Ecology of a Low-Energy Specialist: Food Habits and Reproductive Biology of the Arafura Filesnake (Acrochordidae)

Abstract

Under the hypothesis that low metabolic rates are adaptations to low rates of energy throughput, taxa with unusually low metabolic rates-such as acrochordid snakes-might be expected to show unusually low rates of feeding, growing, maturing and reproducing. Field studies of Acrochordus arafurae in the Alligator Rivers Region of tropical Australia show that these aquatic snakes feed and reproduce less frequently than do most other snake species studied previously. Published data on other acrochordids suggest similarly low rates. A. arafurae feeds exclusively on fishes, including carrion. Live prey are subdued by constriction. The proportion of freshly-captured snakes containing food (5%) is lower in this species than in most other snakes. Feeding frequency may be very low and digestive efficiency may be unusually high in A. arafurae. Reproduction is seasonal, with an average litter of about 17 young (11-25) depending upon maternal body size. Neonates are large (360 mm, 31 g) and relative clutch mass is high (0.53). However, the proportion of adult-sized females that are reproductive (7%) is lower than in any previously studied snake species, suggesting a low frequency of reproduction in individual females. Population densities and biomass of A. arafurae vary among billabongs, but may reach extraordinarily high levels (100 snakes per hectare, >50 kg per hectare).