title: Foraging behavior and success of a mesopelagic predator in the northeast Pacific Ocean: insights from a data-rich species, the northern elephant seal.
abstract: The mesopelagic zone of the northeast Pacific Ocean is an important foraging habitat for many predators, yet few studies have addressed the factors driving basin-scale predator distributions or inter-annual variability in foraging and breeding success. Understanding these processes is critical to reveal how conditions at sea cascade to population-level effects. To begin addressing these challenging questions, we collected diving, tracking, foraging success, and natality data for 297 adult female northern elephant seal migrations from 2004 to 2010. During the longer post-molting migration, individual energy gain rates were significant predictors of pregnancy. At sea, seals focused their foraging effort along a narrow band corresponding to the boundary between the sub-arctic and sub-tropical gyres. In contrast to shallow-diving predators, elephant seals target the gyre-gyre boundary throughout the year rather than follow the southward winter migration of surface features, such as the Transition Zone Chlorophyll Front. We also assessed the impact of added transit costs by studying seals at a colony near the southern extent of the species' range, 1,150 km to the south. A much larger proportion of seals foraged locally, implying plasticity in foraging strategies and possibly prey type. While these findings are derived from a single species, the results may provide insight to the foraging patterns of many other meso-pelagic predators in the northeast Pacific Ocean.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, United States of America. robinson@biology.ucsc.edu
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Robinson
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Costa
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Crocker
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Gallo-Reynoso
authors.forename: Cory D
authors.initials: CD
authors.lastname: Champagne
authors.forename: Melinda A
authors.initials: MA
authors.lastname: Fowler
authors.forename: Chandra
authors.initials: C
authors.lastname: Goetsch
authors.forename: Kimberly T
authors.initials: KT
authors.lastname: Goetz
authors.forename: Jason L
authors.initials: JL
authors.lastname: Hassrick
authors.forename: Luis A
authors.initials: LA
authors.lastname: Hückstädt
authors.forename: Carey E
authors.initials: CE
authors.lastname: Kuhn
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Maresh
authors.forename: Sara M
authors.initials: SM
authors.lastname: Maxwell
authors.forename: Birgitte I
authors.initials: BI
authors.lastname: McDonald
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Peterson
authors.forename: Samantha E
authors.initials: SE
authors.lastname: Simmons
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Teutschel
authors.forename: Stella
authors.initials: S
authors.lastname: Villegas-Amtmann
authors.forename: Ken
authors.initials: K
authors.lastname: Yoda
mesh_terms: D000818:Animals; D001823:Body Composition; D005247:Feeding Behavior; D005260:Female; D010140:Pacific Ocean; D011235:Predatory Behavior; D046048:Seals, Earless / Q000502:physiology*