Ken Ferebee was one of the first to notice. He's a National Park Service biologist assigned to Rock Creek Park, a 1,755-acre swath of woods, ball fields and picnic areas in the heart of Washington, D.C. Since 2004, he'd observed that deer killed by cars were mysteriously being dragged away, and he’d heard strange yips and yowls. Then, a year ago, he saw a coyote dart across a road just after dawn.

The coyote, that cunning canine of wide-open spaces, has come to the nation's capital. And to New York, Chicago, Los Angeles and other cities. In fact, coyotes have spread to every corner of the United States, shifting their behaviors to fit new habitats and spurring researchers to cope with a worrisome new kind of carnivore: the urban coyote.

In a clearing near the edge of Rock Creek Park, Ferebee stomps through dense thornbushes and peeks under the roots of a fallen tree at a coyote den. He says it probably sheltered newborn pups a few months earlier. Ferebee says that largely because of their taste for livestock, "Coyotes have a bad rap, like wolves." He stoops to look for coyote scat. "We’re not going to catch them," he adds. "I don't see it as a bad thing for a park. I see it as good for keeping animal populations in control, like the squirrels and the mice."

Coyotes originally inhabited the middle of the continent, between the Rocky Mountains and the Mississippi River, and Alberta, Canada, and central Mexico. In 1804, Lewis and Clark dubbed the animal the "prairie wolf." In 1823, naturalist Thomas Say gave it the Latin name Canis latrans, or barking dog. One of its most celebrated traits is its trickiness; coyotes have been outsmarting trappers for centuries. Recently, biologist Jon Way, who has been studying the predators in Massachusetts, set a trap near the Boston Airport. Coyotes somehow snagged the rib meat put out as bait without getting caught. In the Navajo version of the creation of the world, old men had just finished embroidering the sky in brilliant patterns when the trickster Coyote ran across their work, scattering the stars.

The coyote's craftiness made the animal a notorious pest to Western sheep farmers and, occasionally, cattle ranchers. In the mid-19th century, cowboys carried sacks of strychnine in their saddlebags to inject into animal carcasses, to poison the coyotes that scavenged them. A 1927 Literary Digest article said Kansas ranked the coyote "in the category of evils alongside beer, cigarettes and Wall Street." Ranchers and hunters, as well as a federal agency called Predator and Rodent Control—a forerunner of today's Wildlife Services—trapped, shot and poisoned more than a million coyotes in the 1900s. It’s still one of America's most hunted animals; in 2003, Wildlife Services killed 75,724 of them.

Yet the coyote has persevered. By the end of the 20th century, the animal had colonized the tundra of Alaska, the tropical forests of Panama and the urban jungle of New York City. (The only major landmass in the eastern United States where you can't find the coyote is Long Island, although they have been spotted trying to swim across Long Island Sound.) How has the coyote pulled off this extraordinary feat? "I guess if you wanted to use one word, it'd be 'plasticity,'" says Eric Gese, a predator ecologist at Utah State University. Coyotes can live alone, as mated pairs, or in large packs like wolves; hunt at night or during the day; occupy a small territory or lay claim to 40 square miles; and subsist on all sorts of food living or dead, from lizards and shoes, to crickets and cantaloupes. Although their native diet consists of small rodents, Gese has seen a pack take down a sick elk in Yellowstone National Park. "Coyotes are without a doubt the most versatile carnivores in America, maybe even worldwide," says Marc Bekoff, an animal behaviorist who has studied them for 30 years.

People unwittingly helped coyotes flourish when they exterminated most of the wolves in the United States. Coyotes became top dog, filling the wolf's ecological niche. Deforestation and agriculture opened up previously dense tracts of forest, and human settlements, with their garbage, vegetable gardens, compost piles and domestic pets, provided food.

The expansion of coyotes into urban areas, though, is recent. Until the 1990s, the farthest that coyotes had ventured into Chicago was to forested reserves near the city limits. But "something happened," says Stan Gehrt, a wildlife biologist at Ohio State University, "something we don't completely understand." Within ten years the coyote population exploded, growing by more than 3,000 percent, and infiltrated the entire Chicago area. Gehrt found territorial packs of five to six coyotes, as well as lone individuals, called floaters, living in downtown Chicago. They traveled at night, crossing sidewalks and bridges, trotting along roads and ducking into culverts and underpasses. One pair raised pups in a drainage area between a day care facility and a public pool; a lone female spent the day resting in a tiny marsh near a busy downtown post office. Perhaps most surprising to Gehrt, Chicago's urban coyotes tended to live as long as their parkland counterparts. No one knows why coyotes are moving into cities, but Gehrt theorizes that shrewder, more human-tolerant coyotes are teaching urban survival skills to new generations.

In Southern California, where coyotes have been living among people since the onset of urban sprawl after World War II, the animals have become more numerous in the past 20 years or so. There have been at least 160 attacks on people in the United States in the past 30 years, most in the Los Angeles County area. The majority were bites, often inflicted while people were protecting their pets. One coyote attack, on a 3-year-old girl playing in her front yard in Glendale in 1981, was fatal. Afterward, residents of the Los Angeles suburb started a campaign to educate people about not feeding coyotes or leaving pet food and garbage unsecured. That, plus an intensive trapping program in the neighborhood, cut down on the coyote population.

The coyote's affinity for life in the big city has surprised many researchers. But odder still is the coyote's propensity for breeding with wolves. Canine species within the genus Canis, which includes coyotes, wolves and domestic dogs, are capable of interbreeding, but they usually stick with their own kind. The "coywolf" hybrid is larger than a purebred coyote. It is found in northeastern Minnesota, southern Ontario and southern Quebec, Maine and New York. Researchers recently studied the genetic profiles of 100 coyotes killed by hunters in Maine. Of those animals, 23 had some wolf genes. Most crosses occur between male wolves and female coyotes. Some of the hybrids go on to mate with other hybrids, creating what one researcher calls a "hybrid swarm" that has the potential to evolve into a new species. Eastern coyotes are heftier than those in the West: one coyote in Maine tipped the scales at 68 pounds, a far cry from the slim 15-pounders in the Great Plains. Researchers don't know if the larger Eastern coyotes carry wolf genes or have independently evolved a larger size. Or they may just have a richer diet, with plenty of access to deer.

Should the urban coyote be viewed with trepidation? "Some people have fears that kids are going to be the next ones to be eaten," says Way. "I tell them coyotes have been at the edges of their neighborhoods for years." Way emphasizes coyotes can be an asset to urban ecosystems, keeping a check on deer, rodents, Canada geese and other animals that thrive on the suburbs' all-you-can-eat buffet.

At his office in Rock Creek Park, just out of range of the park's eerie coyote choruses, Ken Ferebee flips through photographs of the capital's coyotes, taken by a motion-sensitive camera installed in the park. He pauses at one arresting shot: two burly coyotes stare into the camera, heads tilted, yellow eyes glinting. Their expression and confident stance defy the stereotype of a cowardly varmint always running the other direction. These coyotes look curious, fearless and eager to explore the big city.

Christine Dell'Amore is a health reporter for United Press International.