While all whales, dolphins and porpoises fall under the order of Cetacea, the orca’s teeth are what classify them under the suborder Odontoceti, making them “toothed whales”, what makes us think, “If they’re toothed whales, doesn’t that make them whales?” Well, they are classified as toothed whales because of their suborder, but their specific family under the Odontoceti suborder is Delphinidae. Therefore, the short answer, and despite its common name (killer whale), the Orcinus orca is NOT a whale, it’s part of the Delphinidae family, and therefore it is a dolphin, the biggest of the dolphins on earth. It’s probably the most easily recognizable of all cetaceans and very unlikely to be confused with any other species.
|Figure 1: Adult male Orca outside of São Miguel Island, Azores. Photo by: Ida Eriksson|
The “killer whale” name is believed to have been given by ancient sailors who witnessed these animals preying on whales and the name naturally evolved from “whale killer” to killer whale. In other countries this name is also used with some variation, like in Spain and Portugal they are called, ballena-asesina and baleia-assassina, respectively, which means assassin whale.
Orcas, such as other dolphins, display sexual dimorphism, meaning in this case, that the males are larger than the females, it’s fairly easy to distinguish an adult male from a female, since these tend to develop much larger appendages, this includes the pectoral flippers, tail and dorsal fin, which can reach up to 1,8m in size.
Figure 2: Adult male Orca (top) and Adult female Orca (bottom). Note the evident differences in size and shape of the appendages. Illustration by: Ida Eriksson
Regarding its size, as mentioned before, it is a large dolphin, attaining a maximum reported size of 9.8m for males and 8.5m for females, the maximum measured weights are of 6600 kg for a 7.65m male and 4700 kg for a 6.58 female (Yamada et al., 2007).
Figure 3: Adult male Orca breaching outside of São Miguel island, Azores. Note large pectoral flipper typical of mature males. Photo by: Rui Santos
Orcas are highly intelligent animals, they live in society and use highly effective and cooperative hunting techniques, they are at the top of the food chain and they can feed on seals, dolphins, turtles, whales, or fish. Some described hunting techniques of the orcas show how developed the pods are as a society and include: making waves to knock seals off ice shelfs (Gif below) or impeding other cetaceans from coming to the surface in order to suffocate them.
And are also capable of storming beaches in order to catch sea lions and seals.
Video Credits: “Four killer whales in the Antarctic work together to flush their next meal — a seal — off an ice floe and into the water. Reproduced courtesy of Dr Ingrid Visser, Orca Research Trust: http://www.orcaresearch.org/“
Still on the subject of “who is which”, many times is asked if a dolphin is considered a whale, a similar situation to the one above.
Generally, all the large cetaceans are called whales, no matter what order or family they belong to. Therefore, any Odontoceti member with a big size, might belong to the Delphinidae family, but would be called whale. Following this reasoning, bottlenose dolphins and beaked whales belong to the same taxonomic order (Odontoceti), they have similar physiognomy, but however, the former are considered dolphins while the latter whales. When there is no possible doubt to decide whether it is a dolphin or a whale, is when we are talking about baleen whales. Baleen whales, they all belong to the Mysticeti and they all present some characteristics unique to this order. For example, the blowhole: if the animal has two blowholes is a Mysticeti (baleen whale), if it only has one blowhole is an Odontoceti (toothed Whale). But also remember another useful fact: all Mysticeti are whales, but not all Odontoceti are dolphins! For example, the sperm whale and the beaked whales, both belonging to the Odontoceti but yet are whales!
Figure 5: Orcas blowhole on the left (Odontoceti) and, Sei Whale double blowhole on the right (Mysticeti). Photos by: Miranda van der Linde
Written by Lucas Cidade
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