Food Partitioning in Three Syntopic Frogs in a Bornean Plantation

Abstract

In the Brumas Plantation, Tawau, eastern Sabah of Borneo Island, I examined stomach contents of three frog species that are apparently segregating in microhabitat and morphology; Limnonectes cf. kuhlii is riparian, very stocky and always staying near streams or pools; Amnirana niobariensis, with slim body and long limbs, is terrestrial, inhabiting bushes near small pools, and Polypedates macrotis is arboreal, possessing large digital discs, and is found on trees or tall grasses. These three frog species exhibited food partitioning, differing in the amount and size of foods. Young L. cf. kuhlii always had stomach content mass (SCM) up to 3% of body mass (BM), and had the largest average number of small food items. In adult L. cf. kuhlii, few individuals lacked stomach contents, and foods were generally larger than in young frogs. Many A. nicobariensis had no stomach contents, and those with foods usually possessed SCM <2% of BM. Most food items were small in length. Polypedates macrotis tended to take large foods, but many had empty stomachs. Limnonectes cf. kuhlii and P. macrotis exhibited the mean food length smaller than their mouth width. When all frogs were combined, ants occupied the largest portion of all the food items, followed by crickets or grasshoppers, beetles, and spiders in that order.