Stenella frontalis, the Atlantic spotted dolphin, is found in the tropical and temperate waters of the Atlantic Ocean (Wilson and Reeder, 1993).

Biogeographic Regions: atlantic ocean (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Tropical, subtropical, and warm temperate Atlantic, including Gulf of Mexico and Caribbean Sea (Perrin 2002); locality records mapped in Perrin et al. (1987).

As the common name spotted dolphin suggests, S. frontalis has a spotted color pattern on its body. These spots are not present at birth, and generally do not appear until the onset of weaning. The first spots to appear on the calves are dark spots on the animal's ventral surface. As the dolphin approaches puberty, the ventral spots increase in number and size and pale dorsal spots appear as well. The number of spots continues to increase with age, similar to the development of spotting in Stenella attenuata. There is a large amount of variation in the adult color pattern, between populations and between individuals. At times some individuals become so heavily spotted that they appear white from a distance. Spotting seems to decrease with the distance from the continental shores of North America. In the Azores some specimens have had few or no ventral spots, but well developed dorsal spotting.

The beak of S. frontalis is long and narrow, a typical feature of all Stenella dolphins. S. frontalis has a robust head and body, that make it larger in size, but not length, than S. attenuata. Proportionately larger flippers, flukes and dorsal fins are also characteristic of S. frontalis. The average adult body length of the Atlantic spotted dolphin is 166-229cm. The adult S. frontalis females tend to be slightly larger than the males, and an average adult weight is approximately 200 pounds (90k).

The skull of the Atlantic spotted dolphin varies in size with individuals and with geographical region. Skull size is generally correlated with body size. S. frontalis has small conical teeth, 3-5mm in diameter. In each rostral row there are 32-42 teeth, and 30-40 teeth in each mandibular row. S. frontalis have on average a distally broader rostrum and fewer but larger teeth than S. attenuata. At times differentiating between these two spotted dolphins is difficult, especially in areas where they converge geographically. (Ridgway, 1994;   http://wwwa.com/dolphin/index.html, 1999;   http://whales.ot.com, 1999).

Average mass: 90 kg.

Length: 229 cm

Weight: 143000 grams

• Marine

Along the southeastern and Gulf coasts of the U.S., Stenella frontalis inhabits the continental shelf, usually within 250-350 km of the coast. In the Bahamas, the Atlantic spotted dolphin spends most of its time in the shallow water over sand flats. (Ridgway, 1994;   http://whales.ot.com, 1999).

Aquatic Biomes: coastal

Habitat Type: Marine

Comments: Along southeastern U.S.: continental shelf, usually inside or near 185 m contour (within 250-350 km of coast); sometimes moves into very shallow water near shore (usually replaced in shallow water by Tursiops). Offshore distribution poorly known.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

The diet of Stenella frontalis varies with location. They eat a variety of invertebrates, as well as small eels and herring. They have even been known to follow trawlers to eat discarded fish. Other feeding habits include feeding at or near the surface and "tracking" schools of small fish. (Ridgway, 1994;   http://whales.ot.com, 1999).

Animal Foods: fish

Primary Diet: carnivore (Piscivore )

Comments: Eats fishes (e.g., clupeoids, carangids, sciaenids, congrids, gadids, trichiurids, triglids) and squid; may eat fishes discarded from trawlers (Perrin et al. 1987).

Pods usually consist of fewer than 50 individuals, typically 5-15 in coastal waters (Perrin et al. 1987). In the western Atlantic, average first-year mortality rate was 24% (Herzing 1997).

Females are generally sexually mature at 9 years. Males do not reach sexual maturity until their 12th year. There is evidence of year round mating, and gestation is between 11 and 12 months long. Calves are normally born in May and September. There have been some observations of pods segregated by reproductive status as well as sex and age. (  http://whales.ot.com, 1999).

Breeding season: There is evidence of year round mating

Range gestation period: 11 to 12 months.

Average age at sexual or reproductive maturity (female): 9 years.

Average age at sexual or reproductive maturity (male): 12 years.

Key Reproductive Features: year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

In the western Atlantic, lactation lasted up to 5 years; calving interval 1-5 years (mean 3, 3-4 in females whose calf survived the first year); age of first parturition estimated at about 10-12 years; pregnancy rate varied annually, 7-57%; birth rate 6-14% (Herzing 1997).

Stenella frontalis is listed in Appendix II of the Convention of International Trade in Endangered Species of Wild Fauna and Flora (CITES). Those listed in Appendix II, as stated on the CITES web site,are "species which although not necessarily threatened with extinction may become so unless trade is subject to strict regulation." As well as non-threatened species that must be subject to regulation in order to control threatened species. (  http://www.wcmc.org.uk/CITES/english/index.html).

CITES: appendix ii

IUCN Red List of Threatened Species: data deficient

United States

Rounded National Status Rank: NU - Unrankable

Rounded Global Status Rank: G5 - Secure

Comments: Incidental take in the eastern tropical Atlantic tuna purse-seine fishery off West Africa could be considerable; level of incidental take in this and other fisheries needs investigation (see IUCN 1991).

The cost and complexity of the tuna fishery has been increased because of regulations that have been designed to lessen the number of dolphins killed by tuna fisherman.

In the past dolphin flesh was considered a delicacy. Besides being used for food, certain parts of its body were used for medicinal purposes. For example, the oil from the liver was used to treat ulcers. Today zoologists are interested in dolphins because they have a high intelligence level. Due to their high intelligence level, dolphins have been trained to help in underwater salvage operations and have even taken part in military exercises. (Stephen, 1973).

Comments: Taken in subsistence harpoon fishery at St. Vincent, Lesser Antilles; possibly also at St. Lucia and Dominica (Perrin et al. 1987).

Comments: Includes S. plagiodon (S. pernettensis plagiodon of Hall 1981) and several other nominal species (Perrin et al. 1987).