Pygmy killer whale
The only population estimate is of 38,900 individuals in the eastern tropical Pacific Ocean.
The pygmy killer whale (Feresa attenuata) is a small, rarely seen cetacean of the oceanic dolphin family (Delphinidae). It derives its common name from sharing some physical characteristics with the killer whale. It is the smallest species that has "whale" in its common name. In fact, "killer" may be more apt in the case of the pygmy killer whale than its larger relative; when a number of pygmy killers were brought into captivity in Hawaii and South Africa, they were extremely aggressive—even killing other poolmates.
A pod captured in Japan did not display such aggression.
Although it had been described by John Gray in 1874, the pygmy killer whale, until the early 1950s, was known only from two skulls kept at the British Museum. In 1954, Japanese cetologist Munesato Yamada published accounts of a "rare porpoise" discovered in 1952 by whale hunters working from Honshū. He wrote that the individuals he examined had skulls matching those in the museum and that the body had features similar to the killer whale, and proposed the common name lesser (or pygmy) killer whale. Despite its name and features, the pygmy killer whale is not closely related to the killer whale.
The scientific species descriptor attenuata is Latin for 'tapering' and refers to the gradual narrowing from the head to the tail fin.
The pygmy killer is an average-sized dolphin (a little larger and heavier than a grown man) and may easily be confused at sea with other species, in particular the melon-headed whale. These dolphins always move in groups, usually of 10 to 30, but occasionally much larger.
Data from strandings, which seem to be common in the species, indicate a diet of cephalopods and small fish. They have been observed attacking, killing, and eating other cetacean species such as the common dolphin.
Gestation lasts from 10 to 12 months, and results in the birth of a single calf.
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.