False killer whale  (Pseudorca crassidens)

Classified as Data Deficient (DD) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

Despite its name, the false killer whale is not a close relative of the killer whale (Orcinus orca), and, in fact, any resemblance between the two species is relatively superficial (2) (4) (5). The false killer whale’s body is long and slender, with a tall, backwardly curving dorsal fin and uniquely shaped flippers that possess a large bulge at the midpoint reminiscent of an elbow (6) (7). The head tapers into a long, rounded snout, which overhangs the lower jaw and is marked with a crease running above the mouthline (7). The jaws are armed with 8 to 11 pairs of formidable-looking, large, conical teeth, from which the species derives its Latin name crassidens, meaning “thick-tooth” (7). The colouration is almost uniformly black, with the exception of faint grey marks on the heads of some individuals and a whitish chest patch located between the flippers (4) (7).

The false killer whale is incredibly widespread, with populations found in all the world’s major oceans, from northern locations such as the waters around Japan and British Columbia, south to New Zealand and Argentina (1) (5). Although normally found in tropical to warm temperate waters, individuals have been seen in cool waters as far afield as Norway and Alaska (5).

Although the false killer whale is most commonly found in open ocean waters, it also frequents the coastal areas around oceanic islands such as Hawaii, and may enter semi-enclosed seas such as the Mediterranean (5) (7).

The false killer whale’s apparently playful nature and fast, acrobatic swimming mean that individuals are frequently encountered skilfully surfing the bow waves of sea vessels, porpoising or leaping clear of the water surface (6) (7). This rapid locomotion also makes the false killer whale a highly-efficient predator, and it feeds on an array of different prey items, which, depending on its location, may include: salmon, squid, tuna and mahi mahi (5). Groups of false killer whales have also been observed feeding on smaller dolphins and even attacking humpback and sperm whales (4) (5).

A highly social species, the false killer whale usually forms groups, or pods, of between 10 and 50 individuals of mixed sex and age, but these may occasionally merge into superpods of over 800 animals (6). Pods appear to communicate extensively by producing an incredibly diverse array of clicks and whistles (2). Sound is also employed by the animals in the form of echolocation, which is used to sense their environment and locate prey (4).

Breeding is believed to occur throughout the year, but may peak at different times depending on the location (2). After a gestation period of about 15.5 months, the calves are born measuring up to two metres in length and for the first 18 to 24 months are fed on milk (2). The females reach sexual maturity at 8 to 11 years and are estimated live for up to 62 years (4), while the males may only reach maturity at 16 to 18 years (2) and live for around 57 years (4).

The population status of the false killer whale is poorly known; despite this species’ vast range, it does not appear to be particularly abundant at any location. As a result, the false killer whale may be severely affected by relatively low-grade threats. At the current time, the main threat to this species is the worldwide decline in the predatory fish species that constitute a major part of its diet. False killer whales are also frequently caught as bycatch by the commercial fishing industries of many different nations, for example, hundreds are caught each year in the trawl nets used in Chinese coastal fisheries. The false killer whale is also notorious for stealing bait from longlines, which has led to retaliatory cullings, despite the fact that many of the animals are lost due to becoming caught on the hooks and drowned (1).

Huge numbers of false killer whales, in one case over 800, are often involved in beach strandings (6). While there is no clear explanation for this phenomenon, it may be linked to the use of navy sonar and seismic exploration, which has been frequently implicated in causing strandings in other cetacean species such as beaked whales (1) (8).

Before a conservation plan for the false killer whale can be developed, it is imperative that more information about its population status and migratory movements be gathered. Until this happens, the impact of the threats faced by this species will remain unclear (1). Even with evidence to support the decline of this species, it may prove difficult to safeguard the false killer whale from military exercises and the use of sonar, as the development of protective legislation has become a contentious issue (8).

View information on this species at the UNEP World Conservation Monitoring Centre.

To learn more about whale and dolphin conservation visit:

• Whale and Dolphin Conservation Society:
  www.wdcs.org