Are tissue samples obtained via remote biopsy useful for fatty acid-based diet analyses in a free-ranging carnivore?

• Published in: Journal of Mammalogy
• Main Authors: Galicia, Melissa P, Thiemann, Gregory W, Dyck, Markus G, Ferguson, Steven H
• Other Authors: Monteith, Kevin, Natural Sciences and Engineering Research Council of Canada, Environment and Climate Change Canada, Kenneth M. Molson Foundation, Nunavut General Monitoring Plan, Polar Continental Shelf Program, Government of Nunavut, Northern Scientific Training Program, Makivik Corporation, Torngat Wildlife and Plants Secretariat/Co-Management Board, Nunavut Wildlife Management Board, Nunavik Marine Regional Wildlife Board, Nunavik Government, WWF—Canada Arctic Species Conservation Fund, Government of Newfoundland and Labrador, Ministère des Forêts, de la Faune et des Parcs Québec, Nunatsiavut Government, York University, Faculty of Graduate Studies
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2021
• Subjects: Nature and Landscape Conservation; Genetics; Animal Science and Zoology; Ecology; Ecology, Evolution, Behavior and Systematics; Arctic; Davis Strait; Nunavut; polar bear; Pusa hispida; ringed seal; Ursus maritimus
• Online Access: http://dx.doi.org/10.1093/jmammal/gyab041; http://academic.oup.com/jmammal/article-pdf/102/4/1067/39721325/gyab041.pdf

Abstract Fundamental knowledge on free-ranging animals has been obtained through capture-based studies; however, these may be logistically intensive, financially expensive, and potentially inconsistent with local cultural values. Genetic mark–recapture using remote tissue sampling has emerged as a less invasive alternative to capture-based population surveys but provides fewer opportunities to collect samples and measurements for broader ecological studies. We compared lipid content, fatty acid (FA) composition, and diet estimates from adipose tissue of polar bears (Ursus maritimus) obtained from two collection methods: remote biopsies (n = 138) sampled from helicopters and hunter-collected tissue (n = 499) from bears harvested in Davis Strait and Gulf of Boothia, Nunavut, 2010 – 2018. Lipid content of adipose tissue was lower in remote biopsies than harvest samples likely because remote biopsies removed only the outermost layer of subcutaneous tissue, rather than the more metabolically dynamic innermost tissue obtained from harvest samples. In contrast, FA composition was similar between the two collection methods with relatively small proportional differences in individual FAs. For diet estimates in Davis Strait, collection method was not a predictor of prey contribution to diet. In Gulf of Boothia, collection method was a predictor for some prey types, but the differences were relatively minor; the rank order of prey types was similar (e.g., ringed seal; Pusa hispida was consistently the primary prey in diets) and prey proportions differed by < 6% between the collection methods. Results from both methods showed that diets varied by geographic area, season, year, age class, and sex. Our study demonstrates that adipose tissue from remote biopsy provides reliable estimates of polar bear diet based on FA analysis and can be used to monitor underlying ecological changes in Arctic marine food webs.