Wolves in Isle Royale National Park are nearly extinct and why is a bit of a mystery. Researchers from Michigan Technological University (MTU) observed the wolves over the winter during an annual study of the population of the park and found there is only a single group living on the island with three, by now possibly two members. During last winter’s study, there were nine wolves.
It is unclear exactly why the wolves are declining so rapidly on the island at a time when the moose population is booming. During their survey, the researchers saw two additional wolves visit the island but the new wolves stayed only a short time before returning to where they came from.
Researchers from MTU have conducted the study for 57 consecutive years, making it the longest running predator-prey study in the world. The team reports that there are now 1,250 moose living on the island and the predator to prey gap has been growing for four years, leading to a variety of potential problems.
“It’s not the presence of wolves that matters so much, it’s whether wolves are performing their ecological function,” says John Vucetich in a statement.
Vucetich is an associate professor of wildlife ecology and a leader of the study along with Rolf Peterson, a research professor at Michigan Tech.
Last spring the Isle Royal National Park issued a statement stating that there was still a chance of the wolf population would replenish itself. At that time there were nine wolves, and a chance for new animals to move to the island across winter ice bridges.
However, now the wolves population has dropped to three and, for whatever reasons, wolves visiting the island across the ice bridge are choosing not to remain. According to Vucetich, just a year later there is little to no chance of a genetic rescue.
According to the researchers, inbreeding has had a significant negative impact on the island’s wolf population over the last half century and it appears to have reached a critical point with the three remaining wolves.
The wolves are thought to be the alpha couple from the pack and a nine month old pup. The pup, however, does not appear to be healthy. “It has a constricted waistline, hunched posture and seems to have a deformed tail,” said the team.
“Those observations suggest that the pup is not well off. It would not be surprising if the pup was dead a year from today,” said Vucetich.
On the last day of the study the researchers were not able to find the third wolf.
Since 2009, the wolf population has decreased by 88 percent, from 24 to 3. Over the same period of time, the islands moose population has been increasing by 22 percent per year, despite harsh winters.
Now, in addition to concern for the wolves, the team fears for the health of the island overall. The moose population spiked and caused considerable damage to the park in 1996.
“At that time the moose population had considerable impact on forest vegetation. Concerns remain that the upcoming increase in moose abundance will result in long-term damage to the health of Isle Royale’s vegetative community,” Vucetich and Peterson write in the Winter Study annual report.
