Sexual dimorphism and reproductive biology of three species of colubrid snakes from western Java, Indonesia

The reproductive biology of tropical snakes is poorly understood, even for abundant widely distributed taxa. We gathered data on three species of colubrid snakes – Boiga dendrophila (N = 111), Coelognathus flavolineatus (N = 44) and C. radiatus (N = 261) collected for the commercial trade in skins near Cirebon, West Java. Males outnumbered females in all three species, but with seasonal variation in sex ratios. Adult males averaged larger than adult females in B. dendrophila, were similar in size to females in C. flavolineatus, and were smaller than females in C. radiatus. In the latter species, males had relatively longer tails than did females. Females of all three species produced multiple clutches per annum, over most or all of the year, but the intensity of reproduction varied among seasons. Testis volumes varied among months in male Boiga but not in the two Coelognathus species. Mean clutch sizes were similar among species (range of means 8.5–9.7) and were not closely linked to maternal body size. High reproductive rates and a concentration of culling on adult males suggest that the commercial harvest of these species in Java does not threaten population viability.