With one foot braced on the helicopter's landing skid, a veterinarian lifted his air rifle, took aim and fired a tranquilizer dart at a polar bear.

The predator bolted but soon slumped into the snowdrifts, its broad frame motionless beneath the Arctic sky.

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, getting thin strips of fatty tissue. Another drew blood. Each sample was sealed and labeled before the bear was fitted with a satellite collar.