 These small whales are also targeted by terrestrial and pagophilic predators . The polar bear is well adapted for hunting Arctic whales and calves . Bears are known to use sit @-@ and @-@ wait tactics as well as active stalking and pursuit of prey on ice or water . Whales lessen the chance of predation by gathering in groups . This however means less room around the breathing hole as the ice slowly closes the gap . When out at sea , whales dive out of the reach of surface @-@ hunting orcas . Polar bear attacks on belugas and narwhals are usually successful in winter , but rarely inflict any damage in summer . 
