Orcas are often called killer whales, a name that came from whalers. But the orca is the largest member of the dolphin family. Orcas are toothed whales, and the orca is one of close to forty species in the ocean dolphin family. An orca is mostly black on top, with a white belly and a white patch near each eye.

Orcas are found in every ocean, which makes them the most widely distributed of all whales and dolphins. They live in cold seas near the poles and also in warm tropical seas. Orcas move to where the food is instead of following a fixed seasonal route.

Males usually grow to 20 to 26 feet (6 to 8 meters) long. 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. A grown female of the Pacific Northwest weighs about 8,000 to 11,000 pounds (3,500 to 5,000 kilograms).

An orca has about 40 to 56 teeth that interlock when its mouth is closed. The teeth 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, and they have the most varied diet of all the whales and dolphins.

Each group of orcas usually specializes in a few foods. There are three main ecotypes of orcas in the North Pacific: Resident, Transient and Offshore, and each differs in appearance, diet, habitat, genetics and behavior. Resident orcas eat fish, mainly salmon, and Bigg's (transient) orcas mostly eat marine mammals. Orcas pass dialects, hunting strategies and social habits from generation to generation.

Orcas live in family groups called pods. A pod is made up of a few to 20 or more whales that are related to each other. 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, and older female orcas teach younger whales how and where to fish.

A mother orca has one calf at a time. The calf drinks milk for short periods dozens of times a day, and the milk is extremely rich in fat. Calves stay close to their mother and usually nurse into their third year, but start to eat solid food around age one.

Orcas make clicking sounds and listen for the echoes to find things in the water. Orca echolocation can build a detailed picture of the surroundings, and orcas can even tell fish species apart this way.

Orcas hunt together as a team. Some herd schools of fish into a tight ball so the fish are easier to catch. Orcas that hunt herring in Norway herd the fish into a tight ball and then slap their tails to stun the fish. Near Antarctica, some orcas work together to make waves that wash seals off ice floes. An orca can swim fast, but only in short bursts: scientists at the Center for Whale Research say up to 28 knots (50 km/h).

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. Scientists think orcas sleep by resting one half of the brain at a time, as studies show bottlenose dolphins and belugas do. Female orcas live about 50 years in the wild, and some live to at least 90.

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, as of November 2026. In July 2026, a census counted 76 Southern Resident orcas, a group listed as endangered in the United States since 2005.

Words to know

• ecotypes: different habit groups
• pods: orca family groups
• matriline: mother-led family
• blubber: thick body fat
• echolocation: sensing by echoes