Polar Bears and the Shrinking Sea Ice
For the Arctic’s top predator, the ice is not scenery: it is the hunting ground.
By Biosphere Editorial Team · 2026-08-03
The polar bear, Ursus maritimus, is classified as a marine mammal because it depends on the sea. It hunts mainly ringed and bearded seals, waiting at breathing holes or along the edges of the Arctic sea ice.
When the ice disappears
In regions where the sea ice melts completely in summer, polar bears come ashore and live largely off their fat reserves until the ice returns. Studies in Western Hudson Bay, Canada, have linked longer ice-free seasons with poorer body condition and a decline in the population there.
Polar bears live in around 19 subpopulations across the Arctic, and their trends differ: some are declining, others are stable or not well known. Monitoring them is difficult and expensive, which is why many trends are still uncertain.