Melon-headed whale (Peponocephala electra)

The melon-headed whale (Peponocephala electra) is a member of a group of small, dark-coloured whales often referred to as ‘blackfish’ ⁽⁵⁾. As this name suggests, this whale is a black or dark-grey colour, although the lips are a starkly contrasting white and the undersides are pale grey ^{(2) (5)}. A distinct dark eye patch broadens around the face, giving this whale the appearance of wearing a mask, while a faint light band extends from the blow hole to the rounded melon ^{(2) (5)}. The body is long and slim, with a proportionately long tail and, lacking a beak, the forehead curves smoothly from the tip of the nose to the blowhole. The male is larger than the female and has a taller dorsal fin, and the pointed, tapering flippers are comparatively longer ^{(5) (6)}. The melon-headed whale is very similar in appearance to the closely related pygmy killer whale (Feresa attenuate), but may be distinguished by its more triangular head-shape, more pointed flippers, and the possession of substantially more teeth, of which it has between 20 to 26 on each side of both jaws ⁽³⁾.

Also known as

many-toothed blackfish.

Synonyms

Electra electra, Lagenorhynchus electra.

French

Péponocéphale.

Spanish

Calderón Pequeño, Electra.

Size

Head-body length: 2.5 – 2.8 m ⁽²⁾

Maximum weight: 275 kg ⁽³⁾

When swimming at speed, the melon-headed whale makes shallow leaps out off the water, creating huge amounts of spray. Slower moving individuals may be seen to lift the entire head out of the water when surfacing, and occasionally this species will spyhop, a behaviour where the whale rises and holds its position partially out off the water, exposing the underside of its head ⁽⁸⁾. 

Like many other cetaceans, the melon-headed whale is a highly social animal and typically travels in large groups of several hundred, although up to 2,000 individuals have been seen travelling together ⁽⁷⁾. Within the pod, the whales are tightly packed and make frequent and rapid changes in direction ⁽⁸⁾. This species often associates with other cetaceans, and is often seen following or at the edge of groups of Fraser’s dolphin (Lagenodelphis hosei) ^{(6) (7)}. Strong social bonds are formed between whales, and within large pods smaller groups may cooperate together when feeding ^{(6) (7)}. 

This whale feeds on a variety of pelagic fish and squid, although it may also supplement this diet with crustaceans ⁽⁷⁾. It is likely that it feeds deep in the water column and drives its prey upwards, trapping it at the water’s surface ⁽⁷⁾. The timing of breeding is unknown, but may peak between August and December in the southern hemisphere, and between July and August elsewhere ^{(3) (8)}. As is typical of most small cetaceans, the young calves are born after a one year gestation period, and male melon-headed whales have a lifespan of 22 years, while the females may live to 30 years of age ^{(6) (7)}.

The melon-headed whale is found in tropical and sub-tropical waters worldwide, although some whales may follow warm water currents to higher latitudes, such as off South Africa and southern England ^{(1) (5)}.

This whale prefers deep warm waters, rarely straying from continental shelves or oceanic islands. The melon-headed whale may occasionally enter more coastal waters where the water rapidly drops to great depths ^{(1) (5) (7)}.   

The melon-headed whale is classified as Least Concern on the IUCN Red List ⁽¹⁾ and listed on Appendix II of CITES ⁽⁴⁾.

Due to its large range and population, currently estimated at over 50,000, of which around 45,000 reside in the tropical east Pacific, the melon-headed whale is not thought to be threatened with extinction. This species is relatively common in parts of its range, in particular in the Philippine Sea, which is perhaps the species’ stronghold. However, at present there is no information available on population trends, and as its fish prey is likely decreasing from over-fishing, this whale may actually be in decline ⁽¹⁾. 

The melon-headed whale is taken in a number of small net and harpoon cetacean fisheries, including in St Vincent, the Philippines and Taiwan, while it is also killed in the annual dolphin drive at Taiji, Japan, although the number of whales killed in these fisheries and its impact on the population is unknown ⁽¹⁾. A small number of whales are also killed as bycatch in nets for tuna, although this is likely to be a somewhat smaller threat compared to direct fishing ^{(1) (5)}. 

Mass strandings of the melon-headed whale are commonly reported which, although the cause of this is unknown, may be due to outbreaks of parasites or a panic response in the school when a few members accidentally become stranded ⁽⁵⁾. However, one incident on the Hawaiian island of Kauai, when between 150 and 200 whales become stranded on a bay, may be attributed to U.S. Navy training involving the use of sonar ^{(1) (8)}. It is also possible that the use of sonar and seismic exploration can kill whales by causing gas bubble disease ⁽⁹⁾. 

The melon-headed whale could also become threatened by climate change, as rising sea levels and increased surface sea temperatures may potentially alter the abundance and distribution of its prey species ⁽¹⁰⁾.

The melon-headed whale is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that international trade in this species should be carefully monitored ⁽⁴⁾. There is still very little know about this species, partly due to its relative unimportance as a commercial species and offshore habits, and further research is required if the uncertainty surrounding the significance of the threats to this species is to be resolved ^{(1) (6)}.  

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

For more information on the melon-headed whale:

• Convention on Migratory Species:
  http://www.cms.int/reports/small_cetaceans/data/P_electra/p_electra.htm

Find out more about the conservation of whales and dolphins:

• The Whale and Dolphin Conservation Society (WDCS):
  http://www.wdcs.org.uk/

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

Bycatch

In the fishing industry, the part of the catch made up of non-target species.

Cetacean

A whale, dolphin or porpoise.

Cetaceans

A group comprising all whales, dolphins and porpoises.

Crustaceans

Diverse group of animals with jointed limbs and a hard chitinous exoskeleton characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps and barnacles.

Dorsal fin

The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.

Gestation

The state of being pregnant; the period from conception to birth.

Melon

A lump of fatty tissue that forms the bulging forehead of toothed cetaceans (whales, dolphins and porpoises), thought to focus sound during echolocation.

Pelagic

Inhabiting the open oceans.

1. IUCN Red List (June, 2010)
   http://www.redlist.org/
2. Nowak, R.M. (1999) Walker’s Mammals of the World. The Johns Hopkins University Press, Baltimore.
3. Jefferson, T.A. (2008) Clymene dolphin. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds) Encyclopedia of Marine Mammals Second Edition. Academic Press, London.
4. CITES (June, 2010)
   http://www.cites.org/
5. Perryman, W.L. (2002) Melon-headed whale Peponocephala electra. In: W. F. Perrin, B. Wursig and J. G. M. Thewissen (eds) Encyclopedia of Marine Mammals. Academic Press, London.
6. National Oceanic and Atmosphere Administration Fisheries Service (June, 2010)
   http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/melonheadedwhale.htm
7. Jefferson, T.A. and Barros, N.B. (1997) Peponocephala electra. Mammalian Species, 553: 1-6.
8. Convention on Migratory Species (June, 2010)
   http://www.cms.int/reports/small_cetaceans/data/P_electra/p_electra.htm
9. Cox, T.M. et al. (2006) Understanding the impacts of anthropogenic sound on beaked whales. Journal of Cetacean Research and Management, 7: 177-187.
10. Learmonth, J.A., Macleod, C.D., Santos, M.B., Pierce, G.J., Crick, H.Q.P. and Robinson, R.A. (2006). Potential effects of climate change on marine mammals. Oceanography and Marine Biology: An Annual Review, 44: 431-464.