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.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Endangered southern resident population of killer whales Orcinus orca has been shown to be food-limited, and the availability of their primary prey, Chinook salmon Oncorhynchus tshawytscha, has ...been identified as a key covariate for the whales' individual survival and reproduction. We collected aerial photogrammetry data on individual whale size, which will help to better inform energetic calculations of food requirements, and we compared size-at-age data to make inferences about long-term growth trends. A helicopter was used to conduct 10 flights in September 2008, resulting in 2803 images from which useable measurements were possible for 66 individually identifiable whales, representing more than three-quarters of the population. Estimated whale lengths ranged from 2.7 m for a neonate whale in its first year of life, to a maximum of 7.2 m for a 31 yr old adult male. Adult males reached an average (asymptotic) size estimate ( plus or minus SE) of 6.9 plus or minus 0.2 m, with growth slowing notably after the age of 18 yr; this was significantly larger than the asymptotic size of 6.0 plus or minus 0.1 m for females, which was reached after the earlier age of 15 yr. Notably, there was no overlap between the ranges of estimated sizes of adult males (6.5 to 7.2 m) and females (5.5 to 6.4 m). On average, older adults (>30 yr) were 0.3 m (n = 14, p = 0.03) and 0.3 m (n = 5, p = 0.23) longer than the younger whales of adult age, for females and males, respectively; we hypothesize that a long-term reduction in food availability may have reduced early growth rates and subsequent adult size in recent decades.
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