Epidemiology of skin changes in endangered Southern Resident killer whales (Orcinus orca)

Abstract

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.

Comparison of infrared thermography of the blowhole mucosa with rectal temperatures in killer whales (Orcinus orca)

“…The Southern Resident killer whales (SRKW) of the Salish Sea are a critically endangered population, and are threatened by reduced prey availability, vessel noise, polychlorinated biphenyls and other contaminants (Lacy et al, 2017). These factors likely have secondary immune system effects, putting them at risk of pathogens, including, but not limited to, ecto-, endo-and protozoal parasites, Erysipelothrix spp., Salmonella spp., Edwardsiella spp., poxviruses, herpesviruses, morbillivirus, marine Brucella spp, and mucoralean fungi (Gaydos et al, 2004(Gaydos et al, , 2023Huggins et al, 2020;Raverty et al, 2020). The ability to identify potentially pyrexic individuals could improve efforts to investigate disease prevalence and virulence within this population.…”

Infrared Thermography of the Blowhole as a Potential Diagnostic Tool for Health Assessment in Killer Whales (Orcinus orca)

“…As apex predators, killer whales (Orcinus orca) accumulate legacy chemical pollutants, such as polychlorinated biphenyl (PCBs) and mercury, and are one of the most contaminated marine mammals in the world [1][2][3]. While prey availability and anthropogenic factors are among the largest threats to wild populations, infectious disease is also a commonly reported cause of death, possibly due to the immunosuppressive effects of contaminants, malnutrition, or physiologic stress imposed by anthropogenic factors [1,4,5]. The Animals 2024, 14, 1867 2 of 9 validation of non-invasive methods for diagnostics and data collection is important due to the logistic difficulty of collecting direct physiologic samples or measurements from aquatic megafauna [6,7].…”