Exclusion of invasive predators triggers succession, competition and habitat diversification in a small mammal community.

Invasive species can alter small mammal communities. We examined the abundance and demography of 10 Australian desert small mammals inside and outside a fenced reserve after the exclusion of invasive rabbits, cats and foxes. Over 26 years, we found evidence for a species succession response triggered by the removal of endogenous disturbance (predation), similar to exogenous disturbance caused by fire, mining and deglaciation. Smaller rodents responded within 2 years whereas larger rodents became more abundant within the reserve after 5 years, eventually outcompeting the smaller rodents. The dasyurid response was later and more muted. Captures of rodents inside the reserve reached up to 33 times higher than outside after high rainfall years, suggesting that invasive predators have a significant impact and suppress rainfall-induced population booms. Larger rodents expanded their realized niche into non-preferred habitats, and intraspecific competition and species diversity increased. Minimal differences in breeding, body mass or sex ratios between inside and outside the reserve suggested abundance increases were primarily due to release from predation pressure rather than increased resources. Succession was shaped by competition and differences in predator susceptibility influencing reinvasion timing. Results demonstrate that succession dynamics in small mammals can be triggered by the removal of endogenous disturbance as well as changes in vegetation structure.