Encyclopedia
The Orca
or Killer Whale is not a whale, but the largest species of the
oceanic dolphin family . They are sometimes referred to as blackfish, a group including
pilot whales,
pygmy and
false killer whales, and
melon-headed whales. It is the second-most widely distributed mammal on Earth and is found in all the world's oceans, from the frigid Arctic regions to warm, tropical seas. It is also a versatile
predator, eating
fish,
sea turtles,
seabirds,
pinnipeds,
elasmobranchs,
sirenians and even other
cetaceans. This puts the orca at the pinnacle of the marine
food chain. Orcas have been known to attack
baleen whales, in particular
gray and
Blue whales.
Orcas are magnificent
marine mammals, with a fearsome reputation that goes as far back as
Pliny the Elder's description of the species. The name "killer whale" reflects the animal's habit of attacking whales, and does not mean that orcas are a threat to humans. Aside from a boy who was charged while swimming in a bay in Alaska, there have been no confirmed attacks on humans in the wild. There have, however, been isolated reports of captive orcas attacking their handlers at
marine theme parks.
Naming
The name "orca" was originally given to these animals by the ancient
Romans, possibly borrowed from the Greek word which referred to a species of whale.
The term "orc" has historically been used to describe a large fish, whale or sea-monster. It is now considered an obsolete equivalent for "orca."
The name "killer whale" is widely used in common English. However, since the 1960s, "orca" has steadily grown in popularity as the common name to identify the species, and both names are now used - leading to confusion. The species is called
orca in most other European languages, and, as there has been a steady increase in the amount of international research on the species, there has been a convergence in naming.
A pod of orcas is capable of killing a large whale. It is commonly thought that 18th-century
Spanish sailors dubbed these creatures
asesina-ballenas, or "whale killer" for this reason. However, this title was improperly translated into English as "killer whale". The term became so prevalent that Spanish speakers commonly used its retranslation of
ballena asesina.
There are still many, especially in the research community, who prefer the original name, believing it to be an appropriate description of a species that does indeed kill many animals, including other cetaceans. These supporters of the original name point out that the naming heritage is not limited to Spanish sailors. Indeed the genus name "
Orcinus" means "from Hell" , and although the name "orca" is probably not etymologically related, the assonance might have given some people the idea that it means "whale that brings death," or "demon from hell."
The name of this species is similarly intimidating in many other languages. In
Finnish and in
Dutch it is called
miekkavalas and
zwaardwalvis respectively, which means "sword whale". To the
Haida people native to the islands of
Haida Gwaii off the coast of
British Columbia, the animal was known as
skana or "killing demon". The Japanese call them
shachi , whose
kanji character combines the radicals for fish and tiger .
A former name for the species is
grampus. This is now seldom used and should not be confused with the
Grampus genus .
Taxonomy and evolution
The orca is the sole species in the genus
Orcinus. It is one of thirty-five species in the dolphin family. Like the
Sperm Whale genus
Physeter,
Orcinus is a genus with a single, abundant species with no immediate relatives from a
cladistic point of view, thus
paleontologists believe that the orca is a prime candidate to have an anagenetic evolutionary history — that is the evolution of ancestral to descendant species without splitting of the lineage. If true, this would make the orca one of the oldest dolphin species, although it is unlikely to be as old as the family itself, which is known to date back at least five million years.
Three distinct populations
Modern research indicates that there are three distinct population types or classifications of orcas off the western coastline of North America. While each looks similar, they have distinct genetic differences, food preferences, and habits. These are the called the transient, resident and offshore types.
Transient
Transient orcas generally travel in small groups, usually up to 7 or 8 animals. Unlike residents, transients may not always stay together as a family unit. A female's first son will usually stay with her as an adult, but it is not uncommon for subsequent male offspring to disperse once they reach adulthood.
