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Atlantic spotted dolphin

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Title: Atlantic spotted dolphin  
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Subject: Dolphin, Oceanic dolphin, Stenella, Striped dolphin, Bottlenose dolphin
Collection: Fauna of the Atlantic Ocean, Mammals of Western Sahara, Oceanic Dolphins
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Atlantic spotted dolphin

Atlantic spotted dolphin[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Eutheria
Order: Cetacea
Suborder: Odontoceti
Family: Delphinidae
Genus: Stenella
Species: S. frontalis
Binomial name
Stenella frontalis
Cuvier, 1829
Atlantic Spotted Dolphin range
Synonyms

Stenella plagiodon Cope, 1866

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.

Contents

  • Taxonomy 1
  • Description 2
  • Population and distribution 3
  • Human interaction 4
  • Conservation 5
  • See also 6
  • References 7
  • External links 8

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 color phases of the Atlantic Spotted Dolphin occur in four parts: two-tone, speckled, mottled, and fused. The dolphins are in two-tone phase when they are born and occurs for an average of 3.43 years. The coloring is gray-white, with one or no spots. The speckled phase typically occurs between 3 and 4 years of age and lasts for an average of 5 years. The dolphins must develop at least two black spots on the ventral surface and a few light gray spots on the dorsal surface. A dolphin is considered mottled when they develop 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 classified when dark and white spots are on both the ventral and dorsal sides. Dolphins can be in this phase for up to ten years.[4]

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.

The Atlantic Spotted Dolphin exhibits a range of about ten different vocalizations. Each vocalization corresponds with a different behavior, according to a study. Some of the vocalizations include: whistles, genital buzz, burst-pulsed vocalizations, synchronized squawks/barks, and other communication sounds.[5]

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.[6] 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.[7] They are also marked as DD (Data Deficient) of the Conservation Action Plan for the World's Cetaceans.[8]

See also

References

  1. ^ Mead, J.G.; Brownell, R.L., Jr. (2005). "Order Cetacea". In Wilson, D.E.; Reeder, D.M. Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 723–743.  
  2. ^ HammondHammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B. (2008). Stenella frontalis. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 7 October 2008.
  3. ^ a b Herzing, D. (2011). Dolphin Diaries: My 25 Years with Spotted Dolphins in the Bahamas. Macmillan. pp. 132–147.  
  4. ^ Herzing, Denise L. (October 1997). "The life history of free-ranging Atlantic Spotted Dolphins (Stenella frontalis): Age classes, color phases, and female reproduction". Marine Mammal Science 13(4): 576-595. 
  5. ^ Herzing, Denise L. (1996). "Vocalizations and associated underwater behavior of free-ranging Atlantic Spotted dolphins, Stenella frontalis and bottlenose dolphins, Tursiops truncatus". Aquatic Mammals 22.2, 61-79. 
  6. ^ "Bimini Dolphin Discovery". Retrieved 3 April 2014. 
  7. ^ Western African Aquatic Mammals MoU, Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia
  8. ^ Reeves, Randall R. Smith, Brian D., Crespo, Enrique A., di Sciara, Giuseppe Notarbartolo (2003). "Dolphins, Whales and Porpoises". 2002-2010 Conservation Action Plan for the World's Cetaceans. 
  • Whales Dolphins and Porpoises, Mark Carwardine, Dorling Kindersley Handbooks, ISBN 0-7513-2781-6
  • National Audubon Society Guide to Marine Mammals of the World, Reeves, Stewart, Clapham and Powell,and there is no characteristics for survival. ISBN 0-375-41141-0
  • Perrin, William F. (2002). "Stenella frontalis". Mammalian Species (702):1–6.

External links

  • Voices in the Sea - Sounds of the Atlantic Spotted Dolphin
  • Whale and Dolphin Conservation Society
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