Dr Alison Cronin: What's behind all the growling and roaring

IN WILDLIFE programmes you may have seen the classic shot of polar bears standing on their hind legs and sparring.

These bears have highly ritualised behaviour allowing them to assess each other's strength. The reason this has evolved is because they are one of the most dangerous animals in the world so they can't just rip into each other because they would tear each other to bits.

Mercedes is an old bear - nearly 30 - so getting up on her hind legs might not be that easy. But she won't be afraid of Walker. She has been used to an adult male polar bear, so he will seem like a teenager to her.

What they have done at the Highland Wildlife Park is quite forward thinking. They have provided their polar bears with a lot of space so they will be able to walk away - which means there will not be the stress so often associated with polar bears in captivity.

• Alison Cronin is an internationally renowned expert on polar bear behaviour.