January 5, 2006 |
Even in the largest American cities, a historically maligned beast is thriving, despite scientists’ belief that these mammals intently avoid urban human populations.
This animal’s amazing ability to thrive in metropolitan areas has greatly surprised scientists, says Stanley Gehrt, an assistant professor of environmental and natural resources at Ohio State University. Gehrt is in the sixth year of a multi-year study of coyote behavior in urban Chicago.
Since the study began, Gehrt and his colleagues have found that urban coyote populations are much larger than expected; that they live longer than their rural cousins in these environments; and that they are more active at nighttime than coyotes living in rural areas.
Coyotes also do some good – they help control rapidly growing populations of Canada geese throughout North America.
And while his coyote research is concentrated in Chicago , the results likely apply to most major metropolitan areas in North America . Gehrt has even seen a pack of about a dozen on Ohio State ‘s campus in Columbus .
The study began in Chicago in 2000 when Gehrt was a research biologist for the Max McGraw Wildlife Foundation in Dundee , Ill. In the 1990s the foundation was increasingly inundated with complaints about coyotes taking pets and reportedly stalking children.
The number of calls grew, and in the late 1990s the Cook County Animal Control agency asked Gehrt to gather information on coyote populations in metropolitan Chicago .
The study was only supposed to last for a year.
“Nine million people live in the greater Chicago area,” said Gehrt, who is also a wildlife extension specialist at Ohio State . “We didn’t think very many coyotes could thrive in such a highly urbanized area. We also thought that the few animals that were causing problems were probably used to living around people.”
The problem with studying coyotes in general is that the animals are incredibly difficult to catch. They quickly learn how to avoid traps. But Gehrt and his colleagues distributed their traps widely throughout the greater Chicago area and successfully caught several animals. They put radio-tagged collars on the captured coyotes and then let them go.
The original estimates of the greater Chicago coyote population were woefully low. The researchers had expected to find a few small coyote packs here and there throughout the city, with total population numbers in the range of several dozen. But the animals were everywhere.
“We couldn’t find an area in Chicago where there weren’t coyotes,” Gehrt said. “They’ve learned to exploit all parts of their landscape.”
Since the beginning of the study, the researchers have caught and tagged more than 200 coyotes. They estimate that there may be somewhere between several hundred and a couple thousand coyotes living in Chicago .
Some of the animals live in city parks, while others live among apartment and commercial buildings and in industrial parks.
The funding agency, Cook County Animal Control and Conservation Medicine Coalition, renews the study every year because the researchers keep finding results that surprise them. This spring, Gehrt will publish the first round of papers from the last six years’ worth of research.
The major findings include:
* Coyotes help control Canada geese populations. It appears that coyotes are helping to curb the booming Canada goose population in urban areas by eating the eggs from the birds’ nests.
Researchers found that, in Chicago , the annual population growth of Canada geese was reduced to an average of 1 to 2 percent per year, down from the 10 to 20 percent growth rates of a few years ago. Also, while coyotes can clean out several goose nests in one night, they don’t actually eat all of the eggs. Rather, they usually carry the eggs away from the nest and bury them, saving the eggs until later, Gehrt said.
* The prevalence of large packs. Coyotes prefer to hunt alone, but often form packs to defend territories. Gehrt estimates that roughly half of all urban coyotes live in territorial packs that consist of five to six adults and their pups that were born that year. These urban packs establish territories of about five to 10 square miles – a fraction of the area that a rural coyote pack would cover. Consequently, the population densities in the urban area are usually three to six times higher than rural populations.
Those urban coyotes that don’t hunt in packs can cover ranges of 50 square miles or more, often in just one night. “The first solitary coyote we tracked covered five adjacent cities in a single night,” Gehrt said.
* Urban coyotes survive far longer than their rural cousins. A coyote living in urban Chicago has a 60-percent chance of surviving for one year, while a rural coyote has a 30 percent chance of living for another year.
* Most coyotes pose little threat to humans. The problems generally start when people feed coyotes, even if that feeding is unintentional.
“A coyote may eat the food that’s left outside for a pet,” Gehrt said. “It’s not uncommon to see a coyote pass through an urban or suburban neighborhood.
“But most coyotes aren’t thrilled about being seen by people,” he continued. “Urban coyotes are more active at night than their rural counterparts, so humans don’t see a lot of their activity. In many cases, coyotes are probably doing us favors that we don’t realize – they eat a lot of rodents and other animals that people don’t want around.”
The next phase of the study is already underway. Gehrt and his colleagues are conducting genetic study of coyotes’ social system. The researchers want to know if members of a pack are closely related – having such information could help to further explain coyote behavior.