Gray, 1828 - Long-beaked common dolphin
Distinctive Characteristics
It has only recently been discovered that common dolphins represent two species (rather than only one, as was commonly thought). They can be difficult to distinguish in observations at sea. Both are characterized by their slightly falcate dorsal fins, but long-beaked common dolphins have longer beaks, are slightly longer and more slender, and have a somewhat more flat appearance to the melon, which rises from then rostrum at a relatively low angle. The mouth is lined with 47 to 69 sharp, pointed teeth in each tooth row.
All common dolphins are characterized by an hourglass pattern on the side, forming a V below the dorsal fin. In long-beaked common dolphins, the coloration appears somewhat muted, compared to the short-beaked species. The thoracic patch is relatively dark, contrasting less with the cape. The flipper-to-anus stripe is generally moderately to strongly developed. The chin-to-flipper stripe fuses with the lip patch at, or just anterior to, the gape, and remains relatively wide ahead of the eye. The eye patch is lighter and less distinct than it is in the short-beaked dolphin. Light patches on the dorsal fin and flippers are only occasionally present, and tend to be faint when they are.
In the Indian Ocean and western tropical Pacific, there is what appears to be a distinct form of long-beaked common dolphin. These animals have extremely long, narrow beaks, and high tooth counts. It is still unclear if they represent a geographical form of D. capensis or if they are a separate species (D. tropicalis).
Size
Adult long-beaked common dolphins are 2.0 to 2.6 m (males) and 1.9 to 2.3 m (females) long.
Geographical Distribution
Long-beaked common dolphins occur in tropical to warm temperate waters of the world. Although they are sympatric in some areas, the long-beaked species generally occurs closer to shore and in shallower water than the short-beaked. Long-beaked dolphins inhabit several enclosed seas, such as the Gulf of California and South China Sea. All of the common dolphins so far examined from the Indian Ocean and southeast Asia appear to be long-beaked.
Biology and Behaviour
Much of the biological information available for dolphins of the genus Delphinus cannot be reliably applied to one of the other species. Long-beaked common dolphins inhabit more nearshore waters than the short-beaked species, generally occurring within 180 km of the coast.
Herds of less than a dozen to several thousand are formed. These dolphins are capable and willing bowriders, and often exhibit a great deal of aerial activity. One or the other type of common dolphin tends to predominate in the stranding record for southern California for a particular period of time. In the years following the 1982-1983 El Nino event, the long-beaked form was most common.
A wide variety of schooling fishes and squids are taken as prey. In the northern Gulf of California, cooperative feeding techniques are sometimes used to herd fish schools.
Exploitation
This species is commonly taken in gillnets off southern California. Long-beaked common dolphins are only occasionally involved in the eastern tropical Pacific tuna fishery. They are present off Japan, and some have been taken in drive fisheries there. They are also taken by harpoon and drives in Venezuela. Some dolphins of this species have been live-captured, but do not do as well in captivity as the more coastal bottlenose dolphin.
IUCN Status
Insufficiently known.