The theory is that male wolves interbred with female coyotes as the coyotes migrated east.
Now, they are hybrids:
http://mainehuntingtoday.com/bbb/2007/11/17/massachusetts-study-says-eastern-coyote-part-wolf/http://www.pgc.state.pa.us/pgc/cwp/view.asp?a=458&q=150783http://www.scientificamerican.com/blog/post.cfm?id=wylie-coywolf-the-coyote-wolf-hybri-2009-09-23http://www.projectcoyote.org/newsreleases/news_eastern.html...The most plausible scenario is that the eastern coyote is actually a hybrid between coyotes and a small type of wolf. Dr. Brad White’s research team at Trent University reported that the wolves found in southeastern Canada may actually be the same species as the red wolf (Canis rufus, or Canis lycaon as proposed) found in the southeastern United States. This “eastern wolf” is smaller, weighing about 60 pounds, and is thought to be more closely related to the coyote than to the gray wolf because both are theorized to have evolved in the New World whereas the gray wolf originated in the Old World. Thus, White’s research group theorized that the genetic similarity of the coyote and Canis lycaon might facilitate hybridization, especially when populations are low in an area. (In fact, the biggest threat currently facing the red wolf in the southeastern United States is hybridization with coyotes colonizing the periphery of the North Carolina red wolf recovery area.)
I have been collaborating with White’s genetic team, and they recently finished analyzing the genetic results of about 75 of our samples from eastern Massachusetts. Perhaps not surprisingly, they did find evidence for hybridization. They found that our study subjects were mainly eastern coyote, but all also had western coyote and eastern/red wolf genetic influence as well. White believes the eastern coyote should be classified as its own species because all of the samples from the Northeast (including from Massachusetts, New York, Maine, and New Brunswick) grouped more closely to each other than to western coyotes or wolves. Interestingly, biologists call these same Canids “Tweed wolves” in Ontario, and White notes that they are a product of hybridization between eastern coyotes and eastern wolves.
We are still trying to sort through this “canid soup” and have found variability within study areas with some “coyotes” having nearly pure red/eastern wolf and others having much western coyote DNA. We will likely not be able to officially call the eastern coyote a new species until we sample throughout the Northeast and determine where they become less “eastern coyote” and more “western coyote” or “eastern wolflike.” However, it is obvious that the eastern coyote is indeed distinct when I compare the size and physical makeup of eastern and western coyotes; I see a more massive eastern coyote that looks very similar to the red wolves that have graced the covers of past issues of International Wolf....