Spatial segregation in a sexually‐dimorphic central place forager: competitive exclusion or niche divergence?

• Published in: Journal of Animal Ecology
• Main Authors: Orgeret, Florian, Reisinger, Ryan, Carpenter‐Kling, Tegan, Keys, Danielle, Corbeau, Alexandre, Bost, Charles‐André, Weirmerskirch, Henri, Pistorius, Pierre
• Other Authors: Marine Apex Predator Research Unit (MAPRU) Port Elizabeth, South Africa, Nelson Mandela Metropolitan University Port Elizabeth, South Africa, Institute of Marine Sciences, Long Marine Laboratory, University of California Santa Cruz (UCSC), University of California-University of California, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: biologging; intraspecific competition; sexual segregation; kernel density estimates; resource selection functions; central-place foraging; ecological niche theory; wandering albatross; [SDE]Environmental Sciences; Southern Ocean; Diomedea exulans; Wandering Albatross
• Online Access: https://hal.archives-ouvertes.fr/hal-03251989; https://doi.org/10.1111/1365-2656.13552

International audience Sexual competition is increasingly recognized as an important selective pressure driving species distributions. However, few studies have investigated the relative importance of inter‐ vs. intrapopulation competition in relation to habitat availability and selection. To explain spatial segregation between sexes that often occurs in non‐territorial and central place foragers, such as seabirds, two hypotheses are commonly used. The ‘competitive exclusion’ hypothesis states that dominant individuals should exclude subordinate individuals through direct competition whereas the ’niche divergence’ hypothesis states that segregation occurs due to past competition and habitat specialization. We tested these hypotheses in two populations of an extreme wide‐ranging and sexually dimorphic seabird, investigating the relative role of intrapopulation and interpopulation competition in influencing sex specific distribution and habitat preferences. Using GPS loggers, we tracked 192 wandering albatrosses Diomedea exulans during four consecutive years (2016‐2019), from two neighbouring populations in the Southern Ocean (Prince Edward and Crozet archipelagos). We simulated pseudo‐tracks to create a null spatial distribution and used Kernel Density Estimates (KDE) and Resource Selection Functions (RSF) to distinguish the relative importance of within vs. between population competition. KDE showed that only intrapopulation sexual segregation was significant for each monitoring year, and that tracks between the two colonies resulted in greater overlap than expected from the null distribution, especially for the females. RSF confirmed these results and highlighted key at‐sea foraging areas, even if the estimated of at‐sea densities were extremely low. These differences in selected areas between sites and sexes were, however, associated with high interannual variability in habitat preferences, with no clear specific preferences per site and sex. Our results suggest that even with low at‐sea population ...