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. It was first described in 1846 as a species of porpoise based on a skull, which was revised when the first carcasses were observed in 1861. The name “false killer whale” comes from the similar skull characteristics to the killer whale.
The false killer whale reaches a maximum length of 6 m (20 ft), though size can vary around the world. It is highly sociable, known to form pods of up to 500 members, and can also form pods with other dolphin species, such as bottlenose dolphins (Tursiops truncatus). Further, it can form close bonds with other species, as well as partake in sexual (including both heterosexual and homosexual) interactions with them. Conversely, the false killer whale has also been known to feed on other dolphins, though it typically eats squid and fish. It is a deep-diving dolphin, with a maximum recorded depth of 927.5 m (3,043 ft); its maximum speed is around 29 km/h (18 mph).
Several aquariums around the world keep one or more false killers, although the species’ aggression towards other dolphins makes it less desirable. It is threatened by fishing operations, as it can become entangled in fishing gear. It is drive hunted in some Japanese villages. 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.
Description
The false killer whale is black or dark gray, though 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 its flippers are narrow, short, and pointed, with a distinctive bulge on the leading edge of the flipper (the side closest to the head). The average body length is around 4.9 m (16.1 ft), with females reaching a maximum size of 5 m (16.4 ft) in length and 1,200 kg (2,600 lb) in weight, and males 6 m (20 ft) long and 2,000 kg (4,400 lb) in weight. However, on average, males and females are about the same size. Newborns can be 1.5–2.1 m (4.9–6.9 ft) in length.Body temperature ranges from 36–37.2 °C (96.8–99.0 °F), increasing during activity. The teeth are conical, and there are 14–21 in the upper jaw and 16–24 in the lower.
The false killer whale reaches physical maturity between 8 and 14 years, and maximum age in captivity is 57 years for males and 62 for females. Sexual maturity happens between 8 and 11 years. In one population, calving occurred at 7 year intervals; calving can occur year-round, though it usually occurs in late winter. Gestation takes around 15 months. Females lactate for 9 months to 2 years. The false killer whale is one of three toothed whales, the other two being the pilot whales, identified as having a sizable post-reproductive lifespan after menopause, which occurs between ages 45 and 55.
Being a toothed whale, the false killer whale 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.
Behaviour
The false killer whale has been known to interact non-aggressively with several dolphin species: the common bottlenose dolphin, the Pacific white-sided dolphin (Lagenorhynchus obliquidens), the rough-toothed dolphin (Steno bredanensis), the pilot whales, the melon-headed whale, the pantropical spotted dolphin (Stenella attenuata), the pygmy killer whale, and Risso’s dolphin.
The false killer whale may respond to distress calls and protect other species from predators, aid in childbirth by helping to remove the afterbirth, and has been known to interact sexually with bottlenose dolphins and pilot whales, including homosexually. It has been known to form mixed-species pods with those dolphins, probably due to shared feeding grounds. In Japan, these only occur in winter, suggesting it is tied to seasonal food shortages.
A pod near Chile had a 15 km/h (9.3 mph) cruising speed, and false killer whales in captivity were recorded to have a maximum speed of 26.9–28.8 km/h (16.7–17.9 mph), similar to the bottlenose dolphin. Diving behavior is not well recorded, but one individual near Japan dove for 12 minutes to a depth of 230 m (750 ft). In Japan, one individual had a documented dive of 600 m (2,000 ft), and one in Hawaii 927.5 m (3,043 ft), comparable to pilot whales and other similarly-sized dolphins. Its maximum dive time is likely 18.5 minutes.
The false killer whale travels in large pods, evidenced by mass strandings, usually consisting of 10 to 20 members, though these smaller groups can be part of larger groups; it is highly social and can travel in groups of more than 500 whales. These large groups may break up into smaller family groups of 4 to 6 members while feeding. Members stay with the pod long-term, some recorded as 15 years, and, indicated by mass strandings, share strong bonds with other members. It is thought it has a matrifocal family structure, with the mothers heading the pod instead of the father, like in sperm whales and pilot whales. Different populations around the world have different vocalizations, similar to other dolphins. The false killer whale is probably polygynous, with males mating with multiple females.
