The False killer whale (Pseudorca crassidens) is a species of oceanic dolphin that is the only extant representative of the genus Pseudorca. It is found in oceans worldwide but mainly frequents tropical regions. The name "false killer whale" comes from similar skull characteristics to the orca, which has been known as the Killer whale. The False killer whale has a tendency to mass strand given its highly social nature, with the largest stranding consisting of 805 beached at Mar del Plata, Argentina. Most of what is known of this species comes from examining stranded individuals.
The False killer whale is black or dark gray; slightly lighter on the underside. It has a slender body with an elongated, tapered head and 44 teeth. The dorsal fin is sickle-shaped; and flippers are narrow, short, and pointed, with a distinctive bulge on the leading edge of the flipper (the side closest to the head). As a toothed whale, a False killer can echolocate using its melon organ in the forehead to create sound, which it uses to navigate and find prey. The melon is larger in males than in females.
False killer whales have a widespread presence in tropical, semitropical oceans, and occasionally in temperate waters. They usually inhabit the open ocean and deep-water areas, though they may frequent coastal areas near oceanic islands. Distinct populations inhabit the seas near the Hawaiian Islands and in the eastern North Pacific.
False killer whales are highly social animals. They normally gather into pods, which can be very small (including just a few whales) and rather large (containing hundreds of individuals). These large pods consist of smaller groups of 18 individuals on average. False killer whales are very playful and like to leap out of the water in the wake of a ship. They favor riding bow waves of various vessels, preferring faster-moving ships. False killer whales are deep-divers; the maximum known depth is 927.5 m (3,043 ft) and the maximum speed they reach is around 29 km/h (18 mph). False killer whales use a wide variety of clicks and whistles as a form of communication. They also use echolocation, interacting through sounds, which help them detect prey and sense the ocean waters. They generally hunt by day and night.
The diet of this carnivorous (piscivorous and molluscivorous) animal considerably depends on the area of habitat, usually consisting of squid as well as various species of pelagic fish, tuna, wahoo, and mahi mahi. False killer whales also consume smaller dolphins and can prey on humpback and sperm whales on occasion.
The species is known to have polygynandrous (promiscuous) mating system, where both males and females mate with multiple mates. False killer whales mate throughout the year with peak periods, occurring from January to December and in March. The gestation period ranges from 11 to 16 months. Females give birth to a single calf, after which they do not breed for about 6.9 years on average. Soon after birth, the baby is able to swim and is weaned gradually during the period of 18-24 months. Even after weaning, calves often remain in the same group as their mothers. Males of this species become reproductively mature by 8-10 years of age, whereas females reach maturity when they are 8-11 years old.
Currently, the False killer whale suffers from a sharp global decline in the number and size of prey species it consumes. On the other hand, the species is threatened by persistent organic pollutants, which, accumulating in high levels, may expose the animal to the risk of disease susceptibility. In addition, fisheries are another serious threat to these animals: along with being caught on hooks and drowns, False killer whales occasionally take the bait or catches from longlines, causing retaliatory culling. Other notable concerns to the False killer whale population include loud sounds of navy sonar and seismic exploration as well as other human-made sounds, which can be very harmful to these animals.
According to the IUCN Red List, the global population size of the False killer whale is unknown. However, there are estimates of its population in specific areas: in the coastal waters of China and Japan - 16,000 whales; in the northern Gulf of Mexico - 1,038 whales; in the U.S. (Hawaii) - 268 whales; in the eastern tropical Pacific - 39,800 whales. Currently, False killer whales are classified as Data Deficient (DD) on the IUCN Red List.