Wet Beast Wednesday: orca
It's the 4th anniversary of me writing aquatic biology posts for Wet Beast Wednesday. As is tradition, I've picked a cetacean. In past years I've covered the smallest cetacean, the largest cetacean, and the smallest again. This time, I'm covering the biggest badass of the cetacean world. Orcas are arguably the apex predators of the ocean, but there's more to them than just being hardcore.
(Image: a pair of orcas beaching out of the water. They are large dolphns without beaks and with bulbous heads. The body is mostly black, with white underbellies and spots behind the eyes and near the tail. A grey patch is behing the dorsal fin. One of the orcas has its side to the camera while the other has its belly to the camera. End ID)
The orca (Orcinus orca) is also called a killer whale due to their ability to hunt and kill larger cetaceans. Pedants reading this may wish to point out that killer whale is a misnomer since orcas are actually dolphins. However, I can out-pedantic you by pointing out that dolphins are a subset of toothed whales and therefore killer whale is accurate. Orcas are found in a number of different populations with different lifestyles and biological differences (mostly in coloration). It has been suggested that the orca species should be divided into categories like races (when used in biology, a race is an informal category to recognize populations that are distinct from each other but not distinct enough to be considered subspecies) or subspecies, or that they should be be considered separate species. As of now, the Society for Marine Mammology still considers all orcas to be the same species, citing a lack of data to indicate they should be separated into multiple species.
(Image: an orca with its head out of the water and mouth open. The teeth are visible. They are sharp and curved backwards. End ID)
Orcas are the largest of the dolphins. Males are larger than females, typically reaching between 6 and 8 m (20 and 26 ft) and up to 6.6 tons, but can on occasion reach up to 10 m (33 ft) and 11 tons. Females typically reach 5 to 7 m (16 to 23 ft) and 3 to 4 tons, with large females reaching up to 8 tons. Males can also be distinguished from females by their fins. Males have proportionately larger pectoral fins, dorsal fins, and flukes than females. Orcas have a typical oceanic dolphin body plan, though they are more robust than their smaller cousins. Orcas are known for their distinct coloration. Their bodies are mostly black, but with distinct white areas on the underside, reaching up to the sides in places. In addition, a gray saddle patch is located on the back just behind the dorsal fin. Some populations are brown and yellow instead of black and white due to their diets. Orcas do not have the prominent beaks that many dolphin species do, making them stand out among their relatives.
(Image: an orca fully breaching out of the water, showing its full body. End ID)
Orcas are found in marine waters worldwide, having been documented in all oceans and most seas. They will also travel into estuaries and have been documented swimming up to 160 km (100 mi) up rivers. They prefer to live in coastal regions or along pack ice, but some populations do specialize in the open ocean. Orcas are more commonly found at higher latitudes and away from the equator, but tropical populations exist. Orcas are apex predators, meaning they have no predators themselves. Orcas have a very broad diet including fish, marine mammals, invertebrates like squid and krill, sea turtles, and sea birds, but most populations specialize on a few types of prey. It seems that tropical populations are more generalist in their feeding strategies and populations in colder water are more specialized. Most hunting is done in shallow waters but diving several hundred meters deep is also done depending on what prey an individual is seeking. An orca eats an 227 kg (500 lbs) of food every day. Orcas are social animals and use complex group hunting strategies. One of these is called carousel hunting and is used when targeting schooling fish. The pod will work to herd a school into a tight ball by swimming around them, blowing bubbled, flashing their bellies, and slapping their tails. Once the school has been corralled, some of the pod will keep circling the fish to keep them from escaping while other members attack and eat. Pod member will change places to ever orca takes turns feeding and herding. Orcas also hunt sharks, including whale sharks and great white sharks, and have learned to flip the sharks upside down. This triggers a temporary paralysis called tonic immobility which leave the shark as an easy meal. Great white sharks have been known to vacate areas for over a year if they realize orcas are nearby. Orcas will kill animals and then not eat them, a behavior known as surplus killing.
