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

Abstract

Nesting sea turtles appear to avoid brightly lit beaches and often turn back to sea prematurely when exposed to artificial light. Observations and experiments have noted that nesting turtles prefer darker areas where buildings and high dunes act as light barriers. As a result, sea turtles often nest on darker beaches, creating spatial concentrations of nests. Artificial nighttime light, or light pollution, has been quantified using a variety of methods. However, it has proven challenging to make accurate measurements of ambient light at fine scales and on smaller nesting beaches. Additionally, light has traditionally been measured from stationary tripods perpendicular to beach vegetation, disregarding the point of view of a nesting sea turtle. In the present study, nighttime ambient light conditions were assessed on three beaches in central North Carolina: a developed coastline of a barrier island, a nearby State Park on the same barrier island comprised of protected and undeveloped land, and a completely uninhabited wilderness on an adjacent barrier island in the Cape Lookout National Seashore. Using an autonomous terrestrial rover, high resolution light measurements (mag/arcsec 2 ) were collected every minute with two ambient light sensors along transects on each beach. Spatial comparisons between ambient light and nesting density at and between these locations reveal that highest densities of nests occur in regions with lowest light levels, supporting the hypothesis that light pollution from coastal development may influence turtle nesting distribution. These results can be used to support ongoing management strategies to mitigate this pressing conservation issue.

Globally important refuge for the loggerhead sea turtle: Maio Island, Cabo Verde

“…The island of Maio has pristine beaches without light pollution, extensive coastal infrastructure or mass tourism, and with high numbers and densities of loggerhead turtle nests. Given that coastlines globally are becoming increasingly urbanized, illuminated and disturbed (Godoy & Stockin, 2018; Windle et al, 2018; Blackburn et al, 2019; Winger et al, 2019), and that sea turtles are considered conservation-dependent (Godfrey & Godley, 2008), undisturbed rookeries such as Maio are important refuges for conservation. The protection of these unique habitats must be prioritized to conserve coastal biodiversity (Antworth et al, 2006).…”

Commentary: Brightness of the Night Sky Affects Loggerhead (Caretta caretta) Sea Turtle Hatchling Misorientation but Not Nest Site Selection

“…Stanley et al (2020) are not alone in the inappropriate use of SQMs to measure light at the horizon. Other papers and theses have been published with this approach (e.g., Bonner, 2015;Kelly et al, 2017;Price et al, 2018;Windle et al, 2018). We hope that future research on light pollution in coastal environments, and in ecology more broadly, avoids this misuse of the SQM for horizon measurements.…”

Impacts of artificial light at night in marine ecosystems—A review

“…However, less research has been conducted to examine the influence of light pollution on nest site selection by nesting turtles. Among the studies, Salmon (2003) used data from a main nesting area in Florida to test nest site selection in relation to the degree females were exposed to artificial light spill onto beaches; and Windle et al (2018) used a combination of light pollution data and turtle density data to examine the influence of artificial light pollution on nest site selection. Both studies concluded that turtles use darker beaches and select darker sections of beaches.…”

“…However, less research has been conducted to examine the influence of light pollution on nest site selection by nesting turtles. Among the studies, Salmon (2003) used data from a main nesting area in Florida to test nest site selection in relation to the degree females were exposed to artificial light spill onto beaches; and Windle et al (2018)…”

“…For nesting turtles there has been substantial research on factors that influence nest site selection (i.e., the placement of clutches on a beach). Factors including distance from vegetation (most nests being laid closer to the vegetation line—Hays et al, 1995; Kelly et al, 2017), elevation and beach slope (Patrício et al, 2018; Wood & Bjorndal, 2000) and exposure to artificial light pollution (Salmon, 2003; Windle et al, 2018) have all been associated with nest site selection. There is also variation among species and region as to the relative importance of each.…”