Marine turtles are not fussy nesters: a novel test of small-scale nest site selection using structure from motion beach terrain information

Abstract

BackgroundNest selection is widely regarded as a key process determining the fitness of individuals and viability of animal populations. For marine turtles that nest on beaches, this is particularly pivotal as the nesting environment can significantly control reproductive success.The aim of this study was to identify the environmental attributes of beaches (i.e., morphology, vegetation, urbanisation) that may be associated with successful oviposition in green and loggerhead turtle nests.MethodsWe quantified the proximity of turtle nests (and surrounding beach locations) to urban areas, measured their exposure to artificial light, and used ultra-high resolution (cm-scale) digital surface models derived from Structure-from-Motion (SfM) algorithms, to characterise geomorphic and vegetation features of beaches on the Sunshine Coast, eastern Australia.ResultsAt small spatial scales (i.e., <100 m), we found no evidence that turtles selected nest sites based on a particular suite of environmental attributes (i.e., the attributes of nest sites were not consistently different from those of surrounding beach locations). Nest sites were, however, typically characterised by occurring close to vegetation, on parts of the shore where the beach- and dune-face was concave and not highly rugged, and in areas with moderate exposure to artificial light.ConclusionThis study used a novel empirical approach to identify the attributes of turtle nest sites from a broader ‘envelope’ of environmental nest traits, and is the first step towards optimizing conservation actions to mitigate, at the local scale, present and emerging human impacts on turtle nesting beaches.

Leave No Trace ordinances for coastal species management: influences on sea turtle nesting success

“…Sea turtle nest site selection is highly variable, and a female turtle may abandon her nesting attempt at any time for reasons beyond obstructions, including human disturbance, artificial lighting, the presence of predators, and unfavorable sand conditions (Hailman & Elowson 1992, Garmestani et al 2000, Chen et al 2007, Kelly et al 2017, Silva et al 2017. Nests laid too close to the water are at increased risk of inundation and erosion, while nests closer to the dune risk increased predation of the eggs and emergent hatchlings (Fowler 1979, Mazaris et al 2009, O'Connor et al 2017, Ware & Fuentes 2018).…”

Robotic Vehicles Enable High-Resolution Light Pollution Sampling of Sea Turtle Nesting Beaches

“…Research 7 North Carolina State Parks. Retrieved online at https://www.ncparks.gov on other anthropogenic variables in addition to light that may influence a sea turtle's decision to nest should be incorporated in future studies (Mazor et al, 2013;Weishampel et al, 2016;Kelly et al, 2017) and more nuanced multivariate analyses of nesting characteristics can provide a more holistic understanding of what effects nesting activity. Ongoing coastal development can also result in changes in relationships of nesting data and light.…”

“…Technological advancements in the use of unmanned aircraft systems (UAS) can produce highly accurate digital elevation models derived from Structure-from-Motion (SfM) photogrammetry and aerial LiDAR (Seymour et al, 2018;Johnston, 2019). These models can accurately extract environmental and topographical features of a shoreline such as beach slope, locations of buildings, vegetation, and escarpments that can influence nest site selection (Kelly et al, 2017). By coupling drone-based high resolution digital elevation models with high resolution light pollution measurements, this method could accurately estimate where topographical features obstruct the path of anthropogenic light, and which individual lights are most problematic, providing the information needed for well-targeted management policies (Weishampel et al, 2016).…”

“…Therefore, protection of nesting habitat is crucial to ensure these species can recover. Nest site selection is influenced by many environmental factors including sand characteristics, wave energy, terrestrial predation, and nearby oceanic currents (Donlan et al, 2010;Kelly et al, 2017). Nesting sea turtles also face a number of anthropogenic threats such as bycatch in fisheries, interaction with marine debris, and habitat degradation from coastal development, which have all contributed to a global sea turtle population decline (Donlan et al, 2010).…”

“…Researchers have mounted light meters on small tripods aimed at the horizon to collect relative light radiance in various directions (Salmon and Witherington, 1995). Sky Quality Meters (SQM, Unihedron) measure light with wavelengths in the range adult sea turtles are known to respond to and have been used to assess impacts of light pollution on sea turtle nesting behavior; proving to be an accessible, affordable, and accurate tool to measure nighttime sky brightness (Levenson et al, 2004;Bonner, 2015;Constant, 2015;Kelly et al, 2017). SQMs have conventionally collected nighttime light on stationary tripods across dune transects or perpendicular to the dune in specific increments along the beach (Bonner, 2015;Constant, 2015).…”