A COMPILATION OF DATA FROM SATISH BHASKAR’S SEA TURTLE SURVEYS OF THE ANDAMAN AND NICOBAR ISLANDS

NAVEEN NAMBOOTHRI^1&2#, ADHITH SWAMINATHAN² & KARTIK SHANKER^1&2#

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

2Dakshin Foundation, Bangalore India

#naveen.namboo@gmail.com, kshanker@gmail.com

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Information arising from extensive surveys undertaken by Satish Bhaskar have contributed to the majority of our understanding of sea turtles in the Andaman and Nicobar Islands. Between 1978 and 1995, Bhaskar visited most of the islands in the Andaman and Nicobar archipelago, recording information on turtle nesting, tagging a substantial number of turtles, and collecting insightful information on the potential threats to marine turtles in the region. Bhaskar’s work may not have been conducted within a conventional scientific framework, but the significance of the information that his surveys generated cannot be understated. Though there was a lack of continuity and inconsistencies in protocols, his baseline data laid the foundation for sea turtle conservation and research initiatives in the region. Thanks to his efforts, many of the remote beaches of the Andaman and Nicobar Islands are now recognized as important sites for protection.

Bhaskar’s visits to the islands can be sorted into numerous phases. During the first, a preliminary exploratory phase from 1978-1979, he surveyed most islands of the Andaman group (Figure 1), the central Nicobar Group, and Great Nicobar Island (Figure 2). The second phase occurred in 1981 when he visited Great Nicobar Island and Little Andaman Island (Figure 3); during the third phase of 1983-1984, he surveyed most of the Andaman Islands. The fourth phase comprised a better organised and continuous survey of South Reef Island from late-1991 to late-1995. By this time, Bhaskar had visited most islands of the Andaman and Nicobar archipelago and collected substantial data on marine turtles of the region.

Much of this data has been published as reports to donors, and a small proportion has appeared in journal publications. The objective of this paper is to synthesise data from the reports that Bhaskar produced between 1978-1995, in a format that can be used as a reference for future surveys and research and conservation interventions. The data is extracted from his reports submitted to the Wildlife Fund for Nature (WWF), India and the Madras Crocodile Bank Trust (MCBT) (citations listed at the end). For convenience, the data has been sorted at the species level and the spatio-temporal information for each species is grouped.

Figure 1. The Andaman Islands.

Figure 2. Great Nicobar Islands.

Hawksbill Turtles

Bhaskar’s surveys in the Andaman group of islands concentrated strongly on hawksbill turtles, resulting in a substantial amount of information on the spatio- temporal patterns in their nesting. These serve as valuable baseline data.

Nesting hawksbill turtle data during 1978-1995 (Bhaskar, 1979b, 1984, 1993a, 1983b, 1983c, 1994a, 1994c, 1995a, 1995b, 1995c)

Bhaskar surveyed most islands of the Andaman group during his visits in 1978-79 and later in 1983-84 (some islands were visited again in 1993-94 and 1995). The 1978-1979 survey was preliminary in nature wherein he identifies critical sites to be monitored/surveyed in detail and detailed surveys were carried out from 1983-1995. A summary of the nesting hawksbill turtle data collected during these surveys is provided in Table 1.

Figure 3. Little Andaman Island.

Hawksbill turtle nesting data from South Reef Island, 09 July to 18 December 1992 (Bhaskar, 1993b)

During his surveys in 1978-79 and 1983-84, Bhaskar identified South Reef Island as one of the most important sites for hawksbill turtles in the region; North Reef Island and Snark Island were also significant sites. In 1992, Bhaskar tagged and measured hawksbill turtles, and monitored their nesting parameters for a period of approximately 4 months at South Reef Island. A summary of the data is provided below and in Table 2.

• Total number of nests counted = 116 (9th July to 12th December, 1992)
• Total number of turtles tagged= 27 (15 September to 12 December, 1992)
• Average number of nests per hawksbill turtle (calculated as number of nests laid after tagging commenced/ number of hawksbills tagged= 77 nests/27 tagged turtles = 2.85 nests/turtle.
• Estimated number of nesting females= 41
• Hatchling emergence= 21,000 hatchlings (based on eggshell counts).

Figure 4. Little Nicobar Islands

Hawksbill turtle surveys 5th February to 15th April 1993 (Bhaskar, 1993c)

Bhaskar surveyed 37 islands of the Andaman group during this period, recording 536 hawksbill nests. Hump Island was surveyed for the first time and 48 hawksbill nests were found.

