How to Identify the Olive Keelback (Identification Guide)
A plain olive to olive-brown South Asian water snake with faint markings and rough keeled scales, closely tied to ponds and slow streams.
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Key identifying features
The olive keelback (Atretium schistosum) is identified by its uniform olive to olive-brown or grayish-olive back with little bold patterning, faint darker speckling or a subtle pale stripe in some individuals, and a body covered in strongly keeled scales. Its plain coloration combined with a close association with still or slow-moving freshwater habitats is the primary identification approach.
Coloration & pattern
The dorsal color is a fairly uniform olive, olive-brown, or grayish-green, sometimes with faint darker speckling scattered across the back and a subtle pale line running along the lower sides in some individuals. The belly is typically pale yellow to orange-tinged, sometimes with a reddish or salmon wash, especially near the tail, providing some contrast to the plain upperparts.
Head, eyes & scales
The head is moderately broad and only slightly distinct from the neck, olive-colored with minimal bold marking, sometimes showing a faint dark streak through the eye. Eyes are moderate sized with round pupils. Scales are strongly keeled, giving the characteristic rough, ridged texture of keelback snakes.
Size & body shape
Adults typically reach 50 to 70 cm (20 to 28 inches), with a moderately stout, cylindrical body well suited to a semi-aquatic lifestyle, and a tail of moderate length.
Range & habitat where you'll see it
The olive keelback is found across the Indian subcontinent, including India, Sri Lanka, Nepal, and Bangladesh, inhabiting ponds, marshes, slow streams, and rice paddies. It is highly aquatic and often seen swimming or basking near water's edge, feeding primarily on frogs, fish, and other aquatic prey, and is commonly encountered in agricultural wetlands within its range.
How to tell it apart from look-alikes
The checkered keelback shows a bold checkered or blotched pattern that the largely plain olive keelback lacks. The buff striped keelback has clear, bold buff stripes rather than the mostly unpatterned back of the olive keelback. The relatively plain, uniform olive coloration, subtle pale-orange belly wash, and strong aquatic habits distinguish this species from its more boldly patterned relatives.
Frequently asked questions
How can you recognize the olive keelback?
By its mostly plain olive to olive-brown back with little bold pattern, paired with a pale yellow to orange-tinged belly and rough keeled scales.
How does it differ from the checkered keelback?
The olive keelback is largely unpatterned, while the checkered keelback shows a bold checkerboard-like blotched pattern.
Is the olive keelback venomous?
It is a rear-fanged species generally considered to pose minimal risk to humans, though it should not be handled.
Where is the olive keelback typically found?
In ponds, marshes, slow streams, and rice paddies across the Indian subcontinent.
What does the olive keelback eat?
Mainly frogs, fish, and other aquatic prey found in its wetland habitat.