There are many more wolves at Isle Royale National Park than there were a year ago. At the time, the population on the islands in Lake Superior had dwindled to just two, but a reintroduction program was initiated by the National Park Service last fall after a long debate, and has seen some success so far.
Today there are 14 wolves on the island, including the resident pair. The goal is to bring a total of 20-30 wolves to the island in the next three to five years.
All of the animals are fitted with GPS collars that send their locations in real-time to researchers. It provides valuable data to monitor their behavior and the progress on making themselves at home in their new territory.
Watching from afar
The tracking collars show that one female and two males seem to have been traveling together since early April.
“While GPS data indicate these three wolves have been together on numerous occasions, it’s too early to tell whether we have a makings of a wolf pack,” said Mark Romanski, Division Chief of Natural Resources for the park. “But it is reassuring that we have wolves spending time together and feeding.”
The GPS devices can also send a signal when a wolf may have passed away. Researchers received such a signal in late March from the collar on a wolf that had been relocated to Isle Royale about a month earlier.
The researchers were at first frustrated in their attempts to reach the island, recover the carcass, and perhaps learn about the cause of death. When scientists could finally get to the island, they trekked five miles into a large swamp to recover the body and determine the cause of death, to no avail.
“Investigators found no apparent signs of injury or struggle, however, the carcass was in a very deteriorated state due to melting snow and wet conditions, making an accurate cause of death determination impossible,” the agency reported.
Some wolf deaths are to be expected, scientists say, as the natural mortality rate in nearby Michigan is about 25 percent. Statistically, at least one of the 12 wolves brought to the island would die in the course of the year.
This summer, the GPS collars are also letting scientists study what the wolves are eating. They will visit sites where the animals spend significant amounts of time to discern their diets.
Inbreeding issue
New research shows that the population may forever be doomed to decline based on genetics, without ongoing human intervention.
The previous population of wolves is believed to have nearly disappeared as a result of inbreeding. As the population got smaller and smaller, so did the pool of DNA. The animals began to show crooked spines among other symptoms. The pair of wolves that remained on the island, believed to be father and daughter and half-siblings, seemed to have bred in 2014. Their offspring appeared to have a strangely short tail with stripes similar to a raccoon, and a hunched back. That wolf is believed to have died later.
A paper published in late May in the scientific journal Science Advances showed how as a population shrinks — Isle Royale’s wolves once numbered about 50 — the risk of genetic defects rapidly rises, reducing survival rates and reproductive success, further shrinking the population.
“The rapid deterioration of fitness in Isle Royale wolves within just a few generations demonstrates the substantial risks of inbreeding in very small isolated populations,” the scientists wrote. “In the absence of recurring immigration, whether managed or not, the fate of a restored population on Isle Royale is grim.”
A single male wolf crossed to Isle Royale from the mainland in 1997, carrying the first new DNA to the island in decades. The “genetic rescue” temporarily slowed the rate of inbreeding, but nonetheless the problem soon returned, once the male had bred. Soon, he too was related to every other wolf living on the island.
The complex genetic analysis shows that wolves from other small, isolated populations elsewhere may be the best candidates for introduction to Isle Royale. That’s because the genetic problems of inbreeding on Isle Royale seem to arise from both parents carrying the same harmful genes, not because the wolves carry a particularly large number of harmful genes.
More information:
- Isle Royale Wolf Population Update May 29, 2019 – National Park Service
- Genomic signatures of extensive inbreeding in Isle Royale wolves, a population on the threshold of extinction – Science Advances
- Inbreeding Causes Isle Royale Wolf Population Crash – American Association for the Advancement of Science
- Isle Royale wolf rescue faces longterm genetic challenge, researchers say – Great Lakes Echo
- Inbred wolf population on Isle Royale collapses – Science magazine, 2015