The killer whale (Orcinus orca) is a large member of the Delphinidae widely distributed throughout the world’s oceans, especially common in coastal areas and high latitudes. Males reach about 6–9 m in length and females about 5.6–7.7 m, with pronounced sexual dimorphism in the dorsal fin. They have highly developed, pod-based social structures and vocal communication; ecotypes differ in diet and movement patterns. Some populations eat only fish while others hunt marine mammals, and they display a variety of behaviors including cooperative hunting, breaching, and spy-hopping. Reproduction is not strongly seasonal; gestation lasts about 12–15 months and the interval between births is several years. Population sizes and threats vary regionally, and chemical pollution and noise have impacts.