Methods for photographic identification of bowhead whales, Balaena mysticetus

• Published in: Canadian Journal of Zoology
• Main Authors: Rugh, David J., Braham, Howard W., Miller, Gary W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1992
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Balaena mysticetus
• Online Access: http://dx.doi.org/10.1139/z92-090; http://www.nrcresearchpress.com/doi/pdf/10.1139/z92-090

Bowhead whales, Balaena mysticetus, have black skin except for patterns of white along their ventral surface and visible dorsally on their lower jaws, caudal peduncles, and flukes. White scar marks may also be present. These contrasting black and white dorsal patterns were examined in 4871 aerial photographs of bowheads taken from 1976 to 1987 to determine if individual animals could be reidentified when subsequently photographed. The objective of making such reidentifications was to provide important life-history information, such as calving intervals, length-specific growth rates, survival rates, and population abundance. This paper describes procedures developed to categorize whales into 20 file types based on the relative extent of visible white markings. Preliminary analysis of the photographic identification system suggests that it has a high potential for use in population studies but only if whale images are of sufficient quality and quantity to allow for multiple reidentifications. High-quality images are best obtained from aerial photographs taken directly above whales in clear water during good to excellent sea-state conditions without glare. This ensures that sufficient characteristic features, if present, are photographed to permit recognition in subsequent photographs.