoplasma gondii, capable of modifying the behavior of animals and, by extension, of their societies. At least, that’s what a study published in the journal ‘Communications Biology’ suggests.
Toxoplasma gondii It is a parasitic protozoan that reproduces sexually in the digestive tract of felines, but it can infect any warm-blooded animal. From humans to birds and from otters to wolves. These are considered “intermediate hosts” and their infections occur when they ingest resistance forms of T. gondii (“oocysts”), contained in feline feces or by eating another intermediate host.
In non-feline animals T. gondii It usually generates a mild or asymptomatic infection, except in fetuses or immunocompromised individuals, who can develop severe disease. Despite this apparent mildness, the protozoan settles permanently in the muscle or nervous tissue of the infected individual. From his minuscule fortress he seems to take control, at least in part, of complex animals. As complex as a mouse, as a hyena, as you and me.
In many different species it has been found that having T. gondii encysted is related to more intrepid behaviors. This includes greater exposure to risk, less reluctance to face new situations, and loss of fear of predators and indicators of their presence (such as smell).
All these changes generate consequences in the affected individuals. For example, the presence of T. gondii in hyenas it increases the chances that they will die in confrontations with lions, while parasitized sea otters end up more often in the jaws of sharks. One third of humanity hosts T. gondiiand this is related to a greater propensity to suffer traffic accidents, commit suicide or develop psychiatric disorders such as schizophrenia.
In most of the world the main vector of T. gondii is he domestic cat, but there are places where other species of cats take that role. This is the case in Yellowstone, where the main vector of the parasite is the puma.
Cougar parasite makes leading wolves
In the newly published work, researchers from the Yellowstone Wolf Project have studied the relationship between T. gondiithe pumas and the wolves of the National Park.
Thanks to this, they have detected notable differences in the behavior patterns of wolves infected by the parasite.
The team found that infection by T. gondii it was far superior in wolves whose territories overlapped with puma home ranges.
When wolves roamed in areas with high puma densities, the probability of having the parasite was up to nine times higher than when there was little contact with cats. No other factors (sex, age, or fur color of the wolves) were related to this probability.
The researchers conclude that this pattern indicates that wolves are infected with T. gondii from the ingestion of oocysts expelled by pumas. Indirect infection (via parasitized prey) is a much less important route.
This research, carried out over 26 years, verified that the wolves that housed T. gondii they were more likely to engage in certain risky behaviors, such as dispersing in search of new territory or becoming a group leader. Both behaviors imply significant dangers and are associated with a significant risk of dying. But when they are successfully completed, they have a biological reward: the probability of reproducing is greater in wolves that manage to establish themselves in new territories and, above all, in those that become group leaders.
The parasite changes the individual. The individual, to society
Wolves are social animals that establish complex relationships between individuals. In this context, it is very interesting to know how the behavioral changes generated by the puma parasite in individual wolves can be transmitted, as a cultural innovation, to the groups.
The authors of the article propose that the tendency of infected animals to become group leaders would make their intrepid behavior become a group characteristic, learned from uninfected individuals.
Among the risky behaviors that the group can adopt is entering puma territories and increasing interactions with the cat, which would increase the number of infected wolves. If this looks like a loop, it’s because that’s just what the authors propose. According to them, the infection by toxoplasma and the hierarchy that is established in the wolf groups would be continually reinforcing the interaction between pumas and wolves, and the transmission of pathogens between these species.
Study Results
Yellowstone recovery: an example for science
Yellowstone National Park was declared in 1872 and became the first of its kind in the world. Such early protection did not prevent further attacks on its biodiversity, especially through the persecution of large predators such as pumas, brown and black bears and, above all, wolves.
In 1926 the last group of wolves was removed from the national park. Their eradication, added to the enormous decline of the rest of the large carnivores, led to a huge increase in herbivore populations, especially drinking, sister species to our red deer. The park itself killed thousands of deer each year, in an unsustainable effort to control its population.
Yellowstone’s ecosystem was missing key pieces. The same ones that are missing in a good part of Spanish ecosystems. Starting in 1995, a wolf reintroduction project began, an impressive success in managing a natural area based on the recovery of basic ecosystem processes.
The project not only managed to generate a self-sufficient nucleus of wolves, but they have reduced the deer population to the benefit of the individual physical condition of the herbivores themselves. The deer’s decline, coupled with their new use of space (now conditioned by fear of wolves), has generated enormous changes in Yellowstone’s vegetation, landscapes, and ecosystem functioning.
We know all this because Yellowstone has carried out very intense and long-term scientific monitoring of numerous elements of biodiversity. This effort includes wolves since their reintroduction, as well as other species such as pumas. Thanks to the vast amount of information generated, Yellowstone and its fauna continue to teach us fascinating things.
The new work adds another piece to the notion that a tiny parasite is capable of modifying the behavior of large vertebrates. It goes further, showing that the behavioral changes that the parasite causes in individuals are transmitted to societies, and that these social changes can affect key ecological processes (interactions between species, predation), which can generate enormous changes in landscapes. and ecosystems. If anywhere is known of this is in Yellowstone.
It also introduces intriguing food for thought. Humans are social animals, like wolves, and we know that T. gondii is capable of altering our behavior. Is it possible that among the people who lead us there is a disproportionately high presence of T. gondii? How many wonderful adventures and how many terrible messes have we gotten ourselves into following intrepid leaders guided by a protozoan?
This article was originally published on The Conversation.