Orcas: Study of Habitat, Types and Social Behaviours
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Published: Mon, 23 Apr 2018
Called “whale killer” by the Spanish sailors, and also as “killing demon” to The Haida of British Columbia. Whatever it called, mariners have long been astonished by the talent of the large black – and – white dolphins known as Orcas, or killer whales. The biggest members of the dolphin family, Orcas are one of the most iconic species of cetacean which other marine mammals like whales and porpoises. They are apex predators with no other animals that hunt them, except for humans. Killer whales as a species have a sundry diet, although individual population often specialize in particular types of prey. Some feed exclusively on fish, while other hunt marine mammal. Killer whales can be found though out all oceans from the tropical seas to the freezing Arctic and Antarctic.
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There are three types of orcas may be recognizable enough to be considered as different subspecies. The three types may differ in genetics, behaviour, morphology, and ecology. A genetic study suggests that these subspecies has been separated from others killer whales for approximately 750,000 years, which evolution cause them to change separately from each other and creating distinctly physical appearance from each other’s.
- Main Types
- Residents Killer Whales
The most commonly sighted of the three populations. 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 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 population contains three pods–J, K, and L 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).
Their range during the spring, summer, and fall includes the inland waterways of Puget Sound (Washington state),
Strait of Juan de Fuca (boundary between the United States and Canada), and Southern Georgia Strait (between Vancouver Island and British Columbia, Canada).
Their occurrence has also been documented in the coastal waters off of, Oregon, central California, and 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.
- Transients Killer Whales
These subspecies occur throughout the eastern North Pacific, and have primarily been studied in coastal waters. Their geographic range overlaps that of the resident and offshore killer whales. The dorsal fin of transient whales tends to be 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 the large areas of black colour don’t mix 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 of less than 10 whales, smaller than resident social groups. Transient killer whales feed nearly exclusively on other marine mammals. Transients are also referred to as Bigg’s killer whale in honour of Michael Bigg, who was a Canadian marine biologist who is recognized as the founder of modern research on killer whales. The term has become increasingly common and may eventually replace the transient label.
- Offshores Killer Whales
A third population of killer whales in the northeast Pacific was discovered in 1988. They are similar to resident whales, but can be distinguished generally by features such as their rounded fins with multiple nicks on the edge, smaller overall size, and 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 north-eastern Pacific and often occur 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. Genetic analyses indicate that offshore killer whales are reproductively isolated from other forms of killer whales.
- Antarctic Type
- Antarctic (type A) Killer Whale
A large (perhaps to 9.5m), black and white form killer whale. It migrate to Antarctica during austral (summer) where it forages in open (ice free) waters and feeds mainly on minke whales and occasionally elephant seals. During the winter, It probably migrates to lower latitudes, perhaps to the tropics.
- Pack Ice (large type B) Killer Whale
A large, two-toned gray and white form with dark cape pattern and very large eye patch. Often have yellowish cast due to diatoms. Circumpolar, it forages mainly in loose pack ice where it preys on ice seals or Weddell seals, which groups wave-wash off ice floes by creating waves with their tails. Occasionally take Minke whales.
- Gerlache (small type B) Killer Whale
A medium sized, two-toned gray and white form with dark cape pattern and large white eye patch. Often appears yellowish due to diatom infestation. Common around Antarctic Peninsula, especially in Gerlache Strait. Preferred prey unknown but has been feeding on penguins on numerous occasions.
- Ross Sea (type C) Killer Whale
The smallest killer whale known. Adults males reach only 6m. A two-toned gray and white form with a dark grey cape, and often colored yellowish by diatom film. Eye patch is distinctively narrow and slanted. Occurs deep in the pack ice im eastern Antarctica and feeds on fish. Especially common in the Ross Sea.
- Subantarctic (type D) Killer Whale
Recently describe form, known from a dozen sightings. Easily recognized by its tiny eye patch, with rounded head, swept back and pointy dorsal fin. Distributed in subantarctic water and sometimes associated with islands. Preferred prey unknown but reportedly steals fish off long-lines.
