Oligodon hamptoni is a rare species of Kukri Snake known from only two specimens, both collected nearly a century ago in northern Myanmar. Here, we report the third record of this species based on a photograph taken in Mt. Gaoligongshan, Tengchong City, Yunnan Province, China, approximately 235 km northeast of the nearest record in Bhamo District, Kachin State, Myanmar. We also provide a detailed redescription of the holotype, showing that the photo record from Mt. Gaoligongshan can be unambiguously identified to this species. This rediscovery represents the first observation of O. hamptoni in China and is the first report of this species in almost 100 years.

biodiversity, Gaoligongshan Nature Reserve, morphology, Myanmar, snakes, Squamata

Kukri Snakes of the genus Oligodon (H. Boie in Fitzinger, 1826) are a speciose group of colubrid snakes widely distributed across the Asian continent as far west as Turkmenistan and as far east as the Maluku Islands of Indonesia (Green 2010; Uetz et al. 2020). While several species of Oligodon are locally abundant throughout their range, most species in the genus are known from a handful of specimens and are poorly understood by herpetologists (Orlov et al. 2010; Supsup and Carestia 2020).

Oligodon hamptoni Boulenger, 1918 represents one of the rarest Kukri Snake species in mainland Southeast Asia (Cambodia, southern China, Laos, Myanmar [Burma], Peninsular Malaysia, Thailand and Vietnam). It was described based on a single male specimen collected from “Mogok, Upper Burma” (Mogok, Pyin Oo Lwin District, Mandalay Region, Myanmar) approximately 112 years ago. Based on Boulenger’s (1918) original description, the type specimen was a “handsome and very remarkable snake”, which had a vibrant dorsum consisting of a large yellow vertebral stripe situated between a pair of reddish-brown stripes and a bright red venter with alternating black bars across the body. A few years later, Wall (1925) reported a second specimen of this species, an adult female from “Sinlum Kaba” (Sinumkaba, Bhamo District, Kachin State, Myanmar), and provided additional morphological information on the species. Unfortunately, Wall’s specimen was eviscerated and deposited in the osteological collection of the Natural History Museum, London (NHMUK, formerly BMNH), preventing a re-examination of its morphology. Since Wall’s publication, O. hamptoni has been known only from a preserved skull and the type specimen.

On 8 October 2020, one of us (JHY) received a photograph of a moderately-sized colubrid snake from Mt. Gaoligongshan, Tengchong City, Yunnan Province, China (Fig. 1) referable to the genus Oligodon. After further examination, we conclude that this snake can be unambiguously identified to O. hamptoni, thus representing the first record of this species in China and the first observation of this species in almost 100 years. The subsequent rediscovery of this species provides an opportunity to document the live color pattern of O. hamptoni. Herein, we present a detailed description of this poorly known species based on a re-examination of the holotype and the new voucher photograph from China.

Figure 1. 

Distribution of Oligodon hamptoni (red) and Oligodon lacroixi (blue). Star denotes the type locality. Localities: (1) Mogok, Pyin Oo Lwin District, Mandalay Region, Myanmar (type locality see Boulenger 1918); (2) Sinumkaba, Bhamo District, Kachin State, Myanmar (Wall 1925); (3) Tengchong City, Yunnan Province, China (this paper); (4) Chapa (now Sa Pa), Lao Cai Province, Vietnam (Angel and Bourret 1933; Orlov et al. 2010); (5) Jinping County, Honghe, Yunnan Province, China (Yang and Rao 2008); (6) Mengzi, Honghe, Yunnan Province, China (He and Yang 1979); (7) Panzhihua, Sichuan Province, China (Zhao 2006).

We inspected photographs of a snake referable to O. hamptoni from Yunnan Province, China and compared its external features to the holotype specimen (NHMUK 1946.1.1.71) from Mogok, Mandalay Region, Myanmar. The photographs were taken by Mr. Zhuan-Yun Hu, a forestry ranger in Tengchong section of Gaoligongshan National Nature Reserve (TC-GLGS, hereinafter), on his way back home after regular forest patrol. Owing to the incidental nature of the observation, the specimen observed was not collected. Instead, the photographed individual was compared directly to the holotype, along with the published description of a second specimen from Sinlumkaba, Kachin State, Myanmar (NHMUK 1930.5.8.529) given by Wall (1925). The photographs and video taken were deposited in the citizen/community science platform iNaturalist.org and are accessible by the following link (https://www.inaturalist.org/observations/68037252).

The holotype of O. hamptoni had a small ventral incision underneath the tail, which allowed us to confirm the sex of the specimen. Body measurements such as Snout-Vent Length (SVL), Tail Length (TailL) and Total Length (TotalL) were taken using a flexible ruler. All other head and scale measurements were taken using Mitutoyo Digital Calipers and estimated to the nearest 0.1 mm. The measurements taken include: head length, measured from the anterior margin of the jawbone (rictus) to the tip of the rostral scale (HeadL); head width, measured from the widest point between the head (HeadW); snout length, measured from the anterior point of the eye to the tip of the rostral scale (SnL); snout width, measured as a straight-line distance between the median of both nostrils (SnW); eye diameter, measured horizontally from both posterior and anterior margins of the eye (EyeD); interorbital distance, the straight-line distance between both eyes at the border of the supraoculars (IOD); frontal length, the maximum length of the frontal scale (FrontalL); frontal width, the maximum width of the frontal scale (FrontalW). Dorsal scales were counted anteriorly at one head length behind the head, at midbody, namely halfway between the terminus of the head and the vent, and posteriorly at one head length anterior to the cloacal plate (given as anterior–midbody–posterior in the description); ventral scales were counted according to Dowling (1951); the tail tip was not included in the number of subcaudal scales; counts for head scales are given in left/right order. The number of total body scales was calculated as the sum of the number of ventral scales, the cloacal plate (considered a single scale regardless of whether it is single or divided) and the number of subcaudal scales. Relative head scale angle and shape terminology are adapted from Kaiser et al. (2019). Museum abbreviations follow Sabaj (2016) and Uetz et al. (2020) unless otherwise noted.

