Item Details

Analysis of California Sea Lion (Zolophus Californianus) Feeding Habits Using Stable Isotopes: A Potential Record for el Niño Occurrences

Foster, Sabrina Nicole
Format
Thesis/Dissertation; Online
Author
Foster, Sabrina Nicole
Advisor
Macko, Stephan
Abstract

Climate change poses the critical question of how species will alter distribution patterns in response to environmental warming; a clear answer will be required to improve long-term planning for the protection of threatened and endangered species. The California sea lion (Zalophus californianus) has a growing population while close congeneric relatives, the Galapagos sea lion (Zalophus wollebaeki) and the Japanese sea lion (Zalophus japonicus), are vulnerable and extinct, respectively. Increased conflict with fisheries requires improved management and better projections of population response to climate change. Here, stable isotope analysis (δ13C δ15N) of annual growth layers in teeth is used to examine variations in foraging patterns and their connection to short-term warming events, such as El Niño. Results indicate that ontogenetic shift associated with weaning is the most marked change in foraging pattern common to all animals, although such data cannot be used to definitively indicate environmental events such as El Niño. Furthermore, responses for adults could be attributable to facultative feeding behavior, individual variability, sub-adult male migration, or combinations of these factors. Nevertheless, in some individual sea lions, strong El Niño events seemed correlated with a decline in primary productivity (δ3C) as well as average trophic position (δ15N), whereas weaker El Niño events were correlated with a decline in primary productivity with an increase in average trophic position in certain animals. Illustrating how California sea lion populations may respond to warming during short-term El Niño events has the potential to provide insight for predicting responses of this species to different warming scenarios and for informing policy decisions about risks to species presented by long-term population management in the context of global climate change predictions.

Note: Abstract extracted from PDF text

Language
English
Date Received
20140122
Published
University of Virginia, Department of Environmental Sciences, MS (Master of Science), 2009
Published Date
2009-08-01
Degree
MS (Master of Science)
Collection
Libra ETD Repository
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