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Olive ridley turtles nest in large numbers on the east coast of India, with mass nesting sites in Orissa. Genetic studies have shown that the population on the east coast of India is the evolutionary source for global olive ridley populations (Shanker et al. 2004). In the Andaman Islands, sporadic nesting of olive ridleys occurs at many sites (Andrews et al. 2001; Bhaskar 1993), with mini arribadas reported from a few beaches (Bhaskar, 1994).

This study was initiated to monitor the nesting of sea turtles in the Andaman and Nicobar Islands. During the study, threats to marine turtles were also documented. In this paper, we compile and analyze nesting data from 2001 to 2006 at Cuthbert Bay nesting beach in the Middle Andaman Islands. We also provide brief comments on the conservation of marine turtles in the Andaman and Nicobar Islands.

Study area. The Andaman and Nicobar Island are a group of islands in the Bay of Bengal. They extend from 6°45 ́ - 13°41 ́ N (740 km) to 92°12 ́ - 93°57 ́E (190 km). The archipelago consists of >345 islands, islets and outcrops. Cuthbert Bay is located on the northeastern part of Middle Andaman Island (12.7°N, 92.96° E). The beach is relatively long with a gentle slope throughout its length. The northern end is rocky and curves into a small cove edged by large calcified rocks. It is cut at the southern end by a tidal creek flowing to the sea. The creek bifurcates the beach into two segments of ~3.5 km each, though most turtle nesting occurs in the northern half. It is vegetated by shrubs and coastal vegetation, and is dominated by Hibiscus tiliaeceous and Ipomea pescaprae. The beach is subject to various human uses from minor sand mining to the presence of humans and pet/feral dogs from the adjacent village, though the northern half where most of the nesting occurs is less affected.

Figure 1. Map of Andaman & Nicobar Island with an outline of Cuthbert Bay nesting beach.

Cuthbert Bay nesting beach (Fig. 1) was monitored from 2001 to 2006 during the nesting season, which extends from mid-November to mid-April. Surveys were initiated on January 20, 2001 and continued till March 10, 2006. Continuous ground surveys were carried out and beaches were monitored every night during the nesting season. Turtle nests and tracks were counted. Each identified sea turtle emergence was classified as either a "false crawl" or a "nest". A false crawl was identified as an emergence with only a crawl, or a crawl with one or more typically uncovered nest cavities. Crawls with typical nest area excavations were inferred to indicate successful nesting attempts. Successful nesting crawls were categorized as fresh (crawls with visible flipper marks), and old (those with either only the nest excavation mound and/or faint tracks visible). For turtles that were encountered, the curved carapace length (CCL) and width (CCW) were measured using a measuring tape. Olive ridleys were marked by using a small hacksaw to notch the edge of the carapace. Dead turtles and details of nest predation were also documented.

Table1. Number of nests counted at Cuthbert Bay during 2001-2006 monitoring period. * - data from February 20, 2001; no data available for 2002.

Nesting trends and seasonality. Olive ridley, leatherback and green turtles were observed to nest at the Cuthbert Bay nesting beach (Table 1) throughout the monitoring period. In 2001, 32 olive ridley nests were counted. Eight green turtles or tracks were observed, of which 2 nested. There were no reports of leatherback nesting activity.

In the 2003- 2004 nesting season, 368 olive ridleys nests were counted, of which 41 were predated by feral dogs. Sixteen olive ridley turtles were found dead, due to either feral dog predation (6) or possible drowning in fishing nets (10). Several had injuries on their flippers or head which may have been caused by dogs, or due to entanglement in fishing nets. During that season, 9 green turtle nests were counted. Eleven green turtles were found dead on the beach. Fifteen leatherback turtle nests were counted during the season.

Turtle nesting was not high during the next season as a tsunami hit the coast on 26 December 2004. Seventy-two olive ridleys nests, four green turtle nests and two leatherback turtles were enumerated. Fourteen olive ridley turtles were found dead on the beach; as in previous years, these may have been caused by dogs or entanglement in fishing nets. The number of nesting turtles dropped in comparison to previous years at Cuthbert Bay.

