Dolphins: Delphinidae

Physical characteristics: Killer whales, or orcas, are the largest dolphins, measuring 30 feet (9 meters) and weighing up to 12,000 pounds (5,600 kilograms). They have a striking black and white pattern of mainly black above and white below, and they have the tallest dorsal fin of any cetacean. The dorsal fin can reach 6 feet (2 meters) in height. They are the top predators in the ocean.

Geographic range: Killer whales live in all the oceans of the world, but are most abundant in cold water areas such as the Arctic and Antarctic.

Habitat: Killer whales prefer cold water, but can live in warmer temperatures. They tend to live in water that is less than 650 feet (200 meters) deep. Rarely they have been known to swim up rivers such as the Columbia in the United States and the Thames in England.

Diet: Killer whales have the most varied diet of any dolphin. They hunt fish, seals, sea lions, other dolphins, porpoises, and whales. Their Killer whales chase sea lions onto the beach, and then attack them. (© François Gohier/Photo Researchers, Inc. Reproduced by permission.) diet depends primarily on what is available in their region of the ocean. They are swift swimmers and hunt in packs. They can successfully attack a blue whale, the largest animal on the planet, or a great white shark. In some places they chase sea lions up onto the beach and attack them. They are able to swallow a small seal whole. Adults eat 3 to 4 percent of their body weight daily.

Behavior and reproduction: Killer whales live in stable pods. Males often stay with their mothers for years after they are weaned. Like other dolphins, they use echolocation and make sounds to communicate with members of their pod.

Killer whales have pregnancies that last from fifteen to eighteen months and produce a single calf. Calves stay dependent on their mothers for several years. New calves are born only every three to eight years.

Killer whales and people: Most people know of killer whales from exhibits at marine parks and movies. Since they can regularly be seen near shore, they are often the object of dolphin-watching tours. In 1985, the first killer whale was successfully born in captivity. That whale lived to adulthood and produce calves of her own. It is not clear how long killer whales live in the wild. Estimates range from thirty to fifty years.

Conservation status: Killer whales are not threatened. Their main threat appears to be pollution of their habitat. ∎