The winter study of the wolves and moose on Isle Royale is heading into its 57th year.
The wolf-moose study is the longest continuous study of any predator and its prey in the world.
Scientists Rolf Peterson and John Vucetich spend seven weeks on the island in the middle of winter every year. They'll be heading back out in a few weeks.
"This year is like any other year; the number of wolves is the source of great speculation and interest," Peterson says. "We really don't know what to anticipate, but that's typically what I'm doing this time of year is anticipating."
When I spoke with Peterson after the winter study last year, he described the wolves as "barely hanging on," with just nine left on the island. He described the moose as being "on vacation" because the wolf population is so low and moose are doing so well. During the 2014 summer, Peterson observed that, despite the difficult winter, the moose did very well.
"I don't think we found any moose that starved to death. They produced another bunch of calves, but it's pretty hard to judge how big that calf crop is from summer ground observation."
He says that the weather during the past two and a half years has been to the mooses' advantage, which helped to fuel their population increase.
"So, they roughly doubled in the last three years," says Peterson.
A different outlook for the wolves
But the same can't be said for the wolf population on the island. Ice bridges from the mainland don't form as often these days in our warming climate. Last year, an ice bridge did form. But instead of any new wolves coming to Isle Royale, a female wolf left the island and was shot in Minnesota.
"We looked pretty hard for wolf reproduction and we couldn't find any evidence of that," Peterson says. "I have no expectations about what we'll find any more. The [wolf] population is so low that it's just a crapshoot."
The team uses a small plane called "The Flagship" to study the animals in the winter.
Vucetich says that having a high vantage point is essential to the research project.
"The most important thing we can see from the air are the wolves and the moose. It's very difficult to see wolves and moose in a forested landscape like is on Isle Royale. So if we were limited to the ground we would learn next to nothing," he says.
One wolf on the island is radio-collared, so the researchers can find that wolf and his packmates from the plane.
"For other wolves, what we are looking for from the air is tracks — tracks that the wolves leave in the snow," Vucetich says. They also look for moose that the wolves have killed.
Project is full of surprises
Both scientists have spent several decades of their lives studying these animals, but many mysteries still remain.
"One of the great discoveries that came from the project is when a wolf immigrated [to the island] in 1997 and we didn't even come to understand that had happened until more than a decade later. And that was something we weren't necessarily looking for it, we were just keeping our eyes open for anything that might be interesting," says Vucetich.
He says they're "routinely surprised" by what they see.
"So we're just prepared to be surprised and the only requirement is to be paying as close attention as possible so that when something interesting happens we're in a good position to detect it."