Atlantic Spotted dolphin
Stenella frontalis
Threat Index

Max Length:
Male: 2.30 m
Female: 2.30 m
Calf: 0.80 - 1.20 m

Max Weight:
Male: 140 kg
Female: 130 kg

Est. Population: Unknown

Diet: small schooling fish, squid and benthic invertebrates

IUCN Listing: DD
CMS Appendix: Not Listed
CITES Appendix: II
Synonym:
Spotted porpoise, Bridled dolphin, Atlantic spotted dolphin

Related Projects:
None

Classification:
As its name suggests this species is only to be found in the Atlantic Ocean and currently all individuals in its range are categorised as being Stenella frontalis. There is growing evidence however for the existence of two distinct geographic forms, separating out those in the temperate waters of the North Atlantic. Currently however, two general populations are recognised; coastal and offshore, with the offshore population generally smaller and having fewer spots – some offshore adults lack any distinctive spots. The genus ‘Stenella' is likely to be redefined in the near future.

Appearance:
The Atlantic spotted dolphin is a robust, compact animal with a moderately long, chunky beak. The beak has a white tip and may have white 'lips'. There is a distinct crease between the beak and the pronounced melon. The curved flippers have a broad base and pointed tips, and are usually unspotted. The tall falcate dorsal fin has a rounded tip and concave trailing edge whilst the flukes have pointed tips and, as with the dorsal fin, are unspotted. The basic colouration consists of a dark cape, grey sides, and a whitish ventral area. There is a pale blaze on the dark cape below and in front of the dorsal fin, and a faint light grey band between the eye and flipper. Spots appear dark on the belly and light on the back, and in general, increase with age. Newborns are completely unspotted, calves show the development of a few ventral spots, younger individuals are lightly spotted and adults appear more heavily spotted. The Atlantic spotted dolphin is closely related to the Pantropical spotted dolphin and they can be easily confused in areas where their ranges overlap, but the Atlantic species is more robust, darker, and more heavily spotted. This species is more likely to be mistaken for the more similar looking bottlenose dolphin and although size is a good differentiating factor, both can show the absence of spots.

Behaviour:
Atlantic spotted dolphins are very active at the surface. They are fast swimmers and often breach, performing long shallow leaps. They are avid bowriders and are known to approach boats from a distance. They are found in groups of 5-15 among coastal populations, and generally found in larger numbers in offshore populations. They have a complex social structure similar to other small delphinids and are often found in mixed groups with the common bottlenose dolphin. Their diet is wide and varied but in general consists of small fish, cephalopods and benthic invertebrates.

Distribution:
Atlantic spotted dolphins can be found only in the temperate, and tropical waters of the Atlantic Ocean. In the west, they range from southern Brazil north to Cape Cod and in the east they are known from the coast of west and central Africa. In the more coastal limits of their range they can be found in shallow waters although they are mostly found in areas over the continental shelf and are known to occur in deep oceanic waters and around oceanic islands like the Azores. Although the species has been well-studied in some areas of its range (e.g. – the Bahamas), elsewhere data is extremely limited. Atlantic spotted dolphins have been (and continue to be) hunted for food in the eastern Caribbean and in some places in West Africa. Catch data however is lacking and the scale of this threat is unknown despite concerns that numbers may be high. The other major threat to this species is bycatch and incidental entanglement in fishing gear. No population estimate exists for this species and although thought to be abundant in the western portion of its range, the few existing records from the eastern limits show a very different and worrying story. The Atlantic spotted dolphin is listed as Data Deficient by the IUCN (2008).