If the bear is in the inner zone, where Churchill residents live and work, the staff will try to capture it. They do that with large cylindrical traps, baited with seal meat. When the bear enters, it triggers a metal screen, which locks behind it. And since the traps are mounted on the backs of trailers (like the one from the third Indiana Jones film), the bear can be immediately driven away to the Polar Bear Holding Facility.

Built in 1982, the facility has space for 28 inmates, and has held over 2,000 to date. It’s not a long-term prison. Bear families are relocated as soon as possible. If they capture a lone bear in the inner zone, they keep it in jail for a month, to minimize the chance that, once released, it’ll just go back to the same place. When the time is right and the weather clears, the wardens tranquilize the animals, bundle them in nets, strap them to helicopters, and airlift them to a site 70 kilometers north of Churchill. The bears get ear tag radios so that officials can track their movements, and lip tattoos so they can be identified in future years.

The Polar Bear Alert Program has been a tremendous success, for both bears and humans. From a site of fatal conflict, Churchill has become a symbol of co-existence—not to mention a major tourist destination for people keen to see and photograph the bears.

But conflicts are becoming increasingly common. This year, the program staff have so far responded to 386 calls to their hotline—the busiest on record. More bears are encroaching into human spaces, and not just in Churchill. People in Alaska, Norway, and Greenland are seeing the same trend. Earlier this week, a polar bear was killed after wandering into Tuktoyaktuk, Canada; it was the town’s third sighting since September, after a decade of no contact.

These conflicts can be managed, but they are the harbingers of a more unsettling trend. The Arctic is changing, affecting even places like Churchill which lie further south. The ice the bears depend on is disappearing. And the bears are struggling.

The polar bear is a machine for converting seal fat into bear flesh. To capture ringed and bearded seals, it needs ice. So in the spring and summer, when ice melts and disappears, the bears move on shore and enter a long fast. They burn a kilogram of their own fat every day while they wait for the ice to return. In Churchill, this used to happen in early November. “It would get cold, a storm would come in, the ice would spread like gangbusters, and the bears would disappear.”

But this year, the big freeze has been delayed. Visiting in November, Derocher wrote, “I was stunned by how warm it was.” Some parts of Hudson Bay were 10 to 20 degrees Celsius warmer than usual. When the sea ice formed, it soon melted again in, expanding and contracting in an abortive stutter. By the end of November, most of the bay was still ice-free. The bears, instead of stalking out across solid whiteness, were left gazing at endless blue. Only in the last week has there been enough ice for them to head offshore in search of seals.

The late freeze is coupled with an increasingly early thaw, which means that the bears spend less of the year hunting. Come the summer, their fat reserves are lower than usual, and they have to spend more time feeding off those reserves. Some starve to death. Others explore alternative sources of food, including other bears, killer whale leftovers, and human trash—hence, the growing number of calls to the Churchill hotline. Pregnant females abort their cubs. Those that already have cubs can’t find enough food for them. The entire population enters a tailspin. The west Hudson Bay used to have 1,200 polar bears. There are now just 800, and the decline shows no signs of slowing.