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Diet and Eating Habits
A. Food preferences and resources.
1. Active and opportunistic, killer whales are without a doubt top predators in the ocean. In fact, they are the largest predator of warm-blooded animals ever known.
2. Fishes, squids, seals, sea lions, walruses, birds, sea turtles, otters, penguins, cetaceans (both mysticete and odontocete), polar bears, reptiles, and even a moose -- they have all been found in the stomach contents of killer whales.
3. Perhaps the most interesting thing found in the stomachs of killer whales is the remains of other killer whales. How this came to be is uncertain as killer whale predation on other killer whales is rare. Perhaps they scavenged the remains of dead killer whales, as killer whales are known to eat the remains of other animals.
4. The diets of killer whales vary from one region to another.
a. In the Antarctic, killer whales eat about 67% fishes, 27% marine mammals, and 6% squids.
b. In the Bering Sea near Alaska, they eat about 65% fishes, 20% squids, and 15% marine mammals.
c. The diets of resident and transient killer whales differ as well. Resident pods eat a wide variety of fishes and rarely seek out marine mammals. Transient groups primarily eat marine mammals and occasionally eat fishes.
B. Food intake.
Adult killer whales eat approximately 3% to 4% of their body weight in food per day; fully weaned calves can eat up to approximately 10% of their body weight during growth periods.
C. Methods of collecting food.
1. Much like packs of wolves or prides of lions, killer whales often hunt cooperatively in pods for food. They work together to encircle and herd prey into a small area before attacking. When hunting a large whale, a pod of killer whales may attack from several angles.
Killer whales often hunt cooperatively.
a. This event was dramatically witnessed when a SeaWorld research vessel, initially tagging swordfish for a migration study, had a serendipitous encounter with a pod of killer whales attacking a blue whale (Balaenoptera musculus) -- the largest animal living on our planet today. Such an event had rarely been witnessed and never before photographed.
b. Approximately 30 killer whales assaulted an 18.2 m (60 ft.) blue whale. Two killer whales stayed ahead and two lagged behind while others surrounded the blue whale from the sides and underneath in an apparent effort to prevent escape. Some even leaped onto the back of the blue whale in what is believed to be an attempt to drown it.
c. The SeaWorld vessel watched as the group took turns biting flesh and blubber from their prey. After five hours, the herd broke off their attack. Perhaps the killer whales were resting or they may have had their fill, but the final fate of the severely injured blue whale was not known.
2. The conical and interlocking teeth of killer whales are adapted for ripping and tearing but not for chewing. The number of teeth varies among individuals. There are usually 10 to 14 teeth on each side of the jaw -- a total of 40 to 56 teeth. Each tooth is about 7.6 cm (3 in.) long and approximately 2.5 cm (1 in.) in diameter.
3. Killer whales swallow their food in chunks if need be, but their throats are large enough to swallow small seals and walruses whole.
4. Prey, such as these sea lions, may not be safe from killer whales even on land. Some killer whales specialize in sliding out onto sand bars or ice floes to pursue prey. They may also hit ice floes from below to knock prey into the water.
5. Another rare event, an encounter between a great white shark (Carcharodon carcharias) and killer whales, was recently documented off of Southeast Farallon Island near San Francisco, California. Two killer whales were in the area feeding on a California sea lion (Zalophus californianus) -- a favored food of great whites.
a. Perhaps the smell of fresh sea lion blood drew the shark to the area, but once one of the killer whales sighted the great white it immediately charged the shark and contacted it under water. The killer whale pulled the 3 to 4 m (10-13 ft.) shark to the surface in its mouth and the killer whales consumed sections of the great white such as its enormous liver.
b. This is certainly no indication of what may happen every time killer whales face great whites, but it does demonstrate the variety of a killer whale's diet.
6. A pod of 30 to 40 killer whales was seen following a fleet of trawler ships in the northeastern area of the Shetland Islands in the United Kingdom. As the trawlers brought aboard quantities of netted mackerel (Scomber scombrus), the killer whales consumed fishes that slipped from the nets or dead fishes tossed off the ships.
7. Research has shown that resident whales have a wider sound repertoire than transient whales, which may be partially related to their hunting habits.
a. Transients vocalize far less frequently than residents. While resident whales have been observed vocalizing during all forms of behaviors, transients only vocalize during play and after a kill.
b. One theory for this is that resident pods hunting schools of fish may need to rely on a great deal of communication to coordinate their assault. Transients may need to use stealth to approach marine mammals that might be alerted if the killer whales were to vocalize.
Killer whales have a complex relationship with other marine mammals. Killer whales have been observed feeding on fish while in the company of other dolphins, minke whales (Balaenoptera acutorostrata), and Dall's porpoises (Phocoenoides dalli). On another occasion, humpback whales (Megaptera novaeangliae) joined a pod of killer whales that were attacking a Stellar sea lion (Eumetopias jubatus). At other times seals have been seen swimming with killer whales. All of these animals may all be prey of killer whales at other times.
