Atlantic White-Sided Dolphin (Lagenorhynchus acutus)


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Get your copy of “Albert the Orca Teaches Echolocation to The Super Fins” beginning March 2017 at

Atlantic white-sided dolphins have a robust body, short beak, and a distinct color pattern, including a bi-colored beak. Their back, fluke, flippers, dorsal fin, and top beak are black, while their belly and lower beak are white. Their sides are gray, with a white patch that begins below the dorsal fin and is flanked by a yellowish-tan streak that extends to the fluke, or tail. Atlantic white-sided dolphins can sometimes be confused with the white-beaked dolphin, which shares a similar distribution pattern.

Males reach lengths of about 9 feet (3 m) and females grow to about 8 feet (2.5 m). The average adult Atlantic white-sided dolphin weighs about 400-500 pounds (180-225 kg). They have a lifespan of approximately 25 years.

Atlantic white-sided dolphins are highly social and playful animals. They have been seen traveling in small groups of a few individuals and in large aggregations of up to 500 animals. They are commonly observed engaging in acrobatic activities, such as lobtailing and breaching.

Atlantic white-sided dolphins are capable of holding their breath for nearly 5 minutes. They dive to feed on prey, such as fish (e.g., mackerel, herring and hake), as well as squid and shrimp. They are often seen in association with long-finned pilot whales, humpback whales, and fin whales while feeding.

Females reach sexual maturity and begin breeding between 6 to 12 years of age, when they reach lengths of about 7 feet (2.1 m). The gestation period is 11 months and lactation occurs for 12-18 months. Females typically give birth to a single calf about every other year. Breeding season is from May to August, though most calves are born in June and July.

This species is classified as LEAST CONCERN according to the IUCN's Red List.
This species is classified as LEAST CONCERN according to the IUCN’s Red List.


MMPA – Atlantic white-sided dolphins, like all marine mammals, are protected under the MMPA
CITES Appendix II – throughout its range

Species Description

400-500 pounds (180-225 kg)
up to 9 feet (3 m)
black, with white belly and lower beak
about 25 years
fish (like mackerel, herring and hake), squid, and shrimp
highly social and playful animals, commonly seen lobtailing and breaching

RELATIVE SPECIES: Pacific White Sided dolphin, White beaked dolphin, dusky dolphin.

OTHER NAMES: “White Sides”

NEIGHBORING SPECIES: White beaked dolphin, short-beaked common dolphin


THREATS: largely hunted in the Faeroe Islands. Trapped in gillnets.

DIET: Herring, hake, squid and other bottom dwelling species.

MANNER OF FEEDING: Cooperatively surrounding schools of fish at the surface.

BEHAVIOR: Very Social. Can be seen in groups up to 500. Often seen with fin whales and long-finned pilot whales. Leaping out of the water and lobtailing is very common. Mass strandings are also common.

REPRODUCTION: Sexually mature at 6-12 years. Gestation is 11 months. Give birth in June in July every other year.

LIFE SPAN: 25 years


Atlantic white-sided dolphins are found only in temperate waters of the North Atlantic Ocean. They inhabit the oceanic waters of the continental shelf and slope.


Atlantic white-sided dolphins are found in the western North Atlantic from 35°-80° N, from North Carolina to Greenland. This species exhibits seasonal movements, moving closer inshore and north in the summers and offshore and south in the winters.

Population Trends

The most recent stock assessment reports with population estimates are available on our website.


  • incidental capture and entanglement in fisheries, such as trawls, gillnets, and driftnets. Mass strandings of white-sided dolphins are common occurrences in the Northeast U.S. Although the cause of stranding often is unknown, there are several documented strandings related to fishery interactions.

Conservation Efforts

The Atlantic Trawl Gear Take Reduction Team and Plan addresses the incidental bycatch of white-sided dolphins–as well as long-finned pilot whales (Globicephala melas), short-finned pilot whales (Globicephala macrorhynchus), and common dolphins (Delphinus delphis)–in bottom and mid-water trawl fisheries in the Northeast and Mid-Atlantic.

Regulatory Overview

This species is protected under the Marine Mammal Protection Act of 1972, as amended.


Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Lagenorhynchus
Species: acutus


  • Atlantic white-sided dolphins have a yellowish-tan streak on their sides.
  • They are limited to the temperate waters of the North Atlantic.
  • They live in groups of a few individuals to several hundred dolphins.
  • Most calves are born in June and July.
  • A yellow stripe on their side makes them stand out among other white-sided dolphins such as Dusky and Peale’s.