Effects of Tropical Cyclonic Storms on Flying Fox Populations on the South Pacific Islands of Samoa

The South Pacific islands of Samoa have two extant flying fox species, Pteropus samoensis and P. tonganus. Following two severe cyclonic storms, we examined their differential behavioral responses and evaluated the effectiveness of recently established reserves in providing refugia. Although the cyclones disrupted activity patterns and foraging behavior for both species, comparisons with pre-storm data suggested that the more common, widely distributed P. tonganus experienced more severe population declines than the endemic P. samoensis. This differential mortality could be explained by a combination of ecological and behavioral factors. P. tonganus had a greater tendency to enter villages to feed on fallen cultivated fruits, making it more vulnerable to human hunting and predation by domestic animals. In addition, P. samoensis appeared to use survival strategies not observed in P. tonganus. Leaves, which were far more available than flowers or fruits in the immediate post-storm period, comprised a major part of the post-storm diet of P. samoensis. This species also fed on the fleshy bracts of a storm-resistant native liana, (Freycinetia reineckei). In contrast, a seasonally important food of P. tonganus is nectar from the delicate flowers of Syzygium inophylloides (asi), a canopy tree that is very vulnerable to wind damage and has become increasing scarce with the clearing of lowland forest. Rainforest reserves, established prior to the storms, served as adequate refugia for local P. samoensis populations, which appeared to feed relatively close to their roosts, primarily in native forest, but did not protect P. tonganus populations, which traveled outside reserves to forage in areas lacking hunting bans. Although wind damage was patchy and not consistent between storms, areas of high topographic complexity (e.g., volcanic cones and deep valleys) were the most likely to retain areas with some foliage and should be given priority in the design of future reserves.