Table 2. Number of nests of olive ridley turtles (Lepidochelys olivacea) at Cuthbert Bay from 2001-2006. * = data from February 20, 2001; no data available for 2002.

In the 2005-2006 nesting season, the year after the tsunami hit the coast, 93 olive ridley nests were counted and 14 olive ridleys were found dead on the beach. The nesting numbers remained low with respect to the 2003-2004 season. Six green turtle nests were counted, but no leatherbacks or nests were observed on the beach during this season.

There is a clear peak in nesting from January to March, particularly for olive ridley turtles, as has been documented earlier in the islands (Bhaskar 1993) and on the east coast of India (Shanker et al. 2003). Too few leatherback and green turtle nests were documented to infer seasonality, but in general, leatherback turtle nesting peaks from November to March and green turtles nest principally during the monsoon in the Andaman and Nicobar Islands (Andrews et al. 2006a, Bhaskar 1993).

Olive ridley nesting patterns. The number of olive ridley nests at Cuthbert Bay is high in comparison to other sea turtles (Table 1). They usually start nesting in the month of November when several false crawls are observed. The number of nesting turtles increases in January, peaks in February and ends by April (Table 2). However, nesting peaked only in March in 2004-2005, believed to be because of disturbance at the nesting site as a result of the December 2004 tsunami. There was no monitoring in 2002.

Previous surveys indicate that a significant number of olive ridley turtles nest at Cuthbert Bay. In the 1988-89 season, 338 nests were reported from this site (Misra 1990), while over 700 nests were reported from the 1990-1991 and 1991-92 seasons, and over 900 nests during the 1993-94 season (Bhaskar 1994). Small arribadas have been reported to occur at this site in the past. From 1990 to 1992, 100 to 200 turtles were reported to have nested on each of several nights during the season, constituting 60-70% of the total nesting for the season (Bhaskar 1994). During the survey, 2003- 2004 was the best nesting season with 338 nests, and 114 nests in February alone (Table 2). Post tsunami, the number of the olive ridley nests appeared to have declined at this site. This needs to be verified with surveys in the future.

Figure 2. Average clutch size of olive ridley turtles on Cuthbert Bay beach by month and year (black bars represent 2003-04, light grey bars represent 2004-05, dark grey bars represent 2005-06).

The olive ridley population nesting at Cuthbert Bay shows an annual mean clutch size ranging from 110.2 to 121.6. Mean clutch size was greater in 2005-06 than the other years (Kruskal Wallis p < 0.05). Mean clutch size was greater in December and February than other months during 2003-04 (Kruskal Wallis p < 0.05), but there was no significant variation in within-season clutch size during the 2004-05 and 2005-06 seasons (Fig. 2).

At Cuthbert Bay, all nesting females were reported to have curved carapace length (CCL) above 62 cm, which is the minimum recorded size for nesting females in the region (Pandav 2000). The annual mean CCL of nesting females ranged from 68.2-70 cm (Table 3). Unlike the population in Orissa which has been showing a decline in adult sizes (Shanker et al. 2003), the adult size of olive ridley turtles did not appear to change during this period at Cuthbert Bay.

Threats. Sea turtles are protected under Schedule 1 of the Indian Wild Life Protection Act (1972). Though indigenous aboriginal groups in the Andaman and Nicobar islands are exempt from this law, the level of take is fairly low. However, a variety of other threats to sea turtle populations in the Andaman Islands have been reported by several authors (Andrews et al. 2001, 2006b; Bhaskar 1979b; Sivasunder 1996).

Figure 3. Threats to olive ridley turtles at Cuthbert Bay during 2001-2006 (black bars represent total olive ridley tracks encountered; light grey bars represent total olive ridley nests; dark grey bars represent the total nest predation/dead turtles encountered).

