The Atlantic spotted dolphin (''Stenella frontalis'') is a

dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...

found in warm temperate and tropical waters of the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

. 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 Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

quite possibly may be classified as a formal

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

or indeed a species in its own right. Atlantic spotted dolphins in the

Bahamas The Bahamas, officially the Commonwealth of The Bahamas, is an archipelagic and island country within the Lucayan Archipelago of the Atlantic Ocean. It contains 97 per cent of the archipelago's land area and 88 per cent of its population. ...

have been observed mating with bottlenose dolphins. Rich LeDuc has published data that suggest the Atlantic spotted dolphin may be more closely related to the bottlenose dolphins (genus ''Tursiops'') than to other members of the genus ''Stenella''. More recent studies in the 2020s indicate that this is a consequence of

reticulate evolution Reticulate evolution, or network evolution is the origination of a lineage through the partial merging of two ancestor lineages, leading to relationships better described by a phylogenetic network than a bifurcating tree. Reticulate patterns can ...

(such as past hybridization between ''Stenella'' (spotted dolphins) and ancestral ''Tursiops'' (bottlenose dolphins)) and incomplete lineage sorting, and thus support ''T''. ''truncatus'' and ''T. aduncus'' belonging to the same genus. This likely explains why Atlantic spotted dolphins can mate with both species of bottlenose dolphins.

Description

The coloring of the Atlantic spotted dolphin varies enormously as it grows, and is usually classified into age-dependent phases known as two-tone, speckled, mottled, and fused. Calves are a fairly uniform gray-white, with one or no spots. When they are weaned, speckling occurs, typically between 3 and 4 years and lasting for an average of 5 years. A juvenile is considered mottled when it develops merging gray and white spots on the dorsal surface and black spots on the ventral surface. This usually happens between age 8 or 9. A fused pattern is reached when dark and white spots are on both the ventral and dorsal sides. As the animal matures, the spots become denser and spread until the body appears black with white spots at full maturation. In comparison to other dolphin species, the Atlantic spotted dolphin is medium-sized. Newborn calves are about long, while adults can reach a length of and a weight of in males, and and in females. Compared to the much smaller pantropical spotted dolphin, the Atlantic spotted dolphin is more robust. It shares its habitat with the pantropical spotted dolphin and the

bottlenose dolphin The bottlenose dolphin is a toothed whale in the genus ''Tursiops''. They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus contains three species: the common bot ...

. The species exhibits a range of about ten different vocalizations, including whistles, buzzes, squawks and barks, each corresponding with different behaviors.

Behavior

Atlantic spotted dolphins are extremely gregarious animals, which gather in complex social groups of 5–15, often in mixed groups with common bottlenose dolphins. They are fast swimmers and known for their bow-riding and long, shallow leaping behaviors. Their mating system consists of one male mating with several females, and the pod is highly protective over pregnant females. The dolphin's gestational period is ~11 months, and the mother cares for its calf for up to 5 years, with the help of the rest of her group. These animals are cooperative hunters that hunt in groups at night. They strategically encircle their prey, which consists mostly of small fish, benthic invertebrates, and cephalopods such as squid. They can dive to depths of up to and can stay beneath the surface for up to 10 minutes at a time. When showing aggression towards other species, these dolphins make use of more contact behaviors such as biting and chasing than when being aggressive towards members of their species, in which they usually rely on display behaviors.

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

and

Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...

. Off the

, tourism industries to swim with dolphins are available. It is also present in the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

. More infrequent sightings have been made further east, off the

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

and

Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...

. Northerly sightings have been made as far north as

Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer months. The ...

across to the southwestern tip of

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

. They are certainly present further south, too, as far as

Rio Grande do Sul Rio Grande do Sul (, ; ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative units of Brazil#List, fifth-most populous state and the List of Brazilian s ...

in Brazil and across to west

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

, 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. They are usually not held in captivity. Atlantic spotted dolphins are an occasional target of

harpoon A harpoon is a long, spear-like projectile used in fishing, whaling, sealing, and other hunting to shoot, kill, and capture large fish or marine mammals such as seals, sea cows, and whales. It impales the target and secures it with barb or ...

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. They are also marked as Least Concern of the Conservation Action Plan for the World's Cetaceans.

References

*''Whales Dolphins and Porpoises'', Mark Carwardine, Dorling Kindersley Handbooks, *''National Audubon Society Guide to Marine Mammals of the World'', Reeves, Stewart, Clapham and Powell, and there is no characteristics for survival. * Perrin, William F. (2002).
Stenella frontalis
. ''Mammalian Species'' (702):1–6.

External links

Whale and Dolphin Conservation Society
{{Authority control

Atlantic spotted dolphin The Atlantic spotted dolphin (''Stenella frontalis'') is a dolphin found in warm temperate and tropical waters of the Atlantic Ocean. Older members of the species have a very distinctive spotted coloration all over their bodies. Taxonomy The Atl ...

Cetaceans of the Atlantic Ocean Fauna of the Mediterranean Sea Fauna of the Caribbean Mammals of the Dominican Republic Marine fauna of Africa Marine fauna of Europe Marine fauna of North America Marine fauna of South America Biota of the Gulf of Mexico