Blinded by the light – tracking baby sea turtles
Pioneering field research provides new evidence of the dangers of light pollution on water to the survival of wild sea turtle hatchlings during their dispersal from their hatching beaches.
Using the latest micro-technology, scientists from the Australian Institute of Marine Science (AIMS) tracked for the first time, the dispersal of green turtle hatchlings (Chelonia mydas) as they moved through the nearshore waters of Ningaloo Reef in Western Australia.
Releasing a green turtle hatchling at Ningaloo with a tracking device attached. Image: J.Costa
“Up until now, most of our knowledge of how swimming sea turtles respond to artificial light has come from laboratory studies and from observers following hatchlings in a boat. Our experiment provides some of the first field data on wild hatchlings without the potentially confounding influence of boats and observers,” said the study’s lead author, Dr Michele Thums of the Australian Institute of Marine Science.
The movements of turtle hatchlings were tracked with miniature tracking devices in nearshore waters under conditions of natural and artificial light and then assessed for the effect of artificial light on swimming direction and behaviour. The hatchling movements were also compared with measured ocean current patterns.
The study results, published today in the journal Royal Society Open Science reveal that 90% of the tracked hatchlings swam towards the artificial light and spent 23% more time in the area close to shore than the hatchlings tracked without light present.
“So, not only were the sea turtle hatchlings attracted to the light, but they also lingered longer in predator-rich nearshore waters. These changes in behaviour would subject the hatchlings to greater risk of death from predation,” explains Dr Thums.
"This is the first quantitative assessment of the influence of artificial light on hatchlings at sea and provides a basis to underpin direct management actions and advice," said Dr Scott Whiting from the Department of Parks and Wildlife.
"Measurement of oceanographic parameters during the experiments enabled us to isolate the effects of artificial light on the hatchling by discounting the effects of ocean currents” said Prof Pattiaratchi from the The University of Western Australia.
It is widely known that artificial lighting near turtle nesting beaches (e.g. from houses, street lights, etc) attracts turtle hatchlings as they emerge from nests and can cause them to have trouble finding the sea. But, understanding what happens once they reach the sea and how lights on water (e.g. from boat, ports, wharves etc) affect them has been unknown up until now because we lacked a simple means to track them. This study provides key behavioural insights into the extent of impacts to hatchling survival caused by changes in light conditions. The results have implications both for existing and future industrial developments near hatching beaches of marine turtles.
For more information, please contact:
Dr Michele Thums
Australian Institute of Marine Science - Perth
+61 (08) 6369 4020 or +61 (0) 414 604 408
(Australian Western Standard Time,+08:00 hrs)
Mr Steve Clarke
Australian Institute of Marine Science - Townsville
+61 (7) 4753 4444, +61 (0) 419 668 497
(Australian Eastern Standard Time, +10 hrs)