Orca - Killer Whale
Orcinus orca
Killer whales are the largest member of the dolphin family. The public is aware of killer whales from the movie “Free Willie” and from their use in shows at marine theme parks. The name “killer whale” came from the days of whaling when they were referred to as “whale killers”. Over time, the two words were reversed.
Off the northwest coast of North America there are 2 basic types of killer whales, those that primarily eat fish and those that primarily eat marine mammals. The mammal eating variety is seen, although rarely, at Piedras Blancas. When they are around it is both chilling and exciting. Killer whales have been observed in the vicinity of all three Piedras Blancas rocks, apparently hoping to prey on sea lions or seals. They are sometimes around during the gray whale cow/calf migration because the calves are susceptible to attack. Gray whale mothers and calves frequently travel very close to shore and hide in kelp or around the rocks to try to avoid detection from orcas, their number one predator.
Color: Killer whales have sharply contrasting color patterns: jet black bodies with a white chin, white belly and white patch behind the eye. There is a gray “saddle patch” behind the dorsal fin. Distinctive markings make it possible to identify individuals.
Shape: They have a robust heavy body, round head with a slight rounded beak, and large paddle-shaped flippers. Adult males have a very tall dorsal fin, up to 6 feet. Females and calves of both sexes have shorter, more curved dorsal fins.
Weight and length: Adult males are about 26 feet long and weigh around 8 tons. Females are around 23 feet long and weigh 4 tons. At birth they are about 8 feet long, weighing 400 pounds.
Feeding: Their diet is the most diverse of any cetacean and includes fish, marine mammals, birds, turtles, sharks, and squid. Populations in different areas specialize in different prey. The marine mammal eating (“transient”) killer whales feed on over 35 different prey species including cetaceans and pinnipeds. They are the world’s largest predator of warm-blooded animals. They coordinate hunting and can take down much larger prey than themselves. In British Columbia harbor seals are the primary prey. The fish eating killer whales (“residents”) in British Columbia feed on a wide variety of species, preferring the largest and fattest salmon. Killer whales cooperate in feeding activities.
A third type of killer whale referred to as “offshore” is found in waters off British Columbia to California. They appear to be more closely related to residents, but their dietary habits are not known.
Breathing and diving: Killer whales have a single blow hole which produces a low and bushy blow. Transients stay under water 5-20 minutes. Residents rarely stay underwater more than 4 minutes.
Migration: Although they don’t typically engage in long migrations there is movement according to food availability. On occasion, members of the resident pods of the Pacific Northwest have been observed in Monterey Bay.
Movement/behavior: As all cetaceans, killer whales mover through the water with up and down movements of their flukes. They engage in many behaviors, including spyhopping, breaching, flipper-slapping, and lobtailing. Fast swimmers, they can travel up to 34 mph. Transients tend to form groups of 1-7 members that move over a wide area and don’t vocalize much. Residents tend to form groups of 5-25 individuals who vocalize frequently and have a smaller range than transients. They are used in marine theme parks because they adjust to captivity and learn tasks quickly.
Resident killer whales have complex social units. The basic organizational group is the “matriline”, consisting of a female, her sons and daughters, and the offspring of her daughters. A matriline may consist of up to 4 generations. “Pods” are the next level of organization; a group of related matrilines with a common maternal ancestor in the recent past. Pods are less stable than matrilines and may travel apart for periods of time. The next level of social structure is the “clan”, linked by similar vocal dialects. The top level is the “community”, made up of pods that associate together.
Social organization among transients isn’t as clearly understood, although the basic unit is the matriline. However, the offspring may disperse so groups tend to be smaller in numbers and lone males are observed. The difference in social structure probably reflects the difference in foraging activities. Attacks on large whales are carried out by groups of 10-20 killer whales working together.
Sounds: They produce click-like sounds, similar to other dolphins, and a variety of screams, whistles, and pulsed calls for echolocation. Each group has a distinct repertoire. Transients are usually silent while foraging, presumably to avoid alerting potential prey of their presence.
Reproduction: At 10-15 years of age they are sexually mature. Intervals between calves is about 5 years. Mating and calving may occur year-round. Gestation is 15-18 months.
Calves: Calves are nursed for at least a year but begin eating solid food while nursing. Weaning probably occurs between 1-2 years.
Longevity: They can live 50 years more. Males tend to not live as long as females.
Predators: Killer whales have no natural predators other than human beings.
Distribution: Killer whales are widely dispersed around the world, but are most commonly found in cooler waters. Generally, they are found within 500 miles of shore.
Status: Overall, their numbers are considered to be stable, although some populations are depressed. Killer whales have been found shot because they compete with some commercial fishing activities. There are concerns about oil spills and toxic pollution. As apex hunters they accumulate contaminants present in the food chain. Vessel traffic and reduction of fish stocks due to over-fishing are also concerns.