Silent Summer: No Wolf Pup Yips Heard on Isle Royale
On the largest island in Lake Superior, scientists gather year after year to study the dynamics between wolves and moose. For forty years, the scientists have come to take part in this iconic predator-prey study, and for forty years the sound of high-pitched yips have greeted their ears, heralding a new generation of wolf pups. That is, until last summer. It was a summer without yips.
Aerial surveys supported the implications of that silent summer—the wolves of Isle Royale did not produce pups. As the wolf population has declined to eight individuals, all closely related, their ability to survive and reproduce has declined as well in a phenomenon known as inbreeding depression. Wild wolves avoid mating with close relatives, the only option left on Isle Royale. If close relatives choose to mate, the chances that their offspring will inherit undesirable recessive traits increases, resulting in wolf pups that could be deformed or unable to produce viable offspring.
Physical abnormalities had already been witnessed in the wolves. A 2009 paper in Biological Conservation reported that 58 percent of the Isle Royale wolves examined had congenital spinal deformities. Although the defects weren’t crippling, they were widespread, showing up in 12 recently necropsied wolves. Other defects have been observed as well.
The situation has left conservation biologists to ponder whether or not they should intervene. One side believes in letting nature runs its course—even if it means letting the wolves go extinct—and then bringing fresh wolves to the island to control the bountiful moose population. The other side believes that intervention is necessary, and wild wolves and new genetic material should be imported to rescue the population, as was done with the Florida panther.