Eretmochelys imbricata (Linnaeus, 1766)

Figueroa, Alex, Low, Martyn E. Y. & Lim, Kelvin K. P., 2023, Singapore’s herpetofauna: updated and annotated checklist, history, conservation, and distribution, Zootaxa 5287 (1), pp. 1-378 : 69-70

Eretmochelys imbricata (Linnaeus, 1766) — Native.

Testudo imbricata Linnaeus, 1766: 350 . Type material: None designated; type material apparently lost, according to Wallin (1985: 128); UUZM 130 designated as holotype by Thunberg (1828), reidentified as C. mydas by Wallin (1985: 126). Type locality: “[h]abitat in Mari Americano, Asiatico” (= America and Asiatic seas); later restricted to “ Bermuda Islands” by Smith & Taylor (1950a: 315, 1950b: 17), and to “ Belize, British Honduras” by Schmidt (1953: 106).

Hawksbill Turtle

( Figure 8C ; Pulau Satumu)

Singapore records.

Chelone imbricata — Flower, 1896: 860.— Hanitsch, 1898: 9.— Flower, 1899: 618.—Ridley, 1899: 205.— Hanitsch, 1912b: 14.

Eretmochelys imbricata —Sharma, 1973: 24.—K. Lim, 1990a: 11 (Sentosa).—K.K.P. Lim & L.M. Chou, 1990: 56.—K.K.P. Lim & F.L.K. Lim, 1992: 134, 151.—L.M. Chou et al., 1994: 105.—K.K.P. Lim, 1994b: 226, 331.—P.K.L. Ng et al., 1995: 126.—Sharma, 1998: 56.—H.T.W. Tan et al., 2007: 119 (East Coast [= ECP]; Jurong Island).—K.K.P. Lim et al., 2008: 175, 266 ( Singapore Straits).—P.K.A. Ng, 2009: 25, 193.—T.H. Ng & K.K.P. Lim, 2010: 199.—H.T.W. Tan et al., 2010: 158 (East Coast [= ECP]; Jurong Island).—L.M. Chou, 2011: 77–78.—M.A.H. Chua, 2011: 281 (Semakau Landfill [PS]).—P.K.L. Ng et al., 2011: 452.—M.F.C. Ng, 2012: 146.—W. Wong, 2017: 86.—L.M. Chou et al., 2020: 75.—J.S.K. Cham et al., 2021: 1 (Sisters Islands Marine Park).—TTWG, 2021: 95.

Eretomochelys imbricata — Gremli, 1988: 62.

Eretmochelys squamata —H.M. Smith & Taylor, 1950a: 315.

Erectmochelys [sic] imbricata — Diong et al., 2001: 184 (Labrador Beach Park [= LNP]).

“Hawksbill turtles”—K. Lee, 2003: 39 (Pulau Sudong).—Van Miriah, 2002: Local.—B. Lay, 2017b (East Coast Park).—Zheng, 2017a (East Coast Park).—Zheng, 2017b (East Coast Park).—Zheng, 2017c (Southern Islands).—Zheng, 2020c (East Coast Park).—Zheng, 2020d (East Coast Park).—Zheng, 2020e (“between Kusu and Lazarus islands”).—Zheng, 2020g (Changi Coast Walk; East Coast Park; Sentosa).—A. Tan, 2021b (Pulau Hantu).—A. Tan, 2021d (East Coast Park).—A. Tan, 2021g (Sisters’ Island Marine Park).—F. Tan, 2021b (Changi).—Thet, 2021 (Sentosa’s Siloso Beach).—G. Pek, 2022 (Sentosa Cove).—A. Qing, 2022 (“Changi Bay reclamation site”).—Z. Zheng, 2022b (East Coast Park).

Remarks. Raffles (1822) described seeing numerous E. imbricata shells for sale in Singapore, of which at least some were most likely locally-sourced, but this was not stated. After C. porosus and Heosemys spinosa , this would be the third earliest account of any herpetofauna from Singapore, along with the description of a snake (that matches Ptyas fusca ) in the same publication (Raffles 1821). Subsequently, MCZ R-1416 (syntype of E. squamata [= imbricata ]) was collected in Singapore in 1858 by Putnam, and Flower (1896) reported a live specimen shown to him by Hanitsch that was collected “near Singapore early in 1896”. After Flower (1896), no other observation of E. imbricata from Singapore was published until 87 years later when Sharma (1973) noted seeing live ones brought into Singapore ( Table 2 ). The next published observation was of a dead individual with a crushed carapace found on a beach at Sentosa on 3 November 1990 ( Lim 1990a). In the first edition of Singapore’s Red Data Book, Lim (1994b) mentioned E. imbricata was occasionally seen around Singapore, but they were uncertain whether it was a resident species, suggesting that sightings were infrequent and nesting was non-existent. TTWG (2021) also did not identify Singapore as being part of E. imbricata nesting ground, but they do indicate Singapore as part of its foraging range. The first documentation of E. imbricata nesting in Singapore is of one observed nesting at LNP on 20 July 1999 ( Diong et al. 2001). At least by 2007, nesting on Jurong Island and East Coast Park were known (Tan et al. 2007), and recognised in the updated version of the Red Data Book (Lim et al. 2008). Just recently on 26 May 2021, the first observation of E. imbricata mating in Singapore was made at Sisters’ Islands Marine Park ( Cham et al. 2021). The only other published observations of E. imbricata is of Lee (2003) referring to individuals being seen off the western side of Pulau Sudong, and one seen off Pulau Semakau in 2007 ( Chua 2011).

