Colubridae-4-M-O-Check List snakes northern Thailand

OLIGODON  CINEREUS – FORM I

Oligodon cinereus —northern Thai form 1 (pictures above). This is one of the forms/subspecies (or maybe it’s a species in its own) of a “complex” of which the individuals have 17 dorsal rows at mid-body. It has a low number of ventral shields (165-180). The ground color is usually reddish-brown and there are 25-30 narrow, black crossbars, which alternate with much vaguer but similar crossbars—so when these vague crossbars are included there is a total of 50-60 crossbars (A, D, F). Beside these crossbars there may be reticulation, which is shown best when the animal expands its body (A). Of the tripartite head-neck mask, the posterior, third arrow-like part is remarkable: the apex is often notched off, laying in between the two “legs” of the second, central part of the mask. The two legs of the arrow are short, narrow and pointed (D). The belly is (bright) pink in the center, but white with a black “keyboard” pattern in a strip along the corners of the ventral scales (B, C, E). The blackening of the “keyboards” often spills over on the posterior half of the belly and the underside of the tail (E). Specimens of this “form” are usually small (25-45 cm). I came only across them in evergreen forests at high elevations (>1000 m asl) in the provinces Chiang Mai (Doi Saket District), Lampang (Mueang Pan) and Tak (Phop Phra, Umphang). It is possible that these snakes are actually subadults, and that adults are much larger (60-75 cm) , and in which the colors and the characteristic patterns have “faded away”—such a specimen was found in Phop Phra. If this is true, the questions arises why so many juveniles and subadults were seen, and only one / a few adult(s).
A-C. A reddish-brown specimen from Nam Tok Pha Charoen National Park, Phop Phra District, Tak; B and C show the piano keyboard pattern on the belly. D. Head and neck of a specimen from Chiang Mai’s Doi Saket District. E. The same specimen, showing its pink belly with piano keyboard pattern. F. Another specimen from Doi Saket, its color and patterning very similar to D.

OLIGODON CINEREUS-FORM 2

Oligodon cinereus, form 2. Dull brown snake with indistinct “kukri mask” on head and neck, reaching a length of 70 cm. Belly white anteriorly, with vague grey blotches becoming gradually more conspicuous and darker from mid-body towards the vent. Underside tail immaculate white. As form 1 it has 165-180 ventral shields and all other characters except for coloration and patterning are similar to form 1. It is a rare, but widespread snake in the northern region and has been found in deciduous forests at low elevations (400-600 m a.s.l.). The large difference in habitat preference, suggests that it is not just a pale brown form or subspecies of O. cinereus, but possibly a distinct species.
A. Adult from Mae Ramat District, Tak. B. Belly of the same specimen as in A. C-E. male individual from Mueang District, Phayao.

OLIGODON CYCLURUS

Oligodon cyclurus. In Thailand this snake looks very similar to the striped form of Oligodon fasciolatus. The major difference is that O. cyclurus has 19 rows of dorsal scales at mid-body and on the anterior part of the body.  snake. What’s more, the white or soft pink belly of O. cyclurus usually has two rows of vague grey dots (G), or very distinct black squarish blotches (B)—or any grade in between (in the striped O. fasciolatus belly-dots or -blotches are less common). The dorsum always has two pairs of stripes (a broad paravertebral and a narrow lateral one—F), with 12-16 butterfly-shaped crossbars (A), but this pattern can be partly masked in reticulated forms (E). The head scalation (C) and shape of the mask is similar to O. fasciolatus. In O. cyclurus reddish-brown forms are common (very rare in the striped O. fasciolatus). O. cyclurus is only found in the western part of Tak Province (Umphang, Phop Phra, Mae Sot, Mae Ramat and Tha Song Yang District) where O. fasciolatus appears to be absent. A-C. Adult from Mae Ramat District, Tak. E. Subadult from Umphang District, Tak. F-G. Adult from Phop Phra District, Tak.

OLIGODON FASCIOLATUS (non-striped form)

Oligodon fasciolatus or Banded Kukri Snake (form without distinct stripes). This sturdy-built kukri snake has 21 rows of dorsal scales at mid-body and anteriorly of it. The tail is rather short and ends in a stiff point. It can reach a length of 80 cm. The head is hardly distinct from the neck. The upper side is greyish-brown (A, E), sometimes orange-brown (F) with 12-16 dark brown, butterfly-shaped or ovoid crossbars; in between the crossbars are three transverse series of reticulations (E-F). On head and neck is a dark tripartite mask-like mark (B-D); the apex of the third, arrow-shaped part is rarely detached. The belly is white or with a pink center and white corners of the ventral shields, sometimes with the rows of  indistinct grey dots. The hemipenes are forked and covered with papillae. This form of the species is uncommon in the Upper North of the northern region (where striped forms dominate—see below), but is the dominant form in the Lower North, and in Central and Northeast Thailand where it is a common snake. A-B. A juvenile from Nakhon Thai District, Phitsanulok. C. Head and neck of an adult from Soi Dao District, Chanthaburi (in the southeast of Central Thailand). D-E. An adult from Mueang District, Tak. F. A subadult, orange-brown color morph from Nong Hin District, Loei (in the northeastern region)

