WHITE-SIDED DOLPHINS
Pacific white-sided dolphin
Pacific white-sided dolphins (Scientific name: Lagenorhynchus obliquidens) are known for the distinct coloring that give them their name, are a playful and highly social marine mammal. They are also sometimes known as the “hookfin porpoise” because of their large, curved dorsal fin, though they are not technically porpoises. Pacific white-sided dolphins can be seen travelling in schools of thousands, but group sizes are usually between 10 and 100 animals. These extremely playful dolphins are often seen “bow riding” (swimming near the front part of a ship) and jumping, somersaulting, or even spinning in the air. Their lifespan is 36 to 40 years. Some live longer than that. [Source: NOAA]
Atlantic white-sided dolphins (Scientific name: Lagenorhynchus acutus) are found in the temperate waters of the North Atlantic. In the United States, they are found off the coast of North Carolina to Maine. They are named after their distinctive yellowish-tan streak on their sides. They weigh 136 to 181 kilograms (400 to 500 pounds) and reach lengths of up 2.7 meters (nine feet). Their lifespan is about 25 years.
Pacific white-sided dolphins are pelagic, meaning they live in the open ocean and nearshore waters, but are unlikely to be found close to shore. They live in the temperate waters of the North Pacific Ocean. In the United States, they are found off the coast of California, Oregon, Washington, and Alaska. Worldwide, they are found in the southern Bering Sea (around the Aleutian Islands), Sea of Okhotsk, Sea of Japan, and Yellow and East China Seas to the south of Japan. In all, there are three stocks of Pacific white-sided dolphins in U.S. waters. Population trends for the North Pacific stock off the coast of Alaska are unknown. A survey of the two stocks off the coasts of Washington, Oregon, and California from 2008 to 2014 found a population of more than 21,000 dolphins.
Adult Pacific white-sided dolphins are 1.7 to 2.4 meters (5.5 to 8 feet) in length and weigh 136 to 181 kilograms (300 to 400 pounds). They have have a robust body, short rostrum (snout), and large dorsal fin compared to their overall body size. Their back, fluke (tail), and lips are black; their sides, dorsal fin, and flippers are gray; and their belly is white. They have a white or light gray stripe along their sides that extends from the eye to the tail, sometimes referred to as "suspenders." Males are generally larger than females. Pacific white-sided dolphins are most likely to be confused with common dolphins and Dall’s porpoises because they have similar large light-colored flank patches.
Pacific white-sided dolphins feed on a variety of prey, such as squid and small schooling fish (capelin, sardines, and herring). They can dive underwater for more than 6 minutes to feed. They have small conical teeth that help them catch and hold on to their prey; each tooth row contains 23 to 36 pairs of teeth. Instead of using their teeth to chew their food, dolphins use their teeth to grip food before swallowing it whole — head first — so the spines of the fish do not catch in their throats. Pacific white-sided dolphins often work together as a group to herd schools of fish. Each adult eats about 20 pounds of food a day.
Males reach sexual maturity around 10 years and females around 8 to 11. They mate and give birth from late spring to fall, except in the central Pacific, where calves are born in late winter to spring. Gestation is usually nine to 12 months, and calves weigh about 30 pounds at birth and are about 3 to 4 feet. Mothers nurse their calves for up to 18 months. Females usually give birth every 3 years.
Threats to White-Sided Dolphins
Atlantic white-sided dolphin
The worldwide population of Atlantic white-sided dolphins is unknown, but scientists estimate that there are at least 300,000 of them, with about are about 93,000 dolphins in the western North Atlantic stock. During the 1970s and 1980s in the northwestern Atlantic Ocean, this species population significantly increased due to changes in prey.
Pacific white-sided dolphins are not endangered or threatened The Convention on International Trade in Endangered Species (CITES) places both the Atlantic and Pacific white-sided dolphins in Appendix II, which lists species not necessarily threatened with extinction now but may become so unless trade is closely controlled. Both are protected by the Marine Mammal Protection Act (MMPA) throughout their range.
Threats include entanglement in fishing gear and ocean noise Low-frequency underwater noise pollution can interrupt the normal behavior of Pacific white-sided dolphins. Noise interference hinders their ability to use sound, which in turn disturbs their ability to communicate, choose mates, find food, avoid predators, and navigate. [Source: NOAA]
One of the main threats to the Pacific white-sided dolphin is getting caught in fishing gear. Dolphins can become entangled or captured in commercial fishing gear such as gillnets, seines, trawls, trap pots, and longlines. Before a 1933 United Nations moratorium that banned large-scale drift nets, Pacific white-sided dolphins were often captured by Japanese fisheries. In addition, every year between 1978 and 1991, thousands of Pacific white-sided dolphins suffered mortality and serious injury when caught incidentally in high-seas fisheries for salmon and squid. These fisheries were closed in 1991 and no other large-scale fisheries have operated in the central North Pacific since 1991.
