Whether the waters of Lake Superior freeze each winter can decide life or death for the caribou living on Michipicoten Island.
Lately, it has been mostly death.
The Canadian island in northern Lake Superior was once home to hundreds of caribou. As recently as 2002, a study by Ontario's parks service said there were over 200 caribou living there.
Then, in 2014, the lake froze. Wolves walked over to where they had never lived.
The predators decimated the island's caribou population. The most current estimates put the Michipicoten caribou population as low as 30 animals, according to Jolanta Kowalski with Ontario's Ministry of Natural Resources and Forestry.
But last weekend, crews took on an operation to snatch up a few caribou and take them to Lake Superior's Slate Islands, where hopefully they will reproduce.
On the Slates, there aren't any known caribou predators, Kowalski said. "This is their best chance of the population being saved."
Humans were forced to intervene on behalf of these caribou. Ice bridges that could have allowed them to escape the wolves just don't occur as often in the changing climate.
Researchers used a net gun to capture the massive mammals before airlifting them. They're sedated and put into what looks like a "big sleeping bag" to keep them calm for the trip, Kowalski said.
Eight cows and one bull landed safely on the Slates, Kowalski said, and that's where they'll have their best shot at survival.