The value of long-term, community-based monitoring of marine turtle nesting

Abstract

Monitoring of nesting beaches is often the only feasible and low-cost approach for assessing sea turtle populations. We investigated spatio-temporal patterns of sea turtle nesting activity monitored over  successive years in the Lamu archipelago, Kenya. Community-based patrols were conducted on  stretches of beach clustered in five major locations. A total of , nests were recorded: , (.%) green turtle Chelonia mydas nests,  (.%) hawksbill Eretmochelys imbricata nests,  (.%) olive ridley Lepidochelys olivacea nests and  (.%) unidentified nests. Nesting occurred year-round, increasing during March–July, when % of nests were recorded. A stable trend in mean annual nesting densities was observed in all locations. Mean clutch sizes were . ± SE  eggs (range –) for green turtles,  ± SE  eggs (range –) for hawksbill turtles, and  ± SE  eggs (range –) for olive ridley turtles. Curved carapace length for green turtles was – cm, and mean annual incubation duration was . ± SE . days. The mean incubation duration for green turtle nests differed significantly between months and seasons but not locations. The hatching success (pooled data) was .% (n = ,) and was higher for in situ nests (. ± SE .%) compared to relocated nests (. ± SE .%). The results highlight the important contribution of community-based monitoring in Kenya to sustaining the sea turtle populations of the Western Indian Ocean region