Because of the recent discovery that common dolphins in the central Pacific represent two species (rather than only one, as was commonly thought), much of the biological information available for dolphins of the genus Delphinus cannot be reliably applied to one or the other species. Long-beaked common dolphins have the same basic body morphology as the short-beaked species. Besides having longer beaks than short-beaked common dolphins, long-beaked common dolphins are slightly longer and more slender, and have a somewhat more flat appearance to the melon, which rises from the rostrum at a relatively low angle.
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 are faint when they are.
The Indo-Pacific subspecies (D. c. tropicalis) is very similar to the nominal subspecies, the main difference being a longer beak and higher tooth counts.
The mouth is lined with 47-60 (or up to 67 in the tropicalis subspecies) sharp, pointed teeth in each tooth row.
Adult D. c. capensis are 2.02-2.54 m (males) and 1.93-2.22 m (females) long. Specimens of D. c. tropicalis reach similar or slightly greater lengths.
Can be Confused With
The two species of common dolphins may be difficult to distinguish, especially in sightings at sea. The long-beaked species has a longer beak, less steeply-rising melon, more slender body, a more muted color pattern, a wider chin-to-flipper stripe (which often merges with the lip patch, making much of the lower jaw dark), and a lower tendency to have white patches on the fins.
Long-beaked common dolphins inhabit more nearshore and tropical waters than the short-beaked species, generally occurring within 180 km of the coast. They appear to occur in distinct areas and populations are known from the east coast of South America, West Africa, southern Japan and Korea (and possibly China), central California to southern Mexico, Peru, and South Africa. The tropicalis subspecies ranges in the Indo-Pacific from at least the Red Sea/Somalia to southern China.
Ecology and Behavior
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 1982/83 El Niño event, the long-beaked form was most common.
Feeding and Prey
A wide variety of schooling fishes and squids are taken as prey. In at least the northern Gulf of California, cooperative feeding techniques are sometimes used to herd fish schools.
Threats and Status
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. There is a large direct kill off northern Venzuela. In the Indian Ocean and China, they are taken in gillnets, trawls, and purse seines. Some dolphins of this species have been live-captured, but do not do as well in captivity as the more coastal bottlenose dolphin.
Currently, long-beaked common dolphins are “Not Listed” (IUCN) and “Not Listed” (ESA).
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Evans, W.E. 1994. Common dolphin, white-bellied porpoise Delphinus delphis Linneaus, 1758. pp. 191-224 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Volume 5 The first book of dolphins. Academic Press.
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