THE ATLANTICA SPOTTED DOLPHINS

The Atlantic spotted dolphin (Stenella frontalis) is a dolphin found in the Gulf Stream of the North Atlantic Ocean. Older members of the species have a very distinctive spotted coloration all over their bodies.

 

 

 Taxonomy

The Atlantic spotted dolphin was first described by Cuvier in 1828. Considerable variation in the physical form of individuals occurs in the species, and specialists have long been uncertain as to the correct taxonomic classification. Currently, just one species is recognised, but a large, particularly spotty variant commonly found near Florida quite possibly may be classified as a formal subspecies or indeed a species in its own right.
Atlantic spotted dolphins in the Bahamas have been observed mating with bottlenose dolphins.^[3] Rich LeDuc has published data that suggest the Atlantic spotted dolphin may be more closely related to bottlenose dolphin (genus Tursiops) than to other members of the genus Stenella.^[3]

Description

Stenella frontalis, La Gomera

Near South Caicos, Turks and Caicos Islands

A juvenile swimming in the blue water

The coloring of the Atlantic spotted dolphin varies enormously as they grow. Calves are a fairly uniform grey colour. When the calves are weaned, they then begin to get their spots. Juveniles have some dark spots on their bellies, and white spots on their flanks. Their back and dorsal fins are a darker grey than the rest of the body. As the animal matures, the spots become denser and spread until the body appears black with white spots at full maturation.
The Atlantic spotted dolphin has a three-part coloration: dark gray back, lighter sides, and a white belly.
Measurements at birth:

Length: about 35–43 in (89–109 cm)

Weight:

Maximum measurements:

Length:

Male 2.26 m (7 ft 5 in)

Female 2.29 m (7 ft 6 in)

Weight: 310

Male 140 kg (310 lb)

Female 130 kg (290 lb)

This is a medium-sized dolphin in both length and weight. At full size, South American spotted dolphins are about 2.2-2.5 m in length. Compared to the much smaller pantropical spotted dolphin, the Atlantic spotted dolphin is more robust. It lives in common waters with the pantropical spotted dolphin and the bottlenose dolphin.
In common with other species in its genus, the Atlantic spotted dolphin is a gregarious creature. It is a fast swimmer and keen bow-rider, and prone to acrobatic aerial displays.

Population and distribution

 

The species is endemic to the temperate and tropical areas of the Atlantic Ocean. It has been widely observed in the western end of the Gulf Stream, between Florida and Bermuda. Off the Bahamas, tourism industries to swim with dolphins are available.^[4] It is also present in the Gulf of Mexico. More infrequent sightings have been made further east, off the Azores and Canary Islands. Northerly sightings have been made as far north as Cape Cod across to the southwestern tip of Spain. They are certainly present further south, too, as far as Rio Grande do Sul in Brazil and across to west Africa, but their distribution is poorly understood in these areas.
About 20 years ago, only about 80 dolphins were in the Bahamas. Now, almost 200 dolphins are found there. On account of their similar appearance to other dolphins in their range, it is difficult to be sure of the Atlantic spotted dolphin's population. A conservative estimate is around 100,000 individuals.

Human interaction

Some Atlantic spotted dolphins, particularly some of those are around the Bahamas, have become habituated to human contact. In these areas, cruises to watch and even swim with the dolphins are common.
Atlantic spotted dolphins are an occasional target of harpoon fishermen, and every year some creatures are trapped and killed in gill nets, but these activities are not currently believed to be threatening the survival of the species. This species lives in the mesopelagic layer of the ocean. These dolphins are not threatened by extinction, however, commercial trade may affect their evolution and sustainability. Sometimes they are killed by harpoons off St. Vincent.

Conservation

The Atlantic spotted dolphin is included in the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia^[5]