Doug Richardson : They will get used to each other in time

Polar bears in the wild are not particularly territorial, unlike other carnivores. But female polar bears can be defensive - they can become prey to male polar bears - and indeed this is happening more and more now in the wild.

A female polar bear weighs up to 300kg in winter, but a male can be 700kg.

Walker is not attacking Mercedes - he just wants to play. But for Mercedes this is something brand new. She is standing her ground.

Mercedes has had the whole of that four-acre enclosure to herself now for a year. She took a huge amount of interest in the changes we made before Walker arrived - but when he actually got here it was a shock.

Eventually they will get used to each other. He will realise she doesn't want to play and make his own entertainment and she will just get back to her normal behaviour.