During the 1970s to the 1990s, Steller sea lions (Eumetopias jubatus) in Alaska declined severely, resulting in the western stock's listing as endangered under the United States Endangered Species Act. The localized depletion of their main food source around rookeries and haul out sites was the primary cause of their depletion. The western stock has still not recovered to historical levels. Therefore, scientists have continued to study Steller sea lions diet and foraging habits. One approach has been through stable isotope analysis of their various tissues. Analysis of their vibrissae, or whiskers, provides an exact record of an individual's diet from birth to the present. However, scientists so far have only measured stable isotope values of a single vibrissa from an individual, assuming no significant difference among vibrissae within or between cheeks. They have not accounted for the possibility of variable stable isotope accumulation in an individual's different vibrissae. In this study, I tested the assumption of no significant individual variability among vibrissae by examining the δ13C and δ 15N values in all of the vibrissae on five Steller sea lion pups recovered in Alaska. δ15N values did not differ between vibrissae on a cheek or between vibrissae from left and right cheeks. The δ 13C values did not differ between vibrissae within cheeks; however, δ 13C values were significantly different between the left and right cheeks of Lowrie Island Pup and PWS 29 Pup. This between cheek variation is most likely due to small sample size rather than different stable isotope incorporation. The lack of δ15N value variation within or between cheeks, as well as the lack of δ13C variation within cheeks, supports the assumption that stable isotope accumulation is similar between all vibrissae and validates sampling protocols of previous studies collecting just the longest, thick vibrissa from a Steller sea lion. More studies similar to this one are needed to verify these findings and to look at variability in stable isotope incorporation of juvenile and adult Steller sea lion vibrissae as well as other mammal species.
|Commitee:||King, Amanda, Welker, Jeff, Wolf, Nathan|
|School:||Alaska Pacific University|
|School Location:||United States -- Alaska|
|Source:||MAI 52/06M(E), Masters Abstracts International|
|Subjects:||Wildlife Management, Ecology, Zoology, Environmental science|
|Keywords:||Alaska, Carbon stable isotope, Diet, Eumetopias jubatus, Foraging habits, Nitrogen stable isotope, Steller sea lion, Vibrissae|
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