Killer Whale (Orcinus orca)

	Killer Whales (Orcinus orca) Photo: NOAA

	Did You Know? · Killer whales can grow as long as 32 feet (9.8 m) and can weigh as much as 22,000 pounds (10,000 kg)! · Killer whales are actually a member of the dolphin family, Delphinidae. · Killer whales are highly social and often travel in groups of up to 40-50.

	Orphan Orca: Saving Springer video Credit: NOAA

Status
Killer whales are widely distributed in the world's oceans, but the status of most populations of killer whales is unknown. However, only two receive special protections under Federal law:
ESA Endangered - Southern Resident population
MMPA Depleted - AT1 Transient population, Southern Resident population

Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Orcinus
Species: orca

Species Description

Weight:	males can weigh up to 22,000 pounds (10,000 kg); females can weigh up to 16,500 pounds (7,500 kg)
Length:	males can reach 32 feet (10 m); females can reach 28 feet (8.5 m)
Appearance:	black on top with white undersides and white patches near their eyes
Lifespan:	males typically live for about 30 years, but can live as long as 50-60 years; females typically live about 50 years,but can live as long as 80-90 years
Diet:	diet is often geographic or population specific and varies from fish to other marine mammals to sharks
Behavior:	highly social animals; rely on underwater sound for orientation, feeding, and communication; make whistles and pulsed calls, believed to be used for communication and during social activities

Killer whales (Orcinus orca) are the most widely distributed cetacean (e.g., whales, dolphins, and porpoises) species in the world and likely represent the most widely distributed mammal species in the world.

Killer whales are generally considered monotypic (belonging to one species); however, over the years, scientists have proposed several new species, such as dwarf forms in Antarctic waters.¹ Genetic studies and morphological evidence have led many cetacean biologists to now consider the existence of multiple species or subspecies of killer whales worldwide.

Killer whales have a distinctive color pattern, with black dorsal and white ventral portions. They also have a conspicuous white patch above and behind the eye and a highly variable gray or white saddle behind the dorsal fin.

The species shows considerable size "dimorphism". Adult males develop larger pectoral flippers, dorsal fins, tail flukes, and girths than females.

Most information on killer whale life history and biology is from long-term studies of several populations in the eastern North Pacific.

Sexual maturity of female killer whales is achieved when the whales reach lengths of approximately 15-18 feet (4.6 m-5.4 m), depending on geographic region. The gestation period for killer whales varies from 15-18 months, and birth may take place in any month. Calves are nursed for at least 1 year, and may be weaned between 1 and 2 years of age. The birth rate for killer whales is not well understood, but, in some populations, is estimated as every 5 years for an average period of 25 years.

The diet of killer whales is often geographic or population specific:

In the eastern North Pacific, the "resident" killer whale populations mainly feed on
- salmonids, such as Chinook salmon and chum salmon
"Transient" populations in the eastern North Pacific feed on marine mammals, such as (in order of frequency of observation)
- harbor seals
- Dall's porpoises
- harbor porpoise
- California sea lions
- gray whale calves
- Steller sea lions
- elephant seals
- minke whales
- various other species of pinnipeds and cetaceans
Off the coast of Norway, some killer whales feed mainly, often in a coordinated manner, on
- herring
- other schooling fish
In waters off New Zealand, some killer whales feed on
- stingrays
- sharks
In Antarctic waters, there are different types of killer whales. They have each been observed feeding off of various species:
- type 'A' killer whales feed on minke whales
- type 'B' killer whales feed on seals within the seasonal ice pack
- type 'C' killer whales feed on Antarctic toothfish (Dissostichus mawsoni) and other fish species

Killer Whale pod
(Orcinus orca)
Photo: NOAA

Killer whales are highly social animals that occur primarily in relatively stable social groups that often range in size from 2 to 15 animals. Larger groups (rarely as large as several hundred individuals) occasionally form, but are usually considered temporary groupings of smaller social units that probably congregate near seasonal concentrations of prey, for social interaction, or mating. Single whales, usually adult males, also occur in many populations. Differences in spatial distribution, abundance, behavior, and availability of food resources probably account for much of the variation in group size among killer whale populations.

Like all cetaceans, killer whales depend heavily on underwater sound for orientation, feeding, and communication. Killer whales produce three categories of sounds:

clicks
whistles
pulsed calls

Echolocation clicks are believed to be used primarily for navigation and discriminating prey and other objects in the surrounding environment, but are also commonly heard during social interactions and may have a communicative function.

