Investigating Foraging Niches for Tenrecs, Bats, and Rodents at Betampona Réserve Naturelle Intégrale (Central Eastern Madagascar) Using Stable Carbon and Nitrogen Isotopes in Fur and Bone

We used stable carbon and nitrogen isotope values in plants, fur, and bone to establish baseline isotopic variability and investigate food web dynamics for small mammals at Betampona Réserve Naturelle Intégrale (BRNI), which protects an isolated parcel of tropical lowland moist evergreen forest in central eastern Madagascar. We included foliage from four understory plant genera, 13 endemic mammal species (5 bats, 5 tenrecs, and 3 nesomyine rodents), and introduced Rattus rattus and Suncus murinus that were collected along a gradient of degraded to intact forest from the southern boundary to the interior of BRNI as well as nearby villages. Isotopic data indicate niche partitioning among mammal groups, as well as among species within each of the groups. Most species appear to have foraged in the forest understory, although some, bats in particular, may have foraged outside of the protected area. We did not find evidence for competition between introduced and endemic animals but caution that some sample sizes are small. These results provide previously unknown insight into dietary preferences for some of Madagascar’s least studied mammals and establish a foundation for future work at BRNI.