Isle Royale moose numbers remain high
For about a week in February, as temperatures plummeted, an ice bridge formed between Isle Royale and the nearby Ontario mainland.
Scientists crossed their fingers and hoped it would hold long enough for some wayward wolves to meander out onto the island and stay, the first to do so in decades.
But it didn't happen. The ice soon broke up. There was no evidence any new wolves made the crossing. And the island remains stuck with the last two of its native wolves, a father-daughter pair (who share the same mother) unable to reproduce successfully.
That's the report this week released by researchers from Michigan Technological University in their 60th year of studying the relationship between wolves and moose on Lake Superior's largest island.
The two wolves remaining are down from 24 a decade ago thanks to genetic deformities caused by inbreeding. The decline of wolves has led to a surplus of moose, with an estimate of 1,475 over the winter. That's statistically unchanged from 1,600 moose estimated in 2017 and well up from the long-term average fluctuation between 700 and 1,200.
"I don't think there was much change at all in moose. A lot of it is weather conditions during the survey ... Last year's count may have been a little high and this year's a little low," said John Vucetich, one of the Michigan Tech scientists leading the study. "The key point is that their numbers remain very high. The trend for the past five years is going up and there's nothing indicating that's not going to continue."
Vucetich said that as moose numbers approach and likely surpass 2,000, the island's forests will begin to show stress from over-browsing by the big animals. That happened in the mid-1990s when wolf numbers crashed and moose numbers soared to their all-time high of 2,400.
The moose literally ran out of food, reducing balsam and other key species so much the moose started to starve.
"That appears where we are headed without meaningful wolf predation,'' Vucetich said.
That may be about to change, but it's not clear how fast.
In March the National Park Service announced that Isle Royale's decimated wolf population will get a lifesaving infusion of 20 to 30 new wolves over the next three years. The Park Service published its final environmental impact statement after studying the potential of wolf reintroduction for two years and deciding on bringing in new wolves over other options, including doing nothing.
Some people had suggested that the Park Service stay out of the situation and let the island's wolves run their course, saying the definition of federal wilderness is an area not impacted by human action. But others say the problems wolves face — including vastly diminished Lake Superior ice cover due to climate change, which makes it less likely for new wolves to come to the island — show humans already are having an impact.
On Wednesday Phyllis Green, the park's superintendent, said she doesn't know when the final order will be signed by top Park Service officials in Washington to start the wolf reintroduction.
The 45-mile-long, 143,000-acre island is located about 15 miles off Minnesota's North Shore.
Wolves are relatively new to the island, having crossed the ice in the 1940s. Their numbers reached a high of 50 in 1980, and 24 wolves roamed the island as recently as 2009.
Moose came to the island much earlier in the 1900s, peaking at 2,445 in 1995 and hitting bottom at just 385 in 2007.
In the draft environmental study, the Park Service says it will look to capture Great Lakes-region wolves that are known to feed on moose as one of their prey sources, are in good health with no apparent injuries and have the appropriate genetic diversity to sustain a viable population on the island.
Capture and relocation efforts would take place between late fall and late winter. Relocated wolves will be fitted with radio or GPS collars so they can be tracked.
But on Wednesday Vucetich suggested that the Park Service may need to look beyond a one-time infusion of new wolves. Without regular ice bridges and migration of new wolves off the mainland, he said, Isle Royale's new wolves may be doomed to the same future of inbreeding and genetic deformities — unless new wolves are introduced on occasion.
"Looking down the line, maybe every 20 years or so, they are probably going to have to keep adding additional wolves," Vucetich said. "But first we have to get them here to start."