Claim: The killer whale has body parts.

Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea . Thirty extant species are described . They include several big species whose common names contain `` whale '' rather than `` dolphin '' , such as the killer whale and the pilot whales . Delphinidae is a family within the superfamily Delphinoidea , which also includes the porpoises -LRB- Phocoenidae -RRB- and the Monodontidae -LRB- beluga whale and narwhal -RRB- . River dolphins are relatives of the Delphinoidea .   Oceanic dolphins range in size from the 5.6 ft-long and 110 lbs Maui 's dolphin to the 31 ft and 11 ST killer whale , the largest known dolphin . Several species exhibit sexual dimorphism ; the males are larger than females . They have streamlined bodies and two limbs that are modified into flippers . Though not quite as flexible as seals , some dolphins can travel at 34.5 mph . Most delphinids primarily eat fish , along with a smaller number of squid and small crustaceans , but some species specialise in eating squid , or , in the case of the killer whale , also eat marine mammals and birds . All , however , are purely carnivorous . They typically have between 100 and 200 teeth , although a few species have considerably fewer . Delphinids travel in large pods , which may number a thousand individuals in some species . Each pod forages over a range of a few dozen to a few hundred square miles . Some pods have a loose social structure , with individuals frequently joining or leaving , but others seem to be more permanent , perhaps dominated by a male and a harem of females . Individuals communicate by sound , producing low-frequency whistles , and also produce high-frequency broadband clicks of 80-220 kHz , which are primarily used for echolocation . Gestation lasts from 10 to 18 months , and results in the birth of a single calf . Some species are well adapted for diving to great depths . They have a layer of fat , or blubber , under the skin to keep warm in the cold water .   Although oceanic dolphins are widespread , most species prefer the warmer waters of the tropic zones , but some , like the right whale dolphin , prefer colder climates . Some have a global distribution , like the killer whale . Oceanic dolphins feed largely on fish and squid , but a few , like the killer whale , feed on large mammals , like seals . Male dolphins typically mate with multiple females every year , but females only mate every two to three years . Calves are typically born in the spring and summer , and females bear all the responsibility for raising them . Mothers of some species fast and nurse their young for relatively long times . Dolphins produce a variety of vocalizations , usually in the form of clicks and whistles .   Oceanic dolphins are sometimes hunted in places such as Japan , in an activity known as dolphin drive hunting . Besides drive hunting , they also face threats from bycatch , habitat loss , and marine pollution . Dolphins have been depicted in various cultures worldwide . They occasionally feature in literature and film , as in the Warner Bros film Free Willy . Oceanic dolphins are kept in captivity and trained to perform tricks , but breeding success has been poor and the animals often die within a few months of capture . The most common dolphins kept are the killer whales and bottlenose dolphins .