False killer whale

Distribution

False killer whales are generally found in tropical and temperate waters between latitudes of 30° and 30° N.  They are uncommon and poorly studied in most regions. While they appear to occur more frequently in deeper open ocean waters, they can occasionally move into nearshore areas.

False killer whales are native or seasonally present in the following countries and territories:  American Samoa; Anguilla; Antigua and Barbuda; Argentina; Aruba; Australia; Bahamas; Bangladesh; Barbados; Belize; Benin; Bermuda; Bonaire, Sint Eustatius and Saba (Saba, Sint Eustatius); Brazil; British Indian Ocean Territory; Brunei Darussalam; Cambodia; Cameroon; Canada; Cape Verde; Cayman Islands; Chile; China; Cocos (Keeling) Islands; Colombia; Congo; Congo, The Democratic Republic of the; Cook Islands; Costa Rica; Côte d'Ivoire; Croatia; Cuba; Curaçao; Denmark; Djibouti; Dominica; Dominican Republic; Ecuador; Egypt; El Salvador; Equatorial Guinea; Fiji; France; French Guiana; French Polynesia; Gabon; Gambia; Germany; Ghana; Gibraltar; Greece; Grenada; Guadeloupe; Guam; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Honduras; Hong Kong; India; Indonesia; Iran, Islamic Republic of; Ireland; Israel; Italy; Jamaica; Japan; Jordan; Kenya; Kiribati; Kuwait; Liberia; Madagascar; Malaysia; Maldives; Malta; Marshall Islands; Martinique; Mauritania; Mexico; Micronesia, Federated States of ; Morocco; Mozambique; Myanmar; Namibia; Netherlands; New Caledonia; New Zealand; Nicaragua; Nigeria; Niue; Northern Mariana Islands; Norway; Oman; Pakistan; Palau; Panama; Papua New Guinea; Peru; Philippines; Pitcairn; Portugal; Puerto Rico; Qatar; Saint Helena, Ascension and Tristan da Cunha; Saint Kitts and Nevis; Saint Lucia; Saint Martin (French part); Saint Pierre and Miquelon; Saint Vincent and the Grenadines; Samoa; Sao Tomé and Principe; Senegal; Sierra Leone; Singapore; Sint Maarten (Dutch part); Solomon Islands; Somalia; South Africa; Spain; Sri Lanka; Suriname; Syrian Arab Republic; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Timor-Leste; Togo; Tokelau; Tonga; Trinidad and Tobago; Turkmenistan; Turks and Caicos Islands; United Arab Emirates; United Kingdom; United States; Uruguay; Vanuatu; Venezuela, Bolivarian Republic of; Vietnam; Virgin Islands, British; Virgin Islands, U.S.; Wallis and Futuna; Western Sahara; Yemen

Biology and Ecology

Feeding

False killer whales feed on a variety of fish and squid, sometimes taking large fish species like mahi-mahi, tuna, and other predatory fish like sail fish^1-4.  These feeding habits often bring them into contact with longline and other hook and line fisheries targeting these large fish species, and put them in conflict with fishermen when they steal fish from the lines (a phenomenon called depredation)^5-7.  While false killer whales have been known to attack and consume other small dolphin species as these are being released from purse seine nets in the Eastern tropical Pacific, and may harass other larger whales, they are more often seen associating with other dolphins in a non-aggressive manner. In New Zealand they are known to form long term associations with bottlenose dolphins⁸.

Social structure, reproduction and growth

Like Killer whales and sperm whales, there is evidence that false killer whales form stable family and social groups^4,9,10.  False killer whales studied in Hawaii remained around the island chain for a minimum of 20 years and stable associations between individuals were confirmed to last at least 15 years¹⁰.   Both males and females are thought to be able to start reproducing at between 8 and 14 years of age¹¹, and individuals may live as long as 60 years or more.  Unusual for marine mammals, females that no longer produce calves continue to play a role in family groups, possibly looking after the young of other females in the group¹².  False killer whales produce calves only once every 6-7 years, an indication of the maternal investment required to raise their young. Also unusual, false killer whales conduct prey-sharing, a behaviour thought to reinforce social bonds⁹.

Threats and conservation status

Natural Predators

There is little documentation of predators taking false killer whales, although a killer whale attack was observed in New Zealand. At least two false killer whales in Hawaii carry scars from large shark bites, indicating that large sharks target the species from time to time^1,9.  The species has been involved in several mass strandings throughout its range^13-15.

Human-induced threats

False killer whales are often viewed as a nuisance or as competitors by fishermen, particularly when they steal target fish from longlines, which they are known to do in Japan, Hawaii, the Indian Ocean and the Gulf of Mexico ^1,2.   This has led to direct hunts or kills in some fisheries, including in Japan, St. Vincent and Taiwan.  The species is also prone to unintentional entanglement or injury in fisheries gear, which is thought to be unsustainable in the false killer whale population around the Hawaiian islands⁶. Bycatch in other fishing gear such as drift nets and purse seines also occurs, and pollutants, as well as depletion of their large predatory fish prey are thought to present threats to false killer whales around the globe^2,16.  

Conservation status

Due to their predominantly offshore distribution false killer whales are difficult to study and not many populations have been assessed.  As such, the species is designated as Data Deficient on the IUCN Red List of Threatened Species².  The species is not listed on either Appendix of the Convention on Migratory Species (CMS).  There is serious concern, about the false killer whale population around the main Hawaiian islands, which was thought to number between 150 and 200 individuals in 2012, demonstrating a decline since 1989 ^10,17.  As such, this population is designated as Endangered under the US Endangered Species Act.

False killer whales and whale watching

Please see the IWC Whalewatching Handbook