Long-term monitoring of marine turtle nests in northeastern Brazil

Abstract: This study monitored marine turtle nests in a region known as the Potiguar Basin, which stretches from the northern region of Rio Grande do Norte State (5°4’1.15” S, 36°4’36.41” W) to eastern Ceará State (4°38’48.28” S, 37°32’52.08” W) in Brazil. We collected data from January 2011 to December 2019 to identify species of sea turtles that spawn in the basin, to analyze the nesting spatial-temporal pattern and nests characteristics, and to record effects of environmental and anthropic factors on nests. A field team examined sea turtle tracks and nests signs. Turtle clutches were monitored daily until hatchings emerged from the nests. We monitored nests of hawksbill (Eretmochelys imbricata; n = 238) and olive Ridley turtles (Lepidochelys olivacea; n = 103). The nesting season for E. imbricata occurred between December and May and for L. olivacea from March to August. Hawksbills had clutch size, incubation time, number of unhatched eggs, and dead hatchlings higher than olive Ridley turtles; nevertheless, they presented lower hatching success. Precipitation between 0 and 22 mm and relative humidity (RH) higher than 69% increased the hatching success rate for E. imbricata; however, rainfall above 11 mm and RH 64% had the same effect for L. olivacea. Signs of egg theft and human presence (e.g. vehicle traffic and plastic residues on the beach) were recorded and are considered threats to nests. The results of our long-term monitoring study in the Potiguar Basin provide basis for the implementation of mitigation measures and adoption of management policies at nesting beaches in this Brazilian region.摘要：本研究对巴西波蒂瓜尔盆地（Potiguar Basin）区域的海龟巢穴开展监测，该区域范围北起北里奥格兰德州（Rio Grande do Norte）北部（南纬5°4′1.15″，西经36°4′36.41″），南至塞阿拉州（Ceará）东部（南纬4°38′48.28″，西经37°32′52.08″）。研究于2011年1月至2019年12月期间收集数据，旨在识别该盆地内产卵的海龟物种、分析筑巢时空模式与巢穴特征，并记录环境与人为因素对巢穴的影响。野外调查团队对海龟爬行轨迹与巢穴痕迹进行排查，每日监测海龟窝卵直至幼龟破巢而出。 本次监测共覆盖玳瑁（Eretmochelys imbricata；n=238）与橄榄雷德利海龟（Lepidochelys olivacea；n=103）两类物种。玳瑁的筑巢季为12月至次年5月，橄榄雷德利海龟的筑巢季则为3月至8月。相较于橄榄雷德利海龟，玳瑁的窝卵数、孵化时长、未孵化卵数以及死亡幼龟数均更高，但其孵化成功率更低。 对于玳瑁而言，0~22 mm的降雨量以及高于69%的相对湿度（RH）可提升其孵化成功率；而对于橄榄雷德利海龟，降雨量超过11 mm以及相对湿度为64%时可达到同等效果。本研究同时记录了盗卵行为与人类活动痕迹（例如海滩上的车辆通行与塑料垃圾），上述因素均被视为巢穴的威胁因子。 本项在波蒂瓜尔盆地开展的长期监测研究结果，可为该巴西区域筑巢海滩的减缓措施实施与管理政策制定提供依据。