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Marine Life Encyclopedia

Marine Mammals


Orcinus orca


Global: all latitudes in all oceans


Coastal to open ocean (pelagic)


Aggressive predator


Order Cetacea (whales, dolphins, and porpoises), Family Delphinidae (dolphins)

Orcas get their nickname “killer whales” from their reputation of being ferocious predators, exhibiting almost hateful behaviors when toying with their prey. Interestingly, however, killer whales are actually very large dolphins, reaching lengths of 33 feet (10 m) and weights of at least 10 metric tones (22,000 pounds). Orcas and other dolphins are thought to be some of the smartest animals on the planet, challenging the great apes (chimps and gorillas) for the top spot. They are also extremely curious and often approach people to investigate. Their intelligence is likely both a result of and a driver of their complex social structures. They generally live in small groups and organize complex, group behaviors when mating and hunting. They are intelligent, playful, powerful animals – a worrisome combination if you happen to be their preferred prey. Different orca populations specialize on different prey types, including large bony fishes; seals, sea lions, and other large marine mammals; and penguins; among other things.

Individual orcas are known to reach ages of 100 years old. Like all mammals, orcas reproduce through internal fertilization, and females give birth to live young. Juveniles are able to swim from the moment they are born, but they are totally dependent on nursing their mothers’ milk for one to two years.

Though all orcas, worldwide, are considered to be members of the same species, there are several known populations that have slightly different appearances, sizes, and behaviors. These include populations that are somewhat territorial and do not migrate long distances (the so called resident populations) and those that are more migratory in nature (the so called transient populations). Furthermore, some transient populations stay near the coast and overlap with resident populations, while others are oceanic. Some orca scientists believe that these populations may represent different species, and recent research suggests that there may be as many as 16 different species. To date, the new species have yet to be described, and the cosmopolitan species Orcinus orca is considered to cover all individuals around the world, regardless of behavior or appearance.

Though they are powerful hunters and are known to exhibit somewhat tortuous behavior towards large sharks and other marine mammals, killer whales have never been known to attack humans in the wild. This is a somewhat puzzling lack of aggressive behavior, as people would be extremely easy prey for this species. In captivity, however, male orcas have killed several trainers in the last few decades. These large, marine predators are not meant to be kept in small tanks in captivity, and they seem to eventually snap and exhibit aggressive behaviors toward their handlers. In addition to their capture for display in public aquaria, low numbers of orcas have been regularly hunted for food in some regions around the world. In the United States and some other places, this species is given complete legal protection as a result of it being a highly intelligent, marine mammal. Its global distribution and the confusing relationships between populations/potential new species described above contribute to scientists not believing that they have enough data to determine the conservation status of the orca. Further study and continued monitoring are both necessary to understand any potential risks that this species faces.

Fun Facts About Orcas

1. Orcas are the largest members of the dolphin family, growing up to 32 feet (9.8 m) long and 22,000 pounds (10 metric tons).

2. Male orcas can live up to 60 years, while females live much longer, up to 90 years.

3. Orcas are the most widely distributed cetaceans (whales, dolphins and porpoises) and can be found in every ocean.

4. Orcas form social groups consisting of a 3 to 20 members that tend to stay together over multiple generations.

5. Orcas pass down specific communication and hunting skills to younger members, distinguishing one pod’s culture from another.

6. Female orcas are one of only three species that go through menopause, the other two being short-finned pilot whales and humans.

7. Orcas have the most diverse diet of all cetaceans, eating anything from salmon to seals, whales and squid.1

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Kids Environmental Lesson Plans


1 NOAA Fisheries

IUCN Red List

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