Nesting Distances and Elevations

<b>Methods</b>We obtained nesting locations directly from each National Seashore. Nest locations were recorded by trained volunteers and National Park Service biologists through daily, early morning surveys of all beaches. Nesting female sea turtles leave conspicuous marks in the sand that can be used to determine the species and location of a nest if eggs are deposited. We made use of all nest locality data for the years in which Seashores used handheld GPS units for recording precise latitude and longitude (Canaveral National Seashore (CANA): 2013–2016, Cumberland Island National Seashore (CUIS): 2003–2017, Cape Lookout National Seashore (CALO): 2001–2015, Cape Hatteras National Seashore (CAHA): 2005–2016). We quantified the shortest distance between each nest site and high water line using the Near tool in ArcGIS (version 10.4). We used the mean high water line vector, retrieved from NOAA or USGS, for the year closest to the time when each nest was recorded (see Table 2 in publication for years and sources). Based on the angle between nest point and shoreline, we were able to determine which nests were east of the high water line (below the high water mark) and recorded these as negative values. We analyzed the cape areas within CALO and CAHA separately, because cape areas tend to accrue more sand, have wider beaches, and have more year-to-year high water line movement and sediment availability. We based the delineation for a “cape” area on a rectangle encompassing the area where the shoreline forms a distinctly concave shape as the directional orientation changes sharply from the roughly linear orientation of the rest of the island. CANA and CUIS do not have cape areas, and so the beach was analyzed as one for these two Seashores. We analyzed the current elevational distribution of sea turtle nests by extracting digital elevation values for nest sites from USGS digital elevation model (Caffrey et al. 2018).<b>File attributes</b>All data are in meters, park names are NPS abbreviations, two species included: loggerhead sea turtle (Cc), green sea turtle (Cm)<b></b>

<b>研究方法</b>本研究直接从各国家海岸（National Seashore）获取海龟筑巢点位数据。筑巢点位由经过培训的志愿者与国家公园管理局（National Park Service, NPS）生物学家通过每日清晨对全海滩的巡查进行记录。产卵的雌性海龟会在沙地上留下明显痕迹，若巢穴内已产下龟卵，可通过该痕迹判定筑巢物种与点位位置。本研究使用了各国家海岸采用手持全球定位系统（Global Positioning System, GPS）设备记录精确经纬度年份内的全部筑巢点位数据（卡纳维拉尔角国家海岸（Canaveral National Seashore, CANA）：2013–2016年；坎伯兰岛国家海岸（Cumberland Island National Seashore, CUIS）：2003–2017年；瞭望角国家海岸（Cape Lookout National Seashore, CALO）：2001–2015年；哈特拉斯角国家海岸（Cape Hatteras National Seashore, CAHA）：2005–2016年）。本研究借助ArcGIS软件（版本10.4）中的Near工具，计算每个筑巢点位与高潮线之间的最短距离。本研究采用与每处筑巢记录时间最接近年份的平均高潮线矢量数据，该数据取自美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）或美国地质调查局（United States Geological Survey, USGS）（相关年份与数据来源详见论文表2）。基于筑巢点位与海岸线的夹角，本研究可判定哪些巢穴位于高潮线以东（高潮线下方），并将该类距离记为负值。鉴于瞭望角与哈特拉斯角国家海岸内的岬角区域往往沉积更多沙量、海滩更宽阔，且高潮线的年际变动与沉积物可获得性更强，本研究对这两处海岸内的岬角区域单独开展分析。本研究对“岬角区域”的划定依据为：以海岸线呈现明显凹形、且其走向与岛屿其余区域的近似线性走向发生急剧转变的区域为范围绘制矩形。卡纳维拉尔角与坎伯兰岛国家海岸无岬角区域，因此针对这两处海岸将整片海滩作为统一单元开展分析。本研究通过从美国地质调查局数字高程模型（Caffrey等，2018）中提取筑巢点位的数字高程值，分析了海龟筑巢的当前高程分布特征。
<b>文件属性</b>所有数据单位均为米；公园名称采用国家公园管理局（NPS）缩写；涵盖2种海龟：蠵龟（loggerhead sea turtle, Cc）、绿海龟（green sea turtle, Cm）