Impact of severe drought on movement and survival of freshwater turtles in the Gwydir Wetlands, Australia

Abstract

<p><b>Context.</b> The increasing number and length of droughts is a threat for many freshwater turtle populations. <b>Aims.</b> Our study investigated the movement and survival of <i>Emydura macquarii, Chelodina expansa</i> and <i>Chelodina longicollis</i> in drought and flood conditions. <b>Methods.</b> Turtles were captured in the Gwydir Wetland, New South Wales, Australia. We assessed the species composition of live captures and carcasses over the drought to assess relative survival among species. Using radiotelemetry, we compared the movement of <i>E. macquarii</i> and <i>C. longicollis</i> over a severe drought followed by a flood. <b>Key results.</b> For tracked turtles with known fates, 28.6% of <i>E. macquarii</i> and 7.1% of <i>C. longicollis</i>, died during the drought. The proportional composition of captured turtles compared with those of desiccated shells suggested that C. expansa had the highest mortality. <i>E. macquarii</i> and <i>C. longicollis</i> both appeared to navigate terrestrially and moved further in the flood water than in the drought, but <i>C. longicollis</i> moved further generally. <b>Conclusions.</b> Our findings suggest that turtles in isolated wetlands of the northern Murray–Darling Basin are at high risk of mortality during severe drought. Implications. Environmental water delivery during periods of sustained drought will be critical to ensure persistence of populations of long-lived species such as turtles.</p>