Natural History © 1994 Dave Ellifrit


Scientific papers, books and links about orcas and other cetaceans.

Most of what we know about the Southern resident orca community comes from a long-term demographic survey conducted by the Center for Whale Research on San Juan Island. The Center has been conducting photo-identification research on this orca population continually since 1976.

For a general description of orca natural history focusing on the Southern Resident orca community, see Orcas of the Salish Sea.

For a history of the listing of Southern Resident orcas as Endangered under the Endangered Species Act, see Orcas In Our Midst, Volume 2, The Next Generation.

For an introduction to orca natural history and the Salish Sea Watershed the Southern Resident orcas depend on, see Orcas In Our Midst, Volume 1, The Salish Watershed

Offshore orcas
Transient orcas

Some fascinating facts about orcas

  • Newborn orcas are 7-8 feet long, 3-400 lbs.
  • Adult females worldwide are 17-24 feet, 5-9,000 lbs.
  • Adult males worldwide are 22-30 feet, 8-12,000 lbs.
  • Southern resident male orcas are 21-24 feet.
  • Southern resident females are 18-21 feet.
  • Orcas have a 16-17 month gestation period.
  • Females usually have one calf every 4-5 years.
  • Males usually live into their 40s and females into their 60s.
  • Males become sexually mature in their early teens, and fully grown in their early 20's.
  • An adult orca consumes 100-300 pounds of food a day, depending on size and energy needs.
  • Southern Resident orcas rely on salmon, specifically chinook in the summer and chum in the fall, for their survival. Chinook salmon constitutes over 70% of their diet.
  • The brain of an adult orca may weigh 12-15 pounds, or about four times the size of human brains.
  • Like all whales, orcas are voluntary breathers and need to be at least "half awake" at all times. Their brain has the ability to split activities so they sleep with half their brain while the other half keeps the body still breathing.
  • Orcas are the largest members of the dolphin family, or delphinidae.
  • Like all dolphins, orcas use sophisticated biological sonar, called echolocation.
  • Orcas are found throughout the world's oceans, but tend to prefer the cooler, more productive polar and temperate waters.
  • Orcas can swim up to 30 mph and can travel 75-100 miles or more per day.
  • Orcas have no predators.
  • Orcas live in matrilineal family groups presumably led by elder matriarchs. Two or more matrilines may form a pod.
  • Both male and female offspring typically remain with their maternal family for life.
  • Genetic evidence indicates that mating occurs between, and not within, pods.
  • A pod's or maternal family's unique repertoire of calls is called a dialect.
  • The J, K and L pods, which frequent Puget Sound, are known as the southern resident community.
  • Each orca in the Southern Resident community is photographically identified each year by the shape of the dorsal fin, as well as shape of gray markings, called the "saddle patch" behind the dorsal fin.
  • Several pods may belong to a clan that shares certain vocalizations, and several clans may associate as a community.
  • Often when pods of the same clan or community meet after separation, they physically intermingle and engage in vigorous surface activity, accompanied by almost non-stop vocalizations.
  • Communities remain apart from one another, generally staying in separate habitats and using completely distinct vocalizations.
  • A wide variety of types of orcas have been observed, including "residents," which eat only fish, "transients," which eat only mammals, and "offshores," found several miles from shore, but not all orca communities worldwide may fit those descriptions.
    Orca Network's Whale Sighting Network covers the south end of the Salish Sea, from Victoria to Vancouver, BC and from the San Juan Islands to Seattle and Olympia. The Sighting Network is comprised of volunteers who observe and report on the travels and behaviors of the Southern Resident Community of orcas (J, K and L pods), as well as gray whales and other cetaceans in the area.


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