A typical killer whale distinctively bears a black back, white chest and sides, and a white patch above and behind the eye. Calves are born with a yellowish or orange tint, which fades to white. It has a heavy and robust body with a large dorsal fin up to 2 m (6.6 ft) tall. Behind the fin, it has a dark grey “saddle patch” across the back. Antarctic killer whales may have pale grey to nearly white backs. Adult killer whales are very distinctive and are not usually confused with any other sea creature. The killer whale’s teeth are very strong and covered in enamel. Its jaws are a powerful gripping apparatus, as the upper teeth fall into the gaps between the lower teeth when the mouth is closed. The front teeth are inclined slightly forward and outward, thus allowing the killer whale to withstand powerful jerking movements from its prey while the middle and back teeth hold it firmly in place.
Killer whales are the largest extant members of the dolphin family. Males typically range from 6 to 8 metres (20 to 26ft) long and weigh in excess of 6 tonnes (5.9 long tons; 6.6 short tons). Females are smaller, generally ranging from 5 to 7m (16 to 23ft) and weighing about 3 to 4 tonnes (3.0 to 3.9 long tons; 3.3 to 4.4 short tons).
Killer whales have good eyesight above and below the water, excellent hearing, and a good sense of touch. They have exceptionally sophisticated echolocation abilities, detecting the location and characteristics of prey and other objects in their environments by emitting clicks and listening for echoes.
- Life cycle
Female orcas mature usually around age 15. Mothers calve, with usually a single offspring, about once every five years after a 17-month pregnancy. In resident pods, births occur at any time of year, although winter is the most common. Mortality is extremely high during the first six to seven months of life, when 37–50% of all calves die. Killer whales are protective of their young, and other adolescent females often assist the mother in caring for them.
Females breed until age 40, meaning on average they raise five offspring. The lifespans of wild females average 50 years, with a maximum of 80–90 years. The females are known to go through menopause and live for decades after they have finished breeding.
Males sexually mature at the age of 15, but do not typically reproduce until age 21. Wild males live around 29 years on average, with a maximum of 50–60 years. Captive killer whale lifespans are typically significantly shorter, usually less than 25 years; however, numerous individuals are alive in their 30s, and a few have reached their 40s.
- Range and habitat
The killer whale is the most cosmopolitan of all cetaceans and may be the second-most widely-ranging mammal species on the planet, after humans (Rice 1998). Killer whales can be seen in virtually any marine region, from the equator to polar waters. Although they are generally more common in near shore areas and in higher-productivity areas and/or higher latitudes, there appear to be no hard and fast restrictions of water temperature or depth on their range. The distribution extends too many enclosed or partially-enclosed seas, such as the Mediterranean Sea, Sea of Okhotsk, Gulf of California, Gulf of Mexico, Red Sea, and Persian Gulf. However, there are only extralidmital records from the Baltic Sea and no records from the Black Sea.
Killer whales may occur in virtually any marine or estuarine habitat but are most common in areas of high marine productivity, particularly at higher latitudes and near shore (Dahlheim and Heyning 1999; Forney and Wade 2006). Sightings range from the surf zone to the open sea. Movements can be extensive. For instance, some killer whales have been documented to have moved between Alaska and central California, a distance of more than 2000 km. In the Antarctic, they readily enter areas of floe ice in search of prey (Pitman and Ensor 2003). Killer whales in some areas congregate seasonally in coastal channels to forage and occasionally enter river mouths.
Although the available data are far from complete, abundance estimates for the areas that have been sampled provide a minimum worldwide abundance estimate of about 50,000 killer whales. It is likely that the total abundance is higher, because estimates are not available for many high-latitude areas of the northern hemisphere and for large areas of the South Pacific, South Atlantic, and Indian Ocean. However, this population abundance refers to several forms of killer whales that may be recognized as different species or subspecies in the future (Reeves et al. 2004).
- Social structure
Unlike other animals, orcas or killer whales are momentous for their complex societies. Besides human, the only other animals with this complex socials structure are elephants and due to their complexity, many of the marine experts are unease about how humane it is to keep orcas in captive situations.
