Impact of human disturbance on the thermoregulatory behaviour of the endangered ringed sawback turtle (Graptemys oculifera)

Abstract

Abstract Human recreational disturbance of riverine environments may be contributing to population declines of aquatic organisms worldwide. Aquatic turtles that are heavily dependent on basking in sunlight to maintain an optimal body temperature may abandon basking perches because they perceive humans as potential predators. The impact of boat traffic, the availability of basking structures, and various environmental factors on the basking behaviour of the ringed sawback turtle (Graptemys oculifera) was assessed at two sites on the Pearl River, Mississippi, USA. This information was used to model the likely effects of human disturbance on the body temperature of large female turtles. Both the duration of basking and the percentage of turtles in a basking group that abandoned their basking perch were influenced by the availability of alternative basking sites, frequency of boat traffic, boat speed enforcement zones (‘wake’ or ‘no wake’), boat type, air temperature, weather conditions, and Julian day. A simulation model of anthropogenically disturbed and undisturbed adult female ringed sawbacks showed that disturbance probably decreases the mean daily body temperature, especially at higher disturbance probabilities and in May, when the air temperature is low. Management recommendations are provided that minimize the adverse effects of unintentional human disturbance of the ringed sawback to enable more effective conservation of this endangered, endemic species. Such methods are likely to be useful elsewhere as recreational disturbance becomes a greater conservation issue worldwide.