Melon-headed dolphin, Many-toothed blackfish, "melon whale", Electra dolphin, Little killer whale
The Melon-headed whale (Peponocephala electra) belongs to the oceanic dolphin family. It is closely related to the Pygmy killer whale and Pilot whale. Collectively these dolphin species are known by the common name blackfish. Melon-headed whales have a wide distribution and often occur near shore mostly around oceanic islands, such as Hawaii, French Polynesia, and the Philippines.
Melon-headed whales have a robust, dolphin-like body, a tapering, conical head (head shape triangular when viewed from above) with no discernible beak, and a relatively tall, falcate (sickle-shaped) dorsal fin located near the middle of the back. Body coloration is charcoal-gray to dark-gray body. A dark face ‘mask’ extends from around the eye to the front of the melon and larger animals have whitish lips. Melon-headed whales have a dark colored dorsal cape that starts narrowly at the front of the head and dips down at a steep angle below the dorsal fin. The boundary between the darker cape and coloration on the flanks is often faint or diffuse. Both the mask and dorsal cape are often only visible in good lighting conditions. Compared to females, adult males have more rounded heads, longer flippers, taller dorsal fins, and broader tail flukes.
Melon-headed whales are found beyond the continental shelf between 20°S and 20°N. Most commonly they occur in the Philippines Sea. Individuals have also been sighted off the southern coast of Ireland. Melon-headed whales live far from shore in all the world's tropical and subtropical oceans. At the northern fringes of their range, they may also be found in temperate waters.
Melon-headed whales are very social animals. They live in large groups numbering between 100 and 1,000. Within these large groups, they usually swim in smaller groups of 10-14. They have been seen swimming close to each other and touching flippers. Groups of the Melon-headed whales mix with groups of Fraser’s dolphins and socialize with them. They also associate with Humpback whales and Pilot whales. Melon-headed whales spend much of their daytime at the surface resting. When resting near the surface, they create large splashes when they break the water. Several of them rise vertically out of the water to observe their surroundings and then splash back down. This technique is known as spy hopping. These whales are capable of very fast swimming, particularly when startled. In flight, they often make short, low jumps clear of the sea surface, splashing lots of water.
Melon-headed whales are carnivorous. They typically feed on squid and small fish.
Little is known about the reproductive behavior or breeding habits of Melon-headed whales. It is suggested that calves are born year round. Gestation period probably lasts about 12 months after which a single calf is born. At birth calf weighs 10–15 kg (22–33 lb) and is 1 m (3.3 ft) long. Calves are capable of swimming soon after birth. It is known that Melon-headed whales reach reproductive maturity at around 4 years of age.
Melon-headed whales are not hunted specifically, however, they are accidentaly caught in fishing nets or occasionally hunted by fisheries in coastal Japan. This species, like other beaked whales, is likely to suffer from sounds, produced by navy sonar and seismic exploration equipment. Pollution and climate change are another threats to this species.
According to the IUCN Red List, the total population size of the Melon-headed whale is unknown. However, there are estimated populations of the species in the following areas: eastern tropical Pacific - 45,400 whales; Gulf of Mexico - 3,451 whales; Hawaii - 2,947 whales; eastern Sulu Sea (Philippines) - 921 whales. Currently, this species is classified as Least Concern (LC) on the IUCN Red List.
