The Setiu River, located in northeastern peninsular Malaysia, is home to 2 of the world's most endangered freshwater turtles: the eastern Malay Peninsula river terrapin (Batagur affinis edwardmolli) and the painted terrapin (Batagur borneoensis). The taxonomy of these 2 species has been recently revised by Praschag et al. (2007, 2008, 2009). Praschag et al. (2009) concluded that B. affinis edwardmolli occurs in Cambodia and eastern Malay Peninsula and is distinct from B. affinis affinis that occurs in Sumatra and western Malay Peninsula. The rivers of eastern Malay Peninsula, particularly the Setiu, Terengganu, and Dungun rivers still support viable populations of B. affinis edwardmolli. However, these populations are under threat from egg collection, sand mining, incidental catch in fishing gear, dam construction (Sharma and Tisen 2000), and agro-based activities in the hinterland of the rivers.

In Terengganu (Fig. 1), the Department of Wildlife and National Parks (DWNP) carries out egg incubation and head-starting projects involving B. affinis edwardmolli in the Terengganu and Dungun rivers, but other localities have been largely neglected. In view of this, the authors began collecting information on the incidence of nesting and clutch sizes from local egg collectors on the Setiu River in 2004. The nesting banks covered were Tebing Pasir Penarik (lat 5°36′57.35″N, long 102°48′16.44″E), Tebing Pasir Pak Lah Teh (lat 5°35′58.44″N, long 102°47′52.00″E), and Kuala Baharu (lat 5°38′36.65″N, long 102°46′19.90″E) (Fig. 1). These are the main nesting sites and would account for about 90% of nesting activity in the Setiu River. None of them are protected, and they have been subjected to rampant egg collection for decades. During the nesting season (end of January through the end of March), local villagers wait for gravid terrapins to ascend the banks, then capture them and bring them to a secret location to nest. This is done to keep away other villagers who may lay a stake on the eggs deposited. The nesting banks are so intensely monitored that no terrapin escapes detection. Two villagers were employed to collect data on nesting incidence and clutch size, as well as to purchase eggs for incubation. Hatchlings produced were head-started for release (Chan et al. 2008). This note reports on nesting density, nesting activity, and clutch size of B. affinis edwardmolli in the Setiu River from 2004 to 2009.

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Nesting Density and Activity

Data were collected on number of clutches, total number of eggs deposited each year, and clutch sizes (Table 1). Nesting activity was generally low and ranged from 13 to 30 clutches per year. Total number of eggs deposited ranged from 304 (2007) to 847 (2004). As expected, a declining trend (R²  =  0.480) was exhibited over the 6-year period (Fig. 2). Nesting activity at the Setiu River is comparable to that at the Dungun River where 44, 38, and 13 egg clutches were deposited in 2006, 2007, and 2008, respectively (DWNP, unpubl. data, 2009). The Terengganu River, where 99 wild clutches were collected for incubation in 2008 (DWNP, unpubl. data) hosts the largest wild population of B. affinis edwardmolli in Terengganu, and possibly in Malaysia and the world.

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Table 1 Number of clutches, number of eggs deposited, and clutch size in the eastern Malay Peninsula river terrapin (Batagur affinis edwardmolli) in the Setiu River from 2004 to 2009.

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Generally, the first nesting events for the season begin toward the end of January and are completed by the end of March (Fig. 3). Within this 3-month period, 65%–86% of the clutches are deposited between mid-February and mid-March. Batagur affinis affinis in rivers along the west coast of peninsular Malaysia nest from November to February, when sand banks emerge following the monsoon (Moll 1980).

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Clutch Size

The overall average clutch size for nests found from 2004 to 2009 was 26.9 ± 7.5 SD (n  =  132; actual number of clutches recorded was 137, but clutch size data were unavailable for 3 clutches in 2005 and 2 in 2006). This is almost equivalent to the mean clutch size of 26 reported by Moll (1980) for B. affinis affinis from the Perak River along the western Malay Peninsula. The number of eggs per clutch ranged from 7 to 43 and annual average clutch size ranged from 23.4 to 30.1 (Table 1).

Conservation

Batagur affinis edwardmolli in the Setiu River was in grave danger of local extirpation before the project was initiated at this locality. For many decades, 100% of the eggs deposited had been collected for consumption and sale, and with no recruitment; the population consisted only of aging males and females. Since 2004, a total of 1767 eggs, representing 48% of the total eggs deposited, have been procured for incubation (Chan and Chen, unpubl. data, 2009). To date, a total of 986 head-started terrapins have been released into the Setiu River. These comprise terrapins that have been head-started for varying periods, ranging from a few months to 4 years. Detailed information on this aspect of the project will be reported in a separate paper. Although this has given a boost to the dwindling population, an increase in the number of nests will not become obvious in the short term due to the long maturation time of females (estimated to be 25 years by Moll [1980]). Threats from excessive egg collection have been curbed, and fishermen are currently cooperating with the authors to reduce mortality in fishing nets. However, sand mining is still practiced and a recent government-approved large shrimp culture project along the banks of the Chalok River (Fig. 1) is expected to impact negatively on the natural habitat of B. affinis edwardmolli in the Setiu River.