Defaunation affects the populations and diets of rodents in Neotropical rainforests

Abstract Most tropical rainforestshave been defaunatedof large-bodied mammalsand the cascading effects of such extirpations have been poorly studied, particularly on other animals. We used a natural experimentin the Brazilian Atlantic rainforestto investigate the ecological responses of rodentsto the functional extinctionof a dominant terrestrial mammal, the white-lipped peccary( Tayassu pecari). We detected a 45% increase in the abundance and a decrease in diversity of rodentsin defaunatedforests. Two of these species ( Akodon montensisand Oligoryzomys nigripes) are important hosts of Hantavirus, a lethal virus for humans. Stable isotope ratios( δ 13 C and δ 15 N) derived from the hair of rodentsand peccaries and their food resources indicate that at least two rodentspecies shifted to a diet more similar to peccaries in the defaunatedforest. Because most tropical rainforestsare facing dramatic extirpation of large mammals, we can expect changes in the composition and structure of small mammalcommunities with potential consequences for human health even in non-fragmented landscapes.