Transients are often seen cruising along the shorelines hunting for prey, which commonly includes seals, porpoises, and sea lions. Often, to avoid injury, they will disable their prey before killing and eating it. This may involve throwing it in the air, slapping it with their tails, ramming it, or breaching and landing on it. The whole process can be quite lengthy at times, seeming to be like torture for the prey, but is primarily for safety and training for the young orcas.
Female transients are characterized by dorsal fins that are pointier than those of residents. Male transients often have scarred dorsal fins, probably from injuries resulting from hunting and killing prey. Unlike residents, transients often travel and hunt in silence. The range for transient orcas is from southeast Alaska to California.
To kill large mammals like whales, transients gather in a super-pod, formed by two or three groups of transients.
Resident
Resident orcas are the most commonly sighted of the populations, often observed in coastal waters. Female residents characteristically have a rounded dorsal fin tip that terminates in a sharp corner. While nomadic, their range is much smaller, and they are known to visit certain areas consistently.
The resident orcas' diet consists primarily of fish, including
salmon and
herring, and they frequent areas where preferred fish are abundant. They are continually on the move, sometimes traveling as much as 100 miles in a day, but may be seen in a general area for a month or more. Range for resident orca pods may be as much as 800 miles or as little as 200 miles.
Resident orcas live in complex and cohesive family groups known as pods. Resident pods are generally larger than the transient and offshore pods, having up to 50 or more members. Several pods occasionally join to form what are referred to as superpods, sometimes numbering in excess of 150 animals. They can also be seen swimming with
porpoises, other
dolphins and
sea lions, which are common prey for transient orcas.
On November 15, 2005, the United States government listed the Southern Resident population of orcas an endangered species under the Endangered Species Act due to deterioration of the three pods which spend most of the year in Georgia and Haro Straits, as well as
Puget Sound in
British Columbia and
Washington state.
Offshore
Offshore orcas remain offshore, cruising the open oceans and feeding primarily on
fish,
sharks and
turtles. They have been seen traveling in groups of up to 60 animals. Currently there is little known about the habits of this population, but they can be distinguished genetically from the residents and transients. Female offshores are characterized by
dorsal fin tips that are continuously rounded.
Physical characteristics
Orcas are distinctively marked, with a black back, white chest and sides, and a white patch above and behind the eye. They have a heavy and stocky body and a large
dorsal fin with a dark gray "saddle patch" at the fin's rear. Males can be up to 9.5 m long and weigh in excess of 6 tons; it has been reported that especially large males have reached nearer 8 tons. Females are smaller, reaching up to 8.5 m and a weight of about 5 tons. The longest orca ever recorded was a male from Washington state, measuring 9.8 m . Calves at birth weigh about 180 kg and are about 2.4 m long . Unlike most dolphins, the pectoral fin of an orca is large and rounded — more of a paddle than other dolphin species. Males have significantly larger pectoral fins than females. At about 1.8 m , the dorsal fin of the male is more than twice the size of the female's, and is more of a triangle shape — a tall, elongated isosceles triangle, whereas the dorsal fin of the female is shorter and generally more curved. Nicks, cuts and scrapes on these fins, as well as distinctive features of each fin, help scientists identify individuals. There are also minor variations in physical characteristics between resident and transient orcas.
Large male orcas are very distinctive and are unlikely to be confused with any other sea creature. When seen from a distance in temperate waters, females and juveniles can be confused with various other species, such as the
false killer whale or
Risso's dolphin.
Most life history data about orcas has been obtained from long-term surveys of the population off the coasts of
British Columbia and
Washington and by monitoring captive orcas. Due to the completeness of the study and highly structured nature of the pods in this population, the information is detailed and accurate; however, transient groups and groups in other oceans may have slightly different characteristics. Females become sexually mature at around 15 years of age. From then they have periods of polyestrous cycling with non-cycling periods of between three and sixteen months. The gestation period varies from fifteen to eighteen months. Mothers calve, with a single offspring, about once every five years. In analysed resident pods, birth occurs at any time of year, with the most popular months being those in winter. Newborn mortality is very high — one survey suggested that nearly half of all calves fail to reach the age of six months. Calves nurse for up to two years, but will start to take solid food at about twelve months. Cows breed until the age of 40, meaning that on average they raise five offspring. Typically, females live to the age of fifty, but may survive well into their eighties or nineties in exceptional cases. Males become sexually mature at the age of 15, but do not typically reproduce until age 21. Males live to about 45 on average, and to 50 in exceptional cases.
