Low growth rates and delayed maturation in Arafura filesnakes (Serpentes : Acrochordidae) in tropical Australia

We carried out a capture-mark-recapture study on Arafura filesnakes (Acrochordus arafurae) in freshwater billabongs of Magela Creek, in the Australian wet/dry tropics, over a period of four years. Growth increments of snakes (71 males, 77 females) recaptured after periods of >6 months were used to estimate growth curves for this population. Given that acrochordids have low metabolic rates, the hypothesis that growth rates are constrained by mass-specific metabolic rates predicts that A. arafurae would grow more slowly, and mature at later ages, than do most other snakes. Our data strongly supported these predictions. Male filesnakes matured at around five years of age, and females matured even later (commencing at around seven years). Male filesnakes grew more slowly than females during juvenile life and matured at smaller body sizes (87 vs 117 cm SVL). Growth trajectories in female filesnakes were best described by the logistic-by-length model rather than by the von Bertalanffy curve, but both models gave a good fit to data on male snakes. An independent data set based on subsequent long-term recaptures provided further support for the calculated growth trajectories. A trade-off between energy allocation to growth vs reproduction was evident in both sexes; growth rates fell after maturation in males, and female filesnakes grew more slowly during years when they reproduced.