Whistles and pulsed calls are believed to be used for communication and during social activities. Whistles are frequency modulated (pitch changes with time) sounds with multiple harmonics. Pulsed calls are the most common type of vocalization in killer whales and resemble squeaks, screams, and squawks to the human ear. Most calls are highly distinctive in structure, and are characterized by rapid changes in tone and pulse repetition rate. Many calls are repeated, with some clicks reaching up to 4,000 or more pulses per second.²

Killer whales of different populations have specific vocalization types. In addition, even within the same population, dialects are known to exist among different pods of "resident" populations in the eastern North Pacific.³

In the eastern North Pacific Ocean, three distinct forms, or types, of killer whalesare recognized.⁴

residents
transients
offshores

The three types differ in morphology, ecology, behavior, and genetics. A recent genetic study⁵ suggests the transient type has been separated from all other killer whales for approximately 750,000 years and might represent a separate species or subspecies. All three types of killer whales share at least part of a home range, yet they are not known to intermix with one another. The resident and transient types both have multiple populations within their range.

Resident Killer Whales are noticeably different from both transient and offshore forms. The dorsal fin is rounded at the tip and curved and tapering, or "falcate". Resident whales have a variety of saddle patch pigmentations with five different patterns recognized. They've been sighted from California to Russia. Resident whales primarily eat fish.

Resident killer whales in the North Pacific consist of the following populations:

Southern residents
Northern residents
Southern Alaska residents
Western Alaska North Pacific residents

Resident type killer whales occur in large social groups termed "pods," which are defined to be groups of whales that are seen in association with one another greater than 50% of the time. The pods represent collections of matrilines (a matriarch and all her descendents), which have been found to be the stable social unit.

The Southern Resident killer whale ("Southern Resident") population contains three pods, considered one stock under the Marine Mammal Protection Act (MMPA) and as a "distinct population segment" (therefore, "species") under the Endangered Species Act (ESA):

J pod
K pod
L pod

Their range during the spring, summer, and fall includes the inland waterways:

Puget Sound
Strait of Juan de Fuca
Southern Georgia Strait

Their occurrence has been documented in the coastal waters off of:

Oregon
Washington
Vancouver Island
central California
Queen Charlotte Islands

Relatively little is known about the winter movements and range of the Southern Resident stock. Southern Residents have not been observed associating with other resident whales, and genetic data suggest that Southern Residents rarely, if ever, interbreed with other killer whale populations.

Transient Killer Whales occur throughout the eastern North Pacific, and have primarily been studied in coastal waters. Their geographical range overlaps that of the resident and offshore killer whales. The dorsal fin of transient whales tends to be more erect (straighter at the tip) than those of resident and offshore whales.⁶ Saddle patch pigmentation of transient killer whales is restricted to two patterns, and never has the large areas of black pigmentation intruding into the white of the saddle patch that is seen in resident and offshore types. Transient type whales are often found in long-term stable social units that tend to be smaller than resident social groups (e.g., fewer than 10 whales); these social units do not seem as permanent as matrilines are in resident type whales. Transient killer whales feed nearly exclusively on marine mammals.⁷

Offshore Killer Whales are similar to resident whales, but can be distinguished generally--but these characteristics need to be further quantified⁸--by features such as their:

fins, which appear more rounded at the tip with multiple nicks on the trailing edge
smaller overall size
tendency for males and females to be more similar in size (less "sexual dimorphism")

Offshores have the largest geographic range of any killer whale community in the northeastern Pacific and often occur 9 miles (15 km) or more offshore, but also visit coastal waters and occasionally enter protected inshore waters. Animals typically congregate in groups of 20-75 animals with occasional sightings of larger groups up to 200 whales. They are presumed to feed primarily on fish, though they have been documented feeding on sharks. It has even been hypothesized that they may be shark specialists, but further observations are needed to confirm this theory. Genetic analyses indicate that offshore killer whales are reproductively isolated from other forms.

Southern Resident Killer Whale Critical Habitat
(click for larger view PDF)

Killer Whale Range Map
(click for larger view PDF)

Habitat
Killer whales are most abundant in colder waters, including Antarctica, Norway, and Alaska. Killer whales can also be fairly abundant in temperate waters. Killer whales occur, though at lower densities, in tropical, subtropical, and offshore waters.

Following their listing as an endangered species in 2005, critical habitat was designated in November 2006 for the Southern Resident population.