Range
The orca is the second-most widely distributed mammal in the world, after the human. They are found in all oceans and most seas, including the
Mediterranean and
Arabian seas. Cooler temperate and polar regions are preferred, however. Although sometimes spotted in deep water, coastal areas are generally preferred to
pelagic environments.
The orca is particularly highly concentrated in the northeast
Pacific Basin, where
Canada curves into
Alaska, off the coast of
Iceland and off the coast of
northern Norway. They are regularly sighted in
Antarctic waters right up to the
ice-pack and are believed to venture under the pack and survive breathing in air pockets like the
beluga does. In the Arctic, however, the species is rarely seen in winter, as it does not approach the ice pack. It does visit these waters during summer.
Information for off-shore regions and tropical waters is more scarce but widespread, if not frequent; sightings indicate that the orca can survive in most water temperatures. Sightings are rare in Indonesian and Philippine waters. No estimate for the total worldwide population exists. Local estimates include 70-80,000 in the Antarctic, 8,000 in the tropical Pacific , up to 2,000 off Japan, 1,500 off the cooler northeast Pacific and 1,500 off Norway. Adding very rough estimates for unsurveyed areas, the total population could be around 100,000.
Social interaction
Fish-eating orcas in the North Pacific have a complex system of social grouping. The basic unit is the matriline, which consists of a single female and her descendants. The sons and daughters of the matriarch form part of the line, as do the sons and daughters of those daughters and so on down the
family tree. Because females can live for up to ninety years, it is not uncommon for four or even five generations to travel together. These matrilineal groups are highly stable over many years. Individuals will only split off from their matrilineal group for up to a few hours at a time in order to mate or forage. No permanent casting out of an individual from a matriline has ever been recorded. The average matriline size as recorded in northeast Pacific waters is nine animals.
Matrilines form loose aggregations called
pods, consisting on average of about 18 animals. Members of a pod all have the same
dialect and consist of closely related matriline fragments. Unlike matrilines, pods will split apart for days or weeks at a time in order to carry out foraging before joining back together. The largest recorded pod is 49 animals.
The next level of grouping is the
clan. A clan consists of those pods which have a similar dialect. Again the relationship between pods appears to be genealogical, consisting of fragments of families with a common heritage on the maternal side. Different clans can occupy the same geographical area; pods from different clans are often recorded traveling together. When resident pods come together to travel as a clan, they greet each other by forming two parallel lines akin to a face-off before mingling with each other.
The final layer of association, perhaps more arbitrary and devised by humans rather than the other very natural divisions, is called the
community and is loosely defined as the set of clans that are regularly seen mixing with each other. Communities do not follow discernible familial or vocal patterns.
In the northeast Pacific, three communities of fish-eating orcas have been identified:
- The southern community
- The northern community
- The south Alaskan community
It should be emphasized that these hierarchies are valid for resident groups only. Transient groups are generally smaller because, although they too are based on matrilines, some male and female offspring eventually disperse from the maternal group. However, transient groups still have a loose connection defined by their dialect.
The day-to-day behaviour of orcas is generally divided into four activities: foraging, travelling, resting and socializing. Orcas are generally enthusiastic in their socializing, exhibiting a wide range of
breaching,
spyhopping, tail-slapping and head-stands. All-male groups often interact with erect
penises. Whether this interaction is part of play or a display of dominance is not known.
