Can camera traps monitor Komodo dragons a large ectothermic predator?

Camera trapping has greatly enhanced population monitoring of often cryptic and low abundance apex carnivores. Effectiveness of passive infrared camera trapping, and ultimately population monitoring, relies on temperature mediated differences between the animal and its ambient environment to ensure good camera detection. A criterion presumed less certain in ectothermic predators such as large varanid lizards. Here we evaluated the effectiveness of camera trapping to potentially monitor the population status of the Komodo dragons (Varanus komodoensis), an apex predator, using site occupancy approaches. We compared site specific estimates of site occupancy and detection derived from using camera traps and cage traps at 181 trapping locations established across six sites on four islands in Komodo National Park in Eastern Indonesia. Detection and site-occupancy at each site were estimated using 8 competing models that considered site specific variation in occupancy (psi) and varied detection probabilities (p) according to detection method, site and survey number using a single season site occupancy modelling approach. The most parsimonious model [psi (site), p (site*survey); ω = 0.74] suggested that site occupancy estimates differed among sites. Detection probability varied as an interaction between site and survey number. Our results indicated that overall camera traps produced similar estimates of detection and site occupancy to cage traps, irrespective of being paired, or unpaired, with cage traps. However at one site there was some evidence that detection was effected by trapping method but irrespective was too low to produce an accurate occupancy estimate. Overall because camera trapping is logistically more feasible it may provide, with further validation, an alternative method for evaluating long-term site occupancy patterns in Komodo dragons, and potentially other large reptiles, aiding conservation of this species.