POST-NESTING MIGRATORY ROUTES OF LEATHERBACK TURTLES FROM LITTLE ANDAMAN ISLAND

*NAVEEN NAMBOOTHRI1&2#, ADHITH SWAMINATHAN2, B.C. CHOUDHURY3 & KARTIK SHANKER1&2#

1Centre for Ecological Sciences, Indian Institute of Science, Bangalore, India

2Dakshin Foundation, Bangalore, India

3Wildlife Institute of India, Dehradun, India

#naveen.namboo@gmail.com, kshanker@iisc.ernet.in

Download article as PDF

Introduction

Among the seven species of sea turtles, leatherback turtles (Dermochelys coriacea) are known to undertake some of the longest migrations (Pritchard and Trebbau, 1984). Over the last two decades, there has been concern about the drastic decline in the nesting populations of this species in the Pacific Ocean (Spotila et al. 2000), though some nesting populations have increased in the Atlantic Ocean. In India, leatherback turtles are listed under Schedule I of the Indian Wildlife (Protection) Act 1972, which offers the highest degree of protection to wildlife in India.

Current leatherback nesting sites in India are restricted to the islands of the Andaman and Nicobar archipelago (Andrews et al., 2006a, b). Very little is known about the status of leatherback populations from the Indian waters, barring recent work by the Andaman and Nicobar Environment Team (ANET) on Great Nicobar Island. More recently, a monitoring programme has been initiated by the Indian Institute of Science, Bangalore, ANET and Dakshin Foundation, Bangalore on Little Andaman Island. In order to understand where these turtles range and the mortalities to which they are subject, a satellite tracking project was initiated in January 2011.

Methods

Seven female leatherback turtles were tagged with Kiwisat 202 Platform Transmitter Terminals (PTT), (Sirtrack Wildlife Tracking Solutions Ltd., New Zealand) at West Bay, Little Andaman. The transmitters interfaced with the CLS-ARGOS system for deriving surface position coordinates. The location coordinates were filtered and analysed using the Satellite Tracking and Analysis Tool (STAT) (Coyne and Godley, 2005). The PTTs were fitted with a salt-water switch which automatically switched on whenever the turtle surfaced to breath, sending location signals to the nearest geo-synchronised satellite in orbit. The PTTs were programmed with a duty -cycle to transmit continuously for the first three months, and every alternate day for the rest of the period. The PTTs were attached on the most prominent part of the medial carapacial ridge, usually posterior to the widest area of the carapace. Two holes were drilled through the medial ridge with an orthopaedic drill bit, with each hole only penetrating a few millimetres into the carapace. The transmitters were designed specifically for direct attachment to a leatherback turtle, and were secured on one side of the medial ridge using stainless steel cables inserted in surgical tubing, which acted as a sheath for the tether attachment. The cables were secured using stainless steel crimps. Direct attachment through the medial ridge has proven to be a successful alternative to the harness method (Fossette et al., 2008; Byrne et al., 2009). Using the described method, three nesting leatherback turtles were tagged during 2010- 2011 and four turtles were tagged during 2011-2012 nesting seasons.

Results

Of the seven turtles that were tagged, two turtles transmitted for about 6 months (179 and 193 days) and four turtles transmitted for 51 to 92 days; one turtle transmitted only a single data point (Table 1). Four out of six turtles travelled south east of the Andaman and Nicobar Islands, two along the coast of Sumatra, and two beyond Cocos (Keeling) Island towards Western Australia. Two turtles moved south-west of the islands, one of which travelled south of the British Ocean Territory (Figure 1). Turtle 103333, tagged on 04 January 2011, transmitted for 179 days and travelled the longest distance of 7312 km (straight line distance: 4185 km) (Table 1).

Three more turtles will be tagged with PTTs during the 2012-2013 nesting season.

16-6-01Figure 1. Post-nesting migratory paths of leatherback turtles tagged in West Bay, Little Andaman, during 2010-2012

Table 1. Post nesting migratory data of the leatherback turtles tagged in West Bay, Little Andaman.

