Behavioural light thresholds for sea turtle hatchlings

Updated: 2026-07-15

This dataset contributes to understanding how artificial light at night (ALAN) affects green sea turtle hatchlings (Chelonia mydas), a globally threatened species. The research identifies behavioural light-intensity thresholds that disrupt hatchling orientation, providing ecologically relevant evidence to inform coastal lighting management and conservation policy. The data were collected to quantify the behavioural responses of green turtle hatchlings to different artificial light spectra and intensities using a Y-maze experiment. Specifically, the study aimed to determine threshold light intensities that elicit phototactic orientation behaviour and to compare the relative disruptiveness of cool LED, warm LED, and blended wavelength lighting treatments. The dataset was collected under controlled experimental conditions using hatchling green turtles obtained from nesting populations. Before testing, basic morphometric data were collected (mass, size measurements - straight carapace length, and straight carapace width). Behavioural trials were conducted in a laboratory-based Y-maze experimental setup during the sea turtle nesting and hatching season. Specifically, hatchlings were collected between 20th and 26th of February 2025 from beaches along the Jurabi Coastal Park (21° 51' 52.14" S, 114° 0' 52.72" E), North West Cape, Western Australia. Hatchlings were tested on the same night that they were collected and released, without incident, that same night. Behavioural data were collected using controlled Y-maze experiments in which hatchling turtles were exposed to three broad-spectrum artificial light treatments: cool LED, warm LED, and blended wavelength light. The hatchling behavioural choice was recorded as a binary response (i.e., turtles crawled towards the light or towards the dark arm of the Y-maze). In total, we included eight intensities for each light spectra plus a dark (no light) control. The data were collected across seven night replicates. Each night is treated as a separate replicate. A spectrometer (OceanOptics SR6 UV/V 400-50) was used to confirm that the spectra produced by the light closely mimicked the three reference spectra. The spectrometer was calibrated to measure absolute spectral irradiance, providing spectral irradiance measurements generated by the light. The data were analysed using dose–response (intensity–response) curves to quantify the relationship between artificial light intensity and hatchling behavioural response. Specifically, light intensity thresholds were derived using the bayesnec package (v. 2.1.3.0; Fisher et al. 2024) in R (v. 4.4.2; R Core Team 2013) as the no significant effect concentration (NSEC) (Fisher and Fox 2023; Fisher et al. 2023), identifying the highest light intensity where the hatchling’s choice did not differ significantly from the control (i.e., no light in either arm of the maze). The R code used in the analyses is provided. The analysis demonstrated that hatchlings responded to cool LED and blended spectra at significantly lower intensities than to warm LED lighting, indicating that warm LEDs are substantially less disruptive to hatchling orientation behaviour. The following data are available: Y-maze behavioural choice of turtle hatchlings Hatchling morphometrics Absolute spectral irradiance for the cool LED, warm LED, and blended light treatments R code used in the analysis