Melon-Headed Whale

## Description

The melon-headed whale (Peponocephala electra ), also, less commonly, known as the electra dolphin, little killer whale, or many-toothed blackfish, is a small- to medium-sized toothed whale of the oceanic dolphin family (Delphinidae). The common name is derived from the head shape. Melon-headed whales are widely distributed throughout deep tropical/subtropical waters worldwide, however they are rarely encountered at sea. They are found near shore mostly around oceanic islands, such as Hawaii, French Polynesia, and the Philippines.

## Appearance

The Melon-headed whale 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 rounded cone head which gives the animal its common name. The color of the body is light grey except for a dark grey face – sometimes called the "mask". The flippers are long and pointed. The dorsal fin is tall with a pointed tip.

## Distribution

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.

## Behavior

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.

## Diet

Melon-headed whales are carnivorous. They typically feed on squid and small fish.

## Reproduction

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.

## Population

### Population threats

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.

### Population number

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.