Atlantic white-sided dolphins have been incidentally taken in fisheries such as driftnets, gillnets, and trawls in the Atlantic Ocean. In waters off of Ireland, significant numbers of these dolphins have been incidentally caught in mid-water trawls. They have been directly hunted and killed for food and oil in the drive fisheries of the Faroe Islands, Greenland, Newfoundland (Canada), and Norway.
White-Beaked Dolphins
white-beaked dolphin
White-beaked dolphins (Scientific name: Lagenorhynchus albirostris) are generally found in colder temperate and subpolar waters in the North Atlantic Ocean. They are active swimmers and often “surf” the waves created by vessels. They are usually found in groups of five to 30 individuals but sometimes travel in groups of up to 1,500. White-beaked dolphins hunt for food both near the water’s surface and along the ocean bottom. Some fishermen in Canada call these dolphins “squidhounds” because they eat squid and octopi. [Source: NOAA]
The range of white-beaked dolphins includes the waters of eastern North America (Massachusetts to Newfoundland), northern Europe, Scandinavia, Greenland, the United Kingdom, and the Barents Sea. They prefer waters less than 200 meters (650 feet) deep. The distribution of this species varies with the seasons. Most white-beaked dolphins move south and farther offshore during the winter months. They then return north and closer to shore once the ice recedes during the warmer summer months.
White-beaked dolphins are relatively large dolphins. They are about 2.4 to 3 meters (8 to 10.5 feet) long and weigh 180 to 350 kilograms (395 to 770 pounds). Males are usually larger than females. Both males and females have a streamlined, robust body with a small beak and a large, tall, curved dorsal fin. Their body is mostly dark gray or black on the upper sides and back with light gray or white patches on their sides, back, and underside. The dorsal fin, flippers, and flukes are mostly dark. Their beaks, which are very short and thick, also have white “lips.” White-beaked dolphins have 22 to 28 pairs of small, cone-shaped teeth in each jaw.
White-beaked dolphin groups can be organized by age and sex. These dolphins are sometimes seen in groups with other species, such as fin whales, humpback whales, and other small dolphins such as bottlenose and Atlantic white-sided dolphins. White-beaked dolphins are active swimmers. They often breach and jump at the water’s surface. They eat schooling fish (such as, haddock, cod, and herring), crustaceans (such as, shrimp and crabs), and cephalopods (such as, squid and octopi). They typically work together to catch fish at the water’s surface but will also feed along the ocean bottom. They reach sexual maturity when they are 7 to 12 years old. Females are pregnant for about 11 months and give birth to a single calf, usually between May and September. Calves are about 1.2 meters (4 feet) long and weigh about 40 kilograms (90 pounds) at birth.
The worldwide population of white-beaked dolphins is unknown. In U.S. waters, about 2,000 dolphins make up the western North Atlantic stock. CITES places white-beaked dolphins in Appendix II, which lists species not necessarily threatened with extinction now but may become so unless trade is closely controlled. Like all marine mammals, they are protected under the MMPA. Threats include entanglement in fishing gear and ocean noise. White-beaked dolphins are sometimes targeted and hunted for meat and oil in waters off Canada (Labrador and Newfoundland), Greenland, Iceland, and Norway. [Source: NOAA]
Northern Right Whale Dolphins
Northern right whale dolphin
Northern right whale dolphins (Lissodelphis borealis) are generally found mainly in the deep, cold waters of the northern Pacific Ocean. Northern right whale dolphins live for 42 years or longer. They are “acrobatic” swimmers and can leap more than 20 feet over the surface of the water. [Source: NOAA]
Northern right whale dolphins are found in cold and temperate waters from the outer continental shelf to oceanic regions throughout the North Pacific Ocean, between 30° north and 50° north. Their range includes the waters of western North America (northern Baja California to the Gulf of Alaska), Russia (Kamchatka), and Japan. They prefer water colder than 66° Fahrenheit and usually inhabit areas over the continental shelf (the edge of a continent below the ocean’s surface).
