Sexual segregation of gannet foraging over 11 years: movements vary but isotopic differences remain stable

Clark, Bethany L, Cox, Sam L, Atkins, Kelly M, Bearhop, Stuart, Bicknell, Anthony WJ, Bodey, Thomas W, Cleasby, Ian R, Grecian, W James, Hamer, Keith C, Loveday, Benjamin R
et al (show 10 more authors) (2021) Sexual segregation of gannet foraging over 11 years: movements vary but isotopic differences remain stable. MARINE ECOLOGY PROGRESS SERIES, 661. pp. 1-16.

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<jats:p>Sex-specific niche differentiation is common in marine vertebrates, but how this varies long-term is poorly understood. Here we investigated interannual variation in sexual segregation among breeding northern gannets <jats:italic>Morus bassanus</jats:italic>, wide-ranging central-place foragers with slight sexual dimorphism. Over 11 breeding seasons, we used GPS tracking and/or stable isotopes to test for sex differences in foraging trip characteristics (range, duration and timing); spatial distribution; habitat selection; and carbon and nitrogen isotopes in blood. When combining data from all years, females foraged further and for longer than males, yet despite this, the foraging areas of the sexes almost completely overlapped. Males and females selected foraging habitats that differed in terms of oceanography but not fishing vessel density. We also detected temporal segregation: females were more likely to be at sea during the day than at night, while males were more likely to be at sea during the night. However, foraging behaviour quantified by all GPS analyses varied interannually, with sex differences detected in some years but not others. Finally, males had consistently higher red blood cell δ<jats:sup>13</jats:sup>C and δ<jats:sup>15</jats:sup>N than females across all years, which was not driven by size dimorphism, instead likely by prey choice or very fine-scale habitat selection. We conclude that environmental variation influenced short-term sex differences in movement, but sex differences in stable isotopes that integrate behaviour over longer periods reveal more consistent differences. Our results suggest that inferences drawn from single-year studies may not relate to general patterns, highlighting the importance of long-term studies and combining methods.</jats:p>

Item Type: Article
Uncontrolled Keywords: Sex-specific, Ecological niche, Stable isotopes, Biologging, Seabird, Central-place foraging, Northern gannet, Morus bassanus
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 21 Dec 2021 13:49
Last Modified: 18 Jan 2023 21:18
DOI: 10.3354/meps13636
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