Bigger than coyotes but smaller than wolves, their howl is high-pitched and their diet includes deer and small rodents. They are "coywolves" (pronounced "coy," as in playful, "wolves"), and they are flourishing in the northeastern U.S., according to a study published today in Biology Letters.

Although coyote–wolf breeding has been reported in Ontario, where coyotes started migrating from the Great Plains in the 1920s, this study provides the first evidence of coywolves—also known as coydogs or eastern coyotes—in the Northeast. And even though they are more coyote (Canis latrans) than wolf (gray wolves are Canis lupus, and red wolves are Canis rufus), the expansion of these hybrids into western New York State marks the return of wolves to the Empire State.

"It's kind of interesting that we drove this species from the area and it sort of came back in another form," says Roland Kays, curator of mammals at the New York State Museum in Albany and first author on the study.

To get a sense of the pedigree of coyotes in the area, Kays and his colleagues examined the genetic material from samples—mostly tissue, hides and skulls—that museums had archived. The source of these samples was itself a sign of the coywolves' success. As Kays points out, specimens came from hunters who killed the dogs in an effort to stem the growing population. Based on the genetic analyses, the team concluded that mating between female coyotes and male wolves was abundant. The researchers also noted that the coywolves have larger, stronger jaws and bigger skulls overall than the so-called straight western coyotes.

Although hybrids are typically less fit than straight species, the story of coywolves in the Northeast might be one of success. Their strong jaws will enable them to eat the deer that are abundant in the area, while the coyote-like ability to coexist with humans could be an advantage that wolves lack. "Wolves have not made a comeback on their own in the area because they can't deal with human development," Kays says. "In this case, the hybrid has become more adapted."

Another advantage of coyotes and wolves mating is that, unlike many interspecies relationships, their offspring are fertile. Kays points out that it is common for members of the genus, Canis, including coyotes, wolves, and dogs, to "hybridize quite readily." Take that, liger.

Images of coywolves courtesy of Roland Kays at the New York State Museum