Hawksbill turtle surveys, 8th July 1993 to 3rd December 1993 (Bhaskar, 1994a)

A total of 128 hawksbill nests were recorded on South Reef Island between 8th of July and 22nd November 1993. Bhaskar estimated 46 turtles to have nested during this period, marginally more than the previous season (09th July 1992 to 18th December 1992).

Combined hawksbill survey data 1992-1993 (Bhaskar, 1994a)

Bhaskar calculated inter-nesting intervals for 50 turtles during the 1992 and 1993 nesting seasons at South Reef Island. Approximately 92% of the turtles had an interesting period of 12-15 days (see Table 3).

Table 1. A summary of Satish Bhaskar’s nesting hawksbill turtle records and observations from the Andaman Islands.

Bhaskar also surveyed Latouche Island (12 nests), Rutland Island (2), Western Twin (12), Eastern Twin (13), Northern Cinque (18), Southern Cinque (24) and Little Andaman Islands (7) in 1983-84, and South Sentinel (0) in 1995.

Table 2. Summary of the nesting parameters for hawksbill turtles at South Reef Island.

*excluding data from unhatched and eroded nests
**measured after emergence of first hatchlings, 1m from the emerged nest at a depth 35cm

Table 3. Inter-nesting intervals for hawksbill turtles at South Reef Island (1992-1993).

Clutch size was calculated for hawksbill turtles nesting at South Reef Island between 1992 and 1993 (n=114); ~90% of turtles laid between 80-180 eggs per clutch, with ~50% of turtles producing between 100- 140 eggs per clutch (see Table 4). Bhaskar recorded a hawksbill clutch with 215 eggs, which he thought to be the largest recorded for any sea turtle in India.

Table 4. Clutch sizes of hawksbill turtles nesting at South Reef Island, 1992-1993.

Carapace size of nesting hawksbill turtles on South Reef Island, 1992-1995 (Bhaskar, 1995c)

Bhaskar’s measurements of 94 nesting hawksbill turtles indicated that the curved carapace length (CCL) ranged from 64-87cm (mean=77.35cm) and the curved carapace width (CCW) ranged from 58.5-81cm (mean=69.04 cm) (see Table 5).

Hawksbill turtle surveys in 1994 (Bhaskar, 1994c)

In early 1994, Bhaskar surveyed the islands of both the Andaman as well as the Nicobar groups. Hawksbill turtles nested in small numbers at Great Nicobar and several other islands of the South and Central Nicobars. Twenty-six hawksbills were tagged at South Reef Island. No tagged turtles (from 1992 and 1993) were encountered, suggesting that the remigration interval for hawksbill turtles at this location is greater than 2 years. The average inter-nesting interval over the period of study (12th September 1992 -8th September 1994) was 14 days (n=79, range 12-17 days).

Hawksbill turtle surveys in 1995 (Bhaskar, 1995c)

The main aim of this monitoring in this year was to establish remigration intervals for hawksbills nesting on South Reef Island. Only one previously marked turtle, first tagged in 1992, was encountered during this survey. Bhaskar recorded the Inter-nesting similar and lower nesting intensities in the Andaman group of islands, and indicated that additional sites required protection for conservation of the Andaman hawksbill turtle populations. The studies also revealed that the peak nesting season for hawksbill turtles in the region is during the month of September.

Table 5. Curved carapace length (CCL) and curved carapace width (CCW) of hawksbill turtles nesting at South Reef Island, 1992-1995.

Table 6. Number of hawksbill turtle nests laid at South Reef Island, 1992-1995.

Summary of hawksbill turtle data

Bhaskar identified more than 17 islands in the Andaman group as critical nesting sites for hawksbill turtles, including Snark, Latouche, North Reef, Kwangtung and Interview Islands in the North Andaman islands group, Hump Island and South Reef Island in the Middle Andamans, and the Brother Islands, Twin Islands and North and South Cinque Islands in the Southern Andamans. His four year monitoring of nesting hawksbill turtles at South Reef Island provided insight into nesting patterns of the species. Bhaskar found little variation in the number of hawksbills nests (between 108-128, Table 6) and nesting females each year, estimating a total of 41, 46, 32 and 35 turtles respectively during the four year study period from 1992-1995, and suggested that an average of 45 turtles nested every year at South Reef Island. Though the tagging program that Bhaskar conducted revealed little information on the remigration interval of nesting turtles, he encountered one turtle in 1995 that was originally tagged in 1992. He also identified other islands with.

