Every year, field biologists from the Norwegian Polar Institute work on Polar bears in Spitsbergen by anesthetizing them from helicopters. Then, the bears are measured, samples are taken and in some cases a sender is attached to the bear to follow their migrations. Due to adverse weather conditions, the 2010 season was less successful than usual: only 53 bears were caught, including 25 adults, the remaining younger ones. 70 % of these 53 had been caught before.
This kind of work, that often involves following fleeing bears for some distance with helicopters, is controversial, but data regarding population, migration and concentrations of environmental toxins would be difficult to aquire otherwise.
Polar bear family, Spitsbergen

Sources: Svalbardposten, Norwegisches Polarinstitut.