(Image: a pod of orcas engaging in carousel hunting. Multiple whales are swimming in curcles beneath a ball-shaped school of fish that has been forced to the surface. Other orcas are swimming in and out of the school. End ID)
Orcas are possibly the most successful predators of marine mammals. They will hunt both other cetaceans as well as pinnipeds (seals, sea lions, and walruses). While the cetaceans orcas typically hunt are usually smaller then them (such as other dolphins or porpoises), they will also attack larger baleen whales up to and including blue whales. When hunting pods, the orcas will typically attempt to isolate one member and focus on that one. Cetaceans are usually chased to the point of exhaustion before being attacked and killed. When hunting pinnipeds, orcas will also chase and have even been know to follow their prey onto land, temporarily beaching themselves to catch their food before wiggling back into the water. Another strategy is to use their tails to hurl the seal into the air. The result is a stunned and injured if not killed seal that is easy pickings. When hunting among pack ice, orcas will cooperate to force pinnipeds off of ice flows by swimming together to create waves large enough to knock the animal into the water.
(Image: a pair of orcas spyhopping (sticking their heads of of the water) on either side of a small ice flow with a seal on it. End ID)
Orcas have complex social structures reminiscent of those of elephants and higher primates. The exact social structure a group uses appears to depend on whether they primarily hunt fish or mammals. Among fish eaters, orcas gather in groups called matrilines which consist of an old female, her sons and daughters, and the children and grandchildren of her daughters. A single matriline can have up to 4 generations of orcas in it. Males in matrilines are unique in that they will spend their entire life with their parents instead of leaving. Males will seek out members of different matrilines to mate with. In good conditions, multiple matrilines will cooperate in groups called pods. Amongst mammal eaters, groups are more commonly a mother and her immediate offspring. When in social groups, males are typically pushed to the outskirts of the pod or matriline while the females remain in the center. Males may leave their groups and become rovers, swimming either alone or with a small group of other rovers. Rovers will often attempt to join a different group. This may be an adaptation to increase genetic diversity and avoid inbreeding. Individual groups have their own culture, hunting patterns, and behaviors that are passed down from mother to child. Different groups seem to have their own dialects or languages of whale calls that are also passed down. Orcas also appear to make friends, indicated by the two spending more time together, swimming in sync, and making more physical contact.
(Image: pod of 11 orcas swimming just beneath the surface of the water. Some are smaller, possibly being calves. End ID)
Scientists group orcas into different classifications based on their behavior and lifestyles. In the north Pacific, orcas are classified as residents, transients, and offshores. Residents are primarily fish eaters who live in larger groups and rarely travel. Transients primarily eat seals and whales. They prefer smaller groups (though can on occasion assemble in pods of up to 200) and migrate to follow their prey. Transients and residents often share habitat, but rarely interact with each other. Offshores appear to venture far from shore to hunt fish and whales. Not much is known about them, but they may indicate a large oceanic population in the pacific that rarely approaches shore. Orcas around the Galapagos and Hawai'i may also be part of this hypothetical population. North Atlantic orcas used to be defined as type 1 and type 2 based on whether they mainly ate fish and seals or baleen whales. However these classifications are no longer used due to lack of evidence. Orcas around Antarctica are classified as 5 ecotypes based on behavior and appearance. Type A orcas are the most similar to populations north of the equator and eat mainly minke whales. Type B1 and B2 orcas are smaller and live around the pack ice. The larger B1s eat mainly seals while the smaller B2s eat seals and penguins. Type C orcas are the smallest of the Antarctic ecotypes and are seen in the largest groups. Their diet consists of fish. Type B and C orcas are noted for being browns and yellow instead of black and white. This is speculated to be the result of large quantities of diatoms (a type of planktonic algae) in their diet. Type D orcas are noticeably different than others. Their heads are more bulbous, closer to a pilot whale's head, smaller white spots, and a differently-shaped dorsal fin. Not much is known about them but they have been observed eating fish. Mitochondrial DNA studies indicate that Type B and C orcas should be considered separate species recently diverged from the greater population. It has also be suggested that Type D orcas should be considered distinct species as well. As of yet, no official classification change has happened.
