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>