ID

Release Date

CCL (cm)

CCW (cm)

Last Location Date

# Days Transmitted

Distance Travelled (km)

103333    

04-01-2011

154

150

02-07-2011

179

7312

103334

04-01-2011

170

120

14-03-2011

69

1077

103335

05-01-2011

153

112

07-04-2011

92

4600

103402

02-12-2012

161

117

29-04-2012

77

4634

113332

23-01-2012

152

110

24-07-2012

183

6998

113333

23-01-2012

161

117

14-03-2012

51

2690

113334

23-01-2012

160

110

23-01-2012

0

0

Discussion

The patterns that emerged after satellite tracking of leatherback turtles from the Little Andaman Island provided some preliminary insight into their migratory patterns in the Indian Ocean. Upon departure from the West Bay Beach, leatherbacks migrated southward along varied paths, utilizing the broad expanses of the Southern Indian Ocean. While there was no single migratory corridor (Morreale et al., 1996; Benson et al., 2007), multiple turtles were observed to follow similar routes, with some relationship to bathymetry which requires further investigation. As the first telemetry study on leatherback turtles in the region, this provides useful information on their migratory pathways in the Indian Ocean, and highlights potential threats from deep sea fishing operations in the southern Indian Ocean. More data are, however, required to understand patterns of migration and identify specific threats during these migratory journeys.

Literature Cited

Andrews, H.V., S. Krishnan & P. Biswas. 2006a. Distribution and status of marine turtles in the Andaman and Nicobar Islands. In: Marine Turtles of the Indian Subcontinent (eds. K. Shanker & B.C. Choudhury). Pp. 33-57. Universities Press: Hyderabad.

Andrews, H.V., M. Chandi, A. Vaughan, J. Aungthong, S. Aghue, S. Johnny, S. John & S. Naveen. 2006b. Marine turtle status and distribution in the Andaman and Nicobar Islands after the 2004 M 9 quake and tsunami. Indian Ocean Turtle Newsletter 4: 3-11.

Benson, S.R., P.H. Dutton, C. Hitipeuw, B. Samber, J. Bakarbessi, and D. Parker. 2007. Post-nesting migrations of leatherback turtles (Dermochelys coriacea) from Jamursba-Medi, Birds Head Peninsula, Indonesia. Chelonian Conservation and Biology 6: 150-154.

Byrne, R., J. Fish, T. K. Doyle & J.D.R. Houghton. 2009. Tracking leatherback turtles (Dermochelys coriacea) during consecutive inter-nesting intervals: Further support for direct transmitter attachment. Journal of Experimental Marine Biology and Ecology 377: 68-75.

Coyne, M.C. & B.J. Godley. 2005. Satellite Tracking and Analysis Tool (STAT): an integrated system for archiving, analyzing and mapping animal tracking data. Marine Ecology Progress Series 301: 1–7.

Fossette, S., H. Corbel, P. Gaspar, Y. Le Maho & J. Georges. 2008. An alternative technique for the long-term satellite tracking of leatherback turtles. Endangered Species Research 4: 33-41.

Morreale, S.J., E.A. Standora, J.R. Spotila & F.V. Paladino. 1996. Migration corridor for sea turtles. Nature 384: 319–320.

Spotila, J.R., R.D. Reina, A.C. Steyermark, P.T. Plotkin & F.V. Paladino. 2000. Pacific leatherback turtles face extinction. Nature 405: 529–530.

Swaminathan A. N. Namboothri, & K. Shanker. 2011. Post-tsunami status of leatherback turtle nesting at Little Andaman Island. Indian Ocean Turtle Newsletter 14: 1-5.

Taillade, M. 1992. Animal tracking by satellite. In: Wildlife Telemetry: Remote Monitoring and Tracking of Animals (eds. Pride I.G. & S.M. Swi ). Pp. 149-160. Ellis Horwood: New York.