The delayed demographic responses of small mammals to habitat quality and density in the Brazilian Cerrado

Understanding the effects of exogenous and endogenous factors on species demographic rates is crucial to investigate their chances of persistence on natural ecosystems. We used a 9-year time series, based on monthly captures, to test the delayed effects of endogenous (density) and exogenous (rainfall, habitat cover/heterogeneity, fire) factors on the survival and recruitment rates of two small mammals inhabiting the Brazilian Cerrado: the semelparous, scansorial marsupial <i>Gracilinanus agilis</i> and the iteroparous, arboreal rodent <i>Rhipidomys macrurus</i>. As in most short-lived small mammals, we found negative density-dependent effects on the recruitment of both species (3 months delay), which could occur through reduced immigration or fecundity, in addition to the semelparous breeding strategy of <i>G. agilis</i>. Reduced habitat cover following fire events had a negative delayed effect on the survival of <i>G. agilis</i> (3 months after) and <i>R. macrurus</i> (1 year after), albeit it increased the recruitment rates (1-year lagged effect) of <i>R. macrurus</i>. We failed to find any effect of fire on demography of either species. Our results suggest that the irregular and non-cyclical fluctuations in <i>R. macrurus</i> abundance were driven by the interaction between delayed density dependence and changes in habitat quality, while the marked and repeated fluctuations in <i>G. agilis</i> abundance were mainly shaped by the occurrence of semelparity associated with direct density dependence. We emphasize that changes in habitat quality brought by human-made activities may have severe impacts on the dynamics and persistence of forest-dependent small mammals in the Cerrado.