Abstract:
The “residents and raiders” theory emphasizes the importance of conspecific feeding interference in seed dispersal by frugivorous megachiropterans. Agonistic interactions at fruiting trees frequently result in the "ejection" of one bat, which has often first obtained some fruit. The ejected bat then flies to an unoccupied tree, thus dispersing non-consumed seeds. For seeds too large to be swallowed this may be the sole method of dispersal. Raiding and subsequent seed spread only occur when bat populations are sufficiently large, relative to resources, to cause competition for food. If competition similarly affects nectarivorous bats and their floral resources, decline in a bat population could lead to reduced seed set and genetic diversity in their food-plant species. Pteropus scapulatus (Little Red Flying Fox) visit the flowers of dozens of Australian and New Guinean species and are believed to play an important role in the pollination of Eucalyptus and Melaleuca. Feeding-interference and raiding "success" by P. scapulatus eating fruit at Wellington Zoo (New Zealand) was studied to infer the importance of population size on cross-pollination. Decrease in population to resource ratio was correlated with decrease in raiding frequency, suggesting a decreased likelihood of cross pollination. These results highlight the value of management practices that promote the maintenance of large populations of nectarivorous megachiropterans. The effects of dominance and food preference on these behaviours were also evaluated. Dominance was inversely correlated to both dispersal and maturity. Contrary to many reports, females were not always subordinate to males. Fruit preference data may be useful for selecting "distracter" trees in orchards prone to damage by fruit bats and for ex situ husbandry concerns. Implications for population-, orchard-, and captive-management are discussed.
