Defaunation is one of the main drivers underpinning biodiversity loss and disruption of ecosystem processes and function in many systems across the world. A prominent consequence of defaunation are trophic cascades, where extirpation of keystone species can alter top-down and bottom-up regulation of ecosystem structure. For example, the removal of consumers from ecosystems can release their resources from density dependent consumption, with knock-on effects on other ecosystem processes. However, whether behavioural mechanisms such as anti-predator behaviour and social interactions contribute to limiting and/or regulating herbivore numbers and mediate trophic cascades in the wild is still a matter of contention.In large tracts of the Brazilian Atlantic forest, defaunation of keystone herbivores and predators might have led to trophic cascades. In this proposal we suggest to elucidate whether animal behaviour and spatial structure play a critical role in shaping trophic cascades, niche partitioning, community assembly and stability in this ecosystem. We will do so by evaluating the impact of several defaunation scenarios in the movement, habitat use and food selection of large herbivore and small mammals.First, we will evaluate the impact of niche partitioning, competition and predation on large herbivore movement in the Atlantic forest. For this we will use camera-traps in order to assess co-ocurrences in habitat use of white lipped peccaries (WLP) and other large herbivores and their predators, and GPS radio-collar data to investigate whether WLP movements respond to the herbivore-predator composition in their surroundings or at the landscape scale.Second, we will evaluate the impact of large herbivores on small mammal movements and niche partitioning in the Atlantic forest. We will use isotopic techniques to assess how large herbivore presence affects the diet within and across different small mammal species, and fluorescent pigments to investigate the impact of large herbivore presence on small mammal movement and habitat use. We will study responses within and across different small mammal species, so as to evaluate the potential for large herbivores and, indirectly, apex predators, to generate new ecological niches that alter the patterns of coexistence between small mammal species in the system.Third, we will evaluate the impact of herbivore movement and defaunation on spatial structure and community dynamics in the Atlantic forest using a theoretical approach. For this, we will use Individual-Based Models to investigate how defaunation and movement affects scale of interactions and spatial pattern in a spatially explicit approach. In addition, we will assess how defaunation affects stability and diversity of mammalian communities at different spatial and temporal scales using meta-community models.The combination of both empirical and theoretical approaches in a unique "natural" experimental set-up will allow us to evaluate the consequences of the extirpation of keystone mammal species from the Brazilian Atlantic forest. In doing so, we expect to inform conservation actions in these system, shed light on poorly studied and controversial aspects of animal behaviour and contribute to ecological theory.
News published in Agência FAPESP Newsletter about the scholarship: