Polar bears are unable to adapt their behaviour to cope with the food losses associated with warmer summers in the Arctic, according to a report by the BBC.

Scientists had believed that the animals would enter a type of ‘walking hibernation’ when deprived of prey.

But new research says that that bears simply starve in hotter conditions when food is scarce.

The authors say that the implications for the survival of the species in a warmer world are grim.

Polar bears survive mainly on a diet of seals that they hunt on the sea ice – but increased melting in the summer reduces seal numbers and as a result the bears struggle to find a meal.