Scientists have discovered the smallest known city coyote territory near O'Hare International Airport at Chicago, USA. Coyotes have set up a small colony of around a third of a square mile for at least six years, which is about five miles from the airport.

Stan Gehrt, an associate professor of environment and natural resources at Ohio State University, who has led the tracking of the creatures for 12 years, says, "That's an indication that they don't have to go far to find food and water. They're finding everything they need right there, in the suburbs of Chicago. It amazes me."

Coyotes are the biggest mammalian carnivores to thrive in urban areas, Stan Gehrt says.

"The coyote is the test case for other animals. Raccoons, skunks, foxes - they've already been able to penetrate the urban landscape pretty well. The coyote is the most recent and largest. The jury's out with what's going to happen with the bigger ones," Stan Gehrt says.

Larger animals include bears, wolves and mountain lions, which have been seen on the fringes of Chicago already. "They are going to be an even bigger challenge," adds Stan Gehrt.

Over the last 12 years, since tracking began, Stan Gehrt and colleagues have placed around 680 radio collars on coyotes, with around 60 being continually tracked. He believes around 2,000 coyotes live in the Chicago metro area.

At times, this can cause uneasiness among the city's 9 million humans, but Stan Gehrt believes they will have to get used to it.

"It used to be rural areas where we would have this challenge of coexistence versus conflict with carnivores. In the future, and I would say currently, it's cities where we're going to have this intersection between people and carnivores.

"We used to think only little carnivores could live in cities, and even then we thought they couldn't really achieve large numbers. But we're finding that these animals are much more flexible than we gave them credit for and they're adjusting to our cities.

"That's going to put the burden back on us: Are we going to be able to adjust to them living with us or are we not going to be able to coexist?"

The study and its findings were outlined by Stan Gehrt in a talk to EcoSummit 2012, an international conference in Columbus, Ohio.

The difficult part of government-sponsored eradication programs is weighing cost against benefit. When the research started in 2000, some communities near Chicago trapped and killed coyotes discovered in their area. Stan Gehrt believes just 10% of communities operate similar programs now.

He says, "I think those programs will go away, too. It costs money, and it upsets some residents who want coyotes living there. So there is conflict, cost and lack of effectiveness. We have great data in areas where removal was done. You pull them out, and literally within just a few weeks, new coyotes moved in and set up a new pack and began reproducing right away.

One reason way humans flocked to cities was to get away from the risks associated with living near wild carnivores. Now the animals are moving in to urban areas.

Stan Gehrt explains, "The funny thing is that now we have more people on earth and bigger cities than ever, we also now have carnivores moving into cities. It's a two-way street: We're expanding cities into their territories and they're also coming in.

He believes that the urban coyote pup survival rate is five times higher than that of pups in rural areas. In both, humans are the main predator.

"We are the only thing slowing their population down, either with our cars, which is the No. 1 cause of death for coyotes, or when we remove them through hunting or control programs. None of the diseases they're exposed to really impact them at all," says Stan Gehrt.

Coyotes dine on rodents, rabbits and geese, which reduces human exposure to diseases carried by those species and removing nuisance animals. They also eat bugs and deer fawn, the occasional cat or small dog or even fruit.

There is lots of food available in cities, which is why coyote communities can be confined to such small spaces. When they settle, coyotes do not move much. Transient youngsters that have left their parents' pack will attempt to find a vacancy in an existing territory or discover a new area to form their own pack.

Stan Gehrt says, "They're so adaptable and so opportunistic. In adjusting to urban life, they may change dietary items and habitat use, and become nocturnal, whereas in the country they're active day and night. But with other things, they don't change at all. Here, they're able to maintain their social structure, territorialism, packs and mating system, even in the face of all these challenges of trying to live among nine million people."

He recently published a paper outlining how coyotes in Chicago have stayed monogamous while adjusting to their new, urban lifestyle.

He is carrying out more research in new sites at Cleveland, Ohio, and in Nova Scotia, Canada, where coyotes are more aggressive to humans. Typically, coyotes don't attack humans. But anyone who feels threatened, can wave their arms, shout or even throw a rock to scare the creature.

"You're doing them a favour. They show a healthy respect and fear of people and that's the way it should be," adds Stan Gehrt.

The study was financed by Cook County (Ill.) Animal & Rabies Control.