Distribution
Killer whales are the most widely distributed marine mammals. They are found in all parts of the oceans and in most seas from the Arctic to the Antarctic.

In the North Pacific Ocean, killer whales are often sighted in all parts of Alaska, including:

Bering Sea
Aleutian Islands
Prince William Sound
southeastern Alaska

They are also often sighted in other areas of the North Pacific Ocean, such as:

nearshore and intercoastal waterways of British Columbia, Canada and Washington State
along the U.S. Pacific coast in Washington, Oregon, and California
along the Russian coast in the Bering Sea and the Sea of Okhotsk
on the eastern side of Sakhalin and the Kuril Islands

In the North Atlantic Ocean, sightings of killer whales are commonly documented:

up to the pack ice edge in Norwegian waters and around Iceland.

In the South Atlantic and Pacific Oceans, killer whales are frequently sighted

along the pack ice of Antarctica
off the coasts
- Patagonia
- southern Argentina
- New Zealand

Killer Whale spyhopping
(Orcinus orca)
Photo: NOAA

Population Trends
Scientific studies have revealed many different populations/ stocks--or even potentially species or subspecies--of killer whales worldwide. These different populations/stocks of killer whales may exhibit different dietary needs, behavior patterns, social structures, and habitat preferences. Therefore, interbreeding is not expected to occur between different populations/stocks, in spite of the overlap between home ranges. Because of its cosmopolitan distribution, there is no global population assessment for killer whales.

Little information is available on the historical abundance of killer whales worldwide. Nevertheless, it is likely that many populations have declined significantly since 1800 in response to greatly diminished stocks of fish, whales, and pinnipeds (seals and sea lions) in the ocean. The population size of killer whales is difficult to measure in many areas because of their general scarcity as well as their widespread and often unpredictable movement patterns.

During the past few decades, populations have been surveyed primarily through

photo-identification studies
line-transect counts

Photo-identification catalogs for killer whales were first established in the early 1970s for the resident communities of Washington and British Columbia and have since been initiated for most areas where population studies have been undertaken.

Line-transect surveys from ships or aircraft generally occur in large areas of open ocean where photo-identification is impractical. However, this technique cannot be used for gathering most demographic data, such as age of sexual maturity.

As top-level predators, killer whales occur in low densities throughout most of their geographic range. Densities are typically much greater in colder waters than in tropical regions. One estimate put the worldwide population of killer whales at over 100,000 animals.⁹ However, the most recent estimate revised this figure to a minimum of about 50,000 animals.¹⁰ In the northeastern Pacific, from California to the western Aleutian Islands and Bering Sea, at least 2,250-2,700 resident, transient, and offshore whales are currently thought to exist.

The Southern Resident Killer Whale population is currently estimated at about 88 whales, a decline from its estimated historical level of about 200 during the mid- to late 1800s. Beginning in about 1967, the live-capture fishery for oceanarium display removed an estimated 47 whales and caused an immediate decline in Southern Resident numbers.¹¹ The population fell an estimated 30% to about 67 whales by 1971.¹² By 2003, the population increased to 83 whales.¹³ Due to its small population size, NMFS listed this segment of the population as endangered under the Endangered Species Act (ESA). This population is also listed as depleted under the MMPA.

The AT1 Transient Killer Whale group was one of the most frequently encountered groups and was sighted year-round in Prince William Sound in the 1980s. The group was made up of at least 22 members; however, the AT1 group has been reduced by more than half since the 1989 Exxon Valdez oil spill. Several confirmed deaths of AT1 group members were recorded since the 1990s, while other missing animals are presumed dead.¹⁴ In June 2004, NMFS designated the AT1 group of transient killer whales as a depleted stock under the MMPA.

The AT1 Transient Killer Whale group was one of the most frequently encountered groups and was sighted year-round in Prince William Sound in the 1980s. The group was made up of at least 22 members; however, biologists in Alaska have seen no new calves since the AT1 group was first identified in 1984. The AT1 group has been reduced by more than half since the 1989 Exxon Valdez oil spill. Several confirmed deaths of AT1 group members were recorded since the 1990s, while other missing animals are presumed dead.¹⁴ In June 2004, NMFS designated the AT1 group of transient killer whales as a depleted stock under the MMPA. Scientists estimate there are 7 killer whales remaining in this group.

