Killer whale  Orcinus orca

Illustration by Uko Gorter

Orcas are the top predator in the sea, and the largest member of the dolphin family. Also known as killer whales, they are icons of the Pacific Northwest, and the signature species of The Whale Trail.

Three kinds of orcas live in the Pacific Northwest, differentiated by diet, social structure and range.

  • Resident orcas are fish eaters, and prefer Chinook salmon above all others. They live in tightly bound family units called pods, and return predictably to the same feeding grounds each year. Learn more about northern and southern resident pods.
  • Transient orcas eat marine mammals, and travel in smaller family groups. Their range is wider and travel patterns less predictable.
  • Offshore orcas also hunt marine mammals, and live in the open ocean. Not much is known about these pods, but very occasionally they come into the waters of the Salish Sea.

These groups are genetically distinct, and are not believed to interbreed.

The resident orcas of the Pacific Northwest are one of the most well-studied groups of animals in the world. Other studies are currently underway with orca populations in Argentina, New Zealand, Antarctica, Norway, and Russia.

Biology

Their distinctive black and white coloring makes orcas instantly recognizable the world over. The white pattern on the underside of an orca is different between males and females. Other key features are as follows:

  • Dorsal Fins. Orcas have distinctive, triangle-shaped dorsal fins that can grow to be as high as 6 feet on males. Females have shorter, curved dorsal fins while males have taller, straighter fins. The shape of each dorsal fin is unique, and is used to identify individual orcas.
  • Saddle patches. Orcas can also be distinguised from each other by the white marking on their back, just behind the dorsal fin called a "saddle patch." The pattern of the saddle patch is unique like a human fingerprint.
  • The life span of orcas is very similar to humans. Females live an average of 50 to 80 years, while males live an average of 35 to 60.
  • Reproduction. Females are able to start bearing calves in their early teens, and may bear young into their 50s. Since calves are born throughout the year it is assumed that mating occurs year-round.
  • The gestation period for orcas is 14 months. Calves are roughly 3 feet when they are born, and are often assisted to the surface by other orcas. They nurse for approximately one year.
  • The life expectancy for orca calves is not very good. Approximately 50% of calves die before they reach one year old. For this reason, calves less than a year old are not counted in the numbers of the studied populations.
  • Though their eyesight is very good, orcas are primarily acoustic animals. They use sonar and vocalizations to navigate, hunt, and communicate with each other. Pods make unique and shared calls that can also be used to identify one pod from another.

Range

Orcas are one of the most widely distributed cetaceans in the world, and are believed to also be the most widely distributed marine mammal. Orcas live in every ocean, and at both poles.

  • The North Pacific hosts three types of orcas, differentiated by their morphology, behavior, and genetics:  residents, transients and offshores.  These whales often share the same range but are not related to one another and are not believed to intermix.
  • Atlantic orcas are known to live in the waters around Norway, Iceland, Patagonia, southern Argentina, New Zealand and Antarctica. The Antarctic groups also show species differentiation based on the same factors of morphology, diet, behavior and genetics.

 

Diet

Orcas are the top predator of the sea. Their preferred prey differs between ecotypes. For example, resident orcas eat fish, while transient and offshores eat marine mammals. This difference in diet and hunting strategies may have evolved to allow different kinds of orcas to share overlapping ranges, and not compete for the same food.

What orcas eat, and how they catch it, also appears to be a learned activity. Orcas teach their offspring both what to eat and how to hunt.

  • In Patagonia, orcas teach younger orcas how to launch themselves onto beaches to catch unsuspecting seals.
  • In Antartica, orcas work together to create waves that wash seals off ice floes, and into the mouths of other waiting orcas. Cruise ship passengers on a 2008 voyage watched orcas "training" younger orcas in this method for over two hours.

Social Structure and Behavior

Orcas are extremely social animals.  They live in tightly bound units called pods. At certain times of the year, multiple pods come together to form superpods, where mating and other social behaviors are often observed.

  • Resident orca pods are matriarchal, organized around the mothers and grandmothers. Generations of extended families stay together their entire lives.

Like other cetaceans, orcas exhibit a wide range of behaviors, like breaching, spyhopping, porpoising, kelping, tail-lobbing and resting.

  • Breaching is when an orca leaps fully out of the water, often making a spectacular splash when it falls back in.
  • Spyhopping is when an orca lifts it head above the surface, and has a look around. An orca's eyesight is as good as a human's!
  • When orcas porpoise, they swim rapidly along the surface of the water. In short bursts, orcas are the fastest mammal on earth.
  • Resident orcas often play with kelp as they swim through the giant kelp beds around the Pacific Northwest. This behavior has been observed so often that it's come to be known as kelping.
  • Orcas slap their tails against the surface of the water, creating a percussive sound that can be heard for miles. This behavior is called tail-lobbing.
  •  Sometimes they also slap their pectoral fins against the water; this is called a pec slap.
  • When orcas rest, they often line up side by side, in a formation known as a resting line. Like other cetaceans, they are conscious breathers and must stay awake to breathe. Though they rest, they never fall fully asleep like humans.

Current and Historical Threats

While orca populations world-wide are holding steady, human impacts on specific populations have been severe, and in some cases, catastrophic.

  • In the 1960s and 70s, the resident orcas of the Pacific Northwest were heavily hunted for display in marine parks and aquariums. Over one-third of entire population was removed, including most of the calves and the breeding mothers.
  • The southern resident orca population is now listed as Endangered, and the the long-term impact of the captures is cited as a factor in their decline. Other factors include prey abundance (lack of chinook salmon), toxin accumulations, and noise and stress from vessel impacts. If the current trends continue or worsen, the southern residents could go extinct in as few as 100 years.
  • In Southeast Alaska, the AT1 pod of transient orcas was heavily impacted by the 1989 Exxon Valdez oil spill in Prince William Sound. Since then, their numbers have plummeted from 22 individuals to 7. They were designated as Endangered by NOAA Fisheries, and their long-term chances of survival are slim.

Global warming and its impact on ocean conditions is a deepening concern for orcas and other marine species.

Learn More!

Books:

Killer Whales: The Natural History and Genealogy of Orcinus Orca in British Columbia and Washington State (Updated Edition) by John K. B. Ford et al, 2000

Orca: The Whale Called Killer by Erich Hoyt, 1990

See More Readers: Killer Whales -Level 1 by Seymour Simon, 2002

Links:

http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/killerwhale.htm

http://www.acsonline.org/factpack/KillerWhale.htm

Sources

Books:

Killer Whales: The Natural History and Genealogy of Orcinus Orca in British Columbia and Washington State (Updated Edition) by John K. B. Ford et al, 2000

Orca: The Whale Called Killer by Erich Hoyt, 1990

Links:

http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/killerwhale.htm

http://www.acsonline.org/factpack/KillerWhale.htm

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Facts

Length

Adult ♂ : 32 ft (9.6 m)

Adult ♀ : 23 feet (8.2 m)

Birth Length :6-7 ft (1.8-2.1 m)

Weight

Adult ♂ : 9 tons

Adult ♀ : 4 tons

Birth Weight : 400lbs (181 kg)

Life Expectancy

Average 70 years

Photos

The Whale Trail is a nonprofit organization in partnership with
Partners NOAA Seattle Aquarium People for Puget Sound Washington Department of Fish and Wildlife The Whale Museum National Marine Sanctuaries