Orcas are cetaceans, one of nearly 80 different species of whales and dolphins. They are the largest member of the dolphin family. In common with all marine mammals, orcas are warm blooded, air breathing, and they bear their young live. They have highly developed brains, the second largest of any animal on Earth, with nearly 4 times the mass of the human brain. Orcas inhabit all the world’s oceans. The largest populations live in cooler waters; separate populations generally occupy different ocean areas, although sometimes ranges overlap. Typically, orca populations are small, consisting of hundreds or perhaps thousands of individuals. Nowhere are the populations huge. Orcas exist at the top of the predator hierarchy, literally being able to prey upon anything they choose. Perhaps this status has given them the ability to make choices about lifestyles and food preferences. Though there is only one species, Orcinus orca, there are numerous unique races and populations that reflect variations in ocean ecology and geography.
The world’s best known orca populations live in the waters of the Pacific Northwest and Alaska. In British Columbia and Washington State, “northern” and “southern” resident communities occupy fairly defined coastal areas, while a little understood “offshore” community is thought to occupy areas closer to the outer edge of the continental shelf. The range, numbers, and social composition of the resident communities is known in considerable detail. There are just over 80 members of the southern resident community and slightly more than 200 members of the northern resident community. A “transient” community numbering more than 200 individuals has a wider range that includes waters used by the resident communities. There is very little interaction between resident and transient orcas, and they have very different lifestyles and food preferences. Resident orcas eat fish exclusively, whereas transients eat only marine mammals. Modification of this general rule, however, does occur, for example, in the combined mammal-fish diet of one Alaskan group. Elsewhere in the world, food preferences and habits vary widely according to local conditions. The orcas of New Zealand exhibit a preference for stingrays, and the orcas of the Crozet Islands in the southern Indian Ocean hunt elephant seals as well as fish. Historic variations in opportunity probably explain the differences in food preferences we see among the orca populations of today.
Socially, orcas live in matrilines that are closely bonded family groups consisting of a mother and her offspring. Families that associate with each other form the community. Female orcas live long lives (averaging 50 years & can be 80 or more) that give daughters ample time in which to nourish their own offspring who in turn learn habits and traditions which are passed on to succeeding generations. In this way, orca societies achieve stability and long term duration. Orca society is based in long standing cultural and acoustic traditions that have common elements but which vary among populations. One striking common element is the virtual absence of overt aggression within and between families. Orca society is peaceful, and cooperative.