Behavioural ecology of the eastern brownsnake, pseudonaja textilis, and implications for human envenomation

I used surgically implanted miniature radio-transmitters to conduct a broad behavioural ecology study of the eastern brownsnake, Pseudonaja textilis, a large (to 2 m), slender, fast-moving elapid snake responsible for most snakebite fatalities in Australia. In order to minimise trauma to the snake, I modified anaesthesia (use of nitrous oxide to relax the animal prior to induction of surgical—level anaesthesia with halothane); implantation techniques (reliance on “blunt” dissection rather than cutting of tissues after the initial incision; placement of antenna in the peritoneal cavity rather than subcutaneously; anchoring the transmitter in place to avoid slippage in a position anterior to the incision), and removal (use of a "disposable" silicon casing to eliminate problems associated with tissue adhesion to the antenna). Comparisons of changes in body mass of telemetered versus non— telemetered snakes indicated that the transmitters had no detectable effects on growth rate, even in a drought year when such effects might be most obvious. Encounters between humans and dangerously venomous snakes put both participants at serious risk, so the determinants of such encounters warrant attention. I set out to identify factors influencing the probability that a human walking in agricultural land near the town of Leeton (in the Murrumbidgee Irrigation Area in south-eastem Australia) would come into close proximity to a brownsnake. My study area is typical of many of the agricultural landscapes occupied by B. texiis. Over a three-year period, I walked regular transects to quantify the number and rate of snake encounters, and the proportion of snakes above-ground which could be seen. The rate of encounters depended upon a series of factors, including season, time of day, habitat type, weather conditions (wind and air temperature) and shade of the observer’s clothing (light versus dark)