Isle Royale’s revived wolf population appears to be doing well, with several new pups born over the last two years, while the island’s overpopulated moose herd continues to crash.
That’s the report released Monday from scientists at Michigan Technological University who have been studying the relationship between wolves and moose on the island since 1958, what has become the longest running predator/prey study in the world.
This year, however, for the first time in 63 years, scientists were unable to conduct their annual winter aerial survey of the island where dark moose show up well against a snowy backdrop and researchers can estimate the population with confidence. COVID-19 concerns and precautions canceled the winter survey entirely, and scientists have had to base their annual assessment on other data, trends and hunches.
The moose herd was estimated at about 1,800 in early 2020, after the last full survey, but that number has almost certainly dropped dramatically since then with moose unable to find quality food to eat.
“The moose appear to be starving to death,” said Sarah Hoy, one of the lead Michigan Tech researchers on the project. “But without actually being able to be in the field (in winter) there’s no way of knowing how far their numbers have come down.”
Within days of arriving on the island this spring, researchers found the remains of at least 15 moose that had apparently died of malnutrition at the end of winter. Normally they’d find one or two. Researchers also are seeing signs that the island’s forest is being damaged by hungry moose.
“The state of the forest is the worst we’ve seen it since we began monitoring it” nearly 25 years ago, Hoy said. “The moose are eating it faster than it can grow.”
Moose also have been hard-hit by winter ticks, a common parasite that can build to huge numbers — tens of thousands on each moose — during periods with warm summers and shorter winters. So many ticks can build up on a single moose that it reduces their blood supply, further zapping their energy and their ability to survive winter.
“It’s a tough year if you’re a moose on Isle Royale,” Hoy said. “It seems to have been a particularly bad winter for ticks.”
The full year now without new data also is impacting researchers’ ability to track wolf trends on the island. Most of the GPS transmitting collars that adult wolves were carrying have now run out of battery power, leaving scientists in the dark on the exact status and locations.
But researchers are getting a little help from trail cameras and campers — both of which have spotted wolf pups last summer, over the winter and even already this summer — even though most official research has been on hold during the pandemic.
“It appears the wolf population is doing well and likely increasing,” Hoy said.
In their 2020 report, researchers said there were about a dozen adult wolves on the island and at least that many pups. Now, those numbers are likely even higher, as the wolf population trends toward the 25-30 adults that biologists say is sustainable on the island.
“We recovered footage of a group of four wolf pups taken in January 2021 by remote cameras at the east end of Isle Royale,” Hoy said. “Additionally, observations of tracks and scats left by wolf pups last fall at two different locations suggest that there were probably two different litters of pups living at the east end of the island in September 2020.”
National Park Service biologists will be checking more trail cameras and other data, including DNA analysis, and should have a better estimate of wolf numbers later this summer, said Mark Romanski, biologist and natural resources program manager at Isle Royale National Park.
“We know we have new wolves, but we don't know how many have died. We’re in a blind spot because we really know nothing about (wolf) mortality over the last 18 months or so,’’ said John Vucetich, Michigan Tech biologist and lead researcher on the project. “Now that the new packs are sorting themselves out … the mortality should be back to normal and we would expect their numbers to increase.’’
Vucetich said he would guess about 18 adult wolves are now roaming the island with several new pups this year.
At 45 miles long, Isle Royale is the largest island on Lake Superior, sitting about 14 miles off Minnesota's North Shore from Grand Portage. The island is a national park and mostly designated wilderness with few human visitors in summer and none in winter. There are no other major predators on the island, no human hunting is allowed and moose are the only large prey species, making it a unique wild laboratory for the ongoing study.
Moose came to the island around 1900, peaking at 2,445 in 1995 and hitting bottom at just 385 in 2007. Wolves are relatively new to the island, having crossed the ice from the North Shore in 1949. Their numbers reached a high of 50 in 1980, and 24 wolves roamed the island as recently as 2009.
Climate change, spurring far fewer years of ice bridges between the island and the mainland, reduced the number of new wolves venturing to the island in recent decades and reduced the pack's genetic diversity. With no new wolves coming to the island, the animals inbred and developed genetic deformities that doomed their survival, spurring the National Park Service's dramatic wolf reintroduction effort in recent years aimed at maintaining some natural limit on the island's moose.
Wolves were trapped in Minnesota, Michigan and on Ontario islands of Lake Superior and moved to Isle Royale in 2017 and 2018, the basis for the island’s current wolf revival.