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The snake genus Ptyas includes eight species of diurnal, fast-moving snakes that climb well. All species are oviparous. Due to their large size some species are exploited for the leather trade or for consumption.
Ptyas nigromarginata is widely distributed in evergreen and montane forests at altitudes of 1000–2300 m above sea level over a large area of the Himalayas and its foothills from Nepal to the southwestern part of eastern Tibet, China, and far into mountain ranges running to the east in southwestern China (Sichuan, Yunnan and Guizhou) and south and to the southeast in India, Bangladesh, Myanmar, Thailand, and Vietnam. This species seems to be restricted to elevations above 500 m, with an upper limit around 2300 m. Its preferred habitat consists mainly of temperate forests (often with conifers) in the northern parts of its range and montane forest or dense hill evergreen forest in the southern parts. In the most northern part of its range, the hills around the Sichuan Basin, the species has been reported from relatively low elevations of 500 to 1000 m. All records from this area are apparently from before 1935, which may suggest that the species has been locally extirpated or become extremely rare due to habitat destruction and hunting following population expansion from the Basin into the hills. Another possible explanation is that most of the relatively low elevation records around the Sichuan Basin are in fact not valid, as the specimens were confused with P. dhumnades. Only in Tibet have records of P. nigromarginata at such low elevations have been confirmed
With the possible exception of a few localities, nowhere in its range does P. nigromarginata seem to be common. An important factor related to its apparent rarity is its preference for dense, pristine forests and avoidance of human habitations and settlements. Furthermore,these snakes are large: several specimens over 240 cm long have been recorded and one from Arunachal Pradesh (northeastern India) measured 277 cm. Vogel and Hauser (2013) suggest that ow population densities are to be expected for such a large predator, especially in primary forest.
Vogel and Hauser (2013) found no clear evidence that P. nigromarginata and its congener P. dhumnades are sympatric anywhere in their range. The known range of P. dhumnades occupies much of eastern mainland China and Taiwan and is well separated from the most eastern known extension of the range of P. nigromarginata in China’s Guizhou Province. However, P. dhumnades has been reported from Chongqing Municipality, where P. nigromarginata was recorded in the early 20th century and a possible P. dhumnades specimen was sghted in Chengdu, Sichuan Province, in recent years; P. nigromarginatawas was possibly also known from Chengdu in the early 20th century.
Only in some parts of Yunnan and Sichuan of China and northern India is P. nigromarginata apparently not uncommon. In Sikkim (India) ‘villagers reportedly often kill them as they believe that this particular snake will remember the person who tried to hurt it and will chase after him . Also in the Talle Valley (Arunachal Pradesh, India) this species seems not to be rare, as three specimens were found there within a period of one week. A reported specimen from Lijiang was among at least five other specimens captured in nearby forest, suggesting that the species is not uncommon in that part of Yunnan. The species also seems not to be very rare in southern Sichuan, based on the numbers of specimens reported from this region.
(Vogel and Hauser 2013 and references therein)