Photographic identification catalogs of individual killer whales (Orcinus orca) over time provide a tool for remote health assessment. We retrospectively examined digital photographs of Southern Resident killer whales in the Salish Sea to characterize skin changes and to determine if they could be an indicator of individual, pod, or population health. Using photographs collected from 2004 through 2016 from 18,697 individual whale sightings, we identified six lesions (cephalopod, erosions, gray patches, gray targets, orange on gray, and pinpoint black discoloration). Of 141 whales that were alive at some point during the study, 99% had photographic evidence of skin lesions. Using a multivariate model including age, sex, pod, and matriline across time, the point prevalence of the two most prevalent lesions, gray patches and gray targets, varied between pods and between years and showed small differences between stage classes. Despite minor differences, we document a strong increase in point prevalence of both lesion types in all three pods from 2004 through 2016. The health significance of this is not clear, but the possible relationship between these lesions and decreasing body condition and immunocompetence in an endangered, non-recovering population is a concern. Understanding the etiology and pathogenesis of these lesions is important to better understand the health significance of these skin changes that are increasing in prevalence.

We evaluated digital photographs of surfacing Southern Resident killer whales taken by the Center for Whale Research (CWR). Specifically, photographs collected for identification purposes focused on the left and right saddle patch and dorsal fin. Every in-focus, clear photograph taken between 2004–2016 was evaluated for skin abnormalities. Four veterinarians, two veterinary pathologists specializing in marine mammals and two veterinarians with expertise in cetacean clinical medicine, collectively reviewed all images of skin lesions on high-definition screens. Distinct lesions were identified and differentiated by typical pathologic qualifiers. A name and morphologic description were given for each distinct lesion type and every lesion present in an image was recorded by lesion type, date, and individual animal.