Threats
Although all killer whales are protected under the MMPA--and some are protected under the ESA--and they have not been commercially hunted or captured in the past 40 years within the U.S. waters, historic live capture for aquarium display and culling for depredation of fisheries reduced some killer whale populations, especially the Southern Resident stock.

Today, these killer whales still face many threats caused by human activities, such as

contaminants (e.g., PCBs)
depletion of prey due to overfishing and habitat degradation
ship collisions
oil spills

Additional threats may also include

disturbance from such activities as noise from industrial and military activities
entanglement in fishing gear
whale-watching

Outside U.S. waters, directed catch of killer whales still occurs, though these levels are presumed low.

Conservation Efforts
A final recovery plan for the Southern Resident killer whales [pdf] [1.7 MB] was published on January 24, 2008. The Recovery Plan for Southern Resident Killer Whales was based on the Proposed Conservation Plan for Southern Resident Killer Whales (under the MMPA), after comments on it were addressed and required ESA elements incorporated into it. The proposed ESA recovery plan was released for comment in November 2006. Public and peer review comments as well as new research results and references were then incorporated into the final Southern Resident recovery plan.

Conservation measures in the plan include:

Prey Availability: Support salmon restoration efforts in the region including habitat, harvest, and hatchery management considerations and continued use of existing NMFS authorities under the ESA and Magnuson-Stevens Fishery Conservation and Management Act to ensure an adequate prey basis.
Pollution/Contamination: Clean up existing contaminated sites, minimize continuing inputs of contaminants harmful to killer whales, and monitor emerging contaminants.
Vessel Effects: Continue evaluating and improving guidelines for vessel activity near Southern Resident and evaluate the need for regulations or protected areas.
Oil Spill: Prevent oil spills and improve response preparation to minimize effects on Southern Resident and their habitat in the event of a spill.
Acoustic Effects: Continue agency coordination and use of existing MMPA mechanisms to minimize potential impacts from anthropogenic sound.
Education and Outreach: Enhance public awareness, educate the public on actions they can participate in to conserve killer whales, and improve reporting of Southern Resident sightings and strandings.
Respond to Sick, Stranded, Injured Killer Whales: Improve responses to live and dead killer whales to implement rescues, conduct health assessments, and determine causes of death to learn more about threats and guide overall conservation efforts.
Transboundary and Interagency Coordination: Coordinate monitoring, research, enforcement, and complementary recovery planning with international, Federal, and state partners.
Research and Monitoring: Conduct research to facilitate and enhance conservation efforts. Continue the annual census to monitor trends in the population, identify individual animals, and track demographic parameters.

Conservation of the Southern Resident stock is a long-term effort that requires the cooperation and coordination of the Washington and British Columbia communities. The Plan was developed with input from a variety of stakeholders, including federal and state agencies, tribes, non-profit groups, industries, the academic community, and concerned citizens.

Regulatory Overview
All marine mammals, including killer whales, are protected in the United States under the MMPA. The AT1 stock of the North Pacific transient killer whale was designated as depleted under the MMPA after its drastic decline after the 1989 Exxon Valdez oil spill in Prince William Sound, Alaska.

In November 2005, the Southern Resident population was listed as endangered under the ESA and, thus, as depleted under the MMPA. NMFS designated critical habitat in November 2006 for the Southern Resident population.In July 2009, NMFS' Northwest Region proposed vessel regulations to protect the Southern Resident population; the final rule on vessel regulations in Washington state [pdf] (76 FR 20870) published in the Federal Register in April 2011. In April 2010, NMFS initaited a 5-year review of the Southern Residents.

Key Documents
(All documents are in PDF format.)

Title	Federal Register	Date
Vessel regulations in Washington state for Southern Residents	76 FR 20870	04/14/2011
5-year Review Initiated for Southern Residents	75 FR 17377	04/06/2010
Proposed killer whale vessel regulations in Washington state	74 FR 37674	07/29/2009
Recovery Plan for Southern Residents	73 FR 4176	01/24/2008
Critical Habitat Designation for Southern Residents	71 FR 69054	11/29/2006
ESA Listing Rule for Southern Residents	70 FR 69903	11/18/2005
Proposed Conservation Plan for Southern Residents	70 FR 57565	10/03/2005
Status Review of Southern Residents	n/a	12/2004
Depleted Designation of AT1 Transients	69 FR 31321	06/03/2004
Depleted Designation for Southern Residents	68 FR 31980	05/29/2003
Stock Assessment Reports	n/a	various

More Information

Footnotes and Further Reading

Updated: September 23, 2011