An assessment of 'turtle-friendly' lights on the sea-finding behaviour of loggerhead turtle hatchlings (Caretta caretta)

Published source details Robertson K., Booth D.T. & Limpus C.J. (2016) An assessment of 'turtle-friendly' lights on the sea-finding behaviour of loggerhead turtle hatchlings (Caretta caretta). Wildlife Research, 43, 27-37.
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This study is summarised as evidence for the following.

	Action	Category
	Change the colour (spectral composition) of lighting Action Link

Change the colour (spectral composition) of lighting

A replicated, randomized, controlled study in 2013 on unlit beaches in Queensland, Australia (Robertson et al. 2016) found that loggerhead turtle Caretta caretta hatchlings were disoriented by amber ‘turtle-safe’ artificial lights and only disoriented by red ‘turtle-safe’ lights when three torches were used. Fewer hatchlings oriented directly seawards under amber lighting (72–89%), compared to no lighting (97%; statistical significance depended on the number of torches used, see original paper). Under red lighting, overall the proportion of hatchlings that oriented seawards was similar (98%) compared to no lighting (99%), but when three torches were used hatchlings were significantly more likely to orient towards the artificial light (see paper for details). Amber (620 nm peak wavelength, 9.8 light intensity) and red (640 nm, 8.3) ‘turtle-friendly’ LED lights were tested (1–4 torches/trial) during different parts of the lunar cycle and results compared to no lighting (amber: 21 total trials, red: 9). Trials were carried out by releasing <1-day-old hatchlings (20 hatchlings/trial) in an 8 m circular sand arena divided into 12 segments (see paper for more details). Hatchling segment location was recorded after five minutes.

(Summarised by: Maggie Watson, Katie Sainsbury)