Ghost Dogs

Solitary coyotes, usually less than two years old, can cover huge areas. One female inexplicably took off on a nine-day, 100-mile trip to Wisconsin and nearly back, at which point she was killed by a car. Another, which Gehrt’s team calls the Lincoln Park female, travels up to 20 miles some nights, moving between the posh North Shore neighborhood, south along Lakeshore Drive to downtown Chicago, to Cabrini Green’s housing projects. She became a local celebrity when a TV news crew filmed her in Cabrini Green at dusk, likely in search of rodents scurrying about the grassy vacant lots. The Lincoln Park coyote’s GPS collar fell off in November, as expected, after giving her exact location for nine months. Now Gehrt hopes to recapture her and attach a smaller radio collar that should last four years. “We’d like to know how long any coyote can live down there and whether any can reproduce.” Though she was roaming around “acting like a teenager” early last year, by fall she was sticking to a smaller area. That could mean she’ll find a mate. Then she can carve out a territory and begin breeding.

If she does find a partner, she’ll likely be true. “They’re extremely monogamous,” says Gehrt. “In the canid world, with wolves and foxes, there’s cheating going on all over the place. Genetic testing shows that’s not the case with coyotes.” Not that all couples behave the same. “Some are together all the time; others are very independent,” says Gehrt. “They’re a lot like us in that way.”

They’re also devoted caretakers, with both sexes tending to the young. While rural coyote packs often consist of an alpha pair and pups, urban coyotes tend to live in groups of five or six adults that maintain a territory of about three square miles. Only the alpha pair mates; subordinates—typically older siblings—help to raise pups. In April females look for existing dens or dig new ones amid bushes or trees, and have litters ranging from four to seven pups. By summer’s end the young start hunting on their own or with siblings. (Unlike wolves, coyotes hunt alone or in loose pairs.) “One of the big mysteries is when offspring leave,” says Gehrt. “We still don’t know whether it’s voluntary or whether the parents kick them out.”

The biologists have discovered that coyotes have remarkable respect for one another’s territories. Yet the boundaries do shift. A couple may lose—or cede, researchers aren’t sure—a block to an offspring that becomes an alpha. Development might force a pair from a vacant lot. Prime real estate may open up if one mate dies and the other leaves, or if the inhabitants are culled. In that case, what happens next is predictable: Remove coyotes, and new ones will come in and take their place.

Part of what enables raccoons and skunks to thrive in urban environments is their predilection for trash. Coyotes are a different beast. “Before we started our study, it was thought that coyotes are successful in urban areas because they eat garbage and pets,” says Gehrt. “Some coyotes do that, but the majority don’t.” Their burgeoning populations in cities are a testament to their hunting skills.

Fittingly, over lunch in 2003, Gehrt and a colleague, biologist Charles Paine, figured out at least part of their diet: Canada goose eggs. As with many urban areas, geese had moved in and their population was exploding. So Paine was puzzling over why, in the early 2000s, the local growth rate had dropped from 15 percent to about one percent. At the same time, Gehrt had seen coyotes enter tall waterside grasses at night and exit with something white in their mouths. Coyotes, they deduced, were depredating nests.

They set up infrared cameras with motion sensors to test the theory. They were amazed to discover that the fierce birds fled when coyotes approached. If they refused to leave, coyotes would kill the adult, then take an egg. Interestingly, instead of eating the eggs, they buried them, returning for them up to three weeks later. “Coyotes act as a biocontrol on urban geese,” says Gehrt. “When coyotes come in, geese nest somewhere else.” Such displacement may prevent birds from being crowded out or overcrowded, which can result in avian tuberculosis and influenza outbreaks, while also reducing water pollution from huge concentrations of droppings. (One goose can generate more than a pound a day.) Fewer geese also reduces the need for costly solutions, such as poisoning or roundups.

At the same time coyotes are putting a dent in the deer problem. Whitetails, of course, are a major carrier of the potentially fatal tick-borne Lyme disease. Devouring six to eight pounds of vegetation a day, they’re eviscerating native plants and the understory that provides homes to birds like indigo buntings and ovenbirds and small mammals like mice and chipmunks. Coyotes are a natural alternative to expensive and labor-intensive tactics—trapping and relocating, contraception, hiring hunters. Even if, as Gehrt notes, they rarely take down adult deer, they can slow population growth by preying on fawns. Research suggests that in some instances, coyotes take up to 80 percent of fawns, tearing at their throats with inch-long canines before ripping into the flanks.