Diet
The orca is an apex predator, and the array of species on which orcas prey is extremely diverse. Specific populations show a high degree of specialization on particular prey species. For example, some populations in the
Norwegian and
Greenland sea specialise in
herring and follow that fish's migratory path to the Norwegian coast each
autumn. Other populations in the area prey on seals.
The orca is the only cetacean species to regularly prey on other cetaceans. Twenty-two species have been recorded as preyed on, either through an examination of
stomach contents, examining
scarring on the prey's body, or from observing the orcas' feeding activity. Groups of orcas will even prey on larger cetaceans such as
minke whales,
gray whales, female and juvenile
sperm whales or young
blue whales. A group of orcas take a young whale by chasing it and its mother through the sea, wearing them out. Eventually the orcas manage to separate the pair and surround the young whale, preventing it from returning to the sea's surface to breathe. Large whales are typically drowned in this manner. Pods of female
sperm whales can sometimes protect themselves against a group of orcas by forming a protective circle around their calves with their flukes facing outwards. This formation allows them to use their powerful flukes to repel the orcas.
There has also been one recorded case of probable orca
cannibalism. A study carried out by V. I. Shevchenko in the temperate areas of the South Pacific in 1975 recorded two male orcas whose stomachs contained the remains of other orcas. Of the 30 orcas captured and examined in this survey, 11 had empty stomachs — an unusually high percentage which indicates the orcas were forced to cannibalism through a lack of food.
The diet of orcas shows substantial variation among different populations. Fish-eating populations prey on 30 species of
fish, particularly
salmon , herring, and
tuna.
Basking sharks,
oceanic whitetip sharks, and very occasionally even
great white sharks are taken for their nutrient-rich livers. Other marine mammals, including most species of
seal and
sea lion, are taken by mammal-eating populations.
Walrus and
sea otters are taken less frequently. Several species of bird are also taken, including
penguins,
cormorants and
sea gulls.
Cephalopods, such as
octopuses and a wide range of
squids, are also targets.
Possessing great physical prowess as well as intelligence, orcas use complex hunting strategies to find and subdue their prey. They will occasionally throw seals through the air in order to stun and kill them. While salmon are usually hunted by a single orca or a small group of individuals, herring are often caught using carousel feeding: the orcas force the herring into a tight ball by releasing bursts of bubbles or flashing their white undersides. The orcas then slap the ball with their tail flukes, either stunning or killing up to 10-15 herring with a successful slap. The herring are then eaten one at a time. Carousel feeding has only been documented in the Norwegian orca population and with some oceanic dolphin species. Sea lions are killed by
head-butting or by being slapped and stunned by a tail fluke.
A captive orca in
Friendship Cove discovered that it could regurgitate fish onto the surface, attract sea gulls, and eat them. Other orcas then learned the behavior by example.. Orcas at Sea World California have also been observed hunting birds..
More specialized feeding techniques are used by various populations around the world. In Patagonia, orcas feed on
South American sea lion and
elephant seal pups in shallow water, even to the extent of temporarily stranding themselves. Orcas will
spy-hop to locate seals resting on ice floes, and then create a wave to wash over the floe, causing the seal to be thrown into the water where a second orca waits to kill it. This behavior has only been recorded a few times and it is not known how often it occurs. The most recent recorded instance in April 2006 ended with the group of orcas returning the seal to the ice floe once they had shown the younger animals how to properly perform the technique.
On average, an orca eats 500 lbs. of food each day. With this huge variety of prey, and no predators other than man, the orca is very much at the top of the
food chain.
Vocal Behaviour
As with other dolphins, orcas are very vocal animals. They produce a variety of clicks and whistles that are used for communication and echolocation. The vocalization types vary with activity. While resting they are much quieter, merely emitting an occasional call that is distinct from those heard when engaging in more active behaviour.
