Type D Orca
With its distinctive coloration, the orca (or killer whale) is one of the most recognizable denizens of the sea. The "Type D" orca is a unique kind of orca with distinctive physical features.
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Delphinidae
Genus: Orcinus
Species: O. orca
Common Names: Type D Orca, Sub-Antarctic Killer Whale
The behavior of Type D orcas remains mysterious, due to their elusiveness. They frequent the Southern Ocean, which is why they are sometimes referred to as "Sub-Antarctic" ocras. The fact that they are often seen around the long lines of fishermen leads scientists to believe they feed mostly on fish, rather than marine mammals. Their main prey appears to be the Patagonian toothfish.
Little is known about the breeding habits of Type D orcas, though they are probably similar to those of other orca populations. Female killer whales reach maturity around age 10, and can often breed until age 40. Mothers usually give birth to a single calf, and all members of a pod both male and female will usually care for calves.
Orcas are the largest member of the oceanic dolphin family. They can grow over 25 feet in length and weight as much as 6 tonnes (6.6 short tons). They are heavy bodied with large, paddle-shaped fins. Males typically have a straight, tall dorsal fin that can measure nearly six feet high. Their unique coloration makes them quite easy to recognize. They are usually black above and white below, with a large white “eye” patch located just behind the eye and a gray “saddle” marking behind the dorsal fin.
The Type D orca features a number of distinct physical characteristics that set this orca apart from other populations. They have a more pronounced, bulbous head and a very small "eye" patch. While they are rarely observed, identification is quite easy due to these unique features.
Type D orcas were originally identified as part of a mass stranding event in the 1950s, in New Zealand. They are very rarely seen, and have only been observed six times since 2004. The first video of live Type D orcas was taken in 2014.
Scientists long believed that they may represent a unique species of orca. However, recent studies seem to indicate that their unique appearance is due to the small size and isolation of the population, which has resulted in inbreeding that has led to low genetic diversity.
Since they are so rarely encountered, not much is known about the current status of the Type D orca. Their lack of genetic diversity, which often negatively affects animal populations, does not seem to have a harmful effect on the Type D, as they seem to have been thriving for many generations based on DNA studies.
References
https://en.wikipedia.org/wiki/Orca_types_and_populations
https://en.wikipedia.org/wiki/Orca
Shirahai, Hadoran & Jarrett, Brett (2006). Whales, Dolphins& Other Marine Mammals of the World. Princeton, New Jersey: Princeton University Press.
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