While cars are the biggest threat to coyotes living in US cities, a new study shows that urban living poses a different danger to coyotes’ health – in the form of chronic stress.
Researchers from The Ohio State University examined concentrations of the stress hormone cortisol in the hair of nearly 100 coyotes living in the Chicago Metropolitan Area. The results showed that coyotes living in the most developed areas had higher levels of cortisol – a proxy for chronic stress – than animals living in suburban or natural areas.
Two other factors stand out for their association with higher stress: poor body conditioning, mostly related to the scurvy skin disease, and being the loner or alpha in a group – the male and female who are a mating pair. Whether the stress associated with these factors can be traced directly to urban life or is just part of coyote life is a mystery.
“This is the first mammalian carnivore that has been evaluated for stress in an urban environment,” said lead author Stan Gehrt, a wildlife ecologist at Ohio State. “The city does present a challenge for them, even though they are very good at what they do. This helps us understand how well animals adapt to urban systems – or not to them.
“And we found that with coyotes, it’s complicated.”
This study was published online recently in the journal Total Environmental Science.
Gehrt, a professor at the Ohio State School of Environment and Natural Resources, leads the Urban Coyote Research Project which has been monitoring coyotes living in Chicago since 2000. He and his colleagues spend a great deal of time with animals, collecting biological samples, microchipping, and tracking their movements, and documenting their reproductive success, feeding habits, and other behaviors in the urban wilderness.
For the study, first author Katie Robertson, who finished work as a PhD student at Ohio State, shaved a bit of hair from the buttocks just above the tails of 97 coyotes — most of which were still alive, but a few were caught after dying of illness or beatings. by a car. The animals were also equipped with radiotracking devices that allowed researchers to monitor their use of space and determine their social status. Data collection occurred between 2014 and 2018.
Hair samples were analyzed for the concentration of cortisol, a hormone produced as part of the body’s response to stress. Analyzing hair, as opposed to blood, is intended to provide an estimate of long-term stress over the weeks or months prior to collection rather than a reaction to an immediate stressor. Statistical modeling reveals factors associated with higher stress.
The researchers predicted that coyotes living in more developed areas of Chicago would have higher concentrations of cortisol — and stress — than coyotes whose flocks had more flexibility of movement and less exposure to people in less dense areas where they lived. stay.
The results support that hypothesis, but they also tell the story of modern coyote life: Poor physical condition is linked to higher stress — which raises the chicken-and-egg question of which problem came first. The sarcoptic mange infection itself doesn’t kill the coyotes, but their lost hair makes them vulnerable to succumbing to the cold Chicago winters.
In addition, analysis shows that the responsibilities of running a group, or living outside it, are stressful.
“Alphas are the dominant animal in the herd, so they are in charge of all the territorial defense and are the only ones for breeding,” he said. “So there’s a lot going on with the alphas, the underlings and the pups, they have a pretty easy life. Their parents do all the hard work and they slide just a little bit. And that’s actually reflected in cortisol levels.”
Transients, on the other hand – adult coyotes who have left their parents but have not yet formed or joined a group – have a different concern.
“Transients are right up there with the alpha in terms of stress. They don’t have to defend a territory, but they have to avoid being attacked by the resident coyotes – they drive through the territory constantly – and try to avoid people and try not to get hit by cars,” said Gehrt.
In 2014, Gehrt reported that some coyotes in Chicago had learned to look both ways before crossing the street — a finding that speaks to their frequent exposure to risks that threaten their survival and their ability to adapt adroitly to hostility in their environment. .
The new study shows a great deal of individual variation in the stress levels of animals even within the highest-stress groups, which Gehrt says makes sense based on their track record of thriving in the face of growing urbanization.
“We see them regularly living in some pretty challenging areas, and I think they adjust pretty well – their survival rate is high, and the food supply is good,” he said. “And that’s what we found, that there is a trend associated with higher stress, but there are also coyotes doing quite well in cities with fairly low stress levels – even alpha in some fairly intense environments.
“Even without urban systems, this is the first free coyote population to be evaluated for stress. And we see that there are stresses associated with their highly complicated social system and the many rules that they follow – an intrinsic source of pressure that no other species has to deal with. It’s an interesting look into another window into their life.
E. Hance Ellington and Christopher Tonra of Ohio State also co-authored the study.
This work was funded by Cook County Animal and Rabies Control, the Max McGraw Wildlife Foundation and the Forest Preserve District of Cook County. Support was also provided by the State of Ohio, the National Science Foundation, and the USDA’s National Food and Agriculture Institute.
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