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.
source
No comments:
Post a Comment