The distribution of northern right whale dolphins varies with the seasons. They usually migrate within their habitat as the water temperature changes. The dolphins move south during the colder winter and autumn months, then return north during the warmer spring and summer months.
Northern right whale dolphins are relatively abundant. Scientists estimate that there are about 68,000 of them in the entire Pacific Ocean. They are currently listed as species of Least Concern on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. This means it is not currently considered to be threatened with extinction. In the Convention on International Trade in Endangered Species (CITES) they are in Appendix II, which lists species not necessarily threatened with extinction now but may become so unless trade is closely controlled: Throughout Its range.
Northern Right Whale Characteristics and Diet
Northern right whale dolphins are the only species of dolphin in the North Pacific Ocean without a dorsal fin. At sea, they are sometimes mistaken for herds of fur seals and sea lions due to their dark, streamlined body. They weigh 50 to 115 kilograms (130 to 254 pounds and are two to three meters (6.5 to 10 feet) in length. Males are generally larger than females. [Source: NOAA]
The dorsal side of Northern right whale dolphins is shiny and black, while their underside is white. Young dolphins range in color from dark gray-brown to cream. Both males and females have a streamlined body with a short beak, sloping forehead, and a small fluke (tail). Their thin body can make them appear smaller than their actual size.
The southern right whale dolphin (Lissodelphis peronii), a related species, looks similar to the northern right whale dolphin. While both species are in the Lissodelphis genus, they differ in size, features, and color. Southern right whale dolphins are generally larger and whiter on their underside compared to their northern relatives.
Northern right whale dolphins can dive for up to six minutes to feed on small fish and cephalopods (such as squid and octopi) in deep waters. They have 37 to 54 pairs of small, cone-shaped teeth in each jaw.
Northern Right Whale Dolphin Behavior and Reproduction
Northern right whale dolphins usually travel in groups of 100 to 200 individuals but are sometimes found in groups of up to 3,000. They are occasionally seen in mixed groups with other cetacean species, such as Pacific white-sided dolphins, Risso’s dolphins, and short-finned pilot whales. [Source: NOAA]
Northern right whale dolphins are fast swimmers, reaching average speeds of 16 miles per hour and short bursts of 22 miles per hour. They make low, graceful leaps out of the water. When moving near the surface, they rarely show much of their body, but will sometimes lift their tails out of the water and then slap them onto the surface. While they usually avoid vessels, groups of northern right whale dolphins will sometimes "surf" the waves created by vessels, especially when traveling in groups with other cetacean species.
Northern right whale dolphins males and females become sexually mature around 10 years of age. Females are pregnant for about one year and give birth to a single calf, usually during the summer. For females, there is a minimum of two years between each birth. [Source: NOAA]
Threats to Northern Right Whale Dolphins
Northern right whale dolphins, like all marine mammals, are protected under the Marine Mammal Protection Act. While it faced significant bycatch in driftnet fisheries in the past, those fisheries have largely been eliminated. Threats today include net entanglement, hunting in Japan and ocean noise. To manage northern right whale dolphins in U.S. waters, we have placed them into a California/Oregon/Washington stock. Based on the most recent surveys, our scientists estimate that there are about 26,000 dolphins in this stock. [Source: NOAA]
Net Entanglement: One of the main threats to northern right whale dolphins is becoming entangled or captured in fishing gear such as driftnets, gillnets, and purse seines. Entanglement in gear can injure or kill dolphins. During the 1970s and 1980s, many northern right whale dolphins were taken in squid fisheries’ driftnets. These high mortality rates may have decreased northern right whale dolphin stocks. These squid fisheries have since been closed by international law.
Hunting: Northern right whale dolphins are sometimes targeted and hunted for meat and oil in the Dall's porpoise harpoon drive fishery off of Japan.
Ocean noise: Underwater noise pollution interrupts the normal behavior of northern right whale dolphins that rely on sound to communicate and echolocate. If loud enough, noise can cause permanent or temporary hearing loss. Noise interference from vessels, as well as industrial and military activities, disturbs northern right whale dolphins’ feeding, communication, and orientation. [Source: NOAA]
Some dolphin species: 3) Peale’s Dolphin (Lagenorhynchus australis); 4) Hourglass Dolphin (Lagenorhynchus crucigen; 5) Pacific White-sided Dolphin (Lagenorhynchus obliquidens); 6) Dusky Dolphin (Lagenorhynchus obscurus); 7) Irrawaddy Dolphin (Orcaella brevirostris); 8) Australian Snubfin Dolphin (Orcaella heinsohni)
Image Source: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated June 2025