August 19, 2014
In the past century, a new medium-size predator has appeared in the Northeast. Some call it the coywolf; others prefer ”Eastern coyote.” In times past, the animal was called ”coydog.” All monikers are somewhat correct: The most recent genetic analysis suggests that the animal is roughly one-quarter wolf and two-thirds coyote. The remainder of its genome comes from dogs.
The animal is one of several hybrids I wrote about in the magazine this past weekend. The coywolf was born, scientists think, above the Great Lakes, where, in the 19th century, wolf hunting and habitat disturbance prompted different canid species to mate. The resulting wolflike brawn allows the hybrid to hunt the abundant woodland deer, its coyotelike wiliness permits it survive in a humanized landscape and its doglike tolerance of people may help it thrive in one of the most densely populated parts of the country. By all accounts, the hybrid’s genome is one of its major strengths, but the animal’s very adaptability may threaten another species.
The red wolf, which once ranged widely throughout the Southeast, is critically endangered. In 1987, the U.S. Fish and Wildlife Service began releasing captive-bred wolf pairs onto a swampy spit of land in coastal North Carolina as part of a recovery program. The wolves fared well — until the 1990s, when coyotes showed up and began mating with them. If widespread interbreeding continues, it might in theory cause the red wolves to disappear into the larger wave of advancing coyotes.
How, then, could the red wolves be protected from cross-species breeding? Even if you get rid of some of the coyotes, which are probably of the Northeastern hybrid variety, others move in. So Fish and Wildlife officials began capturing the offending coyotes, sterilizing and returning them to the wild: the sterile animals create a kind of buffer zone by holding territory, keeping other fertile coyotes at bay and thus preventing hybridization.
But why do we need that buffer zone? Robert Wayne, a geneticist at U.C.L.A., thinks the red wolf is itself a hybrid. When officials captured what individuals they could find in the 1970s, the beleaguered animal already had coyotes among its ancestors, Wayne says. He argues that red wolves should be allowed to mate with coyotes — that natural selection should sort out the question of what animal is best for that landscape.
David Rabon, who coordinates the Red Wolf Recovery Program, doesn’t agree. Today’s red wolves remain separate from the encroaching coyotes in part because of active, human protection, he says. Without it, they might disappear as large canid predators that play a unique ecological function.
Behind this debate lurks the larger question: What’s the right conservation philosophy when it comes to hybrids? Should we conserve genetic diversity in any form, including hybrids, or only in what are thought to be pure species? Should landscapes — even those most affected by human influence — ”choose” their own animals, or should we endeavor to conserve species as we imagine they once were?
In practice, the answer seems to depend. The prevention of interbreeding is important to conserving the slim, long-legged Ethiopian wolf, of which fewer than 500 remain; otherwise, the canid might melt into a sea of African dogs. By contrast, in Iberia, where gray wolves also occasionally breed with dogs, Portuguese scientists speculate that perhaps dog genes will help the wolf adapt to the humanized landscape. (It’s plausible, says Robert Wayne. Like humans, dogs have evolved an enhanced ability to digest starchy food. The trait could aid a wolf that regularly consumes human refuse.)
In Florida, meanwhile, wildlife managers deliberately hybridized a panther to save it. This Southeastern subspecies of cougar had become so inbred that, in 1995, officials released eight females captured in Texas into the Everglades to prevent genetic meltdown. The Florida panther is now really part Texas cougar — a hybrid. As one scientist told me, when the choice was between a hybrid cat or no cat, conservationists wisely opted for the hybrid.