(Gray, 1846) - Melon-headed whale
Distinctive Characteristics
At sea, melon-headed whales are often difficult to distinguish from pygmy killer whales. Major differences are that the melon-headed whale has pointed flippers and larger numbers of smaller teeth (pygmy killer whales have rounded flippers and only 8 to 13 pairs of more robust teeth). Also, melon-headed whales tend to have a more triangular head shape (when viewed from above or below), and females and young have a beak, albeit very short and poorly defined.
The body is generally charcoal grey to black, with white lips and a white urogenital patch. The black triangular “mask” on the face of melon-headed whales distinguishes them from the more uniformly coloured pygmy killer whales. Melon-headed whales also have a cape that dips much lower below the dorsal fin than that of pygmy killer whales, although its margin is often faint. There is a light stripe from the blowhole to the snout tip, which widens anteriorly.
Melon-headed whales have 20 to 25 small slender teeth in each tooth row.
Can be confused with
Melon-headed whales are difficult to distinguish from pygmy killer whales at sea. Head shape, flipper shape, and the sweep of the cape can be useful in identification. False killer whales can also be confused with this species at a distance.
Size
Melon-headed whales reach a maximum of about 2.75 m. Maximum known weight is about 275 kg. Length at birth is thought to be about 1 m or less.
Geographical Distribution
The range of the melon-headed whale coincides almost exactly with that of the pygmy killer whale in tropical and subtropical oceanic waters between 40°N and 35°S.
Biology and Behaviour
Melon-headed whales are highly social, and are known to occur usually in pods of 100 to 500 (with a known maximum of 2000 individuals). They are often seen swimming with other species, especially Fraser's dolphins, in the eastern tropical Pacific, Philippines, and Gulf of Mexico. Melon-headed whales often move at high speed, porpoising out of the water regularly, and are eager bowriders, often displacing other species from the bow wave.
There is some evidence to indicate a calving peak in July and August, but this is inconclusive.
Melon-headed whales are known to feed on squid and small fish.
Exploitation
A few melon-headed whales are known to be taken in purse seine and driftnet fisheries, and some are killed in drive fisheries in Japan, and in other directed fisheries in tropical regions of the world. Several individuals of this species have been captured for display in oceanaria.
IUCN Status
Insufficiently known.