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

Clark, BL, Cox, SL, Atkins, KM, Bearhop, S, Bicknell, AWJ, Bodey, TW, Cleasby, IR, Grecian, WJ, Hamer, KC, Loveday, BR, Miller, PI, Morgan, G, Morgan, L, Newton, J, Patrick, SC, Scales, KL, Sherley, RB, Vigfúsdóttir, F, Wakefield, ED and Votier, SC 2021 Sexual segregation of gannet foraging over 11 years: movements vary but isotopic differences remain stable. Marine Ecology Progress Series, 661. 1-16.

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Sex-specific niche differentiation is common in marine vertebrates, but how this varies longterm is poorly understood. Here we investigated in terannual variation in sexual segregation among breed ing northern gannets Morus bassanus, wideranging central-place foragers with slight sexual di morphism. Over 11 breeding seasons, we used GPS tracking and/o r 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 be haviour 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 δ13C and δ15N than females across all years, which was not driven by size dimorphism, in stead 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 in tegrate behaviour over longer periods re veal 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.

Item Type: Publication - Article
Additional Information. Not used in RCUK Gateway to Research.: Addresses for other authors are given in the Supplement at
Additional Keywords: Sex-specific · Ecological niche · Stable isotopes · Biologging · Seabird · Centralplace foraging · Northern gannet · Morus bassanus
Divisions: Plymouth Marine Laboratory > National Capability categories > NERC Earth Observation Data Acquisition & Analysis Service (NEODAAS)
Depositing User: S Hawkins
Date made live: 08 Mar 2021 15:06
Last Modified: 08 Mar 2021 15:06

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