How to Identify the Round Island Keel-Scaled Boa (Identification Guide)

Key identifying features

The Round Island Keel-Scaled Boa is identified chiefly by its distinctly keeled body scales, which give the skin a rough, ridged texture rather than the smooth surface typical of most boas. It shares its restricted island habitat with the smooth-scaled Round Island Boa, making scale texture the single most important diagnostic feature between the two.

Coloration & pattern

Coloration is generally light to medium brown or grayish-brown, often with darker, somewhat diffuse blotching or mottling along the back that helps the snake blend into rocky, sparsely vegetated ground. The pattern is subdued rather than bold, consistent with camouflage needs in an arid island environment with sparse plant cover.

Head, eyes & scales

The head is moderately distinct from the neck, without pronounced ornamentation. Eyes are moderate in size with vertically elliptical pupils. The most important identification feature lies in the body scales themselves: each scale bears a raised central ridge or keel, producing a rough, textured feel and appearance rather than a glossy sheen, a trait rare among boas as a whole.

Size & body shape

This species has a moderately built body, generally somewhat stouter than its smooth-scaled relative on the same island, though still fairly slender compared to many mainland boas. The tail is moderate in length. Overall body proportions reflect adaptation to a rocky, crevice-rich island habitat.

Range & habitat where you'll see it

This boa was historically found exclusively on Round Island near Mauritius, inhabiting rocky terrain with sparse vegetation and volcanic soil. It sheltered in crevices and burrows, and its historic population suffered severe declines due to habitat degradation from introduced grazing animals. It remains one of the rarest snake species in the world, with conservation efforts focused on habitat restoration on its native island.

How to tell it apart from look-alikes

The presence of keeled, ridged scales is the clearest way to distinguish this species from the smooth-scaled Round Island Boa, which otherwise shares a similar general body plan, coloration, and restricted range. Careful examination of scale texture, ideally under good lighting or magnification, resolves most cases where the two might otherwise be confused based on coloration or pattern alone.