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

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 of Dendrelaphis.
                                                                  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: n.poyarkov@gmail.com            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
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  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
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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.
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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