During the study, several turtles were found dead each year on the shore either due to possible drowning in fishing nets, or were attacked by dogs when they come ashore to nest. The major threat to sea turtles in the islands is nest predation; several nests get predated by dogs and pigs (Fig. 3) However, nest predation has been estimated at about 3% at Cuthbert Bay, which is low in comparison to 70% in the rest of the Andaman and Nicobar Islands (Andrews 2001). The low predation levels may be due to the presence of researchers and Forest Department personnel on the beach for monitoring. The other threat to sea turtles at Cuthbert Bay is from local people (non- aboriginal groups who have settled in the islands) who consume both meat and eggs, but again, levels of take are low.

Many nesting beaches in the Andaman and Nicobar Islands were severely affected by the December 2004 tsunami (Andrews et al. 2006b). The effect was not as severe at Cuthbert Bay nesting beach as observed at other nesting sites in the Andaman and Nicobar Islands. Olive ridleys and green turtles were observed to have nested here after the tsunami. Surveys carried out in subsequent years (Andrews et al. 2006c) show formation of new beaches and the possible recovery of nesting populations at several sites in the islands.

Table 3. Mean size of female olive ridleys nesting at Cuthbert Bay from 2001-2006 (standard deviation in parentheses).

Conservation and Management. Sea turtle conservation and management on the islands comes under the purview of the Andaman and Nicobar Islands Forest Department (ANFD). The Forest Department has management plans and guidelines for the conservation of marine turtles, with a small protection force posted in some of the critical areas and islands. However, the remoteness of most of the areas and islands, logistics, weather conditions and rough seas make it difficult to monitor and patrol beaches in the islands on a regular basis. The lack of adequate staffing, infrastructure and equipment makes their task even more difficult.

Since 1977, the Madras Crocodile Bank Trust (MCBT) has conducted sea turtle surveys and studies on the islands. Over the last decade, the Andaman and Nicobar Island Environmental Team (ANET), a division of MCBT, has been conducting surveys and monitoring sea turtles in the Andaman and Nicobar Islands. ANET works closely with the Andaman and Nicobar Forest Department and conducts long term monitoring, surveys and research. The team has an on-going environmental education programme for school children and teachers. Together with Kalpavriksh, ANET produced a teachers training manual in two languages for the islands that includes sea turtles. Since 2007, ANET has collaborated with the Indian Institute of Science to carry out a research and monitoring programme principally for leatherback turtles on Little Andaman Island, including tagging and satellite telemetry.

Table 4. Clutch sizes of olive ridleys at Cuthbert Bay from 2003-2006.

Though the islands have several important feeding and nesting populations of sea turtles, the logistic difficulty of establishing and maintaining conservation programmes hampers the formulation of appropriate conservation and management plans. There is a need to work closely with and train local authorities, mainly the Forest Department, towards long term monitoring and protection of these nesting beaches. Periodic surveys across the islands and regular monitoring at index beaches are required. Ongoing research needs to be expanded, especially to in-water studies of green and hawksbill turtles.

Greater awareness needs to be created amongst local settler communities and the administration. There is considerable apprehension amongst environmentalists about plans for tourism and development in the islands. These actions could have severe consequences for sea turtles and in particular, their habitats. Hence, it is imperative that the conservation of marine turtles and their nesting and feeding habitats is incorporated into developmental plans for the islands.

Acknowledgments. We sincerely thank all the people who assisted in the field for data collection, especially the Andaman Nicobar Environmental Team (ANET) and the Madras Crocodile Bank Trust (MCBT). We extend our gratitude to the Andaman and Nicobar Forest Department and to the Ministry of Environment and Forests for providing access to protected areas and permits for monitoring sea turtles. We particularly thank Manish Chandi, Saw Agu and Naveen Ekka from ANET for their help in setting up the field camps. We also acknowledge the work of the late Ambika Tripathy at this site during 2004; Ambika was tragically killed during the 2004 tsunami at the ANET base on Great Nicobar Island along with seven others.

