Pygmy killer whale
The pygmy killer whale (Feresa attenuata) is a poorly known and rarely seen oceanic dolphin.[3] It derives its common name from sharing some physical characteristics with the orca also known as the killer whale. It is the smallest cetacean species that has the word "whale" in its common name.[4] Although the species has been known to be extremely aggressive in captivity, this aggressive behavior has not been observed in the wild.[5]
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 cetologist Munesato Yamada in 1954.[6]
The pygmy killer whale is dark gray to black on the cape and has a sharp change to lighter gray on the sides. The flesh around their lips and on the end of their snout is white while pinkish white skin surrounds the genitals. The average length is just over two meters (6.5 ft.). Upon reaching 2 meters in length, males are considered sexually mature. They have approximately 48 teeth, with 22 teeth on the top jaw and 26 on the lower jaw.[7]
They travel approximately 3 km/hour (2 miles/hour)[8] and are predominately found in deeper waters ranging from 500 m to 2000 m (1600–6500 ft.) in depth.[3]
Pygmy killer whales are most commonly confused with melon-headed whales and false killer whales. For instance, a published paper describing an encounter with a school of pygmy killer whales[5] was later determined to be either a mixture of pygmy and false killer whales or solely false killer whales.[9]
The three species can be differentiated by physical differences between them. One defining difference is, although both species have white around the mouth, on pygmy killer whales the white extends back onto the face. Pygmy killer whales also have rounded-tipped dorsal fins, as opposed to pointed tips. When compared to false killer whales, pygmy killer whales have a larger dorsal fin. Finally, pygmy killer whales have a more clearly defined line where the dark dorsal color changes to the lighter lateral color than either of the other two species.[9]
