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(Cuvier, 1829) - Atlantic spotted dolphin

Distinctive Characteristics

The Atlantic spotted dolphin, in many ways, tends to resemble the bottlenose dolphin more than it does the pantropical spotted dolphin. In body shape, it is somewhat intermediate between the 2, with a moderately long, but rather chunky, beak. There is a distinct crease between the melon and beak.

There is much developmental variation in the colour pattern. Atlantic spotted dolphins begin life with unspotted background coloration. Young animals look much like slender bottlenose dolphins, with a dark cape, light grey sides and spinal blaze (variable in its development), and white belly. Large spotting on both dorsal and ventral surfaces progresses as the animal ages; some individuals become so heavily spotted that the cape margin and spinal blaze are obscured. However, in some populations, adults are essentially unspotted (these are generally in offshore areas).

There are 30 to 42 pointed teeth in each tooth row.

Can be confused with

Atlantic spotted dolphins can be most easily confused with bottlenose dolphins and sometimes with pantropical spotted dolphins. The differences in size and robustness are good clues, but may require a trained eye to distinguish in many sightings at sea. Heavy spotting is a good characteristic for Atlantic spotted dolphins; however, some may be nearly unspotted and some bottlenose dolphins may have spotting and blotches on the belly and sides. Pantropical spotted dolphins also may be difficult to distinguish, but attention to body robustness, snout shape, and colour pattern differences will allow them to be separated. Only the coastal form of the pantropical spotted dolphin is likely to appear very similar to the Atlantic spotted dolphin, but the former is only known from the eastern Pacific.

Size

Adults are up to 2.3 m long and 143 kg in weight. Newborn Atlantic spotted dolphins are 0.8 to 1.2 m long.

Geographical Distribution

This species is found only in the Atlantic Ocean, from southern Brazil to New England in the west, and to the coast of Africa in the east (the exact limits off West Africa are not well known). Their tropical to warm temperate distribution is mostly over the offshore continental shelf, but Atlantic spotted dolphins also inhabit some deep oceanic waters.

Biology and Behaviour

Small to moderate groups, generally of less than 50 individuals, are characteristic of the Atlantic spotted dolphin. Coastal groups usually consist of 5 to 15 animals. These are acrobatic animals and they are known to be avid bowriders. Studies of Atlantic spotted dolphins off the Bahamas that allow people to swim with them show that these animals have a fluid group structure, like that of bottlenose dolphin and other small dolphins.

There is not much known of the species' life history, but tropical populations would be expected to have a protracted breeding season.

A wide variety of fishes and squids are taken by this species.

Exploitation

Atlantic spotted dolphins are taken in a direct fishery for small cetaceans in the Caribbean. Direct takes may also occur off the Azores and off West Africa. Some are probably also taken incidentally in tuna purse seines off the West African coast. However, there are not reliable estimates of the number of animals taken in any of these fisheries.

IUCN Status

Insufficiently known.

Atlantic spotted dolphin (Stenella frontalis)