When beginning to dive, humpback whales often lift their flukes (tails) out of the water when they dive deeply, exposing a distinctive pattern of black and white, which is used by biologists to identify individual animals. When feeding, humpbacks appear to be frolicking, rolling and blowing in groups. They also breach the surface frequently, doing huge belly flops as they slam back into the sea.
When feeding, humpbacks may stay submerged for as long as 30 minutes, but most dives do not last longer than 15 minutes. After diving, humpbacks rest on the surface, blowing every few seconds. One phenomenon that fascinates everyone is "bubble-net" feeding. The whales work cooperatively to trap fish in a huge circle of bubbles. Then, they zip upwards through the school of trapped fish with their huge mouths wide open. The water filters out through the comb-like baleen lining the mouth, but the fish are trapped. Amazing to watch!
Alaskan humpbacks winter in Hawaii, but they do not feed anywhere but in Alaska. While moving to and from Hawaii, the huge mammals do not feed. They breed and bear their young in Hawaii, but do not feed there, either. Since adults range from 40-55 feet in length and weigh many tons, they certainly have to feed all summer long!