Feeding ecology of Philippine fruit bats: patterns of resource use and seed dispersal

Information on diet composition of, feeding patterns in, and seed dispersal by pteropodids was gathered in a primary tropical rain forest area in southern Negros Island, Philippines. Seeds and marked remains of food plants were collected: (1) in 1 m x 1 m seed traps laid out at 3-m intervals along four orthogonal transects around selected fruiting figs, and (2) randomly from the forest floor within a 100 m x 100 m area surrounding these trees. Identity of consumers was determined directly through visual observation and from netting around sampling trees and/or indirectly through analysis of palatal imprints on ejecta. Food habits were recorded for nine species of fruit bats: Acerodon jubatus, Cynopterus brachyotis, Haplonycteris fischeri, Harpyionycteris whiteheadi, Nyctimene rabori, Ptenochirus jagorii, Pteropus hypomelanus, P. pumilus and P. vampyrus. Figs (F. Moraceae) were found to be a major part of the diet of these bats in the area: at least 11 out of 30 Ficus species identified from the area were being eaten in varying amounts. Other components of the diet included fruits of 11 other plant species belonging to seven families. There was some evidence of consumption of leaves and moss. In general, data suggest differential choice of fruit along lines of fruit colour (i.e., bright versus dull-coloured fruits), on the basis of available crop density and on plant height. No size relationships between bats and the fruits consumed were evident. Analysis of seed shadow patterns strongly indicates that feeding patterns differ between large-sized bat species (> 150 g body mass) and smaller species. Most splats and ejecta generated by large bats were concentrated beneath the crown of the source tree, indicating consumption of fruits on the tree itself. In contrast, smaller bats used feeding roosts in the immediate vicinity of, but not in, a focal feeding tree. Mixed-species seed clumps were found beneath these feeding roosts. This difference in behavioural patterns of fruit consumption causes a more heterogeneous pattern of seed scattering than would be expected of a single-taxon (i.e. fruit bats as a whole) visitor coterie. The potential importance of these fruit bats as seed dispersers in forests is further supported by seed germination tests; gut-passed seeds of Ficus chrysolepis show higher percentages of germination than do seeds from fruits or ejecta.