Trophic niche partitioning between two prey and their incidental predators revealed various threats for an endangered species

• Published in: Ecology and Evolution
• Main Authors: Rioux, Ève, Pelletier, Fanie, St‐Laurent, Martin‐Hugues
• Other Authors: Canada Foundation for Innovation, Natural Sciences and Engineering Research Council of Canada, Université du Québec à Rimouski, Canada Excellence Research Chairs, Government of Canada, Environment Canada, Fonds de recherche du Québec – Nature et technologies, Ministère des Forêts, de la Faune et des Parcs
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2022
• Subjects: Rangifer tarandus
• Online Access: http://dx.doi.org/10.1002/ece3.8742; https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.8742; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ece3.8742

Abstract Documenting trophic niche partitioning and resource use within a community is critical to evaluate underlying mechanisms of coexistence, competition, or predation. Detailed knowledge about foraging is essential as it may influence the vital rates, which, in turn, can affect trophic relationships between species, and population dynamics. The aims of this study were to evaluate resource and trophic niche partitioning in summer/autumn between the endangered Atlantic‐Gaspésie caribou ( Rangifer tarandus caribou ) population, moose ( Alces americanus ) and their incidental predators, the black bear ( Ursus americanus ) and coyote ( Canis latrans ), and to quantify the extent to which these predators consumed caribou. Bayesian isotopic analysis showed a small overlap in trophic niche for the two sympatric ungulates suggesting a low potential for resource competition. Our results also revealed that caribou occupied a larger isotopic niche area than moose, suggesting a greater diversity of resources used by caribou. Not surprisingly, coyotes consumed mainly deer ( Odocoileus virginianus ), moose, snowshoe hare ( Lepus americanus ), and occasionally caribou, while bears consumed mainly vegetation and, to a lesser extent, moose and caribou. As coyotes and bears also feed on plant species, we documented trophic niche overlap between caribou and their predators, as searching for similar resources can force them to use the same habitats and thus increase the encounter rate and, ultimately, mortality risk for caribou. Although the decline in the Gaspésie caribou population is mostly driven by habitat‐mediated predation, we found evidence that the low level of resource competition with moose, added to the shared resources with incidental predators, mainly bears, may contribute to jeopardize the recovery of this endangered caribou population. Highlighting the trophic interaction between species is needed to establish efficient conservation and management strategies to insure the persistence of endangered populations. ...