Turtle hatchlings. Credit: Suzanne Long (AIMS)
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The impacts of artificial light on marine turtles

Friday, 13 December 2019  | 

Six of the world’s seven marine turtle species occur in Australia and all are protected by international and national agreements and legislation. Light pollution in the coastal zone is considered a key threat to marine turtles.

In Australia, a large number of important turtle nesting sites are exposed to light pollution along the industrialised Northwest Shelf of Western Australia and the urbanised coast of Queensland. Marine turtle hatchlings generally emerge from their beach nests at night and show an innate ability to orientate towards the sea, being attracted toward the lower, brighter horizon of the sea surface.

Artificial lighting along the coast can confuse and misdirect newly emerged hatchlings by appearing brighter than the sea surface horizon. This can result in hatchlings being attracted away from the sea, increasing their risk of death by predation, dehydration or exhaustion. If hatchlings reach the ocean, artificial light on and around water (e.g. boats at anchor, jetties) can continue to disorientate them, potentially causing them to linger in nearshore waters with similar results. There is also evidence that light pollution can disrupt and deter the nesting behaviour of adult female turtles.

To reduce the impacts of lights on turtles, the Commonwealth Department of Environment and Energy is developing guidelines to manage artificial light around wildlife. The guidelines outline best practice lighting design including starting with natural darkness and only adding light when needed, and using smart controls (motion sensors, timers, etc). They recommend lowering light intensity and avoiding lights with blue wavelengths, which are particularly disruptive to turtles. Further, lights should be kept close to the ground, directed and shielded and surfaces should be non-reflective.  The implementation of these recommendations to new and existing projects near turtle nesting beaches will reduce the impacts of artificial light on marine turtles.

Supporting Research

Title
Aims
Mazor T., Levin N., Possingham H. P., Levy Y., Rocchini D., Richardson A. J. & Kark S. (2013) Can satellite-based night lights be used for conservation? The case of nesting sea turtles in the Mediterranean. Biological Conservation 159, 63-72.
To examine the influence of night time lighting on sea turtle nesting distribution over a 19 year period using satellite imagery obtained at two different spatial resolutions
Witherington B. E. (1992) Behavioral responses of nesting sea turtles to artificial lighting. Herpetologica 48, 31-39.
To examine the effects of two light types on the nesting behaviour of green and loggerhead turtles
Price J. T., Drye B., Domangue R. J. & Paladino F. V. (2018) Exploring the role of artificial lighting in loggerhead turtle (caretta caretta) nest-site selection and hatchling disorientation. Herpetological Conservation and Biology 13, 415-422.
To examine the effects of light illuminance levels on nest site-selection and hatchling disorientation of loggerhead turtles
Wilson P., Thums M., Pattiaratchi C., Meekan M., Pendoley K., Fisher R. & Whiting, S. (2018) Artificial light disrupts the nearshore dispersal of neonate flatback turtles Natator depressus.Marine Ecology Progress Series 600, 179-192.
To determine the effects of two types of artificial light on the nearshore dispersal of flatback turtle hatchlings and the relative importance of natural and artificial cues on this process.
Wilson P., Thums M., Pattiaratchi C., Whiting S., Pendoley K., Ferreira L. C. & Meekan M. (2019) High predation of marine turtle hatchlings near a coastal jetty. Biological Conservation 236, 571-579.
To assess the impact of a jetty with artificial lights on the predation rates and movement patterns (using acoustic tracking devices) of flatback turtle hatchlings as they swim through the nearshore zone.
Weishampel Z. A., Cheng W-H. & Weishampel J. F. (2016) Sea turtle nesting patterns in Florida vis-à-vis satellite-derived measures of artificial lighting. Remote Sensing in Ecology and Conservation 2, 59-72.
To assess trends in light levels and its effects on turtle nesting behaviour over a 21-year period at different scales
Kamrowski R. L., Limpus C., Moloney J. & Hamann M. (2012). Coastal light pollution and marine turtles: assessing the magnitude of the problem. Endangered Species Research 19, 85-98.  
To assess the proportion of marine turtles in Australia potentially at risk from light pollution.
Thums M., Whiting S. D., Reisser J., Pendoley K. L., Pattiaratchi C. B., Proietti M., Hetzel Y., Fisher R. & Meekan M. G. (2016) Artificial light on water attracts turtle hatchlings during their near shore transit. Royal Society Open Science 3, 160142.
To examined the effect of artificial light on water on the near shore trajectories of turtle hatchlings dispersing from natal beaches.
Lorne J. K. & Salmon M. (2007) Effects of exposure to artificial lighting on orientation of hatchling sea turtles on the beach and in the ocean. Endangered Species Research 3, 23-30.
To determine whether turtle hatchlings that have been previously misoriented by artificial lighting (attracted landward instead of seaward) can later recover from that experience, and orient normally to find the sea and swim away from the shore from a dark beach. This is needed because misoriented or disoriented hatchlings are sometimes found alive on the beach, either late at night or the morning after failing to locate the sea and some guidelines (in this case, Florida Fish and Wildlife Conservation Commission guidelines) recommend that these hatchlings should be moved closer to the water, or released in shallow water near the shore.
Harewood A. & Horrocks J. (2008) Impacts of coastal development on hawksbill hatchling survival and swimming success during the initial offshore migration. Biological Conservation 141, 394-401.
To investigate of the impacts of beach lighting on hatchling predation rate and swimming success during the initial swim away from shore
Erb V. & Wyneken J. (2019) Nest-to-surf mortality of loggerhead sea turtle (Caretta caretta) hatchlings on Florida’s east coast. Frontiers in Marine Science 6, 1-10.
To quantify the mortality of loggerhead hatchlings on their crawl from nest to sea and to identify the sources of the mortality at a number of different sites on Florida's east coast
Limpus C. & Kamrowski R.L. (2013) Ocean-finding in marine turtles: the importance of low horizon elevation as an orientation cue. Behaviour 150, 863-893.
To document the importance of horizon cues for ocean-finding in hatchlings under natural field conditions.
Salmon M., Wyneken J., Fritz E. & Lucas M. (1992) Seafinding by hatchling sea turtles: role of brightness, silhouette and beach slope as orientation cues. Behaviour 122, 56-77.
To assess the effects of visual and slope stimuli, alone and in combination, on green and loggerhead hatching seafinding.
Witherington B. E. & Bjorndal K. A. (1991) Influences of wavelength and intensity on hatchling sea-turtle phototaxis: implications for sea-finding behavior. Copeia 1991, 1060-1069.
To assess the preferences for light intensities and colour on loggerhead and green hatchlings during sea finding.
Pendoley K. & Kamrowski R. L. (2015) Influence of horizon elevation on the sea-finding behaviour of hatchling flatback turtles exposed to artificial light glow. Marine Ecology Progress Series 529, 279-288.
To assess the response of flatback hatchlings to common industrial light types a different intensities and elevation
Australian Government (Draft) National Light Pollution Guidelines for Wildlife including Marine Turtles, Seabirds and Migratory Shorebirds. Department of the Environmental and Energy, Canberra. 202 p
The purpose of these Guidelines is to raise awareness of the potential impacts of artificial light on wildlife and provide a framework for assessing and managing these impacts on susceptible listed wildlife.