(above, Western coyote; left, gray wolf; below, Eastern coyote)
Eastern coyotes, long considered vermin by farmers, were pretty much eradicated by 1900. But as wolves were also wiped out, the environment became more hospitable to coyotes, which often compete with wolves for food (a pack of coyotes has been known to take down a 550 pound elk). So the midwestern coyotes started to migrate back East. But as they did so, they took a northern detour, around the Great Lakes, and en route interbred extensively with Canadian gray wolves. By the time they reached the Northeast, they had grown much larger.
When a coyote mates with a wolf, the offspring is known as a coywolf. Technically, the coyotes seen in the Northeastern U.S. are mostly coywolves. (Lest you think me the boy who cried wolf, this has been confirmed by DNA evidence. In one study done in Maine, of 100 coyotes collected, 22 had at least 50% wolf ancestry, and one was actually 89% wolf.)
Many scientists believe that the so-called red wolves found in the eastern part of the U.S. (especially in North Carolina) are not a true separate species of wolf, but simply coywolves. Analyses of mitochondrial DNA shows that red wolves are mostly descended from coyotes, and genetically they are halfway between coyotes and gray wolves.
Coyotes have also been known to mate with dogs, with the resulting offspring known as coydogs. However this is a much rarer pairing; around my neighborhood the coyotes are evidently much more apt to kill and eat the dogs, especially the smaller ones. (I must admit, those foofy little dogs spark that same instinct in me.)
Coyotes -- of every variety -- are famously adaptive creatures which can thrive in a wide variety of environments from desert to forest to urban. One coyote was captured in New York's Central Park in 1999, another in 2006, and yet a third was spotted there in 2010. Three coyotes were spotted near Columbia University in 2010 as well. Tests have shown that they are better than dogs at "observational learning." (Translation: they're smarter. This must be why they were found near Columbia rather than the Fashion Institute of Technology.)
Full grown western coyotes range from 25-35 pounds. Eastern coyotes range from 30 to 50 pounds; the largest have been known to reach 75 pounds. Coyotes are athletic as well as smart, able to reach speeds of 43 miles per hour while in pursuit. (Usain Bolt's top speed is 27 miles per hour, and he is undoubtedly more of an outlier for his species.)
The larger coyotes found in the Northeast are more dangerous simply by virtue of their size. This is how 19-year-old folk singer Taylor Mitchell was killed by two coyotes while hiking in Nova Scotia recently: harder to imagine this happening with two 25 pound western coyotes.
Coyote packs are generally smaller than wolf packs, and the relations between individuals tend to be more fluid. (Thus you hear of an alpha male wolf, but not an alpha male coyote.) Coyotes usually hunt in pairs, but there can be up to six involved in a kill.
I've seen maybe five coyotes in my backyard in Connecticut in the past decade. I've always been impressed by the way they move: they prance elegantly, almost like foxes, rather than trot like dogs. And I've always been surprised by their size: they usually seem to be about the size of German Shepherds.
If you live in the Northeast and see a large coyote in your backyard, think wolf.