Relative Abundances of Frogs and Lizards in Forests of Southeast Asia

Abstract

Large samples of frogs and lizards from eight lowland forested environments distributed in Borneo, Malaya, and northeastern Thailand are used to compare abundances. Frogs and lizards were divided into riparian and non-riparian subsamples, and each of those into arboreal and terrestrial categories. Non-riparian lizards were further divided into diurnal and nocturnal groups. The two forests in Thailand lie in an area having a pronounced dry season and prolonged intervals of extremely high temperatures in contrast to the Indo-Malayan environments which lack those features. The differential effects of drought and high temperatures on portions of the environment during the day and the varying susceptibilities of the taxonomic and ecological groups probably are responsible for differences observed in relative abundance. Frogs of all categories were more numerous in Borneo and Malaya than in Thailand. Diurnal arboreal lizards were much more abundant in Borneo and Malaya, whereas terrestrial ones, nocturnal and diurnal, were more abundant in both Thai forests. Nocturnal arboreal lizards showed a mixed picture. LARGE SAMPLES OF AMPHIBIANS and reptiles collected in lowland forests in Sarawak (10 37' N-3? 21' N), West Malaysia (30 11' N-30 22' N), and northeastern Thailand (140 30' N) provide material for comparison of abundances of these animals in various types of forests in Southeast Asia. Although we have only a single, time-limited sample from each locality, and only a single sample from several types of environments, the likelihood of replication is so small relative to likelihood of destruction of the forests that analysis seems justified in spite of these sampling deficiencies. Brown and Alcala (1961) reported on collections of amphibians and repriles from montane forests in the Philippines, but no comparison will be made with their samples in this paper because of the known effect of elevation on abundances of amphibians and reptiles (Scott 1976). Furthermore, low species richness in the Philippine samples adds another complicating factor. Comparison with Scott's (1976) analysis of densities of litter herpetofaunas in Central America is dealt with elsewhere (Inger 1980).