Foraging strategy and breeding constraints of <I>Rhinophylla pumilio</I> (Phyllostomidae) in the Amazon lowlands

Abstract

Bat diversity peaks in neotropical lowland forests, where 70-100 species may coexist in local assemblages. Understanding of factors that promote and maintain this diversity requires a thorough knowledge of the ecology and behavior of individual species. We studied the movement pattern, focusing on range size and foraging strategy, of the small frugivorous bat Rhinophylla pumilio (Phyllostomidae), with particular emphasis on constraints females have to deal with when rearing young. Because of the scattered distribution of its main food resource, infructescences of epiphytes, we hypothesized that R. pumilio should spend most of its flight time searching for food. Because its small body size incurs higher flight costs in comparison to larger fruit-eating bats, we further proposed that it should feed within small foraging areas that are close to each other and that commuting flights between foraging areas should be short and infrequent, resulting in small home ranges. Furthermore, we predicted that lactating females would change range size as well as activity budget by performing more search flights to increase food intake for milk production and more commuting flights to feed their young during nighttime. We radiotracked 9 females (4 nonreproductive, 4 lactating, and 1 subadult) and 2 males in the primary rain forest of Nouragues, French Guiana, for a total of 49 nights. Supporting our initial prediction, the foraging strategy of R. pumilio was mostly restricted to short (40- to 120-m) search flights in a single, rather small foraging area (3.5-14.1 ha). We observed a decrease in flight distances and size of foraging area, and an increase in total flight time throughout the night in lactating females that probably transported their young and nursed them in their foraging areas at night. Finally, we propose that the sensitivity of R. pumilio to forest fragmentation reported in previous studies may in part be caused by its foraging strategy because it consists mostly of short-distance search flights that make it difficult or impossible, particularly for lactating females, to regularly cross broad expanses of inhospitable matrix in fragmented forests. Fragmentation may therefore decrease breeding success and foster population decline in this species.