Orcas are called killer whales, a name that came from whalers. But the orca is the largest member of the dolphin family. An orca is mostly black on top, with a white belly and a white patch near each eye. Orcas live in every ocean in the world, in cold seas near the poles and also in warm tropical seas. They move to where the food is instead of following a fixed seasonal route.

Male orcas usually grow to 20 to 26 feet (6 to 8 meters) long, and females are smaller, usually 18 to 22 feet (6 to 7 meters). A grown male usually weighs 12,000 pounds (5,400 kilograms) or more, and a grown female of the Pacific Northwest weighs about 8,000 to 11,000 pounds (3,500 to 5,000 kilograms). As of November 2026, the biggest orca on record weighed more than 20,000 pounds (9,000 kilograms). A layer of blubber 3 to 4 inches thick lies under an orca's skin, and the stored fat gives energy when prey is scarce.

An orca has about 40 to 56 teeth that interlock when its mouth is closed, and they grow to about 10 centimeters (4 inches) long. The teeth do not chew food: they tear it into chunks, or the food is eaten whole. Orcas eat fish, squid, seabirds and sea mammals such as seals. Orcas have the most varied diet of all the whales and dolphins, but each group of orcas usually specializes in a few foods. Orcas in different places eat different foods, and young orcas learn how to hunt from older ones.

There are three main ecotypes of orcas in the North Pacific: Resident, Transient and Offshore. Each differs in appearance, diet, habitat, genetics and behavior. The three ecotypes share part of their habitats, but they are not known to interbreed with each other. Resident orcas eat fish, mainly salmon, and Bigg's (transient) orcas mostly eat marine mammals. The Southern Resident orcas of the Pacific Northwest eat mostly Chinook salmon. Orcas pass dialects, hunting strategies and social habits from generation to generation.

Orcas hunt together as a team. Some orcas herd schools of fish into a tight ball so the fish are easier to catch. Carousel feeding is a hunting method in Norway where orcas herd herring into a ball and slap their tails to stun the fish. Near Antarctica, some orcas work together to make waves that wash seals off ice floes. Young orcas learn how to hunt from older ones.

Orcas have outstanding eyesight above and under the water, but daytime underwater visibility is usually not more than fifty meters. So sound does much of the work. Orcas make clicking sounds and listen for the echoes to find things in the water. Echolocation clicks are brief pulses of ultrasonic sound, and the echoes give the orca a sense of distance and texture within hundreds of feet to hundreds of yards. Orca echolocation can build a detailed picture of the surroundings, and orcas can even tell fish species apart this way. An orca hears through its lower jaw, and the sound travels on to the bones of its ear.

Orcas call to each other with whistles and calls, and each pod has its own sounds. Each Pacific Northwest pod has its own dialect, a vocabulary that stays stable over time and helps hold the group together. Orca calves are born with the ability to communicate, and are believed to recognize their mother's calls before birth. Orcas use sound to find food, talk to each other and find their way in the water.

A matriline is a mother orca with her sons and daughters and her daughters' calves, and these families form pods. In resident orca families, grown sons and daughters stay with their mother for life. Older female orcas teach younger whales how and where to fish. Female orcas stop having calves around age 40, then can live for decades more. Menopause is known in humans, killer whales, false killer whales, beluga whales, narwhals, short-finned pilot whales and probably bottlenose dolphins. Female orcas live about 50 years in the wild, and some live to at least 90.

Killer whales have uniquely high levels of contaminants because of their long lifespan, position at the top of the food chain and large quantities of blubber. Increased vessel noise causes Southern Resident orcas to call louder, which uses more energy.

Scientists estimate there are around 50,000 orcas in the world, as of November 2026. The eastern North Pacific holds about 2,500 orcas, and its populations are the best studied. In July 2026, a census counted 76 Southern Resident orcas. The Southern Resident orcas are listed as endangered in the United States, since 2005.

Words to know

• ecotypes: habit groups
• echolocation: sensing by echoes
• dialect: a group's sounds
• blubber: thick body fat
• menopause: end of calves