First record of Ptyas nigromarginata in Thailand
Green Rat Snake – Ptyas nigromarginata (Blyth, 1854)
Thai name (proposed): ngu sing khieo – งูสิงเขียว
In Thailand this beautiful rat snake was first recorded in 2012. To this date, it is only known from the mountains of northern Nan province near the Laotian border.
The photograph above was taken in Phu Kha National Park at an elevation of 1600 m.
This snake often reaches a length of 180 cm, but occasionally much larger specimens, up to 270 cm, have been recorded (in North India). The head is brown and distinct from the body. The large eyes are black, the pupil is round. The infralabials and throat are white.
Most of the body is green, medially mossy green, laterally pale green, which extends to the corners of the ventral scales. A small intermediate area between the white throat and the neck is yellow. The dorsal scales are smooth or (medially) feebly keeled.
At about two thirds from the head there is an yellowish brown intermediate zone, followed posteriorly by two pairs of black stripes that run to the end of the tail: one pair of paravertebral stripes and one pair of lateral stripes. The color between these stripes is greyish white.
The belly is white, but the corners of the ventral scales are pale green.
The specimen in the picture was on the brink of crossing the road cutting through the national park on a sunny morning in mid-May. It had just emerged from the evergreen mountain forest, which is known as ‘ancient forest’ due to the occurrence of a number of rare ‘relict’ tree species, such as the single stem fish-tail palm (Caryota gigas), only known from the national park, and the flowering tree Bretschneidera sinensis, the only species of the family Bretschneideraceae.
In Thailand this snake is probably also a relict. It is best known from mountainous areas at higher latitudes (and higher altitudes, up to 2200 m) in northern India, Bhutan and southern China (Yunnan, Sichuan).
■ (left): Details of head and neck. Notice the large eye, the sharp contrast between the brown supralabials and white infralabials, and the small yellow zone between throat and neck just behind the most posterior infralabials.
■ (centre): Ancient forest in Nan’s Phu Kha National Park where the Green Rat Snake occurs. ■ (right): Map of northern Thailand showing the site (black dot) where this snake was recorded.
Reference: Gernot Vogel and Sjon Hauser, 2013. Addition of Ptyas nigromarginata (Blyth, 1854) (Squamata: Colubridae) to the snake fauna of Thailand with preliminary remarks on its distribution. Asian Herpetological Research 4 (3): 166-181.