Herpetology Notes, volume 14: 795-798 (2021) (published online on 19 May 2021)

A range extension for Dryophiops rubescens (Gray, 1835) with the first record of the species from Vietnam

James Holden1 and Nikolay A. Poyarkov2,*

Dryophiops rubescens (Gray, 1835), the keel- 170 m). The snake was basking on a vertical trunk of bellied whip snake, is an arboreal colubrid snake of Dipterocarpus alatus at a height of ca. 15 m above the the subfamily Ahaetuliinae (Figueroa et al., 2016). ground (Fig. 2A) in polydominant semi-deciduous This poorly known species inhabits lowland forests monsoon tropical forest with dense canopy. When and forest edges, and ranges thoughout the Sundaland disturbed by a long stick during an attempt to capture it, biogeographic province, from the Isthmus of Kra in the snake quickly moved higher up the trunk of the tree. southern Thailand southward through the Thai-Malay Though we failed to collect the specimen, a number of Peninsula into Sumatra and Borneo, the Mentawai and photos were taken using a Panasonic Lumix FZ1000ii Natuna Archipelagos, and Java (Das, 2011; Chan-ard camera shot at 400 mm. Our identification of the specimen et al., 2015; Fig. 1). Dryophiops rubescens was also as D. rubescens was confirmed by L. Lee Grismer (pers. reported from north of the Isthmus of Kra in western comm.). Photo vouchers were deposited in the photo Thailand, in Phetchaburi and Tak Provinces, and from depository of the La Sierra University Digital Collection, southeastern Thailand in Prachin Buri, Chachoengsao, Riverside, California, USA (LSUDC 12654–58). Chanthaburi and Trat Provinces (Chan-Ard et al., 2015; The specimen was identified as a member of D. Thai National Parks, 2021; P. Pawangkhanant, pers. rubescens based on the following morphological comm.). Finally, the species was reported from Phnom characters (Das, 2011): slender, compressed body with Aural in Kampong Speu Province, Cambodia (Grismer head distinct from neck; large, slightly bulging eyes et al., 2007; Fig. 1). While these records from mainland with a horizontal pupil; rostral protuberance absent Southeast Asia confirm the presence of D. rubescens in (Fig. 2D); and an inconspicuous greyish tan dorsum Cambodia and Thailand, records from other mainland with scattered small dark-brown and pale markings regions have yet to be published. (Fig. 2B,C); labials with dark-brown markings (Fig. In February 2021, we recorded an arboreal snake in the 2C,D); dark streaks on forehead, dark-brown postocular Nam Cat Tien section of Cat Tien National Park, Tan Phu streaks (Fig. 2D), and a cream venter (Fig. 2B). District, Dong Nai Province, Vietnam. The specimen was The observed snake is markedly different from the not collected, but the photographic record unambiguously superficially similar, sympatric arboreal colubrids of allowed identification as D. rubescens. We here present the genus Ahaetuella Link, 1807 by overall body shape the first record of the genus and species for Vietnam, with and colouration and the absence of an enlarged rostral additional information on its natural history. scale or a rostral protuberance. It also differs from An adult D. rubescens was observed on 18 February members of the genus Dendrelaphis Boulenger, 1890 2021 at ca. 13:30 h by J. Holden on the trail to Bau by its greyish-brown colouration, lacking the broad Sau Lake (11.4505°N, 107.3644°E, WGS 84; elevation black postocular stripes, extending to the neck and body flanks, characteristic ofDendrelaphis . Our observation of D. rubescens represents the first record of the genus and species for Vietnam (Nguyen et 1 Forest Floor Lodge, Cat Tien National Park, Tan Phu, Dong al., 2009). The new locality in Cat Tien National Park Nai, Vietnam. 2 Department of Vertebrate Zoology, Biological Faculty, currently represents the easternmost distributional limit Lomonosov Moscow State University, Moscow, 119234, of the species in mainland Southeast Asia, ca. 350 airline Russia; and Joint Russian-Vietnamese Tropical Research and km east from the nearest known population in Phnom Technological Center, Nghia Do, Cau Giay, Hanoi, Vietnam. Aural Wildlife Sanctuary, Aoral District, Kampong Speu * Corresponding author. E-mail: [email protected] Province, Cambodia (Grismer et al., 2007). This record © 2021 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0. of D. rubescens is of certain biogeographic interest since 796 James Holden & Nikolay A. Poyarkov

Figure 1. Distribution of Dryophiops rubescens (Gray, 1835). The occurrence of this species throughout Sundaland is shown in red. In Indochina localities are marked using numbered red circles, including 11 for Thailand (1 – Phuket Province; 2 – Thap Put District, Phang Nga Province; 3 – Khao Sok National Park, Surat Thani Province; 4 – Kaeng Krachan National Park, Phetchaburi Province; 5 – Umphang District, Tak Province; 6 – Phop Phra District, Tak Province; 7 – Tha Song Yang District, Tak Province; 8 – Khao Yai National Park, Prachin Buri Province; 9 – Khao Ang Rue Nai Wildlife Sanctuary, Chachoengsao Province; 10 – Khao Soi Dao National Park, Chanthaburi Province; 11 – Ko Chang District, Trat Province) and one for Cambodia (12 – Phnom Aural, Kampong Speu Province; Grismer et al., 2007). The new locality in Vietnam (13 – Cat Tien National Park, Dong Nai Province) is indicated by the red star. All localities except 10 from Chan-ard et al. (2015) and Thai National Parks (2021). Locality 10 is via personal communication of P. Pawangkhanant.