Resident killer whales have a complex yet stable social grouping system. Different from other mammal species, resident live their mother for their entire lives. As females could reach age of 90, they could be as many as four generation traveling together forming matrilineal which is very stable. Individuals sometimes separate for only a few hours at a time for mating or forage.
Pods, form from loose aggregations of closely related matrilineal which commonly consist of one to four or five matrilineal. Pods may separate for weeks or months at a time, unlike matrilines. One research shows that DNA testing shows that resident males almost always mate with females from other pods.
The next rank of resident socials structure is Clans which composed of pods with same dialect. They often mingling with pods from different clans as the clan ranges overlap. The final rank of relationship is called community. It is interpreted as a set of clans that frequently commingle, although they do not share vocal patterns.
Same as other cetaceans, orcas depends heavily on underwater sounds for orientation, feeding and communication. Clicks, whistles and pulsed called are the three categories of sounds they produced. Clicks are believed to be used primarily for navigations and discerning prey and other object in the surrounding environment. It is also commonly heard during social interactions.
Orcas dialects are different between pods due to the similarity of the call differentiate one pod from the other. Dialects are usually generated within the orca’s birth pod. Differences between dialects can be not only between pods but between ecotypes, which are specific populations within a species that have a geographical and genetic variability.
After the sperm whale, orcas have the second-heaviest brains among marine mammals. They have been trained in captivity and described as intelligent. Orcas also often impersonate others, and seem to intentionally teach skills to their younger pod members. People and marine biologist have interacted closely with orcas numerous times and said that the orcas show playfulness, curiosity, and ability to solve problems.
As apex predators, there is nothing that can stop them from hunting and preying on everything. They will eat anything, but not always willingly.
- Hunting strategies and prey
The main diet of resident orcas but they will hunt and eat smaller and deeper-dwelling fish if they have to. The favourite of the resident orcas is the Chinooks salmons as it has been observed that it make up 65% of all the salmons consumed. Resident also eats lingcod, halibut, squid and other types of fish.
Better known as killer whales, it’s this prey which gave them the notorious name. Orcas have dined on whales in all shape and sizes. They will attack eventually anything even the largest animal in the world, the blue whale. But the common victim to this “wolves of the sea” is the Minke whale. Other whales documented to be attacked by orcas are Fin, Humpbacks, Grey, Bowhead, Sei and even the fearsome Sperm whales. Orcas also often hunt the fragile whale calf. Individuals of the pods take turn tiring the calf by blocking it form re-surfacing to breath witch will slowing suffocate and eventually drowning the calf, while the other distract the mother. They often will only eat the lips and tongue, and let the whale body to sink. In the far north, belugas and narwhals are also have been preyed upon.
- Porpoises and dolphins
Porpoises are faster swimmer than the orcas making it harder to catch. Hunted by the Transient’s attacks, they cooperate by letting one orca to chase the porpoises to flea directly into the pod. Once caught, the orcas will launch the porpoises out of the water by hitting them with their tails. Once too injured to swim away, the orcas will strip the porpoises down to their bones and lungs. Same technique has been observed to be used on bottlenose dolphins. Orcas also use direct chase to catch the dolphins.
With great intelligent, the orcas have figured out to goes above and beyond other oceans notorious predator, the sharks. There even recorded documentary of the Great White falling victim to a pod of orcas. They use their 5-inch-long teeth to grab hold of the sharks fins and turn it upside down underwater witch cause tonic immobility that leaving the shark to suffocate within minutes as they need to move to breath. After the shark had suffocated, then the orcas would start feeding on it.
- Sea lions, leopard seals, and penguins
Orcas have many techniques to catch these preys. The most dramatic is using the wave as cover to caught prey off guard on the beach. Next technique is “wave-hunting” where orcas will spy-hop to locate any prey on ice floes, and then swim in groups to create waves that washes the prey off the ice and into the water where other orcas lie to snatch the prey. Another method of hunting for orcas is waiting until the prey come to them. They wait at edges of the ice for unsuspecting prey that want to enter the water or slips and fall into the water.
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