Distribution and diving behaviour of nesting sea turtles at Redang Island 

Research sponsored by Berjaya Cares Foundation (2011 – 2013)

 

Above: Green turtle (Chelonia mydas) nesting at Chagar Hutang equipped with transmitters (acoustic and radio transmitters) and Time Depth Recorder (TDR). (Photo credit: Raais Mohd Azhar)

Redang Island is known to be one of the important nesting sites for the green and hawksbill turtles in Terengganu. In 2005, the three major nesting beaches were declared as Turtle Sanctuaries hence the collection of sea turtle eggs stopped at this island. Biological data collected by Universiti Malaysia Terengganu through its long-term sea turtle conservation program, had shown that in one breeding season, a female green turtle may lay up to 12 clutches of eggs, each with an interval of 10 days. The nesting sea turtles will remain very near to their nesting beaches, roaming around Redang for about four to five months until they had finish laying their eggs for that season, before returning to their respective foraging grounds. Un-controlled boat and tourist activities during this breeding period might disturb or endanger the sea turtles.

In recent years, we observed an increasing number of adult sea turtles which died around Redang waters. In 2010, we found eight dead green turtles, all with cracks on their carapace, suggesting that these turtles were hit by boat propellers. Because of this worrying problem, we designed a research aimed to determine the distribution and diving behaviour of sea turtles during their breeding season at Redang Island.It is hope that results from this study could be used to formulate a better management strategyin order to help save the sea turtles of Redang.

Diving behaviour and movements of nesting sea turtles was tracked using a combination of transmitters (acoustic and radio transmitters) and Time Depth Recorder (TDR). Deployment of transmitters and TDR was conducted on the nesting beach, only after the turtles had finished laying eggs. The turtles were then tracked daily by boat equipped with hydrophones, antennas and receivers for as long duration as possible to gain an understanding of their daily movement patterns (inter-nesting habitat). Exact location, activity and time sighting were recorded to correlate the turtle behaviours with TDR dive profiles. When the turtles came up again to lay their eggs (between 9 – 12 days), the TDR wasretrievedand diving data was downloaded to a computer for analysis.

 

Research updates:

Nov – Jan 2011:     Purchasing of equipments

Mar – Oct 2012:      Deployment of transmitters and tracking of sea turtles (Phase 1). A total of nine individual green turtles were tracked

Mar – June 2013:    Deployment of transmitters and tracking of sea turtles (Phase 2). A total of six individual green turtles were tracked.

July – present:        Data Analysis and report writing