“To do this, we take their (fatty) tissue, cut it in very thin slices and expose it to the stresses they face, in other words pollutants and stress hormones,” said Pirard, who developed the method.

Moments after the bear collapsed, the chopper circled back and landed. Researchers spilled out, boots crunching on the snow.

One knelt by the bear’s flank, cutting thin strips of fatty tissue. Another drew blood.

Each sample was sealed and labelled before the bear was fitted with a satellite collar.

Scientists said that while the study monitors all the bears, only females were tracked with GPS collars as their necks are smaller than their heads — unlike males, who cannot keep a collar on for more than a few minutes.

Arctic lab

For the scientists aboard the Norwegian Polar Institute’s research vessel Kronprins Haakon, these fleeting encounters were the culmination of months of planning and decades of Arctic fieldwork.

In a makeshift lab on the icebreaker, samples remained usable for several days, subjected to controlled doses of pollutants and hormones before being frozen for further analysis back on land.

Each tissue fragment gave Pirard and her colleagues insight into the health of an animal that spent much of its life on sea ice.

Analysis of the fat samples showed that the main pollutants present were per- and polyfluoroalkyl substances (PFAS) — synthetic chemicals used in industry and consumer goods that linger in the environment for decades.