Killer whales 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. They discovered that individual killer whales could be distinguished using the shape of and nicks in the dorsal fin, along with 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 a precise count of the population rather than an estimate. This methodology introduced 'photo-identification' as a valuable research tool and a foundation for modern killer whale research. Since then, photo-identification has been used to investigate questions related to life history, social structure, population dynamics, acoustics and feeding ecology.
Images Tiu Similä
...and in Norway?
Long-term killer whale research in Norway was pioneered by Tiu Similä in 1986. Similä maintained a consistent data collection effort in northern Norway from 1986 through 2005, especially during the winter months of high abundance of Atlantic herring in Vestfjord-Ofotfjord-Tysfjord (Lofoten). In addition, Dag Vongraven and Anna Bisther from 1987 through 1996 catalogued killer whales occurring in the wintering (Lofoten) and spawning grounds (Møre) of the herring. In 2002, the winter distribution of the herring drastically altered, with the stock over-wintering in the 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 pods entering the usual fjords, and thus leading to a break of several years in the data collection. During winters of 2007, 2008 and 2013 Sanna Kuningas took over the photographic effort, enabling the update of the former catalogue and ensuring the longitudinal ID-study to continue.
In 2013, Norwegian Orca Survey (NOS) launched 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, NOS started to systematically collect ID-photographs as a logical progression of previous efforts. The resulting ID-catalogue constitutes a real baseline for ongoing and future studies and for the effective long-term monitoring and conservation of the Norwegian killer whale population.
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. Photographs should be of sufficient quality and close range for these features to be discernible and usable for photo-identification.