Toothed whale melon consists of fat, and the skull of any such creature containing a melon will have a large depression. The melon size varies between species, the bigger it is, the more dependent they are on it. A beaked whale, for example, has a small bulge sitting on top of its skull, whereas a sperm whale's head is filled mainly with the melon. Bottlenose dolphins have been found to have signature whistles unique to a specific individual. These whistles are used for dolphins to communicate with one another by identifying an individual. It can be seen as the dolphin equivalent of
Whale shark feeder, targeting concentrations of plankton or fish. It is able to ram filter feed or can gulp in a stationary position. This is in contrast to the passive feeding basking shark, which does not pump water. Instead, it swims to force water across its gills. A juvenile whale shark is estimated to eat 21 kg (46 pounds) of plankton per day. The BBC program "Planet Earth" filmed a whale shark feeding on a school of small fish. The same documentary showed footage of a whale shark timing its arrival to coincide with the mass spawning of fish shoals and feeding