1Insitute of Climate Change, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia
2Lang Tengah Turtle Watch, 17 Jalan Tunku, Bukit Tunku, Kuala Lumpur, Malaysia
3Institute of Oceanography and Environment, Universiti Malaysia Terengganu, Kuala Nerus, Terengganu. Malaysia
4Fisheries Research Institute Batu Maung, Batu Maung, Penang. Malaysia
5Fisheries Research Institute Langkawi, Langkawi, Malaysia
6The Datai Langkawi, Jalan Teluk Datai, Langkawi, Kedah, Malaysia
Of the seven species of sea turtle worldwide, four have extensive records in Malaysia: the green (Chelonia mydas), hawksbill (Eretmochelys imbricata), olive ridley (Lepidochelys olivacea), and leatherback (Dermochelys coriacea) turtle. The records of these turtles in Malaysia consist of primarily nesting (Hendrickson, 1958; Siow & Moll, 1982; Mortimer et al., 1993; Chan et al., 1999; Chan, 2006, 2013; Hamann et al., 2006; Mohd Salleh et al., 2012, 2018) and stranding data (Chan, 2006; FRI, 2020). Unfortunately, most of the strandings are of dead turtles, including 90.1% (n = 90/99) of the records from Malaysian waters in 2019 (FRI, 2020). The cause of mortality has been attributed to bycatch, illegal take, mortal injuries (including vessel strike), ingestion of plastics, exposure to oil slicks, and diseases such as fibropapillomatosis (Siow & Moll, 1982; Chan, 2006; Joseph et al., 2019). These are concerning as it indicates the insidious effect of anthropogenic activities on sea turtles in Malaysia.
In comparison to the other four species, not much is known about loggerhead sea turtle nesting in Malaysia, except for the historical mention of loggerhead turtle nesting in small numbers in Sarawak (Leh, 1985). The nesting of loggerhead turtles in Malaysia was also mentioned by Chuang (1961), but this may have been a misidentification of an olive ridley turtle as a loggerhead, as the photo shown is of the former species. The in-water presence of loggerhead turtles has been recorded in the South China Sea (Kobayashi et al., 2011); however, these records are sparse and little is known about the loggerhead turtles in Malaysia and Southeast Asia (Chuang, 1961; Leh, 1985; Abdul Rahman et al., 2021). In 2019, a stranded loggerhead sea turtle was found entangled in a ghost net off the coast of Pulau Kendi (5.235° N, 100.192° E), an island south of Penang Island on the western coast of Peninsular Malaysia. This was the first documented loggerhead sea turtle encountered in the Straits of Malacca. The turtle was rehabilitated and released later in the same year (Abdul Rahman et al., 2021).
On 8th December 2020, a female loggerhead turtle carcass with a wound at the top of the carapace was washed ashore at the west end of the beach of The Datai Langkawi Resort (6.426° N, 99.669° E), Langkawi, Malaysia (Figure 1). The carcass was severely decomposed (State 3 sensu López-Barrera et al., 2016), with the skin and scales peeled off, bloated carcass, and bad smell (Figure 2). The curved carapace width (CCW), curved carapace length (CCL), and the dimension of the wound were measured by the Datai Langkawi Resort (WC Lim) and Langkawi Fisheries Research Institute (SMA Syed Mahiyuddin). Photos were taken at all four sides (anterior, posterior, left and right side) and the facial scutes for the carcass (Figure 2a-e). The carcass measured 80cm (CCW) by 90cm (CCL). Based on the CCL, the specimen in this study was an adult female (Baptistotte, 2003, Casale et al., 2011; Ishihara & Kamezaki, 2011; Tucek et al., 2014; Patel et al., 2015). The open fracture (Figure 2b) on the carapace measured 16cm wide and 45cm long. The split wound was most likely from an anthropogenic source, suspected to be either vessel strike or human mishandling.
Figure 1. Map of (a) Langkawi and Teluk Datai where the carcass of loggerhead turtle was discovered; and (b) The two most recent records of loggerhead turtles in the Straits of Malacca (This study and Abdul Rahman et al. 2021). The grey area in the map represents the terrestrial domain of Malaysia.
Figure 2. (a) Anterior, (b) Posterior, (c) Left, and (d) Right view of the loggerhead turtle carcass. (e) The left facial scale pattern of the loggerhead turtle found in this report and compared to (f: in red box) the individual found in Abdul Rahman et al. (2021).
