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Hétérogénéité individuelle, variabilité temporelle et structure spatiale comme sources de variation démographique chez les grands herbivores de montagne

Abstract : In Northern hemisphere, populations of large herbivores have to cope with major environmental modifications linked to the increase of their density and to global change which strongly impacts their habitat (climate change, modification of human activities and habitat fragmentation). Understanding how these species adjust their life history strategies in response to such modifications is central for population ecology and for management issues. In this context, this work aimed to identify the sources of variation of survival and reproductive tactics in 3 species of mountain ungulate (Pyrenean chamois Rupicapra pyreneica, Alpine chamois Rupicapra rupicapra, and Mediterranean mouflon Ovis gmelini musimon × Ovis sp.). Using capture-mark-recapture monitoring we specifically investigated the role of individual heterogeneity, climate change, and spatial heterogeneity in shaping vital rates.This work relied on mixture models and an innovative combination of robust-design into a multi-events framework to explore demographic data collected at different spatio-temporal scales. Fixed heterogeneity appeared as a major demographic component in the 3 studied species by highlighting in mouflon and Pyrenean chamois two groups of females with contrasted reproductive performance, and by providing evidence in chamois of among-females differences in survival rates linked to the quality of their habitat. These models allowed us to provide evidence for the terminal investment hypothesis in female mouflon and to decompose reproductive effort in females of Pyrenean chamois from gestation to weaning, to unveil that lactation only led to cost on subsequent reproduction. Our results also highlighted the major influence of winter and spring climatic conditions on demographic parameters in the 3 studied species, and confirmed the general trend that climate effects are often species- and site-specific. Our findings provided evidence that Pyrenean chamois and mouflon evolved contrasted life history strategies, although both species share strong similarities in terms of body mass, ecological traits and phylogenetic position.Finally, our work stresses the importance of conducting comparative demographic studies, based on longitudinal monitoring of marked individuals, at inter-specific, inter-population and within population levels, to better understand and predict the future of large herbivores populations in the current context of global changes.
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Quentin Richard. Hétérogénéité individuelle, variabilité temporelle et structure spatiale comme sources de variation démographique chez les grands herbivores de montagne. Biodiversité. Université Grenoble Alpes, 2016. Français. ⟨NNT : 2016GREAV070⟩. ⟨tel-01949894⟩

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