The observed Oligodon hamptoni we document in this paper represents the first record of this species from China. With the recent description of Oligodon lipipengi Jiang, Wang, Li, Ding, Ding & Che, 2020 from Tibet (Che et al. 2020), this raises the number of Oligodon species known from China to fifteen. Additionally, the record from Yunnan Province represents the first live photographs ever taken of this species, and the first observation in almost 100 years.

Since Wall’s (1925) publication, no other O. hamptoni specimens have been found in Myanmar and the species is still represented by only one preserved specimen in museum collections. Therefore, an assessment of the phylogenetic position of O. hamptoni in relation to other members of the genus is challenging. Boulenger (1918) noted that the species shared several characteristics with another Oligodon he described from the same locality, Oligodon herberti Boulenger, 1905 (now a synonym of the species O. catenatus), but ultimately remarked that O. hamptoni was, “a much heavier snake… the largest and handsomest of all Oligodons”. Pope (1935) suggested that O. hamptoni and the then recently described O. lacroixi were conspecific because he noted that there were very few differences in scalation between the two taxa. Smith (1943) also stated that O. lacroixi was “like hamptoni”, but ended up recognizing both species in an informal species-group he classified as the “dorsalis-erythrogaster-hamptoni group”, which also included O. catenatus, Oligodon dorsalis (Gray, 1853), O. erythrogaster and Oligodon mcdougalli Wall, 1905. This classification scheme was followed by Dowling and Jenner (1989), but rejected by Wagner (1976), who elected to group O. hamptoni and O. lacroixi with Oligodon brevicauda Günther, 1862 and O. dorsalis. While we lack sufficient data from most species present in these groups to make further comments, unpublished research suggests that many of the characters used to group taxa within Oligodon may need to be re-assessed (Lee and Yushchenko et al. in prep). At the time of Pope (1935)’s publication, O. lacroixi was known from very few individuals and was considered rare. Subsequent fieldwork in Yunnan Province, China and north Vietnam has revealed additional specimens, and the species has been re-described in detail (Orlov et al. 2010). Enough morphological differences exist between the two taxa to warrant their separation; mainly, the lack of a loreal, six infralabials and 1+2 temporals in O. lacroixi (vs. loreal present, five infralabials and 1+1 temporals in O. hamptoni) along with their differentiating color patterns (Table 2). However, the two taxa are clearly similar and may share a close relationship with one another. Several drainage basins separate the distributions of both species, with O. hamptoni occurring within the confines of the Ayeyarwady (Irrawaddy) river drainage and O. lacroixi occurring east of the Salween (Nujiang) and Mekong (Lancang) river drainages. These rivers and corresponding mountain ranges may have acted as biogeographic barriers, separating the two taxa by vicariance. However, such a hypothesis can only be tested if additional specimens of O. hamptoni are discovered.

We cannot accurately assess the conservation status of O. hamptoni based on this singular observation. We do note, however, that the location of this observation is adjacent to the TC-GLGS, a member of the UNESCO World Network of Biosphere Reserves. Given the close proximity of O. hamptoni to the reserve, we can assume that the species likely occurs within this region. If true, O. hamptoni seems to be very elusive in TC-GLGS because one of us (JHY) had spent 57 field days in the reserve to conduct herpetological surveys between 2014 and 2018, which covered 1360–3000 meters in altitudinal range and different seasons, but did not obtain any record of this species (Yang et al. 2019). Based on the criteria of the IUCN Red List, we recommend listing O. hamptoni under the “Data Deficient” category. The surrounding habitat and altitudinal range of our observation is similar to the other two records of O. hamptoni from Myanmar, which are situated between 1,200–2,000 meters. The remoteness, combined with the ongoing political instability of northern Myanmar, makes it difficult to ascertain whether future surveys will be able to detect this species any time soon. Nonetheless, we predict that O. hamptoni occurs throughout the highlands of the Ayeyarwady drainage basin in Myanmar where suitable habitat exists, particularly in northern Mandalay Region, Shan State and southern Kachin State. The abundance of newly described amphibians and reptiles in the Gaoligongshan National Nature Reserve indicates that much of the region is still unexplored by herpetologists (Yang et al. 2016a, b; Yang and Huang 2019; Yang et al. 2019). We anticipate that future amphibian and reptile surveys here and in adjacent areas in Myanmar will undoubtedly make other new discoveries, and perhaps rediscover additional lost species.

We thank Zhuan-Yun Hu (Gaoligongshan National Nature Reserve) for providing photos/videos and observation data on the snake from Mt. Gaoligongshan. We also thank Patrick D. Campbell (Natural History Museum, London) for permission to examine the holotype of O. hamptoni and other specimens under his care. PY and NAP thank the Russian Science Foundation (RSF grant No. 19-14-00050 to NAP) for financial support.

We thank Patrick David (Muséum National d’Histoire Naturelle, Paris) and an anonymous reviewer for their helpful comments on an earlier version of this manuscript.