The big male arched his back and presented his giant dorsal fin at its full height - more than 1. 5 metres. A nick at the top of the fin, a distinctive quarter-round chip, indicated that this was Top Notch, or A5. As the mature male's fin sliced the water, researchers also saw the scarred back of an older female named Scar, A9 - Top Notch's mother. For almost 20 years, the research team had been following Scar and Top Notch. Scar's female calves had gone on to have their own families, but the thirtyish Top Notch was still travelling with his mother, in the company of a third whale, a now mature male calf that Scar had given birth to in 1971 or 1972.
This account of Scar and her big boys is taken from field notes written a few months before Scar died in 1990, at about 58 years of age. The only thing that seems to alter such longterm associations is death. After their mother's death, Top Notch and his brother continued to travel together.
Since the early 1970s, researchers off Vancouver Island have followed and photographed orca families, or pods. With tens of thousands of photographs taken, it is the most intensive dolphin or porpoise study in the wild. Every orca in three communities along the British Columbia/Washington coast has been identified some 330 individuals.
Two separate communities of resident whales can be seen in the area every month of the year - 250 whales in 19 pods. The northern community ranges from northern Vancouver Island to Alaska, while the southern community lives off southern Vancouver Island and in Puget Sound, Washington. The third community is made up of transient whales -about 80 whales in 30 pods.
Periodic visitors all along the British Columbia/Washington coast, the transient whales do not associate with the residents at all. With pointed dorsal fins, they also look slightly different from the other orcas, and they travel in smaller groups of only 2 to 7 individuals per pod, while resident pods have 5 to 50 individuals. Their diet is also distinctive. Transients eat mainly marine mammals, including seals, sea lions and, occasionally, dolphins and whales. Residents eat fish such as salmon.
The photo-identification method has been the lifework of the late Michael Bigg and his associates, Graeme Ellis, Ian MacAskie, John Ford and Ken Balcomb, although many others have contributed to the study. The photographs are the key, serving as "fingerprints" that researchers can use to identify each individual and to determine which orca travels with which other individuals. Thousands of photographs showing two or more orcas close to each other have verified field sightings.
Analyzing such associations, some two dozen researchers engaged in the study have determined that the social order of the resident orcas apparently revolves around the female adults. The smallest resident whale unit is a maternal group that is composed of a mother and her offspring. Male offspring stay with their mothers. 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. Within each community are "clans" -groups of pods that share certain 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. The three clans in the northern community and the one clan in the southern community have no sounds in common; they actually sound as different as orcas from Iceland and Antarctica. Dialects used by animals living in the same region are unique to orcas. Humans are the only other species with true dialects.
Rauno Lauhakangas