How to Identify the Urutu (Identification Guide)
The urutu is identified by its triangular head, grayish-brown body with dark trapezoidal blotches, and moderately large pit viper build found in South America.
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Key identifying features
The urutu (Bothrops alternatus) is a pit viper found in parts of Brazil, Argentina, Uruguay, Paraguay, and Bolivia. It is identified by its broad triangular head, a body pattern of dark, alternating trapezoidal or D-shaped blotches, and a generally heavy, robust build typical of larger lancehead vipers.
Coloration & pattern
The body ground color is typically grayish-brown, olive-brown, or tan, marked with a series of dark brown blotches that are often trapezoidal or D-shaped and alternate irregularly along either side of the spine, sometimes appearing to meet or nearly meet at the midline. The blotches are frequently outlined with lighter scales, adding to the contrast against the background color.
Head, eyes & scales
The head is broad and strongly triangular, distinctly wider than the neck, a hallmark feature of lancehead vipers. A dark stripe often extends from the eye toward the jaw. Pupils are vertically elliptical, and a heat-sensing pit lies between each eye and nostril. Scales are keeled, giving the body a rough, textured surface.
Size & body shape
Adults commonly reach 3 to 4 feet, with some individuals growing somewhat larger, and the body is notably thick and heavy for its length, giving the urutu a stocky overall appearance compared to more slender lanceheads. The tail is relatively short and tapers to a blunt point.
Range & habitat where you'll see it
The urutu is found across parts of southern Brazil, Uruguay, Paraguay, northern Argentina, and Bolivia, favoring grasslands, marshes, and areas near water within subtropical and temperate zones. It is often encountered in open or semi-open habitats rather than dense rainforest, reflecting a preference for grassland and wetland-adjacent terrain.
How to tell it apart from look-alikes
The urutu's alternating trapezoidal or D-shaped blotches, often bordered with lighter scale edges, help distinguish it from other regional lanceheads such as the jararaca, which tends to show more triangular blotches on a more slender body. Its notably heavy, stocky build for its length is another useful distinguishing trait. As with all lanceheads, the triangular head, vertical pupils, and heat-sensing pit separate it from non-venomous colubrids sharing a blotched pattern.
Frequently asked questions
What does the urutu's blotch pattern look like?
Dark brown trapezoidal or D-shaped blotches that alternate along either side of the spine, often edged with lighter scales.
How does the urutu's build compare to other lanceheads?
It has a notably thick, stocky body for its length compared to more slender lancehead species.
Where is the urutu typically found?
In grasslands, marshes, and wetland-adjacent habitats across southern Brazil, Uruguay, Paraguay, northern Argentina, and Bolivia.
How can you distinguish the urutu from the jararaca?
The urutu has alternating trapezoidal or D-shaped blotches and a stockier body, while the jararaca tends to be more slender with triangular blotches.