Pilot Whale , common name for two species of the dolphin family. The short-finned pilot whale occurs in tropical and warm temperate waters throughout the world's oceans, from the equator to about latitude 40° north and south. The long-finned pilot whale occurs in the North Atlantic Ocean as far north as Greenland, Iceland, and northern Norway; a separate southern-hemisphere group occurs in cold temperate to Antarctic waters. Although their range once included the North Pacific Ocean, long-finned pilot whales have not been sighted there recently. The two species both occur in some temperate areas, especially around South America and in the North Atlantic. Pilot whales of both species grow to about 6 m (about 20 ft) in length. Males are slightly larger than females, and the long-finned pilot whales are slightly larger than the short-finned. Members of both species have a large, rounded head and a very large dorsal fin. They are generally black to dark brown or gray, with a light patch, sometimes called a saddle patch, just behind the dorsal fin. A second light patch is common on the upper belly to just below the chin. Pilot whales communicate by means of complex rasping sounds and squeals, and they can probably identify one another by these calls. They use echolocation to make out their surroundings-that is, they send out high-frequency clicks that bounce off prey and other objects and use the returning echoes to distinguish the objects. Pilot whales are deep divers that feed primarily on squid. They are very gregarious, and groups commonly number in the low hundreds. Each male probably mates with several females. Females give birth to a single calf, and although they can no longer bear young after age 35, they often continue to suckle young for at least 14 more years. This suggests that females take prolonged care of their young and that they may also care for the young of sisters and possibly of daughters. Groups of pilot whales run aground more often than do groups of other whale species. Such strandings of the long-finned species are common in New England and off the coast of New Zealand. It is not known whether mass strandings are triggered by navigational error, disease, or both, but it is clear that the close-knit society of pilot whales is so cohesive that when several individuals strand themselves, others will do so as well. Because schools of pilot whales are so cohesive, it has been relatively easy to hunt them, especially by methods in which a school is herded into the shallows of a coastal bay and gaffed or clubbed. Historically, such hunting of pilot whales was much more prevalent; hunting of long-finned pilot whales is still conducted off the coast of Greenland and around the Faroe Islands of Denmark, and hunting of short-finned pilot whales still occurs off the coast of Japan. It is believed that pilot-whale populations in the North Atlantic have been reduced by hunting .