Eretmochelys imbricata was the first species of herpetofauna, and one of six vertebrates, placed on NParks species recovery programme (NParks 2016a; NParks 2016b). In an effort to protect E. imbricata and keep it nesting in Singapore, NParks initiated a turtle management programme in 2016 which through the help of trained volunteers survey suitable areas for signs of turtles and patrol beaches for turtle tracks, nesting females, nests, and hatchlings (NParks 2018). Prior to this initiative, from 2005 to 2016, only 66 turtle sightings were documented compared to 80 nesting-specific encounters from nine separate locations between 2017 and 2018. On 29 September 2018, NParks strengthened its conservation efforts of E. imbricata by opening a turtle hatchery at Sisters’ Islands Marine Park (NParks 2018). Within its first year, 150 turtles were hatched and released at the hatchery ( CNA 2019). Additional published reproductive evidence include: 32 hatchlings at ECP on 16 August 2017 (Zheng 2017a); a nesting female laying eggs at ECP on 24 August 2017 (Zheng 2017b), of which approximately 100 successfully hatched on 12 November 2017 ( Lay 2017b); 46 eggs that hatched on 2 November 2017 on one of the Southern Islands, after the nest was first discovered on 8 September 2017 when a Varanus salvator was seen feeding on the eggs (Zheng 2017c); a nesting female on 23 May 2020 at ECP (the first observation of turtles mating in Singapore) on 26 May 2021 (Zheng 2021g); a female seen on the beach at ECP on 2 July 2020 that was reported to not have nested (Zheng 2020d); 100 hatchlings seen at ECP on 18 June 2021 (A. Tan 2021d), 85 hatchlings that hatched at Siloso Beach on 31 October 2021 from a nest that was discovered on 3 September 2021 (Thet 2021), 100 hatchlings that were rescued at Changi on 16 December 2021 (F. Tan 2021b), and; nesting turtles that were seen at a reclamation site along Changi Bay (Qing 2022). In an effort to learn more about nesting and the movement of adult females, nesting females are being tagged for identification with metal flipper tags (Zheng 2020d) and two females were fitted with satellite radiotransmitters after nesting on a beach at ECP (Zheng 2020d). Preliminary data showed that the two turtles spent some time traveling along the southern coast of Singapore (between Sentosa and Changi) before heading to Pulau Batam, Indonesia (Zheng 2020g). Eretmochelys imbricata is the only marine turtle documented to nest in Singapore.

Occurrence. Restricted to southern coastline, Singapore Strait, and Southern Islands. Uncommon. Nesting numbers are increasing.

Singapore conservation status. Critically Endangered.

Conservation priority. Highest.

IUCN conservation status. Critically Endangered [2008].

LKCNHM & NHMUK Museum specimens. Singapore (no locality) : ZRC.2.5425– ZRC.2.5429, ZRC.2.142 (no date); East Coast Park : ZRC.2.3529– ZRC.2.3532 (05-Oct-1996) , ZRC.2.4644 (1996), ZRC.2.6849– ZRC. 2.6852 (15-Sep-2009); Labrador Beach [ LNR] : ZRC.2.4761– ZRC.2.4770(20-Jul-1999); Singapore Straits : ZRC. 2.6198 (29-Jun-2006); Sisters’ Islands [ SIMP] : ZRC.2.7287 (12-Sep-2017) .

Additional Singapore museum specimens. Singapore (no locality): MCZ R-1416 [syntype of E. squamata ], NMW, RMNH, USNM .

Singapore localities. Changi—Changi Bay—East Coast Park—Kusu Island—Labrador Nature Reserve—Lazarus Island—Pulau Hantu—Pulau Jurong—Pulau Satumu—Pulau Semakau—Pulau Sudong—Sentosa— Singapore Straits—Sisters’ Islands Marine Park—Southern Islands (not specified).

Genus Lepidochelys Fitzinger, 1843 (1 species)

Thalassochelys (Lepidochelys) Fitzinger 1843: 30 (type species: Chelonia olivacea Eschscholtz, 1829 , by original designation; gender feminine).

Figures

FIGURE 8. A) Caretta caretta, B) Chelonia mydas, C) Eretmochelys imbricata, D) Lepidochelys olivacea, E) Dermochelys coriacea, F) Dermochelys coriacea, G) Trachemys scripta, and H) Batagur borneoensis. Photographs by: Halvard Aas Midtun [A], Marcus A.H. Chua [B], Karenne Tun [C], Ashesh Rathor [D], Tan Heok Hui [E], Alastair Rae [F], Holly Siow [G], and Kelvin K.P. Lim [H].