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False Killer Whales, Pseudorca crassidens

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Description & Behavior

False killer whales, Pseudorca crassidens (Owen, 1846), receive their name for their resemblance to Orcinus orca. "Pseudes" in Greek means false. Like its namesake, they are dolphins, not whales, and the fourth-largest member of the Delphinidae family. Adults measure between 4.3-5.96 m and weigh a maximum of 1,360 kg. The longest adult male on record measured 5.96 m long, and the longest female on record measured 5 m. They are mostly black on the dorsal (upper) surface, fins, flanks, and flippers, with lighter coloring on the ventral (under) surface. Their flippers are somewhat unusual in that they feature an "elbow" similar to that of long-finned pilot whales.

The false killer whale

False killer whales are a very gregarious species often found in large groups of hundreds or more. They also join other cetacean species, commonly bottlenose dolphins. Their long lumbar vertebrae enable them to be active swimmers, and they are known for their speed and agility as well as for their breaching behavior. False killer whales use sounds similar to those of dolphins for sonar and to communicate with each other.

The average life span is estimated at 58 years for males and 62 years for females.

World Range & Habitat

False killer whales, Pseudorca crassidens, are a wide-ranging species found in all tropical, subtropical, and warm temperate seas. They are known to inhabit waters ranging in temperature from 9-31°C, although they prefer the warmer waters. False killer whales are typically oceanic, coming closest to shore around oceanic islands. Little is known about the migratory patterns of false killer whales, and no data exist at this time for global population figures though they are typically found in groups of 10 to 20 individuals which may be part of larger schools of hundreds of false killer whales spread over very large areas.

Feeding Behavior (Ecology)

False killer whales, Pseudorca crassidens, feed mainly on squid and large pelagic fish such as dolphin fish aka mahi mahi, Coryphaena hippurus (most commonly observed prey in Hawaiian waters). They feed mainly during the day (diving repeatedly to over 200 m) consuming up to 5% of their body weight (from captive individuals). Cetacean diets are typically assessed by examining the stomach contents of stranded animals or fisheries bycatch animals. Related: BBC News: How whales and dolphins focus sound beams on prey

Life History

Generally the life history of false killer whales, Pseudorca crassidens, is similar to that of orca (killer whales); individuals mature slowly, reproduce infrequently, and are long-lived. Females reach sexual maturity around 10 years (8.25 to 10.5 years), males much later at 18 years. Females ovulate once annually giving birth to a single calf following a 15-month gestation period.

Conservation Status & Comments

False killer whales, Pseudorca crassidens, are not hunted commercially. They are caught as bycatch, particularly off the coast of Hawaii where longline fishing for tuna and swordfish is common. It is thought that the small Hawaiian population, estimated at 123 false killer whales, may be genetically extinct, meaning that there are so few left that they are becoming genetically similar, which causes genetic defects which will eventually lead to their total extinction. There is also a larger (estimated 484 individuals) offshore Hawaiian population though little is known about them at this time (see the Baird Report below).

False killer whales, Pseudorca crassidens, are classified as Data Deficient on the IUCN Red List of Threatened Species:

DATA DEFICIENT (DD)

A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status. A taxon in this category may be well studied, and its biology well known, but appropriate data on abundance and/or distribution are lacking. Data Deficient is therefore not a category of threat. Listing of taxa in this category indicates that more information is required and acknowledges the possibility that future research will show that threatened classification is appropriate. It is important to make positive use of whatever data are available. In many cases great care should be exercised in choosing between DD and a threatened status. If the range of a taxon is suspected to be relatively circumscribed, and a considerable period of time has elapsed since the last record of the taxon, threatened status may well be justified.

References & Further Research

Jefferson, T.A., S. Leatherwood, and M.A. Webber, FAO species identification guide, Marine mammals of the world, Rome, FAO. 1993. 320 p. 587 figs.
Robin W. Baird, A review of false killer whales in Hawaiian waters: biology, status, and risk factors, Report prepared for the U.S. Marine Mammal Commission, December 23, 2009 (PDF 1.1MB)

Research Pseudorca crassidens » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SCIRIS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS

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