Female polar bears with cubs generally avoid adult male bears, which sometimes attack the young and eat them. If their paths cross, highly protective mother bears can become very ferocious. They are capable of driving off much larger males if they think their cubs are threatened.

In fact, mother bears have been known to rear up and leap at helicopters carrying research scientists when they thought they were getting too close to their cubs.

Biologists have also observed "adoption" among polar bears. In one case, a female was tagged with a different set of cubs from the ones she was accompanying just months before.