Spatial ecology of endangered big-headed turtles (Platysternon megacephalum): Implications of its vulnerability to illegal trapping

Most populations of big-headed turtles (Platysternon megacephalum), a species distributed in 6 countries in Southeast Asia, have been heavily depleted because of severe hunting pressure for the food and pet trade. As with many other Southeast Asian turtles, low densities of individuals and few remaining populations have limited our ability to study, and thus understand, the ecology of this stream-dwelling species. We conducted a radiotelemetry study on 31 adult big-headed turtles to investigate their home range, movements, and habitat use. The home ranges of big-headed turtles were small, with a mean 100% home-range length of 97m and 100% minimum convex polygon size of 996m². Movements by male and female big-headed turtles did not differ and both sexes moved longer distances in wet seasons than in dry seasons. Both males and females showed non-random habitat use, preferring to stay in pools rather than in other in-stream or terrestrial habitats. Stream width and depth, and substrate type affected microhabitat use. Big-headed turtles were highly aquatic and movements in terrestrial habitats were rare. Thus, turtle populations are concentrated in streams where they may be easily targeted by illegal trappers. We recommend increasing patrol efforts along streams to remove any traps or fish hooks. Innovative methods, such as installation of infrared-triggered cameras equipped with remote viewing near or along streams, may be needed to tackle illegal turtle trapping effectively.