Green Turtles

During the exploratory phase, Bhaskar (1979b) recorded only one green turtle nest from South Andaman (clutch size 93 eggs, with an average egg diameter of 41.8mm). He predicted that the peak nesting season for green turtles ranged from May to September, although they also nested throughout the year. In 1981, while en route to the Nicobars, Bhaskar recorded one green turtle nest at South Bay on Little Andaman Island. Intense surveys of green turtles began in 1983-1984. Data collected during the entire survey period (1978-1995) for green turtles is provided in Table 7. Green turtle nesting data for South Reef Island is provided in Table 8.

Green turtle nesting data from South Reef Island, 1992-1995

Bhaskar monitored the nesting of green turtles and tagged nesting females at South Reef Island (Bhaskar 1993b, 1994a, 1994c, 1995c). Some useful information from the study is summarized in Table 8.

Bhaskar monitored the inter-nesting intervals for 52 green turtles at South Reef Island over a period of four years, and determined a range from 11-14 days with an average of 12.5 days (Bhaskar 1994c, 1995c). In addition, Bhaskar measured a total of 22 nesting green turtles over a period of 4 years from the South Reef Island (refer table 9) and found the Curved Carapace Length (CCL) to range from 86.5–100.5cm and the Curved Carapace Width (CCW) to range from 76.5-94.8cm.

Table 7. Number of green turtles nesting on the Andaman and Nicobar Islands, 1978-1995.

Summary of green turtle data

The most important discovery of Bhaskar’s surveys of the Andaman group was the identification of South Sentinel Island as perhaps the largest nesting site for green turtles in the region (Bhaskar 1995b). The surveys also helped identify Interview Island as one of the largest green turtle nesting sites in the North Andaman group and South Brother Island, south of South Andaman. His monitoring of green turtle nesting at South Reef Island was not as rigorous as that of his hawksbill turtle studies. However, his observations indicate that green turtle nesting in the region peaks during the monsoon season (July-August) and the inter- nesting interval is, on average, 12.5 days. In 1993, the minimum incubation period for hawksbill nests was 54 days, and 57 days for green turtle nests. The tagging efforts did not yield many returns, however, based on an average of 4 nests per turtle per season, Bhaskar estimated that 10- 15 turtles nested on South Reef Island each season (Bhaskar 1995c).

Table 8. Number of green turtle nests laid at South Reef Island, 1992-1995.

Table 9. Size of nesting green turtles at South Reef Island, 1992-1995. Numbers indicate the range and average (in parentheses).

Olive Ridley Turtles

Information on olive ridley turtles was sparse from Bhaskar’s initial surveys in 1978-1979. There is a single nest record at South Andaman, with a clutch size of 119, from 1978 (1979a). His survey of the Nicobar Islands (Great Nicobar and Little Nicobar islands) and the Little Andaman Islands in January-March 1981 helped identify some important olive ridley nesting sites (Bhaskar 1981a). Alexandria Bay, Dagmar Bay and Renhong beaches yielded 33, 104 and 2 nests, respectively. Olive ridley nests were also recorded on South and West Bays, Little Andaman Island (Bhaskar, 1981a). In 1994, Bhaskar compiled the data on olive ridley nesting at Cuthbert Bay, Middle Andaman, collected by the Andaman and Nicobar Forest Department (Bhaskar 1994b). He described the nesting at this location as an arribada-type event, with a large number of turtles nesting within a few days (see Table 10). The analysis revealed that about 50-75% of the olive ridley nesting happens occurred on a few nights, usually between mid-January and end of February.

Combining his data from the Nicobars and other surveys, Bhaskar tried to determine the total number of olive ridley turtles nesting in the entire Andaman and Nicobar archipelago (see Table 11) (Bhaskar, 1994b). He estimated a total of 502 turtles for the Andaman group of islands each season and a total of 198 turtles for the Nicobar group. Bhaskar’s assumption of 1.5 nests per turtle per season may be an underestimate for the region, and possibly led to an overestimation of the number of individual turtles. However, considering many of sites in the Andaman and Nicobar had not yet been surveyed, the estimate may have been lower than the actual population size.

