Much like the orientation vocalizations of a bat, these pulses, or clicks, return as echoes when the sound bounces off objects in the dolphin's path. The animal uses the echoes to navigate and to judge the distance to, and location of, prey as small as shrimp.
Dolphins also produce whistling sounds when excited or communicating with other dolphins.
These sounds arise from the larynx. Porpoise, common name applied to six species of small whales closely related to dolphins. Porpoises are generally smaller than dolphins and have rounded conical heads that lack the dolphin's characteristic beak. Porpoises have triangular rather than hooked dorsal fins, and instead of vaulting completely out of the water like dolphins do, they make wheel-like rolls, surfacing about four times a minute to breathe. Belugas travel in schools of several thousand, feeding on fish, octopus, crabs, snails, and squid.