New pictures show that polar bears are beginning to cannibalise each other as global warming destroys hunting grounds.

The images, taken in Hudson Bay, Canada, around 321km north of Churchill, Manitoba, show a male polar bear carrying the bloodied head of a polar bear cub it has killed for food.

Polar bears usually subsist on seals, which they hunt from a platform of sea ice.

But the melting of sea ice as a result of rising global temperatures has made it more difficult for polar bears to hunt seals at sea, confining the bears to land.

This has led to malnourishment and starvation as polar bears are unable to build sufficient fat reserves for winter.

Drowning is also more common as bears are forced to swim further out to sea to find food.