A female polar bear with her cubs on Bely Island. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

A polar bear on Bely Island. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

A polar bear on Vilkitsky Island. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

A polar bear on Vilkitsky Island. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

A landing on the island during the 2019 Yamal-Arctic expedition. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

Specialists take basic measurements of a polar bear. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

A female polar bear after being collared. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

A female polar bear with her cubs on Bely Island. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

Specialists take basic measurements of a polar bear. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

Specialists take basic measurements of a polar bear. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

Specialists take basic measurements of a polar bear. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

Specialists take basic measurements of a polar bear. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

Zoologists take biological samples of a female polar bear. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

Specialists take basic measurements of a polar bear. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

A female polar bear after being collared. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences

A female polar bear after being collared. Photo by the Severtsov Institute of Ecology and Evolution at the Russian Academy of Sciences