The vast majority of theses in this collection are open access and freely available. There are a small number of theses that have access restricted to the WWU campus. For off-campus access to a thesis labeled "Campus Only Access," please log in here with your WWU universal ID, or talk to your librarian about requesting the restricted thesis through interlibrary loan.
Individual Variability in Foraging Success of Harbor Seals (Phoca vitulina) Preying on Pacific Salmon (Oncorhynchus spp.) Informs Predator Management
Date Permissions Signed
Date of Award
Department or Program Affiliation
Biology, Marine and Estuarine Program (MESP)
Master of Science (MS)
Acevedo-Gutiérrez, Alejandro, 1964-
Schwarz, Dietmar, 1974-
Anderson, Roger A. (Roger Allen)
The complexities of trophic dynamics complicate the management of predator populations. In some cases, targeted culling campaigns are meant to control predator populations. In these campaigns, predators are considered ‘rogue individuals’ based on visitation rates to a site. This definition carries the underlying assumption that all predators impact prey equally, however, individual variability in foraging success may compromise such an assumption. Thus, to test the hypothesis that foraging success varies among individual predators, I studied harbor seals preying on adult Pacific Salmon during the 2014-2019 fall salmon runs. I analyzed individual harbor seal visitation rate and foraging success based on photographs and field observations, and I employed Generalized Linear Mixed-Effects Models to determine individual variability in metrics of foraging success. Individual harbor seal identity better explained both total foraging success and the odds of success of a given foraging event when compared to models based on visitation rate alone. My data suggest that considering intraspecific variability and classifying ‘rogue individuals’ based on foraging success is a more accurate protocol for managing predator populations than relying solely on visitation rate of the predators.
predator, prey, trophic, management, culling, rogue individual, harbor seal, Pacific salmon, Phoca vitulina, Oncorhynchus spp.
Western Washington University
Subject – LCSH
Harbor seal--Food--Washington (State)--Whatcom Creek; Pacific salmon--Predators of--Control--Washington (State)--Whatcom Creek; Food chains (Ecology)--Washington (State)--Whatcom Creek; Predation (Biology)--Washington (State)--Whatcom Creek
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Freeman, Grace, "Individual Variability in Foraging Success of Harbor Seals (Phoca vitulina) Preying on Pacific Salmon (Oncorhynchus spp.) Informs Predator Management" (2021). WWU Graduate School Collection. 1042.