Assessing seasonal changes in body condition for spotted (Phoca largha), ringed (Pusa hispida), and bearded (Erignathus barbatus) seals
Anthropogenic global warming is causing unprecedented changes to occur within Arctic ecosystems. As sea ice continues to decline in both thickness and extent, ice-adapted species will be particularly affected. Specifically, Arctic seals are reliant on sea ice during critical life-history stages and...
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USF Scholarship: a digital repository @ Gleeson Library | Geschke Center
2020
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| Online Access: | https://repository.usfca.edu/thes/1344 https://repository.usfca.edu/cgi/viewcontent.cgi?article=2451&context=thes |
| Summary: | Anthropogenic global warming is causing unprecedented changes to occur within Arctic ecosystems. As sea ice continues to decline in both thickness and extent, ice-adapted species will be particularly affected. Specifically, Arctic seals are reliant on sea ice during critical life-history stages and many of their preferred prey depend on reliable patterns in annual sea ice cover. Thus, ongoing changes will likely affect the ability of Arctic seals to carry out key life-history tasks and maintain positive energy balance. One way to assess energy reserves is through examination of body condition. For seals, this is often done by measuring overall blubber content, which individuals use as an onboard energy reserve; however, fat stores can be difficult to accurately assess in free-ranging individuals. Therefore, I worked with captive spotted (n=4), ringed (n=3), and bearded (n=1) seals to determine the most accurate methods to quantify blubber content, defined seasonal changes in body condition, and evaluated best-practices for field assessments of wild seals. I found the traditional truncated cones method [Gales & Burton, 1987, Aus. J. Zool. 35, 207-217] was most accurate in estimating energy stores for all three species. Using this method, I documented predictable changes in body condition that appeared to be linked to specific annual events. Finally, I identified simple indices of body condition to increase efficiency and accuracy in field settings. The results presented here improve our understanding of routine seasonal changes in body condition for three species of Arctic seal and should improve health assessments of wild populations. |
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