Class - Mammalia
- Mammals are characterized by the following features:
- Mammals breathe air with lungs.
- Mammals are "warm-blooded": they maintain a constant, high body temperature independent of their surroundings.
- As a rule, mammals bear live young. (Two primitive mammals are exceptions to this rule: the duckbilled platypus and the spiny anteater both lay eggs.)
- Mammals nurse their young with milk.
- Mammals have hair, at least at some stage in their development. A whale's smooth skin is an adaptation for swimming, and whales lose their hair before they are born. A newborn calf sometimes has a few sparse hairs around the rostrum.
Order - Cetacea
- Cetacea is a scientific order of large aquatic mammals that have forelimbs modified into flippers, a horizontally flattened tail, one or two nostrils at the top of the head for breathing, and no hind limbs. Cetaceans include all whales, dolphins, and porpoises.
- The word "cetacean" is derived from the Greek word for whale, kētos.
- Biochemical and genetic studies suggest that even-toed ungulates, especially hippopotamuses (Family Hippopotamidae), are cetaceans' closest living terrestrial relatives. (Sheep, cows, pigs, and giraffes are also examples of even-toed ungulates.) These animals and whales probably share a common ancestor.
- Living cetaceans are further divided into two suborders: the Odontoceti (toothed whales) and the Mysticeti (baleen whales).
killer whale, Orcinus orca
gray whale, Eschrichtius robustus
Suborder - Odontoceti
- Odontoceti is a scientific suborder of whales characterized by having teeth and a single blowhole. The word "Odontoceti" comes from the Greek word for tooth, odontos.
Family - Delphinidae
- Dolphins and their immediate kin are included in the scientific family Delphinidae. This family is represented by about 36 species, including bottlenose dolphins, pilot whales, and false killer whales. The killer whale is the largest member of the dolphin family.
bottlenose dolphins, Tursiops truncatus
false killer whales, Pseudorca crassidens
killer whales, Orcinus orca
Genus Species - Orcinus Orca
- The Latin name Orcinus translates as "belonging to Orcus," Orcus was a Roman god of the netherworld, and this genus name is likely a reference to the ferocious reputation of the killer whale. In Latin, orca translates "large-bellied pot or jar," but orc- also refers to a whale.
"Orca" is the Latin word for the shape of a barrel or cask.
- Killer whales earned their name not because they kill people, but because they kill other whales. They were called "whale killers" by sailors who witnessed their attacks on larger cetaceans. One Spanish name for a killer whale is ballena asesina, which translates to "assassin whale".
The name "killer whale" was originally "whale killer".
- Despite the widespread distribution and many geographically isolated populations of killer whales, most scientists consider them all the same species.
- A biological review team of NOAA (National Oceanic and Atmospheric Administration) Fisheries concluded that the resident, fish-eating killer whales of the North Pacific comprise a distinct (as yet un-named) subspecies.
Killer Whale Stocks
- As a management tool, scientists categorize a geographically isolated and genetically distinct group of whales as a whale stock. Killer whales are represented by several stocks.
- Researchers have identified three forms of killer whales in Antarctic waters. They categorize the Antarctic killer whales as "type A," "type B," or "type C." Differences in the whales' appearance and behavior lead some experts to suggest that these may be three different subspecies.
- In the eastern North Pacific Ocean, observers have recognized that various groups of killer whales show physical and behavioral differences. They categorize pods of eastern North Pacific killer whales into three ecotypes: "transient", "resident", and "offshore".
- Researchers analyzed samples collected from 73 whales in the eastern North Pacific and found significant genetic differences among transient whales and two separate groups of resident whales.
- The offshore ecotype has been identified but not as well studied as the resident and transient ecotypes. It appears to be more closely related to the resident ecotype than to the transient ecotype.
- Experts identify killer whale populations based on the whales' call patterns, body shape, and coloration. In the future, analyzing biochemical and chromosomal characteristics may help define genetic relationships among pods and regional populations of killer whales.
- The earliest fossil whales have been estimated to be about 50 million years old. Scientists theorize that the ancestors of whales were ancient (now extinct) land mammals.
- While the fossil record is poor in regard to modern cetaceans, most modern forms of both odontocetes and mysticetes appear in the fossil record five to seven million years ago.
- In Italy, experts have uncovered Pliocene (two to five million years old) fossils that seem to be related to modern killer whales. The fossil skull of a whale that has been named Orcinus citoniensis had smaller teeth - and more of them - than modern killer whales. Scientists have identified large, fossil delphinid teeth, mostly from the Pliocene, as those of an Orcinus species.
Killer whales were once wrongly classified as fish.
Aristotle was the first to correctly classify killer whales as mammals in his Historia Animalium.