Only females leave the maternal group to form their own maternal groups, although they probably stay in the same subpod with their mother and other sisters or cousins. When the subpod reaches a certain size, it may form a new pod around the dominant female. Another way to investigate the relationships among orca pods in a community is to listen to them. Orca dialects were discovered by John Ford in the late 1970s. Working off Vancouver Island, Ford discovered that no two orca pods sound exactly alike.
Every pod has some unique sounds.
Ford says that because the sounds of each pod are probably learned from the mother, the number of shared sounds between pods likely reveals how closely related the pods are. Ford came to the conclusion that pods with dialects 90 percent the same probably had a recent common ancestor. Pods with only 25 to 50 percent similarity are more distantly related. Dialects used by animals living in the same region are unique to orcas. Humans are the only other species with true dialects.