Abstract
To understand and predict the fate of species over time, it is necessary to understand the different factors shaping their dynamics. Within communities, species interact with each other, through numerous interspecific interactions (e.g. competition, predation), but also with individuals of their own species, as well as with their environment (e.g. climatic conditions, habitat). The complexity of the analyses lies in the need to work at different biological levels, from the individual to the community. It is therefore necessary to develop methods that could accommodate different data sources. Integrated population models (IPM) allow, in their simplest form, to combine data at the individual scale (e.g. capture-recapture) and at the population scale (e.g. counts) into a single analysis and thus offer the possibility to estimate demographic parameters and population sizes. Their extension to the multispecies scale allows the analysis of the effect of the estimated population size of one species on the demographic parameters of another species while taking into account other factors such as environmental covariates and propagating all sources of uncertainty. Therefore, these models could allow a better understanding of the role of interspecific interactions in species dynamics. Thus, the aim of this PhD thesis, at the interface between modelling and ecology, is to highlight the potential of multispecies IPMs by applying them to relevant systems of interacting species.Through three case studies, different interspecific interactions (predation, competition) as well as different factors (climatic covariates, habitat quality, phenology) have been analysed to understand the mechanisms underlying the dynamics of these species. A first case study consisted in a predator-prey system of seabirds (the blue petrel Halobaena caerulea and the Brown skua Catharacta lonnbergi). The effects of predation relationships were analysed while taking into account the climatic conditions at sea to highlight their respective roles on the species dynamics. A second analysis focused on a tit system (the great tit Parus major and the blue tit Cyanistes caeruleus) to analyse the effects of competitive relationships. In this analysis, the effect of habitat was also taken into account to determine its influence on interspecific relationships. Finally, a last case study focused on the competition between two warbler species with different migration strategies (the blackcap Sylvia atricapilla and the garden warbler Sylvia borin). In this system, breeding phenology was taken into account to understand how it can modulate interspecific interactions.Overall, the multispecies IPMs were well adapted to the different case studies and provided a better understanding of the role of interspecific interactions in species dynamics. In the skua-petrel system, the model highlighted the major effect of prey availability in species dynamics. In the tit system, they generalized competition processes known at the scale of a few sites to the whole French population, while nuancing them according to the habitat quality. Finally, for warblers, they showed the effect of breeding phenology on the intensity of interspecific interactions. Numerous work perspectives remain to be explored in order to exploit further the potential of these models. Among them, it will be interesting to extent these models to more than two-species systems by using a large number of species to study the dynamic of communities. These models could also allow the projection of species dynamics under different climatic and/or management scenarios and thus be used for conservation purposes.