Climate change implications for the nest site selection process and subsequent hatching success of a green turtle population

Abstract

Sandy beach habitat where sea turtles nest will be affected by multiple climate change impacts. Before these impacts occur, knowledge of how nest site selection and hatching success vary with beach microhabitats is needed to inform managers on how to protect suitable habitats and prepare for scientifically valid mitigation measures at beaches around the world. At a highly successful green turtle (Chelonia mydas) rookery at Akumal, Quintana Roo, Mexico, we measured microhabitat characteristics along the beach crawl (rejected sites) and related nest site conditions (selected sites) to subsequent hatching success rates for 64 nesting events. To our knowledge, this is the first study to report environmental data along the nesting crawl for a green turtle population and the first to use natural breaks in the data to describe their preferred habitat ranges. Our results indicate that turtles were likely using a combination of cues to find nest sites, mainly higher elevations and lower sand surface temperatures (Kruskal-Wallis test, H = 19.84, p < 0.001; H = 10.78, p < 0.001). Hatching success was significantly and negatively correlated to sand temperature at cloaca depth (Spearman’s ρ = −0.27, p = 0.04). Indeed, the preferred range for cloaca sand temperatures at the nest site (26.3–27.5 °C) had significantly higher hatching success rates compared to the highest temperature range (Tukey HSD = 0.47, p = 0.05). Sand temperatures at various depths were intercorrelated, and surface and cloaca depth sand temperatures were correlated to air temperature (ρ = 0.70, p = 0.00; ρ = 0.26, p = 0.04). Therefore, rising air temperatures could alter sand temperature cues for suitable nest sites, preferred nest site ranges, and produce uneven sex ratios or lethal incubating temperatures. Elevation cues and preferred ranges (1.4–2.5 m) may also be affected by sea level rise, risking inundation of nests.