The Polar Bear Programme aims to study the polar bear habitat in the Russian Arctic

At present, the most serious threats that face polar bears are industrial development in the Arctic, such as shipping and oil drilling, habitat pollution and destruction, and poaching

It took researchers who were working continuously under harsh weather conditions almost a month to catch and immobilise four male polar bears. Two polar bears were fitted with satellite-tracked collars

The researchers rely on signals transmitted by the collar that is still attached to the animal for charting migration routes. Taking into account ice drifts in this area, the animal could travel at a speed of about 10 kilometres a day

Researchers around the world usually place satellite-tracked collars on female polar bears as the shape of their heads and necks allows the animals to wear the collars for a long time

During the expedition the researchers only encountered female polar bears accompanied by their cubs, and catching them would have jeopardised the life of the young. For that reason, they decided to attach collars to two males instead

Aerial surveys and observations from helicopters also allowed the researchers to record the other animals inhabiting the area. All in all, the researchers counted 22 polar bears, including three females with cubs and a breeding pair

Experts in various fields took part in the expedition: zoologists, environmentalists and climatologists, specialists on marine mammals, immobilisation specialists

After the polar bears had been caught and immobilised the researchers took blood, fur and feces samples for genetic and veterinary analysis

The researchers also tried out another method of catching the polar bears by using special traps with food inside (this method is likely to be widely used in the future in warmer seasons)

The female stops growing when she reaches maturity while the male keeps growing and gaining weight throughout his life