ANDREWS, H.V., S. KRISHNAN & P. BISWAS. 2001. The status and distribution of marine turtles around the Andaman and Nicobar archipelago. A GOI-UNDP national sea turtle project report, IND/97/964. Centre for Herpetology/Madras Crocodile Bank trust, Tamil Nadu, India.

ANDREWS, H.V. & K. SHANKER. 2002. A significant population of leatherback turtles in the Indian Ocean. Kachhapa 6: 17.

ANDREWS, H.V., S. KRISHNAN & P. BISWAS. 2006a. Distribution and status of marine turtles in the Andaman and Nicobar Islands. In: K Shanker & B.C. Choudhury (Eds.). Marine Turtles of the Indian Subcontinent University Press, Hyderabad. India. pp. 33-57.

ANDREWS, H.V., A. TRIPATHY, S. AGHUE, S. GLEN, S. JOHN & K. NAVEEN. 2006b. The status of sea turtle populations in the Andaman and Nicobar Islands. In: K. Shanker & H.V. Andrews (Eds.). Towards an Integrated and Collaborative Sea Turtle Conservation Programme in India: A UNEP/CMS-IOSEA Project Report. Centre for Herpetology/ Madras Crocodile Bank Trust, Tamil Nadu, India.

ANDREWS, H.V., M. CHANDI, A. VAUGHAN, J. AUNGTHONG, S. AGHUE, S. JOHNNY, S. JOHN & S. NAVEEN. 2006c. Marine turtle status and distribution in the Andaman and Nicobar Islands after the 2004 M9 quake and tsunami. Indian Ocean Turtle Newsletter 4: 3-11.

BHASKAR, S. 1979a. Sea turtles in the South Andaman Islands. Hamadryad 4: 3-5.

BHASKAR, S. 1979b. Sea turtle survey in the Andaman and Nicobars. Hamadryad 4: 2-26.

BHASKAR, S. 1993. The status and ecology of sea turtles in the Andaman and Nicobar Islands. ST 1/93. Centre for Herpetology, Madras Crocodile Bank Trust, Post Bag 4, Mamallapuram, Tamil Nadu- 603104, India.

BHASKAR, S. 1994. Andaman & Nicobar Sea Turtle Project. Phase V1- A,VII & VIII. Reports to Centre for Herpetology/Madras Crocodile Bank Trust, Post Bag- 4, Mamallapuram- 603104, Tamil Nadu, India.

BHASKAR, S. 1995. Andaman & Nicobar Sea Turtle Project. Phase V. Report to Centre for Herpetology/ Madras Crocodile Bank Trust, Post Bag- 4, Mamallapuram- 603104, Tamil Nadu, India.

BHASKAR, S. 1996. Renesting intervals of the hawksbill turtle (Eretmochelys imbricata) on South Reef Island. Hamadryad 21: 19-22.

KAR, C.S. & S. BHASKAR. 1982. Status of sea turtles in the Eastern Indian Ocean. In: K.A. Bjorndal (Ed.). Biology and Conservation of Sea Turtles. Smithsonian Institution Press, Washington, DC, USA. pp. 365-372.

MISRA, A. 1990. Olive ridley turtle- breeding and behavior. Tigerpaper. 17: 29-32.

SHANKER, K., B. PANDAV & B.C. CHOUDHURY. 2003. An assessment of the olive ridley turtle (Lepidochelys olivacea) nesting population in Orissa, India. Biological Conservation 115: 149-160.

SHANKER, K., J. RAMA DEVI, B.C. CHOUDHURY, L. SINGH & R.K. AGGARWAL. 2004. Phylogeography of olive ridley turtles (Lepidochelys olivacea) on the east coast of India: implications for conservation theory. Molecular Ecology 13: 1899-1909.

SIVASUNDAR, A. & K.V. DEVI PRASAD. 1996. Placement and predation of nests of leatherback sea turtles in the Andaman Islands, India. Hamadryad 21: 36-42.