otos by R. Garvie (top and inset) and S. Leatherwood (bottom)._)]

[Illustration]

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
gray, 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 Two grayish areas--one in
white and white along side, front, the other below and
visible behind and below behind dorsal fin, visible as
dorsal fin as animal rolls. animal rolls.

BEAK

All black. Sometimes white in parts of
range though western Atlantic