Isle Royale, a forested island in Lake Superior which has been home for many years to the longest-running continuous study of a predator-prey system in the world, is in danger of losing the “predator” part of that system: the gray wolf.
For approximately 65 years, a population of wolves has coexisted with a population of moose on the “closed” island ecosystem, allowing scientists to study closely an isolated ecosystem with minimal human influence. The original population of wolves likely walked approximately 18 miles over ice “bridges” which connected the island with mainland Ontario during cold winters, but such ice bridges no longer form regularly, severely reducing the ability of the island wolf population to intermingle with mainland populations. This past year’s unusually cold winter was the first in several years in which the ice was thick enough to form a bridge to the mainland, and instead of new wolves coming in, one island wolf, Isabelle, attempted to leave via the bridge (and was shot by a hunter).
Lacking genetic contribution from mainland animals, the wolf population on the island is becoming inbred, with bone deformities and other issues possibly relating to reproduction: only 3 pups were born in 2013. The population has been declining for more than a decade, and there are only nine wolves remaining on the island.
A simple solution to this problem would be to gather up some mainland wolves and introduce them to the island, in a mimicry of natural migration processes, and duplicating the effects of “Old Grey Guy“, a single male wolf who migrated to the island in 1997 and sired dozens of pups, giving the island population a much-needed influx of new genes.
This year’s annual report by the Isle Royale institute features recent calculations by Phil Hedrick, a geneticist at Arizona State, which suggest that the Isle Royale wolves have not been losing genetic diversity as quickly as expected given their small, isolated population. This implies that other wolves, in addition to “Old Grey Guy”, have been making their way to the island, undetected, over the years and adding their genetic contributions. John Vucetich, director of the Isle Royale research project, says this is a strong argument in favor of a human-engineered “genetic rescue”, since the wolves have been “rescued”, naturally, several times in the last 65 years.
The National Park Service has announced that it has no plans to import wolves to the island in the near future, but has said it plans to “explore the consequences of such an action”. In the meantime, the moose population has doubled in the past three years, essentially unchecked by wolf predation, and stands to “eat through” the 206-square-mile island’s vegetation. Culling the big herbivores is unlikely to be a viable option — the island is difficult territory during moose hunting season and the carcasses would be extremely hard to remove.
The National Park Service does not have long to make a decision on the wolves. Within only a couple of years, the middle-aged wolves on the island could be wiped out by injury or illness and the moose population continues to expand.
The common notion that we should “let nature take care of herself and not be meddling presumes that Mother Nature is intact,” Rolf Peterson, former director of the project, said. “But we started cutting off her fingers some time ago.”