Defaunation affects the populations and diets of rodents in Neotropical rainforests

Most tropical rainforests have been defaunated of large-bodied mammals and the cascading effects of such extirpations have been poorly studied, particularly on other animals. We used a natural experiment in the Brazilian Atlantic rainforest to investigate the ecological responses of rodents to the functional extinction of a dominant terrestrial mammal, the white-lipped peccary (Tayassu pecan). We detected a 45% increase in the abundance and a decrease in diversity of rodents in defaunated forests. Two of these species (Akodon montensis and Oligoryzomys nigripes) are important hosts of Hantavirus, a lethal virus for humans. Stable isotope ratios (delta C-13 and delta N-15) derived from the hair of rodents and peccaries and their food resources indicate that at least two rodent species shifted to a diet more similar to peccaries in the defaunated forest. Because most tropical rainforests are facing dramatic extirpation of large mammals, we can expect changes in the composition and structure of small mammal communities with potential consequences for human health even in non-fragmented landscapes.