Run-ins are on the rise between
coyotes and city-dwelling humans, and scientists aren’t sure why. Now
researchers in Alberta think they’ve found a piece of the puzzle. Coyotes are
more likely to creep into human spaces if they’re unhealthy.
Conflict between humans and coyotes
has increased during the last 20 years, write University of Alberta
graduate student Maureen Murray and her coauthors. Yet coyotes were
expanding their range for decades before that. They’ve spread to inhabit nearly
every part of North America. What makes some coyotes today march
downtown and ride the light rail while others stay in a city’s fringes and parks, never
meeting a person?
To explore the question, the
researchers captured 21 wild coyotes in Edmonton, Alberta over the course
of three years. They fitted the animals with GPS collars to track their movements.
They also clipped a little hair from each animal’s nape for chemical analysis.
And they recorded every coyote’s sex, age, and weight, as well as
whether it looked mangy. Coyotes are susceptible to a type of mange caused
by the mite Sarcoptes scabiei. Along with making their fur fall
out, the itching causes coyotes to bite and chew their skin, which can
lead to more infections. Mangy animals may also have trouble keeping warm.
Eleven of the captured coyotes were
healthy; ten had mange. During the study, four of the healthy
coyotes were killed by cars. Meanwhile, six of the diseased coyotes
died—four from exposure, and two from being euthanized after run-ins with
humans.
Two of the coyotes didn’t send back
enough GPS data for the researchers to use. From the rest of the collared
animals, they detected a clear pattern: diseased coyotes roamed farther. They covered ranges that were nearly four times as big as
a healthy coyote’s home turf. They were more than five times as likely to come
into developed areas, such as commercial or residential zones. And they
wandered equally during day and night—unlike healthy coyotes, which are
mainly nocturnal.
By analyzing the carbon and nitrogen
isotopes in the coyotes’ hair clippings, the scientists could learn about their
diets. The carbon signature of corn, which is packed into processed foods,
showed the scientists that diseased coyotes were eating about a third more
human food and trash than healthy coyotes were. (Another potential
coyote food that bears the signature of corn: our pets.) Nitrogen analysis
showed that diseased coyotes were also eating further down the food chain than
healthy ones, consuming almost 90% less prey.
A healthy coyote may never need
to wander downtown. It spends its energy defending a small territory, maybe
inside a city park, where it comes out at night to hunt and forage. But a sick
coyote wanders widely and at all times of day. It looks for easy sources
of food anywhere it can find them—like backyards and alleys. That means it’s
more likely to bump into a human along the way.
Murray says the link between poor
health and using human resources probably applies to coyotes in many places.
Mangy animals may be especially desperate in a far northern city like
Edmonton, though, because of the cold temperatures.
“Our results can help mitigate
human-coyote conflict by providing information about why coyotes use human
resources,” Murray says. If wildlife managers can prevent disease among
coyotes, they might reduce the number of animals that come searching for human
food. And keeping the streets clear of things a sick coyote might
eat—compost, processed food waste, fallen fruit, and even spilled birdseed—could
also prevent coyote run-ins.
If urban centers are providing food
and shelter for sick coyotes, helping infectious animals survive longer, and
bringing them into contact with other coyotes, Murray thinks this could help
explain why encounters between coyotes and humans are on the rise. Keeping
these animals healthy and away from our trash heaps may mean that more coyotes
live out a good life—that is, one where a human never sees them.
This
post has been edited to clarify that all of the coyotes in the study lived
inside the city.
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