(Image: a pod of 4 type B2 orcas, one of which appears to be a calf, swimming at the surface of the water. They have lighter skin, grey or brown instead of black, and the white patches are yellow instead. End ID)
(Image: the head of a type D orca. It is much more bulbous and blunt than other orcas heads and the white patch behind the eye is much smaller. End ID)
Orcas can mate year-round, though winter births seem to be the most common. Males will seek out females from other pods or matrilines to keep from inbreeding. Forced mating is rare. Instead, the male will attempt to court the female through various methods. Males will fight each other over access to females. Once the male frees his willy into the female, he will return his group and provides no further care. Gestation takes 15 to 18 months, after which a single calf will be born measuring about 2.5 meters (8 ft) and 181 kg (400 lbs). Once born, the calf needs to suckle multiple times per day. The mother's milk consists of 40 to 60% fat to help the calf grow rapidly and build up its layer of blubber. Studies show that most orca pregnancies spontaneously abort themselves and roughly 1 in 5 calves will reach a year old. Infanticide is rare, but there has been at least one documented case of a male and his mother teaming up to kill a calf to force the calf's mother to mate again. Calves will experiment with solid food soon after birth, but will not fully wean until around age 3. As the calf grows, its mother and grandmother will teach it the group's hunting methods and culture. Females typically give birth every 5 years or so. Orcas are one of only a handful of mammals that experience menopause and can continue to live for a long time after becoming non-reproductive, the others being belugas, narwhals, short-finned pilot whales, false killer whales, and humans. It is believed that post-menopausal females continue to contribute to the reproductive success of the species by offering care, training, and protection to their grandchildren. Male orcas become sexually mature at around 15, but they often don't successfully mate until around age 21 due to competition from other males. Males usually live to be about 30, but some have been known to live to 60 and can successfully mate all their lives. Females become sexually mature around age 13 and reach their peak fertility at age 20. Menopause occurs at around age 40. Females can live to 80, though there are unverified reports of individuals living to over 100.
(Image: a pod of orcas swimming at the surface. Between two of them is a calf, which looks like a smaller version of an adult. End ID)
Orcas are currently classified as data deficient due to lack of data regarding possible multiple species and subspecies. conservation needs are usually evaluated by population, not species-wide. Orcas in general are threatened by pollution, habitat loss, loss of food due to overfishing, and climate change. Orcas historically were hunted by whalers and fishers due to perceiving them as threats to fisheries. They have also been known to cooperate with humans hunting whales and sharks by leading boats to prey in exchange for scavenging the scraps after the humans are finished. Wild orcas have been reported to be highly curious about humans, often coming to examine boats. Attacks on humans by wild orcas are extremely rare and none of them have been fatal. Oddly, starting in 2020, orcas living around the Iberian Peninsula started attacking sailboats by ramming the rudders to damage them. Multiple boats have been sunk by this behavior, though no fatalities have been reported. Why this is happening is not clear. It could be play behavior, with the orcas treating the boats like toys. It could potentially be the result of the orcas viewing the boats as threats, possibly after one got wounded by a boat strike. It could also be a fad. Orcas have been known to go through phases of certain behavior becoming popular seemingly for fun. An example of this comes from 1987 in the Puget Sound, where orcas started wearing dead salmon on their heads. Different orca pods in Iberia seem to be teaching each other the boat ramming bahavior.
(Image: an orca breaching next to a boat full of people. End ID)
All fatal attacks on humans have come from orcas in captivity. Because of popular public opinion on them and how impressive they are, orcas became popular exhibits in aquariums. Orcas in captivity show shortened lifespans, heightened stress, and more aggressive behavior. Most captive orcas were captured from the wild as calves, forcibly removed from their families and moved into highly inadequate exhibits. These exhibits are far smaller than the natural range of an orca, not allowing them the freedom of movement they need. They are also forced to live in closer quarters than they would in the wild, with no way to get away from each other. In addition, they are trained to perform unnatural behavior like circus tricks and closely interacting with humans. Public opinion has been turning against keeping orcas in captivity and Seaworld, one of the largest organizations keeping captive orcas, has announced they will be ending their captive breeding program. There has been little success in releasing captive orcas. Because most are born in captivity or captured as calves, they never learned the skills needed to survive in the wild. The first successful release of a captive orca happened in 2002, when an orphaned orca named Springer was released and reintegrated into her familial pod. SHe has since had 2 confirmed calves. The majority of releases result in the orcas failing to thrive and dying due to being unable to adapt to wild life. I personally think it should be illegal to keep orcas in captivity with the exception of short-term rehabilitate and release projects to help injured orcas as I don't think it's possible to ethically keep cetaceans in captivity due to an inability to provide for their needs.
(Image: Springer the orca on the way to being released. She is on a boat held in place by a hammock-like apparatus. Her body is covered with wet towels to help keep her from overheating. Multiple scientists are on the boat examining her and keeping her safe. End ID)
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