Large‐scale molecular diet analysis in a generalist marine mammal reveals male preference for prey of conservation concern

Abstract Sex‐specific diet information is important in the determination of predator impacts on prey populations. Unfortunately, the diet of males and females can be difficult to describe, particularly when they are marine predators. We combined two molecular techniques to describe haul‐out use and...

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Bibliographic Details
Published in:Ecology and Evolution
Main Authors: Austen C. Thomas, Dietmar Schwarz, Alejandro Acevedo-Gutiérrez, Christa M. Kohnert, Sara M. Spitzer, Theresa R. Keates
Format: Article in Journal/Newspaper
Language:English
Published: John Wiley and Sons Inc. 2018
Subjects:
Online Access:http://europepmc.org/articles/PMC6202700
https://doi.org/10.1002/ece3.4474
https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fece3.4474
http://onlinelibrary.wiley.com/wol1/doi/10.1002/ece3.4474/fullpdf
https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ece3.4474
https://www.onlinelibrary.wiley.com/doi/full/10.1002/ece3.4474
https://www.ncbi.nlm.nih.gov/pubmed/30386584
https://pubmed.ncbi.nlm.nih.gov/30386584/
http://europepmc.org/abstract/MED/30386584
https://cedar.wwu.edu/cgi/viewcontent.cgi?article=1057&context=biology_facpubs
https://works.bepress.com/dietmar_schwarz/25/
https://cedar.wwu.edu/biology_facpubs/58/
https://academic.microsoft.com/#/detail/2891343279
Description
Summary:Abstract Sex‐specific diet information is important in the determination of predator impacts on prey populations. Unfortunately, the diet of males and females can be difficult to describe, particularly when they are marine predators. We combined two molecular techniques to describe haul‐out use and prey preferences of male and female harbor seals (Phoca vitulina) from Comox and Cowichan Bay (Canada) during 2012–2013. DNA metabarcoding quantified the diet proportions comprised of prey species in harbor seal scat, and qPCR determined the sex of the individual that deposited each scat. Using 287 female and 260 male samples, we compared the monthly sex ratio with GLMs and analyzed prey consumption relative to sex, season, site, and year with PERMANOVA. The sex ratio between monthly samples differed widely in both years (range = 12%–79% males) and showed different patterns at each haul‐out site. Male and female diet differed across both years and sites: Females consumed a high proportion of demersal fish species while males consumed more salmonid species. Diet composition was related to both sex and season (PERMANOVA: R 2 = 27%, p < 0.001; R 2 = 24%, p < 0.001, respectively) and their interaction (PERMANOVA: R 2 = 11%, p < 0.001). Diet differences between males and females were consistent across site and year, suggesting fundamental foraging differences, including that males may have a larger impact on salmonids than females. Our novel combination of techniques allowed for both prey taxonomic and spatiotemporal resolution unprecedented in marine predators.