This is one story I had heard about in college and find really fascinating. Killer whales, more formally known as Orcas, have subdivisions of their species that behave in drastically different ways .
Apparently, the title of whale is often considered a misnomer as these guys are supposedly genetically dolphins (as they are in the Delphinidae family). However, this leaves me a little confused as all dolphins are part of the larger classification, the suborder Odontoceti, or toothed whales. Apparently there is not total agreement as to whether dolphins are really just toothed whales. But I digress…
At any rate. They’ve (you know… the disembodied “they”? Guess I should change this to a more appropiate but no less vauge “researchers”) found that orcas have several different ecotypes. This means basically that there are subgroups of orcas that are adapted to different living conditions. There are three described killer whale ecotypes which include offshore, transient, and resident orcas.
The least studied ecotype is the offshore Orcas. They are a fairly recent discover. These dolphins (whales?) are found further from the coast than the other two types, and appear to be genetically and phenologically distinct.You might describe them as orcas gone rogue =).
Both resident and transient orcas will often be found closer inland. Resident populations tend to be the social butterflies of the species. They form larger pods and tend to be more tightly knit. They are piscivorous (fish) feeders.
Transient pods are smaller, usually no larger than six individuals. They are stealthier hunters, focusing their attention on marine mammals as prey. Transient orcas also had an interesting role in the disappearance of Alaskan sea otters. Sea otters were considered keystone species in the local foodweb and their disappearance led to a proliferation in sea urchins which in turn led to the decline of kelp beds that provide invaluable habitat for other organisms.