Using community-based monitoring to estimate demographic parameters for a remote nesting population of the Critically Endangered leatherback turtle

Abstract

Leatherback turtles are exposed to many anthropogenic hazards in the Pacific, but too little is known about their demography to reliably estimate abundance and develop hazard mitigation strategies. Most populations nest in remote locations, and leatherbacks do not generally breed annually, which results in biased demographic parameter estimates using traditional capturemark- recapture (CMR) analysis. We estimated survival and breeding probabilities for a remote nesting population using a long-term community-based CMR study coupled with a multistate open robust design (MSORD) statistical modelling approach. This approach accounts for skipped breeding behaviour and the staggered seasonal arrival and departure of the nesters. The study comprised CMR histories for 178 nesting leatherbacks tagged at Lababia beach on the Huon Coast of Papua New Guinea over a 3 mo seasonal sampling period for 10 austral summer nesting seasons (2000-2009). The best-fit MSORD model comprised constant adult survival (accounting for transients), constant conditional breeding and time-dependent arrival, departure and detection probabilities. The annual survival probability was constant over the 10 yr at ca. 0.85, which is lower than estimated for other leatherback populations but likely reflects a lower probability of nest beach fidelity that has been inferred previously using satellite telemetry. The annual breeding probability for female leatherbacks that skipped the previous nesting season was 0.41. The probability of breeding in consecutive seasons was 0.06, indicative of a skipped breeding behaviour. These first estimates of annual survival and breeding probabilities for a Pacific leatherback stock provide a basis for developing an understanding of regional population dynamics and assessing risk of exposure to anthropogenic hazards such as coastal development and fisheries.