it provides further evidence for the presence of Sundaic of southern Vietnam. This record is also interesting elements in the herpetofauna of lowland tropical forests since it suggests that the heterogeneous topography of Range Extension for Dryophiops rubescens 797 mainland Southeast Asia has not limited this species’ References distribution. This is not surprising given the rich history Chan-ard, T., Nabhitabhata, J., Parr, J.W. (2015): A Field Guide to the of inundations and land bridges, which repeatedly Reptiles of Thailand. New York, USA, Oxford University Press. separated and reconnected the Indochinese and Sundaic Das, I. (2010): A Field Guide to the Reptiles of South-east Asia. landmasses during the Pleistocene (Voris, 2000). London, United Kingdom, New Holland Publishers. Several other Sundaic snake species were previously De Koninck, R. (1999): Deforestation in Viet Nam. Ottawa, recorded in southern Vietnam, but these did not have Ontario, Canada, International Research Centre. Figueroa, A., McKelvy, A.D., Grismer, L.L., Bell, C.D., Lailvaux, vouchers or photographic evidence (e.g., Python S.P. (2016): A species-level phylogeny of extant snakes with brongersmai – Orlov et al., 2003; Boiga dendrophila description of a new colubrid subfamily and genus. PLoS ONE – Nguyen et al., 2009; Ahaetulla mycterizans (unpubl. 11(9): e0161070. data), and Tropidolaemus wagleri – Orlov et al., 2003). Grismer, L.L., Chav, T., Neang, T., Wood, P.L., Jr., Grismer, J.L., As with D. rubescens, these species are all associated Youmans, T.M., et al. (2007): The herpetofauna of the Phnom with lowland tropical forests, which in the last 40 years Aural Wildlife Sanctuary and checklist of the herpetofauna were subject to greater anthropomorphic conversion of the Cardamom Mountains, Cambodia. Hamadryad 31(2): 216–241. (including logging, agriculture, road construction, and Kuznetsov, A.N., Kuznetsova, S.P. (2011): Botany of Bidoup-Nui other human activities) than mountainous areas (De Ba National Park. In: Biodiversity and Ecological Characteristics Koninck, 1999; Kuznetsov and Kuznetsova, 2011; of Bidoup-Nui Ba National Park, p. 37–105. Nguyen, D.H., Laurance, 2007; Meijer, 1973; Meyfroidt and Lambin, Kuznetsov, A.N., Eds., Hanoi, Vietnam, Academy of Science 2008), and they may now be extinct in Vietnam. and Technology Publishing House for Science and Technology. Additional, intensive field survey efforts in the Laurance, W.F. (2007): Forest destruction in tropical Asia. Current remaining parts of lowland tropical forests of southern Science 93(11): 1544−1550. Meijer, W. (1973): Devastation and regeneration of lowland Vietnam are urgently needed for obtaining a better dipterocarp forests in Southeast Asia. BioScience 23(9): understanding of their actual herpetofaunal diversity. 528−533. The discovery of D. rubescens in Cat Tien National Meyfroidt, P., Lambin, E.F. (2008): Forest transition in Vietnam Park is unexpected given that its herpetofaunal diversity and its environmental impacts. Global Change Biology 14(6): is considered to be one of the best-known in southern 1319−1336. Vietnam, with long-term herpetological surveys and Nguyen, S.V., Ho, C.T., Nguyen, T.Q. (2009): Herpetofauna of monitoring program being conducted in the park at Vietnam. Frankfurt am Main, Germany, Edition Chimaira. Orlov, N.L., Ryabov, S.A., Nguyen, S.V., Nguyen, T.Q. (2003): least since 2007 (Vassilieva et al., 2016). It is likely that New records and data on the poorly known snakes of Vietnam. previous surveys failed to record this species due to its Russian Journal of Herpetology 10(3): 217–240. secretive canopy dwelling nature, and due to the general Thai National Parks (2021): Thai National Parks. Available at: inaccessibility of the canopy for frequent sampling. The https://www.thainationalparks.com. Accessed on 18 February last published reptile species list of the national park 2021. includes at least 104 species (Vassilieva et al., 2016). Vassilieva, A.B., Galoyan, E.A., Poyarkov, N.A., Geissler, P. Our record brings the total number of reptile species (2016): A Photographic Field Guide to the Amphibians and Reptiles of the Lowland Monsoon Forests of Southern Vietnam. known for the Cat Tien National Park to 105, and the Frankfurt am Main, Germany, Edition Chimaira. total number of reptiles known for Vietnam to 470. This Voris, H.K. (2000): Maps of Pleistocene sea levels in Southeast further underlines the role of Cat Tien National Park as a Asia: shorelines, river systems and time durations. Journal of key territory for preservation of herpetofaunal diversity Biogeography 27(5): 1153−1167. in Vietnam.

Acknowledgments. We are thankful to L. Lee Grismer, Parinya Pawangkhanant, and Gernot Vogel for providing important information and confirmation of our identification. We also thank L. Lee Grismer for his assistance with photo material deposition and for pre-peer reviewing our manuscript. We thank an anonymous reviewer and the associate editor for many useful comments which helped us to improve the earlier version of this manuscript Lastly, we thank the Russian Science Foundation partial funding of fieldwork (RSF 19-14-00050 to NAP). 798 James Holden & Nikolay A. Poyarkov

Figure 2. Dryophiops rubescens (Gray, 1835) from Cat Tien National Park, Dong Nai Province, Vietnam. (A) General view of the basking individual on the trunk of Dipterocarpus alatus. (B, C) Frontal views. (D) Close-up of the head showing the distinctive dark-brown postocular streak. Photos by James Holden, accessioned as LSUDC 12654–57.

Accepted by Justin Bernstein