ASPECTS OF THE FEEDING BIOLOGY OF FRUIT BATS (PTEROPODIDAE) ON LOMBOK-ISLAND, NUSA-TENGGARA, INDONESIA

Ingested pollen was assessed from the alimentary tract of 10 pteropodid bat species from 4 areas on Lombok I. during September and October 1987. A total of 28 pollen types was recorded. The common small and medium sized bats visited, on average, from 2.5 to 5.2 plant species per night, with a maximum of 10 visited in one night. The overall pollen diet generally differed between Eonycteris spelaea, Rousettus amplexi-caudatus and Macroglossus minimus, irrespective of area. These species also differed from Cynopterus brachyotis, C. horsfieldi and C. titthaecheilus. However, C. brachyotis, C. horsfieldi and C. titthaecheilus were similar to each other and with M. minimus. Of the less frequently collected species, Aethalops alecto appeared to have a pollen diet closest to Cynopterus brahyotis. The larger fruit bats : Pteropus lombocensis, Acerodon mackloti and Dobsonia peroni have a pollen diet which appeared distinct to the smaller species. The extent of pollen dietary niche overlap reflected the above pollen dietary groupings. For the six common pteropodid species there was a trend for increased pollen dietary niche overlap to occur with increasing body size (forearm length) between species pairs, but not with morphological characters related to the feeding apparatus. The extent of nectarivory of the six common species was highly positively correlated with total tongue length and not to sub-familial systematic position. There is some evidence that E. spelaea feed in social groups with juveniles usually associating with adult females, and for M. minimus to feed in a more solitary manner. E. spelaea, M. minimus and R. amplexicaudatus were primarily nectarivorous. Cynopterus spp. had a pollen dietary niche breadth approaching these nectarivorous species at near-coastal sites, but this decreased at the inland, higher altitude sites. Conversely the pollen dietary niche breadth of E. spelaea, M. minimus and R. amplexicaudatus increased at these inland sites. These changes are discussed. Only C. titthaecheilus and C. brachyotis had substantial numbers of individuals that injested plant epidermis. Insects were injested incidentally. Plant seeds were present only in Cynopterus spp. and then uncommonly.