Fate of Isle Royale wolves is unclear
Duluth, Minn. — The National Park Service still hasn’t announced what, if anything, it plans to do about the dwindling wolf population on Isle Royale.
And time is running out if the NPS plans to introduce more wolves to the big island in hopes of bolstering a floundering population.
In his talk at the International Wolf Symposium in Duluth, Minn., Oct. 10-13, Rolf Peterson described the history of wolves and moose on the remote island in Lake Superior.
Peterson, a research professor at Michigan Technological University in Houghton, is the project leader on Isle Royale. The wolf and moose study has been ongoing since 1958 – the longest-running study of a predator-prey relationship in the world.
Neither wolves, nor their primary prey, moose, were native to the island. Originally, caribou lived there, but they disappeared in the early 1900s. Moose made it to the island, likely by swimming, in the early part of the 1900s.
They thrived for a couple of decades with no predators to keep them in check. Wolves crossed an ice bridge from Ontario to the island in the late 1940s. Since then, wolves and moose have maintained an interesting balance in a unique, isolated setting.
It may be simplistic to think that when the moose population goes up, the wolf population goes up, but although that has been somewhat true, disease, ticks, severe winters, and inbreeding have thrown curveballs at the ecology of the island. The long-term study has yielded sometimes surprising results.
Currently, there are only eight wolves on Isle Royale – the lowest number ever recorded. As many as 50 once inhabited the island around 1980. Inbreeding seems to be the major cause of the decline.
“Spine abnormalities have increased from the 1960s,” Peterson said. “Every animal we’ve examined since 1994 has had spinal abnormalities.”
These spinal abnormalities are a result of inbreeding. In a healthy wolf population, about 1 percent of wolves have this condition, known as lumbrosacral transitional vertebrae.
“In 2009, the alpha female died giving birth,” Peterson said. “She died with seven other pups ready to be born. That’s unheard of in any wild place.”
That wolf’s death while giving birth is thought to be linked to inbreeding, as well, and may have been a result of her spinal condition. In 2012, no wolf pups were born on the island. In 2013, two or three pups were born. Little will be known about these pups until the next month-long aerial survey, which is scheduled for late this winter.
From their peak around 1980, Isle Royale wolves have struggled. First came canine parvovirus – a disease introduced to the island inadvertently by humans. But a lack of new genetic material in the population began to be an issue for survivors of the disease. Wolves got a break in 1997 when a lone male wolf, dubbed M93 by researchers, crossed the ice from Canada. That wolf infused new genetics into the gene pool and the wolf population immediately rebounded for a few seasons. M93 was so successful in his breeding that today, the genetics of all Isle Royale wolves can be traced back to him. Since his arrival, however, no new wolves have reached the island and the gene pool has stagnated.
The chances of more wolves crossing the ice are declining, due to climate change.
“There’s a disappearing ice phenomenon,” Peterson said. “We have less than a 10 percent opportunity for ice, and the opportunity for wolves to renew the genetic potential is largely gone.”
Peterson said there has been only one ice bridge from Canada since M93 crossed in 1997.
As wolves have struggled, the moose have thrived.
“Moose numbers almost doubled from 2011 to 2013,” Peterson said. “Moose had been at a really low level for almost a decade. Now they’re just booming.”
Aerial surveys in February estimated the moose population at 975 animals. That’s on an island 45 miles long and 8 miles wide. The Isle Royale moose population had reached as high as nearly 2,500 animals in the mid-1990s, before a tough winter caused the population to crash. Overbrowsing and a lack of food to go around likely contributed to that crash.
So now the NPS, which administers Isle Royale National Park, is at a crossroads.
“They all agree they’re (wolves) probably not going to make it,” Peterson said.
Should the NPS intervene? The Park Service released wolves into Yellowstone National Park in 1995, but it was reintroducing a species that was native to the area. That decision remains controversial to this day. Wolves were not native to Isle Royale, or if they were at some point, they disappeared, only to reappear in the 1940s. If the NPS takes no action and the wolves do disappear, the moose population likely will continue exponential growth. During the 2013 winter survey, the Isle Royale researchers observed the highest number of twin calves ever recorded in the 55-year history of the survey.
Left unchecked by wolves, the moose population likely will continue its rapid growth, but then crash eventually after it consumes all available food. So yet again, the result would be the demise of a non-native species.
However, the cost could be long-term or possibly irreparable damage to the native ecology of Isle Royale. Already, native trees such as balsam fir are declining due to overbrowsing by moose, as well as other trees and forbs.
Even native scavengers such as ravens and foxes, which have come to depend on wolf kills, also are in decline, Peterson said.
The NPS has three options to manage the wolf population of Isle Royale: do nothing, restore the population after wolves go extinct on the island, or conserve the population by introducing new genes.
There has been no talk of a possible fourth option – allowing moose hunting on Isle Royale to control the population.
So far, no decisions have been made. Any action will set a precedent for management in other national parks.
“They said they’ll have a decision by the end of the year,” Peterson said. “But I don’t know what that means. Then will they start a process?”
Even if the NPS does implement a genetic rescue as Peterson hopes, it’ll be a short-term fix; not a permanent solution.
“They’ll need to do it again because of the lack of ice due to climate change,” he said.
Time may be running out for Isle Royale’s eight remaining wolves. Will the NPS introduce wolves or stand aside and let nature take its course?