Forest Fragmentation and Its Effects on the Feeding Ecology of Black Howlers (Alouatta pigra) from the Calakmul Area in Mexico

Abstract

Information on food selection and feeding habits is critical for species conservation, particularly in the context of forest landscapes heavily transformed by human activities. In this study, we examined the degree to which A. pigra feeding habits differed between two sites in the conserved forest of the Calakmul Biosphere Reserve (CBR) and two forest fragments outside the reserve, and how monkeys select the trees on which they feed. Our results suggest that howlers tended to exploit a smaller set of fruit and leaf species in the conserved sites, whereas their diet was more diverse in the fragments. This can be explained probably by the role, at CBR, of Ficus sp. in howlers’ diet, as it was highly selected and represented half of all feeding events. Chesson’s electivity index showed that howlers in fragments selected 12 of the 16 species used for feeding; while in CBR, they selected 9 of the 10 species used for feeding. At both types of forests, feeding trees were taller and were greater in diameter than non-feeding trees. Trees exploited by howlers for feeding have commercial dimensions and most of these species are commercially logged. As a result, in fragments and logged forests, howlers have to face the lack of continuity in the canopy and the loss of many vital trees for feeding. We expect howler monkeys to survive in fragmented sites if tree species important in their diet are conserved.