Wolves become geared to take over as leaders of a pack when infected with the parasite Toxoplasma gondii, research has shown.
Furthermore, the infection with the microscopic organism can alter the behavior pattern of wolves to such a degree that the dynamics of an entire ecosystem may be changed dramatically.
The microscopic organism, infamous for only being able to reproduce in the bodies of our domestic cats, as well as other felines, can infect most warm-blooded animals. In the case of humans, it can cause a disease called toxoplasmosis. While typically symptomless, the disease may be fatal for a weakened immune system.
One quite chilling aspect of this parasite’s life cycle is that it has evolved ways of maximizing the chances of its offspring to get back inside a feline for further reproduction. This is why this parasite is dubbed “mind-altering”, or “mind-hijacking.”
Previous studies revealed that rats infected with the parasite are prone to taking greater risks, and even being drawn towards feline urine. In that case, cats are, of course, likelier to catch and eat them.
But, back to the wolves…specifically, gray wolves (Canis lupus) populating the territory of Yellowstone National Park, largely in the northwest area of the US state of Wyoming, but also Montana and Idaho.
Scientists led by biologists Connor Meyer and Kira Cassidy of the Yellowstone Wolf Project studied behavioral data on wolves, accumulated over 26 years. They also analyzed the blood samples of 229 wolves and cougars, which also populate the area. The wolves were believed to become occasionally infected after eating dead cougars, or ingesting cougar feces.
As they were gauging the infection rate with this parasite, the researchers hit upon two things.
Firstly, those wolves whose territory overlapped with cougars were more likely to be infected with T. gondii. But there was also a behavioral consequence. They found that such wolves were eager to take greater risks. Here are some of the numbers the research came out with:
Infected wolves were 46 times more likely to become a pack leader.
Infected wolves were 11 times more likely to leave their pack and check out new territory
Infected male wolves had a 50 percent probability of leaving their pack within six months (compared with 21 months for the uninfected).
Infected females had a 25 percent chance of leaving their pack within 30 months (compared with 48 months for not infected).
It was speculated that T. gondii raised testosterone levels, triggering a greater degree of aggression and a powerful desire for dominance – the sort of traits a pack leader might require.
Screenshot of Diagram showing the hypothesized wolf-cougar-T. gondii feedback loop.
© Photo : Meyer, Cassidy et al.,
Furthermore, the research determined something that was dubbed a feedback loop, rooted in overlap of territory and infection.
"Due to the group-living structure of the gray wolf pack, the pack leaders have a disproportionate influence on their pack mates and on group decisions. If the lead wolves are infected with T. gondii and show behavioral changes … this may create a dynamic whereby behavior, triggered by the parasite in one wolf, influences the rest of the wolves in the pack," stated the study.
The conclusion was that an infected pack leader would be lured to follow the scent of cougar urine, leaving the rest of the wolves facing a potentially greater rate of T. gondii infection. Thus, a whole ecosystem could be affected by a tiny parasite.