Pygmy hippopotamus population that freely breeds in zoos around the world. Between 1970 and 1991 the population of pygmy hippos born in captivity more than doubled. The survival of the species in zoos is more certain than the survival of the species in the wild. In captivity, the pygmy hippo lives from 42 to 55 years, longer than in the wild. Since 1919, only 41 percent of pygmy hippos born in zoos have been male. While the common hippopotamus was known to Europeans since classical antiquity, the pygmy hippopotamus was unknown outside its range in West Africa until the 19th century. Due
Pygmy killer whale Pygmy killer whale The pygmy killer whale ("Feresa attenuata") is a poorly known and rarely seen oceanic dolphin. 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. Although the species has been known to be extremely aggressive in captivity, this aggressive behavior has not been observed in the wild. The species had been described by John Gray in 1874, based on two skulls identified in 1827 and 1874. The next recorded sighting was in 1952 which led to its formal naming by Japanese