- For the most part, killer whales in the wild are visible only when they are at the surface, so it is inherently challenging to document and study whale behavior.
- Possibly the most-studied killer whales in the wild are the resident killer whale communities of the eastern North Pacific Ocean.
- Much of what we know about killer whales comes from studying these whales.
- We know less about transient whales in the same area, partly due to the fact that they are harder to observe because they are more evasive and less predictable. Offshore whales are even less studied, but they travel in larger groups of 30 to 60 individuals and are seldom seen in coastal waters.
- Regional groups of killer whales can be very different from one another in diet, appearance, dialect, and genetics. Experts use caution when generalizing about killer whales, knowing that the many regional stocks of killer whales that have not been as well studied may be quite different from the eastern North Pacific resident whales.
- Killer whales live in cohesive long-term social units called pods. A pod is a group of individuals that travel together the majority of the time.
- Sometimes smaller pods may join to form groups of 50 or more individuals (up to 500 in some cases) which are sometimes referred to as herds or aggregations.
- Pods usually consist of males, females, and calves of varying ages. Females and juveniles generally remain in the center of the pod, while adult males swim at the wings.
Pods usually consist of males, females, and calves of varying ages.
- The most fundamental social unit in a pod is a matrilineal group, which may include two or three generations of whales. A two-generation matrilinealgroup consists of a female whale and her offspring. A three-generation matrilineal group also includes her "grandchildren," the offspring of her female offspring. Individuals in a matrilineal group travel closely together.
- A clan is a social level above the pod level. Clans are made up of pods in an area with similar dialects and are thought to be related. These pods may have developed from one ancestral pod that grew and fragmented over time.
- A community is a group of killer whales that share a common range and associate with one another.
- There may be several pods within a community. In the eastern North Pacific, pods of southern residents, northern residents, and transient killer whales each make up a separate community.
- Pods from one community have not been observed traveling with those of another, even when their ranges overlap.
- There is an occasional exchange of members between pods, especially during breeding season.
- Resident pods tend to travel within specific ranges while transient groups' ranges are unpredictable. Resident pods were observed to remain within a range of about 800 km (500 mi.) of the coastline. Residents travel direct routes, moving generally from headland to headland along the coast. Transients may spend twice as much time traveling as their movements tend to be circuitous, often following the contours of the shoreline. Transient whales have been sighted within a 1,450 km (900 mi.) range.
- Killer whales in a pod establish strong social bonds. Observers note that certain individuals are regularly seen associating with one another.
- The strongest association bonds in a pod are the mother/calf bonds.
- A mother killer whale stays close to her newborn calf and attentively directs its movements.
- The mother/calf bond weakens as a young killer whale matures, but for resident whales of the eastern North Pacific, it lasts throughout adulthood. In fact, these resident killer whales societies are unique in that a juvenile killer whale does not leave its mother or disperse from its maternal pod when it matures.
- In transient pods of the eastern North Pacific Ocean, a whale may leave its mother to travel alone or with other whales.
The killer whale social hierarchy is matriarchal or female-dominant.
- As with many species, a social hierarchy exists within a group of killer whales. The hierarchy is female-dominant.
- Killer whales within a pod may rank themselves and establish dominance by slapping their tails against the water, head-butting, jaw-snapping, biting, raking (tooth-scratching), and various other vigorous postures and gestures.
- SeaWorld observers noted that calves receive social discipline from their mothers and other significant adults. Discipline may be in the form of restraining (corralling the calf thus restricting its movements) or raking (tooth scratching).
Tooth scratches can leave a killer whale with scars, but generally
these scratches are superficial.
- Killer whales often hunt together. (See Diet: Food Preferences & Resources and Diet: Methods of Collecting Food)
- Interactions between resident and transient pods have not been observed. When they are traveling in the same area, they most often appear to ignore each other. At other times, transient whales actively avoid resident whales.
- Whale watchers and researchers have named certain common whale behaviors.
- Killer whales may do some of these behaviors to relieve an itch, as their outer skin layer is continually sloughed as they swim. The growth of killer whale epidermal (skin) cells is about 290 times faster than that of a human forearm.
- Killer whales in the Johnstone Strait in British Columbia rub their bodies along the pebbly bottoms of shallow bays (sometimes called "rubbing beaches"). Why is unclear: they may do it for tactile stimulation, or it may help remove external parasites.
- Behavioral studies of several cetacean species in zoological parks suggest that killer whales are among the most curious of cetaceans, with great tendency to "play" and to manipulate objects.
- A killer whale may strand if it is affected by a severe, debilitating illness or injury, or if it is too weak to swim or hunt for food. (See Longevity and Causes of Death.)
- In some areas, killer whales temporarily slide up onto ice or sand to pursue prey. This behavior is not considered stranding.
Interaction with other Marine Mammals
- Killer whales prey on many species of marine mammals. (See Diet.)
- Killer whales have also been observed harassing other marine mammals, without eating them.
- At other times, killer whales have been seen feeding in the same area with other marine mammals, with no apparent reaction by the killer whales. Some species, including those that are known prey for killer whales (minke whales, Dall's porpoises, and seals, for example) have been observed swimming with killer whales.
- Other marine mammals may flee or avoid killer whales, but at times they seem to ignore them. Sometimes other marine mammals appear to be attracted to killer whales.