Fish-eating resident groups of orcas in the Northeast Pacific tend to be much more vocal than transient groups living in the same waters. Scientists surmise that the main reason for this lies in the different hearing abilities of their prey. Resident orcas feed on fish, particularly Pacific salmon, a prey with poor underwater hearing that cannot detect orca calls at any significant distance. Transient orcas on the other hand feed mainly on marine mammals and occasionally on seabirds. Because all marine mammals have excellent underwater hearing, transients probably remain silent for much of the time to avoid detection by their acoustically-sensitive prey. For the same reason, mammal-hunting orcas tend to restrict their echolocation, occasionally using just a single click rather than the long train of clicks observed in other populations.
Resident pods have group-specific dialects. Each pod has its own
vocal repertoire or set of particular stereotyped underwater calls . Every member of the pod seems to know all the call types of the pod, so it is not possible to identify a single animal using voice alone; only identification of a dialectal group is possible. A particular call type might be used by only one group or shared among several. The number of call types shared by two groups appears to be a function of their genealogical relatedness rather than their geographical distance. Two groups that share a common set of ancestors but have grown apart in distance are likely to have a similar set of call types. Calls are learned behaviour traits that are copied between related individals through vocal mimicry.
See also: Whale songOrcas in history
Although only scientifically identified as a species in 1758, the orca has been known to humans since prehistoric times. The
desert culture of the
Nazca created a
Nazca line presumably representing an orca sometime between 200 BC and AD 600.
Indigenous tribes in the
Pacific Northwest of
North America such as the
Tlingit,
Haida, and
Tsimshian featured the orca prominently in their
religion and artwork.
The first description of an orca is given in
Pliny the Elder's
Natural History . The aura of invincibility around the all-consuming orca was well-established by this time. Having observed the public slaughter of a whale stranded at a harbor near
Rome, Pliny writes, "Orcas, , are the enemy of [other whales]... they charge and pierce them like warships ramming."
Probably inspired by Pliny's description, creatures by the name of
orca or "orc" have appeared throughout the history of Western literature. In
Ludovico Ariosto's epic poem
Orlando Furioso, the
orca was a sea-monster from whom the damsel Angelica was rescued by Orlando , in an episode modelled on the story of
Perseus and Andromeda. This Orca-like sea monster first appears in
English in
Michael Drayton's
Polyolbion, an epic poem about Brutus the Trojan, the mythical founder of
Great Britain. It later appears in
John Milton's epic poem
Paradise Lost is an epic poem [i] by the 17th-century English [i] poet John Milton [i]. ...
; book 10 speaks of "The haunt of Seales and Orcs, and Sea-mews clang."
Orcas and modern man
Hunting
Orcas were targeted in commercial
whaling for the middle part of the twentieth century once stocks of larger species had been depleted. Commercial hunting of orcas came to an abrupt halt in 1981 with the introduction of a moratorium on all whaling.
The greatest hunter of orcas was
Norway, which took an average of 56 animals per year from 1938 to 1981.
Japan took an average of 43 animals from 1946 to 1981. . The
Soviet Union took a few animals each year in the Antarctic, with the extraordinary exception of the 1980 season when it took 916.
Today, no country carries out a substantial hunt. Japan usually takes a few individuals each year as part of its controversial program of
scientific research as specified in IWC constitution. A similarly small level of subsistence whaling is carried out by
Indonesia and
Greenland. As well as being hunted for their meat, orcas have also been killed because of competition with fishermen. In the 1950s the
United States Air Force, at the request of the Government of Iceland, used
bombers and
riflemen to slaughter orcas in Icelandic waters because they competed with humans for fish. The operation was considered a great success at the time by fishermen and the Icelandic government. However, many were unconvinced that orcas were responsible for the drop in fish stocks, blaming overfishing by humans instead. This debate has led to repeated studies of North Atlantic fish stocks, with neither side in the whaling debate giving ground since that time.
Orcas are also occasionally killed out of fear of their reputation. No human has ever been attacked by an orca in the wild, but sailors in Alaska shoot the animal occasionally out of concern for their own lives. This fear has generally dissipated in recent years due to better education about the species, including the appearance of orcas in
aquariums and other aquatic attractions.
