Photo-Identification of Sea Otters Using Nose Scars

Abstract: We evaluated the use of naturally occurring nose scars to identify individual sea otters (Enhydra lutris) in Simpson Bay, Prince William Sound, Alaska, USA. We spent 520 hours over 103 days conducting photo-identification surveys from June to August 2002 and 2003. Altogether, we identified 114 individuals. The number of sightings per individual ranged from 1 to 26, with an average of 3.3. The maximum number of sightings of an individual within a single year was 19. We saw 54 otters (47%)on >1 day, with an average of 8.1 sightings per individual for those seen more than once. We identified 8 individuals (19% of those identified in 2002) in both years. Males and otters of undetermined sex that we first sighted in June had the highest re-sighting rates. We considered 45% of all individuals encountered identifiable from nose scars. Nose scars were present in 63% (n = 19) of males, 45% (n = 45) of females, and 40% (n = 49) of otters of undetermined sex. Our results are similar to the results of photo-identification studies of other marine mammals, suggesting that this technique may be a useful tool for the individual identification of sea otters as well.