Buff Striped Keelback

The buff striped keelback (Amphiesma stolatum) is a species of nonvenomous colubrid snake found across Asia. It is a typically non-aggressive snake that feeds on frogs and toads. It belongs to the subfamily Natricinae, and is closely related to water snakes and grass snakes. It resembles an Asian version of the American garter snake. It is quite a common snake but is rarely seen.

Taxonomy

Based on morphological characters including hemipenial morphology, dentition, and external scalation, in 1960 the genus Natrix sensu lato was divided into several genera, revalidating the genus Amphiesma with the type species A. stolatum.

Anatomy and morphology

A small, slender snake, the buff striped keelback is generally olive-brown to gray in colour. The head and the body are of the same colour.

The body of the buff striped keelback is short, and it has a long slender tail which is almost a quarter of its length. Two yellow stripes along the length and to the sides of the spine are the distinctive feature of this snake. These stripes are diffuse at the head and are especially bright on the second half of its body.

The keelback has irregular blackish crossbars on the body. Near the head the crossbars are prominent, whereas on the second half of the snake they become diffuse.

The sides of the head are yellow, and the head tapers to form a distinctive neck. The nape is red during the breeding season. The chin and throats are white or sometimes yellow. The lips and area in front of and behind eye are yellowish. The forked tongue is black. The eyes have large round pupils with golden flecks on the iris.

The underside is pale cream and has small black spots scattered along both the margins. It has keeled scales on the dorsal surface of the body.

Morphs

There are two distinct colour varieties – a typical variety, found everywhere, with grayish-blue interscale colour. The second variety, erythrostictus, is common mainly in coastal areas and has bright vermillion interscale colour. The interscale colours become visible only when the snake puffs itself up when agitated.

Identifying characteristics

Scalation has been described as:

The nasal shield does not touch the second supralabial (upper lip shield);

The rostral touches a total of 6 shields. These are two inter-nasals, two nasals and the first supralabial on each side;

Supralabial 8 (3rd to 5th touching eye);

Presence of single temporal shield;

Nineteen rows of costals which are strongly keeled except for the outer row which is perfectly smooth;

Presence of stripes;

Ventrals 118–161, usually divided;

Anal divided;

Subcaudals 46-89, paired.

Size

The Buff Striped keelback is usually 50 to 80 cm (about 19.7 to 31.5 inches) in total length. Females are usually longer than the males.

Distribution