Co-operating with humans
More unusually, orcas have also be known to co-operate with humans in the hunting of whales. One famous incidence of this was near the port of Eden in South-Eastern
Australia in the 1920s. A pod of orcas, led by a dominant male called Old Tom, would assist whalers in hunting
baleen whales. The orcas would find the target whales, shepherd them into Twofold Bay and then alert the whalers to their presence and often help to kill the whales. In return the whalers allowed the orcas to eat the tongue and lips of the whale before hauling it ashore.
Captivity
The orca's intelligence, trainability, striking appearance, playfulness in captivity and sheer size have made it a popular exhibit at aquariums and various aquatic theme parks. The first orca capture and display occurred in
Vancouver in 1964. Over the next 15 years around 60 or 70 orcas were taken from Pacific waters for this purpose. In the late 1970s and the first half of the 1980s, orcas were generally taken from Icelandic waters . Since that time, orcas have been successfully bred in captivity and wild specimens are considerably rarer. Orcas in captivity may develop pathologies such as
dorsal fin collapse, seen in 60-90% of captive males.
Several theories exists as to why the dorsal fin collapse occurs, namely that the cartilage that holds the fin erect is not yet strong enough to support the fin when the orca is placed in captivity. The hardening of the cartilage occurs in late adolescence, in which the orca spends much time in deep ocean waters, and it is theorized that the pressure the water exerts on the fin allows it to remain supported while the cartilage hardens. In captivity, however, the tank the whales reside in lack sufficient water pressure to produce this effect, and the fin collapses before the cartilage that would support it in nature solidifies. Another theory exists that states that the whale is almost always in a state of turning in a tank, since it is not large enough to allow swimming in one direction for any normal duration. The constant turning exerts pressure on the dorsal fin, which in turn causes it to collapse.
There have been incidents with orcas in captivity attacking humans. In 1991, a group of 3 orcas killed a trainer named Keltie Byrne at Sealand in
Victoria, British Columbia , apparently not knowing she could not survive underwater. In 1999, at the
SeaWorld park in
Orlando, Florida, one of the same orcas allegedly killed a
tourist who had sneaked into the orca's pool at night. In late July 2004, during a show at the SeaWorld park in
San Antonio, Texas, an orca pushed its trainer of ten years underwater and barred the way to the rim of the pool; the trainer could only be rescued from the animal after several minutes.
One of the more infamous incidents involving orca aggression took place in August 1989, when a dominant female orca, Kandu V, struck a newcomer orca, Corky II, with her mouth during a live show. Corky II had been imported from Marineland California just months prior to the incident. According to reports, a loud smack was heard across the stadium. Although trainers tried to keep the show rolling, the blow severed an artery near Kandu V's jaw, and she began spouting blood. The crowd was quickly ushered out, and after a 45-minute hemorrhage, Kandu V died. Opponents of these shows see these incidents as supporting their criticism.
SeaWorld continued to be under criticism from the Born Free Foundation over its continued captivity of the orca Corky II, who they want returned to her family, the A5 Pod, a large pod of orcas in
British Columbia,
Canada .
Orcas in captivity have vastly reduced life expectancies, on average only living into their 20s. In the wild, females may live into their 80s. The captive environment also bears no resemblance to their wild habitat, and the social groups that the orcas are put into are completely foreign to those found in the wild . Critics claim that captive life is stressful due to small tanks, false social groupings and chemically-altered water. Organisations such as the WSPA and the Whale and Dolphin Conservation Society campaign against the captivity of orcas. It should be noted that the technology to track orcas in the wild has only recently been developed. In the past, scientists have used visual identification of the whales and estimated their ages. While this does provide ideas of ages, it is not 100% accurate, which means the ages of most whales are merely estimated. The only whales whose ages are known for certain are those whose births have been recorded and those born in captivity.
