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.
Mammals breathe air with lungs.
Mammals nurse their young.
The word "cetacean" is derived from the Greek word for whale, kētos.
Genus, Species - Orcinus orca
The name "killer whale" was originally "whale killer".
Killer Whale Ecotypes (Forms)
Scientists currently recognize at least 10 distinct ecotypes (or forms) of killer whales. These ecotypes differ at the molecular level and display distinct differences including variations in size, habitat, color pattern, dorsal fin shape, vocalizations, prey type, and hunting strategies.
In the Northern Hemisphere, there are five recognized ecotypes.
Type 1 and type 2 killer whales inhabit the eastern North Atlantic.
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 (also referred to as "Bigg's killer whales" in honor of early killer whale researcher Michael Biggs) 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.
A fourth potential killer whale ecotype in the Pacific inhabits the Eastern Tropical Pacific (ETP).
There are five recognized ecotypes in the Southern Hemisphere.
Antarctic type A killer whales.
Small type B — this ecotype may also be called "Gerlache killer whales" because they are regularly found around the Gerlache Strait off the western Antarctic Peninsula.
Large type B — this ecotype is sometimes referred to as "pack ice killer whales".
Type C — also referred to as "Ross Sea killer whales".
Type D — this ecotype may also be called "Subantarctic killer whales".
Experts identify killer whale populations based on the whales' call patterns, behavior, body shape, and coloration. Current and future studies analyzing biochemical and chromosomal characteristics may help distinguish genetic relationships among pods and regional populations of killer whales.
Most modern forms of both odontocetes and mysticetes appear in the fossil record five to seven million years ago.
DNA analysis supports the theory that the hippopatamids are the closest living relatives to cetaceans.