Resource partitioning in a community of Philippine skinks (Sauria: Scincidae)

Abstract

Eleven species of variously sympatric species of skinks were studied in southern Luzon, Philippines. In snout-vent length these species varied from 27 to 117 mm. Species diversity was found to be positively correlated with vegetation density. The food analyses were based on a total of 2481 adult specimens collected in monthly samples of about 30 individuals of each species for a period of one year. Excised stomachs contained 10,739 food items. Food size, volume, and seasonal representation were stressed in the analyses of each species. Additionally, seasonal insect abundance data were obtained for all of the major microhabitats of the lizard species. Annual abdominal fat accumulation and degradation cycles were investigated in all species. We found almost no evidence of food niche partitioning in most species investigated; exceptions were species that lived in unusual environments (arboreal, semiaquatic, marine littoral) inhabited by single species. However, food selection may be playing a role in the distribution of some terrestrial species living in close contact on the floor of local moist evergreen forests. There is no clear basis for suggesting that prey were selected on the basis of nutritional value. Nor was there a significant correlation between predator and prey size or volume-partly because several species frequently fed on inordinately large prey. Seasonal switching of prey types was common among almost all the species. The only exceptions were those that lived in very stable environments, such as the marine littoral. In all instances, such switching could be shown to be directly related to local insect abundances. Only about half of the local skinks possess abdominal fat at any time of the year. Of those that do, the annual accumulation and degradation cycle is similar in both males and females. In every species examined the cycle can be shown to be linked to seasonal insect abundance. The Caramoan Peninsula of southern Luzon contains a number of habitats, and no species of skink ranges through all of them. The local forest is richest in number of species, and this is believed due to its greater structural complexity. Among species inhabiting similar habitats there is significant ecological replacement, both horizontally as well as vertically.