The effect of food hardness on feeding behaviour in frugivorous bats (Phyllostomidae): an experimental study

Most New World leaf-nosed bats (Phyllostomidae) are frugivores. Many of the se species are sympatric and mechanisms of resource partitioning including vertical stratification and divergent foraging strategies have been describ ed. This study investigates a previously unexplored but potentially signifi cant factor in resource partitioning: the relationship between feeding beha viour and fruit hardness. Data summarizing ingestive and fruit processing b ehaviours were collected during feeding experiments from five sympatric fru givorous phyllostomid species: Artibeus jamaicensis, Dermanura phaeotis, St urnira lilium, Carollia perspicillata, and Glossophaga soricina. Individual s were the subjects of feeding experiments that consisted of eating hard an d soft fruits of similar size, shape, and mass. Variables analysed from vid eotapes of the experiments describe how fruits are placed in the mouth duri ng ingestion, the frequency of head movements during biting, the number of bites used to remove a piece of fruit, and the number of chews used to proc ess each mouthful of fruit. Results of chi-square, log-linear, R x C, and K ruskal-Wallis tests demonstrate that feeding behaviours vary significantly with fruit hardness both within and between species. Artibeus, Dermanura, a nd Sturnira are behaviourally specialized for feeding on relatively hard fr uits. However, Carollia, and probably Glossophaga, lack these behavioural s pecializations. Both mechanical and ecological implications of intra- and i nterspecific behavioural variation are discussed. Differences in fruit hand ling behaviour are also used to make explicit predictions regarding intersp ecific variation in masticatory morphology. This study demonstrates that th e relationship between fruit hardness and feeding behaviour may be an integ ral part of frugivore ecology. Overall, resource partitioning among phyllos tomid frugivores is a result of complex interactions among and between bats and their food plants. Controlled experimental studies such as this one pr ovide a crucial means of dissecting these complex interactions and gaining insight into the basis of frugivore diversity.