Understanding the consequences of biotic and environmental variability on the population dynamics of mammals is fundamental to assessing the impacts of direct and indirect anthropogenic actions, as global climate disruption. Long-term studies of small mammals in temperate ecosystems have elucidated the roles of climate or interspecific interactions in their dynamics. However, the lack of long-term studies in the tropics is a major impediment to generalise between these species and ecosystems. We analyse the population dynamics of seven small mammals from two contrasting adjacent tropical dry forests in a protected area in western Mexico. We modelled the population dynamics using an 18 year live-trapping database, evaluating the effects of intra- and inter-specific interactions, climate, and primary productivity. Our analyses showed effects of both biotic and abiotic factors on the dynamics of all species. Intra- and inter-specific interactions negatively affected five and two species, respectively. Precipitation caused positive effects on every species, either by directly enhancing their survival (five species) or by triggering changes in primary productivity (two species). Extreme climate events left intense signals; either positively, for two invasive species inhabiting these forests, or causing population declines for another species and temporarily extirpating the dominant one. Our results suggest dramatic interactions between the sharp precipitation reductions and the higher probability of extreme climate events - both predicted by global climate disruption models - and other anthropogenic pressures that these forests are suffering from (habitat loss, over-exploitation). We show how well-preserved forests are resilient sources to prevent these - the World’s most endangered - forests from annihilation.