Spanier Matthew J
Associated Colleges of the Midwest, Apartado 10265, San José, Costa Rica.
Rev Biol Trop. 2010 Dec;58(4):1237-46. doi: 10.15517/rbt.v58i4.5408.
Leatherback sea turtles (Dermochelys coriacea) nest on dynamic, erosion-prone beaches. Erosive processes and resulting nest loss have long been presumed to be a hindrance to clutch survival. In order to better understand how leatherbacks cope with unstable nesting beaches, I investigated the role of beach erosion in leatherback nest site selection at Playa Gandoca, Costa Rica. I also examined the potential effect of nest relocation, a conservation strategy in place at Playa Gandoca to prevent nest loss to erosion, on the temperature of incubating clutches. I monitored changes in beach structure as a result of erosion at natural nest sites during the time the nest was laid, as well as in subsequent weeks. To investigate slope as a cue for nest site selection, I measured the slope of the beach where turtles ascended from the sea to nest, as well as the slopes at other random locations on the beach for comparison. I examined temperature differences between natural and relocated nest sites with thermocouples placed in the sand at depths typical of leatherback nests. Nests were distributed non-randomly in a clumped distribution along the length of the beach and laid at locations that were not undergoing erosion. The slope at nest sites was significantly different than at randomly chosen locations on the beach. The sand temperature at nest depths was significantly warmer at natural nest sites than at locations of relocated nests. The findings of this study suggest leatherbacks actively select nest sites that are not undergoing erosive processes, with slope potentially being used as a cue for site selection. The relocation of nests appears to be inadvertently cooling the nest environment. Due to the fact that leatherback clutches undergo temperature-dependent sex determination, the relocation of nests may be producing an unnatural male biasing of hatchlings. The results of this study suggest that the necessity of relocation practices, largely in place to protect nests from erosion, should be reevaluated to ensure the proper conservation of this critically endangered species.
棱皮龟（蠵龟）在动态的、易受侵蚀的海滩上筑巢。长期以来，侵蚀过程及由此导致的巢穴损失一直被认为是影响卵成功孵化的一个障碍。为了更好地了解棱皮龟如何应对不稳定的筑巢海滩，我在哥斯达黎加的甘多卡海滩调查了海滩侵蚀在棱皮龟巢穴选址中的作用。我还研究了巢穴迁移（甘多卡海滩为防止巢穴因侵蚀而损失所采取的一种保护策略）对正在孵化的卵的温度的潜在影响。我监测了在巢穴产卵期间以及随后几周内，自然巢穴所在位置因侵蚀导致的海滩结构变化。为了研究坡度作为巢穴选址的一个线索，我测量了海龟从海中上岸筑巢处的海滩坡度，以及海滩上其他随机位置的坡度以便进行比较。我用热电偶测量了自然巢穴和迁移后巢穴所在位置的温度差异，热电偶放置在棱皮龟巢穴典型深度的沙子中。巢穴沿着海滩长度呈非随机的聚集分布，且位于未遭受侵蚀的位置。巢穴处的坡度与海滩上随机选择的位置有显著差异。自然巢穴深度处的沙子温度明显高于迁移后巢穴所在位置的沙子温度。这项研究的结果表明，棱皮龟会积极选择未经历侵蚀过程的巢穴位置，坡度可能被用作选址的一个线索。巢穴迁移似乎在无意中使巢穴环境变凉。由于棱皮龟的卵会经历温度依赖型性别决定，巢穴迁移可能会导致孵化出的幼龟出现不自然的雄性偏向。这项研究的结果表明，为保护巢穴免受侵蚀而广泛采用的迁移措施的必要性应重新评估，以确保对这种极度濒危物种的妥善保护。