Marine parks with orcas
- SeaWorld San Diego, California: 7 orcas -
- SeaWorld Orlando, Florida: 8 orcas -
- Seaworld San Antonio, Texas: 6 orcas -
- Miami Seaquarium, Florida: 1 orca - Lolita
- Six Flags Marine World, Vallejo, California: 1 orca - Shouka
- Marineland Niagara Falls, Ontario, Canada: 3 orcas -
- Marineland Antibes, France: 5 orcas -
- Loro Parque Tenerife, Canary Islands: 4 orcas -
- Mundo Marino, Argentina: 1 orca - Kshamenk
- Kamogawa Sea World, Japan: 6 orcas -
- Taiji Whaling Museum, Japan: 1 orca - Nami
- Port of Nagoya public Aquarium, Japan: 1 orca - Ku
- Izumito Sea-Paradise, Japan: 1 orca - Asuka
Popular culture
As late as the 1970s, orca were depicted negatively in fiction as ravenous predators whose behavior caused heroes to interfere to help a prey animal escape. The poorly-received
film Orca features the story of a male orca going on a vengeful rampage after his pregnant mate is killed by humans. Many consider this an obvious attempt to duplicate the success of
Jaws, although it can also be considered to show the animals as being much more like humans, with intelligence and a great capacity for love and tenderness as well as vengeance.
However, the increased research of the animal and its popularity in public venues brought about a dramatic rehabilitation of the animal's public image to that of a respected predator that poses little actual threat to humans, much as the North American Wolf's image has been changed.
The film
Free Willy focused on the quest for freedom for a captive orca. The orca starring in the movie, Keiko, was originally captured in
Icelandic waters. After rehabilitation at the Oregon Coast Aquarium in Newport, Oregon, he was later returned to the waters of the
Nordic countries, his native habitat, but continued to be dependent on humans until he died of
pneumonia in December 2003.
A coast-
Haida styled orca has also been the logo of the
NHL's
Vancouver Canucks hockey franchise since they changed jerseys in the 1996-97 season. This logo is an orca breaking through cracked ice, in the shape of a "C". This is likely a reference to
OrcaBay, the company which owns the team, or because orcas are often seen on the west coast where Vancouver is located. The team mascot is also an orca named "Fin".
Environmental threats
The
Exxon Valdez was the original name of an oil [i] tanker [i] owned by the former Exxon [i] ...
oil spill had an adverse effect on orcas in Prince William Sound and the Kenai Fjords region of Alaska. One resident pod was caught in the spill; though the pod successfully swam to clear water, eleven members of the pod disappeared in the following year. The spill had a long-term effect in reducing the amount of available prey, such as salmon, and has thus been responsible for a local population decline. In December 2004, scientists at the North Gulf Oceanic Society said that the AT1 transient population of orcas, now only numbering 7 individuals, has failed to reproduce at all since the spill. This population is expected to go extinct.
.
Like other animals at the highest trophic levels of the
food chain, the orca is particularly susceptible to poisoning via accumulation of
Polychlorinated biphenyls in the body. A survey of animals off the
Washington coast found that PCB levels in orcas were higher than those in
harbour seals in
Europe that have been sickened by the chemical. Samples from the blubber of orcas in the
Norwegian Arctic show higher levels of PCBs,
pesticides and brominated flame-retardants than in
Polar bears. However, no direct evidence of sickness in orcas has been found. The most likely effect, if any, would be a reduced rate of reproduction or decreased ability to fight off disease . On November 15, 2005, the United States government listed the Southern Resident population of orcas as an endangered species under the Endangered Species Act due to deterioration of the three pods which spend most of the year in Georgia and Haro Straits, as well as
Puget Sound in British Columbia and Washington.
Other environmental pressures facing orcas include extensive
whale watching which some research indicates changes orca behavior. Heavy ship noise can interfere with the acoustic communication and echolocation of orcas.
Famous Orcas
- Keiko — performed in the first of the three Free Willy movies.
- Shamu — performs along with Baby Shamu and Grandba
