Shieldtail Snakes: Uropeltidae

Almost all of the forty-seven species of shieldtail snakes have a head that gets narrower and narrower until it comes to a point at the end. In some species, the head gets narrower from side to side, and in others it narrows from top to bottom. The pointed snout is covered with thick scales made of fingernail-like material, and in some snakes, a particularly large scale makes a roof over the top of the snout. Many species have a large scale at the very end of the tail. This large scale looks something like a shield, which is how the snakes got their common name of shieldtails. The large tail scale may have ridges, or keels, or it may be covered with spines. Often, the snake has other thick and keeled scales that form a flattened oval just in front of the shield scale. If the snakes live in wet areas, these keels and spines can pick up and hold mud, which may form into a large clump.

Many species are brown, gray, or black. Some have dark bands. A number of species have white or yellowish white outlines around their belly scales, which can make them look rather speckled. Some shieldtails have bright yellow bellies marked with dark spots, and blue, so-called iridescent (IH-rih-DEH-sent) backs that shimmer different colors when the light strikes them. A few species in Sri Lanka look like members of the cobra family. This type of copying, called mimicry (pronounced MIM-ick-ree), actually causes some birds that might otherwise attack the snakes to stay away.

Although it cannot be seen from the outside, shieldtail snakes are different from other snakes in the kind of muscle tissue that they have in the trunk, or portion of the body between the head and the tail. In snakes, the tail begins at the vent, a slitlike opening on the underside of the snake. The muscles in the front part of the trunk in shieldtails have red muscle fibers in addition to the white muscle fibers present in other snakes. The red fibers can work longer than the white ones without tiring out, and scientists believe that these long-lasting fibers help the snake, which spends much of its time digging.

Shieldtail snakes are mostly small snakes, with most adults growing to less than 12 inches (30 centimeters) in length. Some grow longer, and a few such as the Rhinophis oxyrhynchus and Uropeltis ocellatus can reach nearly 24 inches (61 centimeters) in length.