SOME STUDIES ON THE MORPHOLOGY AND BIOLOGY OF THE COMMON HOUSE GEKKONIDAE IN SINGAPORE

Abstract

Some aspects of the biology of the common house geckos in Singapore were investigated. Of the five species recorded, the three more common ones were Gehyra mutilata (Wiegmann), Hemidactylus frenatus Dumeril & Bibron and Platyurus platyurus (Schneider). The taxonomy and systematic status of the five species are reviewed and the morphological characteristics discussed. Various bionomic aspects and their distribution were considered. Changes in the species populations, detected after comparison with earlier reports by other authors, were attributed to the rapid pace of modernisation in Singapore. The 3 commoner species were investigated for the anatomy, histology and histochemistry of their alimentary canals. Differences were observed and discussed but, on the whole, they conformed to the basic reptilian plan. The structure of the gut agreed with the geckos' feeding habit. Analysis of the food contents in the alimentary system revealed that although geckos were mainly insectivorous, the diet was not restricted. Herbivorous feedinc; is recorded in Platyurus platyurus for the first time. Composition of the diet showed that availability rather than selectivity of food was the main factor influencing their diet. Differences in prey size could be correlated with predator size as well as sexual size dimorphism of the predator. This system increases the efficiency of the species in exploiting its habitat. The digestive enzymes indicate that the main sites of digestion occurred in the stomach and the anterior part of the small intestine, with the pancreas serving as an important organ of digestion. The enzymes present also indicate that the geckos can digest food of plant origin but the lack of cellulose reduces this ability considerably. Investigations of the eggs, incubation period and hatchlings show that the incubation period is short and that there are no breeding seasons. Hemidactylus frenatus had the shortest incubation period. Use of a common egg-laying site by females of different species is observed here for the first time. Growth of hatchlings was found to be rapid and sexual maturity was reached within 4 to 6 months after hatching. Tail regeneration rate was also found to be rapid, requiring between 14 and 20 weeks for a complete regeneration. The fastest regeneration rate was observed in Hemidactylus frenatus and the significance of this as a contributory factor to its success is discussed.