OLIGODON FASCIOLATUS (striped form)

Oligodon fasciolatus (striped form). This form is buff or pale brown and has 2 distinct pairs of stripes, one broad paravertebral pair and a narrow often vague lateral pair (A, C, H). As the form without stripes, it usually has some 14 butterfly-shaped crossbars. In some specimens the reticulation is dominating and the stripes are not very distinct (B and E). Striped forms without reticulation and crossbars are not common (H). The belly is usually immaculated white. The tripartite mask on head and neck D and F) is very similar to that of the non-striped form. A. Striped form with 15 crossbars from Mae On District, Chiang Mai. B. Reticulated form (stripes masked) from Mueang District, Chiang Mai, C. Juvenile from Mueang District Mae Hong Son (stripes and 14 crossbars). D. Head of subadult from Mae Rim District, Chiang Mai (with stripes and crossbars). E. Subadult from Mueang District, Chiang Mai: reticulated form (stripes indistinct). F. Frontal view of upper side head of juvenile from Pang Mapha District, Mae Hong Son. G. Forked hemipenis with papillae and without spines of specimen from Nan’s Bo Kluea District. H. Striped form (without distinct reticulations and crossbars) from Mueang District, Phayao.

Oligodon inornatus (no picture)

OLIGODON JOYNSONI

Oligodon joynsoni, one of the kukri snakes with 17 rows of dorsal scales at mid-body. It reaches a length of 80 cm. Dorsum is light brown, pinkish-brown (A, B, D) or dark brown (G) with a vague paravertebral stripe, and usually with 25-30 narrow dark crossbars alternating with reticulations, sometimes vague (A) or absent (B). The head-neck-mark (D-E) is tripartite and similar to  form 1 of Oligodon cinereus, rather vague in the lighter colored forms (B). The belly is white with black squarish blotches (keyboards pattern) in the dark forms (H), or immaculate pale pink (I) in the light-colored forms. The snake’s appearance can be very similar to O. cinereus, but the species is larger and more slender, and has 185-200 ventral shields (in O. cinereus usually less that 180). It is widespread in northern Thailand, but uncommon, occurring in mountain forests or cultivated areas at elevations of 600-1200 m. A. Adult specimen from Wiang Pa Pao District, Chiang Rai. B. Adult, pale pinkish-brown specimen from Mae Wang District, Chiang Mai. C. Hemipenes of male from Doi Saket District, Chiang Mai. D. Male from Doi Saket District, Chiang Mai. E. Head of brown specimen from Mae Taeng District. F-H. Dark brown specimen from Mae Taeng District, Chiang Mai. I. Belly of same specimen as in A.
55. Oligodon mouhoti
56. Oligodon sp.

OLIGODON TAENIATUS

Oligodon taeniatus, the Striped Kukri Snake. A little snake that reaches a length of about 50 cm. Above it is buff with a broad (dark) brown pair of paravertebral stripes and a pair of thinner lateral stripe (A and G). The paravertebral pair and the pale series of vertebral in between are ornamented with oake yellow spots on the edges of the scales (A an d C). The belly is pale pink anteriorly but bright pink (scarlet) posteriorly.  Black squarish dots/blotches adorn the belly, posteriorly they are arranged in a piano-keyboard pattern, anteriorly smaller and vaguer (E-F). The underside of the tail is scarlet, without black blotches. The mask on head and neack is tripartite, but the shape seems to be rather variable (C-D). The hemipenes are forked near the base, elongated, smooth without spines or large papillae (H). A-C. Specimen from Watthana Nakhon District, Sa Kaeo (eastern Central Thailand). D. Pattern of the underside of an individual from Nakhon Sawan’s Mueang District, E-G. A male individual from an undulated paddy field in Phichai District, Uttaradit.

OREOCRYPTOPHIS PORPHYRACEA PORPHYRACEA (RED MOUNTAIN RACER)

Oreocryptophis porphyracea porphyracea, the Red Mountain Racer (pictures above). Colorful mountain snake that can reach a length of about 110 cm. Juveniles (A, B, D) are bright red with black crossbars, in adults the bright red becomes dark, brick red, as do the crossbars, however, black lines still show the contours of the original pattern (C). It is widespread throughout the northern region at elevation more than 900 m asl. A. Juvenile from Omkoi District, Chiang Mai. B. Juvenile from Nan’s Tha Wang Pha District. C. Showing coloration of dult specimen from Umphang District, Tak. D. Juvenile from Umphang District, Tak.

OREOCRYPTOPHIS PORPHYRACEA COXI (RED MOUNTAIN RACER, SUBSPECIES COXI)

Oreocryptophis porphyracea coxi. This striped-subspecies of the Red Mountain Racer is known to occur in Loei (Northeast Thailand) and the adjacent mountains of the northern region. I came across it in the Lom Kao District of Phetchabun and Nakhon Thai District of Phitsanulok.
59. Orthriophis taeniurus (helfenbergeri)