Atlantic spotted dolphin
 
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Stenella frontalis 

Names

Azores : Toninha pintada - POR : Golfinho pintado - ITA : Stenella maculata Atlantica - GB : Atlantic spotted dolphin - GER : Atlantisher fleckendelphin - JAP : Kasuri iruka - NEDER : Atlantisch gevlekte dolfijn

Biology

The spotted dolphins can reach up to 2.3 m in length and their weight can reach 140 kg. The males are slightly larger than the females. Each jaw has 30 to 42 pairs of conical teeth. Newborns are 0.8 to 1.2 m. Gestation lasts 9 to 11 months and lactation can take 1 to 2 years. Births in the Azores are more frequent during May and June. The spotted dolphin that we can observe in the Azores is notoriously smaller in size, and less spotted than the coastal species that appear in Central America. The pigmentation of the body changes with age. The young animals are lighter, gradually increasing their spots with age. The adult has a robust and fusiform body. The dorsal part is darker than that ventral region. This species eats mainly meso and epipelagic fish and also cephalopods. Each dolphin has its own vocalisation, known as " whistle signature ". They can emit clicks up to 150 kHz as a method for echolocation and prey searching. Their communication whistles range from 6.5 to 13.3 kHz.

Observation

Very active, the spotted dolphins are, no doubt, one of the most " friendly " cetaceans observed. They come to " play ", sometimes for several hours, in the bow waves, making them an easy prey for unscrupulous fishermen. Interestingly, however, these animals easily allow divers to enter the water with them. We found them in 29 % of our trips to the ocean, and they were more frequently observed from June to December. They live in groups of 10 to 15 individuals and sometimes more. They can be confused with the Tursiops truncatus, especially the young animals that still have no spots, but their beak is slender and longer than that of the bottlenose dolphins. They can swim to 18 knots speed and they breath every 3 to 4 minutes and sometimes can stay submerged for 1 minute.

Cetaceans in the Azores