Table 10. Olive ridley nesting at Cuthbert Bay, Middle Andaman Island, indicated an arribada-type event, with peak nights during the nesting season.

Table 11. Estimates of olive ridley turtles nesting in the entire Andaman and Nicobar archipelago.

*based on the assumption that olive ridleys nest 1.5 times on an average per season (however, Bhaskar himself observed that ridleys often nest 2-3 times per season)

**based on an average estimate for a single season

Leatherback Turtles of the Andaman and Nicobar Islands

The first confirmation of leatherback nesting in the region came from Bhaskar’s initial surveys (Bhaskar, 1979a), when he recorded leatherback nesting on Jahaji Beach at Rutland Island. Surveys during subsequent years lead to the discovery of a significant leatherback nesting beach at West Bay (70 nests) and a few nests at South Bay on Little Andaman Island, important nesting sites at Alexandria Bay and Dagmar Bay on Great Nicobar Island (Bhaskar, 1981). He counted similar numbers during his subsequent visit to Little Andaman (Bhaskar, 1984), but much larger numbers were counted from the Great Nicobar Island during complete season surveys in 1991-92 (summary provided in Table 12).

Bhaskar’s surveys confirmed leatherback turtle nesting and identified nesting beaches in the Andaman and Nicobar Islands. Important nesting sites in the Andaman group were West and South Bay beaches on Little Andaman Island and Jahaji beach on Rutland Island. Surveys of the Nicobar Islands revealed some of the largest leatherback nesting sites for the entire archipelago. The most important beaches of the Nicobar group were Alexandria and Dagmar Beaches on the west coast and Galathea Bay Beach on the east coast of Great Nicobar Island, and Pulo Kiyang and Dahayu beaches on Little Nicobar Island. Based on multiple years of data, Bhaskar (1994b) estimated the number of leatherback turtles nesting per year in the Andaman and Nicobar archipelago (see Table 13).

Table 12. The number of leatherback turtle nests laid per year in the Andaman and Nicobar Islands.

*Nesting was observed but numbers of turtles were not recorded
** 811 nests were recorded for the entire Great Nicobar Island; an additional 139 nests were recorded along other beaches of the west coast of Great Nicobar Island.
– indicates that surveys were not carried out

*No. of turtles calculated based on the assumption that leatherback turtle lay, on average, 4.9 nests per season **165 nests were recorded during 1993-94 surveys, however, a conservative average of 110 is considered

Threats to Sea Turtles in the Andaman and Nicobar Islands

In addition to collecting data on nesting in the Andaman and Nicobar Islands, Bhaskar documented the threats to sea turtles in the region. Some of the major onshore natural predators of turtle eggs and hatchlings were monitor lizards (the most significant and widespread predator), wild pigs, civet cats, estuarine crocodiles, Nicobar serpent eagles, hermit crabs and ghost crabs. Bhaskar identified feral dogs and pigs as most destructive to marine turtle nests on beaches close to settlements; feral dogs were recorded as being of particular concern on important nesting beaches such as Galathea Bay, Little Nicobar, Little Andaman and Cuthbert Bay. Sharks and other predatory fishes (such as trevallie and barracuda) were identified as potential predators of different turtle life stages at sea.

During the surveys of the North and the Middle Andaman Islands, Bhaskar observed intense egg harvest by humans at East, Excelsior, Delgarno, Trilby and East Turtle Islands.

Egg harvesting was less intense on Point, Paget, Reef, North Reef, Latouche, Kwangtung, Whitecliff, Thornhill, West, Pocock and Sound Islands. During his surveys, he interviewed local fishermen and indigenous communities in order to identify nesting sites, seasons, species etc and to understand the various issues that sea turtles in the region face.

Bhaskar identified shark fishing as one of the most serious threats to green turtle populations of the Andaman and Nicobar Islands. Based on interviews with local shark fishermen in 1994, he estimated an average mortality of 10 green turtles (mostly juveniles of sub-adults) per month. In 1994, five shark fishing groups existed in Mayabunder alone, and operated on a year-long basis; Bhaskar estimated that at least 600 green turtles were killed as incidental bycatch each year in this location alone. Considering many such fishing operations operated out of other localities in the Middle and South Andaman Islands, Bhaskar predicted that approximately 1500 green turtles were killed in the region every year. As early as 1994, Bhaskar described that green turtle populations in the region as decimated. Considering that the large predator fishery has substantially increased in the islands in the past decade, a higher level of mortality can be expected as a result of current operations. It is therefore very important to undertake monitoring of marine turtle populations in the region, especially at the same sites surveyed by Bhaskar, to understand population trends.

