Residents can afford to be noisy, as herding fish is not as sneaky an enterprise as nabbing harbor seals. The fish hunters sometimes stun their prey with powerful tail-slaps. Both kinds of killer whales belong to the same species, Orcinus orca , but they have remained apart long enough to have begun diverging physically. A transient's dorsal fin is pointier and the patch of gray on its back, called a saddle patch, is slightly longer. The only thing keeping them apart so far are cultural differences.
Residential pods are amazingly stable groups, organized for life around mother-calf bonds.
So you end up with a big matrilineal family tree. Decades ago, scientists assumed the biggest bull in a pod was some kind of harem master. Mating, which people rarely see in the wild, may take place most commonly during summer gatherings of the pods when a male slips away from his mother for a brief encounter with a female from another pod. Other than humans, killer whales are the most widely distributed mammals in the world. They are found in every ocean, from the Arctic to the Antarctic, but are most numerous in the waters covering high-latitude continental shelves.