Diamond-back Water Snake (non-venomous)

Description: A medium- to large-sized snake, averaging 70-90 cm in total length, but may reach 140 cm. Body stout and robust, with a long tail. Scales roughly keeled. Ground colour greyish-olive, with distinctive ¡§figure-of-eight¡¨ diamond-shaped bands over dorsum and flanks. Bands brown and with light centres; edged in black especially on lower flanks. Spaces between bands may have a single dark brown spot in the middle. Head long and rather triangular; copper-red on top. Iris light orange. Labials olive-coloured. Underside of body white with incomplete black bands. Adult males have small papillae on the chin shields.

Habits and habitat: Inhabits large, rocky streams in forested areas. In general, the streams have moderate current, large deep pools, an abundance of fish and overhanging vegetation which the snake uses as a perch. Unlike Opisthotropis spp., is seldom found hiding under rocks but usually rests 50-200 cm above the water and ay climb as high as 8 m. Several snakes may use the same perch site. When disturbed, will drop into the water, and either swim away on the surface or dive to the bottom. Strictly nocturnal, but is occasionally seen active at dusk on drizzly days. Forages in quiet pools and avoids cascading water. Bites savagely and defecates when captured. Assumes a S-shaped stance before striking. Is sympatric with Opisthotropis lateralis and O. kuatunensis. Probably lost much suitable habitat due to the construction of reservoirs and catchwaters.

Diet: Feeds on small fish and will occasionally eat frogs.

Reproduction: Oviparous. One female was reported to contain over 20 eggs.

Distribution: First recorded in Hong Kong in 1978 in the Shing Mun Reservior area at 150-250 m. Has subsequently been recorded from Shek Kong and near Lam Tsuen. Locally common in a few New Territories streams. Occurs throughout central and southern China.

Diagnostic features: Stocky body build; elongated, triangular head, copper-red in colour; diamond-shaped brown patterns along entire body length; roughly-keeled scales.