Bhaskar also reported extensive illegal capture of turtles for meat by the mainland settlers, as well as by foreign poachers. He reported poaching of turtles on South Sentinel Island, one of the last remaining strongholds for green turtles in the region, as well as in some remote locations of Great Nicobar. Hawksbill and green turtles were the preferred turtles for consumption, followed by olive ridleys. Leatherback turtles were usually not killed for consumption. Sand mining was the most serious anthropogenic threat to nesting beaches in close proximity to human settlements, particularly in areas with dense human populations.

Bhaskar recommended that several sites be protected, including Snark Island, Kwangtung Island, Latouche Island, North and South Reef Islands, North and South Cinque Islands, North and South Brother Islands, and South Sentinel Island. These sites were regarded as important for conserving hawksbill and green turtles. He recommended that sand mining from nesting beaches be reduced, and strong regulations be placed on the shark fishing industry. He believed the proposal to construct a free port and an oil terminal at Galathea Bay, Great Nicobar Island, would lead to the elimination of nesting areas at Galathea Beach, Saphed Balu and Indira Point. However, Bhaskar’s passion for marine turtles never made him a complete protectionist; for example he never recommended a ban on the hunting of turtle by the Nicobaris or other indigenous communities. Instead, he recommended an awareness programme for the communities about the damage caused by feral and domestic dogs and pigs to sea turtle nests.

Bhaskar frequently recommended that more comprehensive surveys and monitoring programmes were required. Leatherback monitoring programmes in Galathea Bay of the Great Nicobar Island (2000- 2004) and South and West Bay of the Little Andaman Island (2007–present) were initiated because of the information he generated through his surveys. There is no better way to honour his body of work than to further the research he initiated in the islands.

Literature cited

Bhaskar, S. 1979a. Sea turtle survey in the Andamans and Nicobars. Hamadryad 4: 2–26.

Bhaskar, S. 1979b. Sea turtles in the South Andaman Islands. Hamadryad 4: 3– 6.

Bhaskar, S. 1981. Sea turtle survey of Great Nicobar and Little Andaman Islands. Report. WWF-India.

Bhaskar, S. 1984. Sea turtles in North Andaman and other Andaman Islands. Report. WWF-India.

Bhaskar, S. 1993a. The Status and Ecology of Sea Turtles in the Andaman and Nicobar Islands. ST 1/93. Centre for Herpetology, Madras Crocodile Bank Trust, Tamil Nadu, India.

Bhaskar, S. 1993b. Andaman and Nicobar Sea Turtle Project. Phase- II: South Reef Island. Unpublished Report, Centre for Herpetology/Madras Crocodile Bank Trust, Tamil Nadu, India.

Bhaskar, S. 1993c. Andaman and Nicobar Sea Turtle Project. Phase- III. Unpublished Report, Centre for Herpetology/Madras Crocodile Bank Trust, Tamil Nadu, India.

Bhaskar, S. 1994a. Andaman and Nicobar Sea Turtle Project. Phase- IV. Unpublished Report, Centre for Herpetology/Madras Crocodile Bank Trust, Tamil Nadu, India.

Bhaskar, S. 1994b. Andaman and Nicobar Sea Turtle Project. Phase- V. Unpublished Report, Centre for Herpetology/Madras Crocodile Bank Trust, Tamil Nadu, India.

Bhaskar, S. 1994c. Andaman and Nicobar Sea Turtle Project. Phase- VI. Unpublished Report, Centre for Herpetology/Madras Crocodile Bank Trust, Tamil Nadu, India.

Bhaskar, S. 1995a. Andaman and Nicobar Sea Turtle Project. Phase- VIa. Unpublished Report, Centre for Herpetology/Madras Crocodile Bank Trust, Tamil Nadu, India.

Bhaskar, S. 1995b. Andaman and Nicobar Sea Turtle Project. Phase- VII. Unpublished Report, Centre for Herpetology/Madras Crocodile Bank Trust, Tamil Nadu, India.

Bhaskar, S. 1995c. Andaman and Nicobar Sea Turtle Project. Phase- VIII. Unpublished Report, Centre for Herpetology/ Madras Crocodile Bank Trust, Tamil Nadu, India.