The individual in this report was larger than the individual (CCW=75cm; CCL=82cm) reported by Abdul Rahman et al. (2021). The identity of the individual was determined (Figure 2e-f) by comparing the left facial scute of the carcass with the records in Abdul Rahman et al. (2021) using manual visual comparison via photo-ID method as described in Schofield et al. (2008) and Long (2016). The comparisons confirmed that the two reported loggerhead sea turtles were different individuals.
This incident is the first official record of a loggerhead sea turtle carcass washing ashore on the coast of Malaysia and one of few for the region. The distance between locations of the current report and Abdul Rahman et al. (2021) was approximately 144km. The records suggest that there are loggerhead turtles in the waters of Malaysia. Previous studies mentioned loggerhead turtles migrating to the South China Sea, possibly for foraging (Charuchinda et al., 2002; Kobayashi et al., 2011). However, the ecological importance of Malaysia for the loggerhead turtle population in this region is still unknown due to lack of records and study.
Nevertheless, the distribution of loggerhead sea turtles in the adjacent Indian and Pacific Oceans are well known. There are at least 107 nesting sites of loggerhead sea turtle across these oceans and many in-water sightings (Wallace et al., 2010). In the Indian Ocean, most of the nesting and foraging loggerhead turtles are concentrated in the west and north-west Indian Ocean, including Oman (one of the largest rookeries in the world) and eastern African nations (Hughes, 2010; Rees et al., 2010; Nolte et al., 2020; Willson et al., 2020; Lohe & Possardt, 2021), and Western Australia (Hamann et al., 2013). There are smaller nesting populations in Tamil Nadu (India), Sri Lanka, and the coast of Thailand, which is adjacent to the northern Straits of Malacca (Dodd Jr., 1988; Charuchinda et al., 2002; Ali et al., 2004;). Sporadic reports and tracking studies found that loggerhead sea turtles do pass through the Andaman Sea or South China Sea (adjacent to the southern end of Straits of Malacca) (Charuchinda et al., 2002; Ali et al., 2004; Kobayashi et al., 2011). Thus, the Straits of Malacca might be a common migratory route or foraging ground of loggerhead sea turtles; more data is required to understand the importance of this habitat.
Based on the state of decomposition, the loggerhead turtle had died within the month prior and drifted ashore. The northern end of the Straits of Malacca passes through the Andaman Sea before going into the Eastern Indian Ocean. The Straits of Malacca experiences northeastern monsoon sea surface current (SSC) system in December, whereby the SSC experiences northerly movement from the southern to northern end of Straits of Malacca and ends in the eastern Indian Ocean. This is due to the water movement driven by the push from the strong monsoon current of South China Sea, pushed into the southern channel of the Straits of Malacca (Haditiar et al., 2016). Furthermore, there is an eddy of SSC between Langkawi Island and Tarutao Island during the monsoon period (Rizal et al., 2010; Syamsul Rizal et al., 2012; Isa et al., 2020). Hence, the period where the carcass was found (December) suggests that the turtles might met its demise at the northern islands of the Andamans (e.g., Tarutao Island) or was a migratory individual from the South China Sea.
The state of both loggerhead turtles raises concerns about the threats to sea turtles in Malaysian waters. The individual found in 2019 was entangled in a ghost net before it was rehabilitated and released by authorities (Abdul Rahman et al., 2021), while the individual reported in this study was possibly killed by human activity(s). Busy water ways, especially in the Straits of Malacca, and under-regulated maritime and fishery industries might pose serious threats to sea turtles and other marine megafauna (Balakrishnan & Varkkey, 2017; Wong & Yong, 2020) and require further investigation.
WHB was supported by Universiti Kebangsaan Malaysia grant, Young Lecturers Incentive Grant (GGPM-2021-056), in collaboration with The Datai Langkawi. We thank the Malaysian Department of Fisheries and Mohd Tamimi Ali Ahmad (Fisheries Research Institute Rantau Abang) for allowing the handling of the carcass and releasing the data for publication. All necessary permits for sampling and observational of the specimen were obtained from the competent authorities. The study is compliant with Convention on Biological Diversity and Nagoya protocols. The authors would like to express their sincere appreciation for Rushan Bin Abdul Rahman and Nicolas J. Pilcher PhD. for their feedback on an early draft of the manuscript.
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