ATLANTIC WHITE SIDED DOLPHIN (T) 



Lagenorhynchus acutus (Gray 1828) 



Other Common Names 



Atlantic white-sided porpoise, jumper (Newfoundland). 



Description 



Atlantic white-sided dolphins reach about 9 feet (2.7 m) in 

 maximum length and are robust in form with a small but 

 distinct beak (less than 2 inches [5.1 cm] long). 



The dorsal fin is tall, distinctly back curved, and pointed 

 on the tip. The tail stock is extremely thick and does not 

 narrow laterally until very near the tail flukes. 



The back is distinctly black, the belly white. The sides 

 have zones of g^ray, tan, and white. 



The single most distinctive feature of Atlantic white-sided 

 dolphins is an elongated oval zone of white and yellowish 

 white along the sides from just below the dorsal fin to the area 

 above the anus. These patches of lighter coloration, clearly 

 demarcated from each other and from the surrounding 

 coloration, are frequently visible simultaneously with the 

 dorsal fin as the animals roll at the surface to breathe. Even 

 alone this feature permits positive identification of the 

 species. The dorsal fin is often part gray, part black. The beak 

 is all black. 



Natural History Notes 



Atlantic white-sided dolphins are known to congregate in 

 herds of perhaps a thousand animals, though smaller herds 

 are far more common. The species is often wary of ships and 

 does not ordinarily ride the bow wave. Like a number of other 

 species, white-sided dolphins have been reported in 

 association with Atlantic pilot whales. 



May Be Confused With 



At sea, Atlantic white-sided dolphins are most likely to be 

 confused with the white-beaked dolphins, with which they 

 overlap in distribution. Though they are very similar in 

 general appearance, the two can be distinguished in the 

 following ways: 



Atlantic White-Sided 

 Dolphin 



White-Beaked Dolphin 



COLORATION 



Elongated band of yellowish 

 white and white along side, 

 visible behind and below 

 dorsal fin as animal rolls. 



Two grayish areas— one in 

 front, the other below and 

 behind dorsal fin, visible as 

 anirtial rolls. 



BEAK 



All black. 



Sometimes white in parts of 

 range though western Atlan 

 tic animals are usually dark. 



To 9 feet (2.7 m). 



MAXIMUM SIZE 



To 10 feet (3.1 m). 



DORSAL FIN 



Often part black, part lighter Uniformly dark, 

 gray. 



Distribution 



Atlantic white-sided dolphins are distributed, primarily 

 offshore, in the cool waters between the Gulf Stream and the 

 Labrador Current. They have been observed from Hudson 

 Canyon, off New York City, north to southern Greenland and 

 perhaps Davis Straits. Their normal range shares a southern 

 boundary with the white-beaked dolphin but does not extend 

 as far to the north. 



Stranded Specimens 



In addition to the features described above for living 

 animals at sea, stranded Atlantic white-sided dolphins can be 

 distinguished from white-beaked dolphins by the following: 



Atlantic White-Sided 

 Dolphin 



White- Beaked Dolphin 



NUMBER OF TEETH 



30-40 per side per jaw, 

 sometimes more in upper. 



22-28 per side per jaw; have 

 larger individual teeth— to 6 

 mm in diameter. 



FLIPPERS 



Lower portion of forward 

 margin more curved. 



Lower portion of forward 

 margin less acutely curved. 



VENTRAL COLOR 



White coloration of belly 

 extends high onto sides of 

 body. 



White coloration of belly 

 extends to lower jaw but not 

 above flippers on sides. 



CAUDAL CRESTS 



Tail stock strongly compres- 

 sed laterally; taller, narrows 

 rapidly just in front of flukes. 



Tail stock less laterally 

 compressed, tapers more 

 gently towards tail flukes. 



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