Filtered streetlights attract hatchling marine turtles

Published source details Sella K.N., Salmon M. & Witherington B.E. (2006) Filtered streetlights attract hatchling marine turtles. Chelonian Conservation and Biology, 5, 255-261.
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This study is summarised as evidence for the following.

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

Change the colour (spectral composition) of lighting

A replicated, controlled study in 2000–2001 in a laboratory in Florida, USA (Sella et al. 2006) found that filtering lights did not prevent loggerhead Caretta caretta or green Chelonia mydas turtle hatchlings from crawling towards a light source, though fewer turtles crawled towards filtered compared to unfiltered lights. Turtles crawled preferentially towards an orange, red or unfiltered light source, but showed no directional preference when no light source was present (data reported as average crawl angle). In addition, more turtles crawled towards a filtered light source over no light in two of four trials (68–84% of individuals), and towards an unfiltered light source over no light in two of two trials (96–100% of individuals). In 2000, turtles were placed in a circular arena where they could crawl in any direction, and in 2001 in a “T-maze” where they could crawl in one of two directions. Light sources were presented at the edge of the arena (orange, red, unfiltered or no light; 30 turtles/treatment) or in one arm of the T-maze (orange, red or unfiltered light; 25 turtles/treatment). High pressure sodium vapour lights were used that mimicked streetlights adjacent to turtle nesting sites (equivalent to 40 or 60 m away). In 2000, hatchlings were obtained from a beach hatchery, and in 2001 from natural nests. Each hatchling was used in only one trial and then released in to the wild. Behaviours were monitored with a video camera and monitor.

(Summarised by: William Morgan)
Use low intensity lighting

A replicated, controlled study in 2000–2001 in a laboratory in Florida, USA (Sella et al. 2006) found that lowering the intensity of a light source led to lower preference for moving towards that light source in laboratory trials with loggerhead Caretta caretta or green Chelonia mydas turtle hatchlings. Hatchlings preferentially crawled towards unfiltered light over orange or red light in four of four trials, but preference for unfiltered light decreased as its intensity decreased (from 2 of 4 trials to 0 of 4 trials with decreasing intensity). At the lowest intensity, turtles showed preference for the filtered light in two of four trials. In comparisons between orange and red filtered light, turtles showed no preference in six of eight trials, but preferred red light when the orange light intensity was reduced to its lowest level (2 of 2 trials). Hatchlings were presented with a choice of two lights to crawl towards. High pressure sodium vapour lights were covered with an orange, red or no filter and the less filtered light in each comparison was tested at four intensity levels. The highest intensity used matched that of a beach adjacent streetlight located 40 or 60 m from a nest, and intensity was reduced using a neutral density filter. In 2000–2001, hatchlings were obtained from two beaches, with 25 used in each trial. Each hatchling was used in only one trial and then released in to the wild.

(Summarised by: William Morgan)