Killer whales (Orcinus orca) are wide-ranging mammals with an
estimated life span of 50-100 years, meaning that research into their life history and ecology requires long-term studies. In 1970, a census of the killer whale population ranging in coastal waters of British Columbia, Canada, was initiated by the late Dr Michael Bigg and colleagues. The scientists discovered that individual killer whales could be distinguished using the shape of and nicks in the dorsal fin, along with the pigmentation pattern and naturally acquired markings of the saddle patch. Therefore, by analyzing photographs of surfacing killer whales, it was possible to catalogue individuals enabling an exact count of the population rather than an estimate. This methodology introduced 'photo-identification' as a fundamental tool in modern killer whale research worldwide. Since then, photo-identification has been used to investigate individual- and group-specific patterns in behavior, diet, acoustics, health condition and more.
Images Tiu Similä
...and in Norway?
Photo-identification studies of Norwegian killer whales were
pioneered by Dr Thomas Lyrholm in 1983 and then by Dr Tiu Similä from 1986. Similä and colleagues collected identification photographs from 1986 through 2005 in northern Norwegian fjords (Tysfjord-Vestfjord) where the Norwegian Spring Spawning stock of the Atlantic herring (and
hundreds of killer whales!) spent the winter months. From 1987 through 1996, colleagues Dag Vongraven and Anna
Bisther joined forces and ID-photographed killer whales both at herring wintering (Tysfjord) and spawning grounds (Møre). In 2002, the herring drastically altered its winter
distribution, moving to offshore waters north of Vesterålen. This change occurred over several years, with reduced numbers of herring entering the fjord system each year. This transition resulted in fewer killer whale groups entering the usual fjords, thus leading to a break of several years in the data collection. During the winters of 2007, 2008 and 2013 Dr Sanna Kuningas took over the photographic effort, enabling the ID-catalogue to be updated and ensuring the longitudinal photo-identification
study to continue.
In 2013, Norwegian Orca Survey initiated a research effort dedicated to monitoring the occurrence and ecology of killer whales on a year-round basis in Northern Norway. As part of this initiative, Norwegian Orca Survey started to systematically collect ID-photographs as a logical progression of previous efforts. The resulting ID-catalogue has been the absolute foundation of multiple past and ongoing studies.
Fin shape, nicks in the dorsal fin, and pigmentation and scarring patterns of the saddle patch are the features we use as 'finger-prints' to identify individual killer whales. These natural markings, often acquired through physical contact with conspecifics, are permanent after five years of age, making them highly reliable for individual identification. For photographs to be usable for identification, they should be of sufficient quality and taken from relatively close range so that individual features can be discernible.
Did you know?
Adult males have a distinctively taller dorsal fin than adult females (and of subadults)
Shape and size of the dorsal fin, pigmentation of the saddle patch and natural scars all contribute to making each and every killer whale distinctive and identifiable. Get familiar with the different fin categories below before browsing the Catalogue.
Did you know?
Nicks and scars are permanent features that may last for decades as observed for this female (NKW-943)
Tiu Similä (1995)