SHIELDTAIL SNAKES: Uropeltidae

PHYSICAL CHARACTERISTICS

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.

GEOGRAPHIC RANGE

Shieldtail snakes live in southern India and in Sri Lanka or Ceylon, which is located off India's southern coast.

HABITAT

Shieldtail snakes make their homes in forests that may be in low areas or on the sides of mountains, usually preferring places with moist or wet ground. They also live in gardens and farm fields, including rubber plantations. Unlike most digging snakes that only push through loose soil, the shieldtails will also tunnel through quite hard, clay soils. In addition, they will scoot under leaves or logs.

BURROWING BY JERKS

Some scientists believe that the shieldtail snakes burrow through the ground with an odd jerking movement. According to this idea, the snakes twist up the backbone behind the head so that it is curved back and forth and then quickly push the backbone out straight to burst the head forward. In other words, the back acts like a spring that is squeezed together and then let loose. By repeating this movement and scooting up the body each time, the snake digs through the soil. This is the same type of jerking movement used by pipe snakes, but pipe snakes use it to force the head forward as a way of gulping down large prey.

DIET

Shieldtails mainly eat worms, but some species will also eat caterpillars and termites, and at least one species in captivity will eat earwigs. Earwigs are small insects with a pair of pincers on the end of the body. After studying how several species eat worms, scientists found that the snakes either grab the worm at the end or in the middle and quickly drag them back into the burrow. The bodies of those worms caught in the middle fold in half as they are dragged into the snake's narrow burrow.

BEHAVIOR AND REPRODUCTION

The shieldtails stay hidden underground most of the time, but many will come up to the surface after a good rain, and at least one species will then begin hunting for worms. If the snakes feel threatened, they will wiggle away while looking for some loose soil and then force the head into the ground to start tunneling. They are expert diggers and can tunnel quickly. If prodded with a stick or otherwise attacked, the snake will coil around the stick or other object and begin waving the tail end of the body. Apparently, predators are confused into thinking the tail is the head. The snake can survive an attack to the tail much better than an attack to the head, so the tail waving may save its life. It is also possible that some predators may be scared off by the tail-waving behavior.

Female shieldtail snakes give birth to baby snakes rather than laying eggs. Typically, they have two to five young at a time, with larger females giving birth to a larger number than younger mothers. Births likely occur between March and September. Scientists know little else about their behavior or reproduction.

SHIELDTAIL SNAKES AND PEOPLE

These snakes and people rarely encounter each other.

CONSERVATION STATUS

These species are not listed as endangered or threatened, but scientists know little about the size of the snakes' populations.

NILGIRI BURROWING SNAKE (Plectrurus perrotetii): SPECIES ACCOUNT

Physical characteristics: One of the larger species in this family, the Nilgiri burrowing snake can reach 17.3 inches (44 centimeters) in length. They are tube-shaped snakes with purplish brown to brown backs and bellies that are often either a light brown or yellowish color. In some species, the bellies are spotted with a lighter color, and each of these spots is located right in the center of a belly scale. The head is flattened from top to bottom. The tail is tipped with a spiny, cup-shaped scale.

Geographic range: The snake lives in Nilgiri and the Anamalai Hills in southern India.

Habitat: Most of the snakes found by people are buried about 4 to 6 inches (10 to 15 centimeters) deep in the very rich soil of gardens or farm fields. The snakes especially like soil with lots of manure mixed into it. Farmers and gardeners often use manure, which contains many nutrients, to fertilize their soil and help their plants to grow. The snakes live high up on hillsides.

Diet: The Nilgiri burrowing snake eats mainly worms.

Behavior and reproduction: They spend much of their time in burrows, but if the weather turns cooler, they will move out of their homes and explore piles of manure that farmers and gardeners have left above the ground. They give birth to baby snakes rather than laying eggs. Females have three to six babies at a time, usually in July or August. Scientists know little else about their behavior or reproduction.

Nilgiri burrowing snakes and people: These snakes and people rarely see or bother each other.

Conservation status: The Nilgiri burrowing snake is not listed as endangered or threatened, but scientists know little about the size of the snake's population. ∎

FOR MORE INFORMATION

Books

Burnie, David, and Don Wilson, eds. The Definitive Visual Guide to the World's Wildlife. New York: DK Publishing, 2001.

Deraniyagala, P. E. P. A Colored Atlas of Some Vertebrates from Ceylon. Vol. 3, Serpentoid Reptilia. Colombo, Sri Lanka: Government Press, 1955.

Frank, N., and E. Ramus. A Complete Guide to Scientific and Common Names of Reptiles and Amphibians of the World. Pottsville, PA: NG Publishing, 1996.

Grace, Eric, ed. Snakes. San Francisco: Sierra Club Books for Children, 1994.

McDiarmid, R. W., J. A. Campbell, and T. A. Toure. Snake Species of the World, Vol. 1. Washington, DC: The Herpetologists' League, 1999.

Mehrtens, John M. Living Snakes of the World in Color. New York: Sterling Publishing, 1987.

Pough, F. H., R. M. Andrews, J. E. Cadle, M. L. Crump, A. H. Savitzky, and
K. D. Wells. Herpetology, 2nd ed. Upper Saddle River, NJ: Prentice Hall, 2001.

Rajendran, M. V. Studies in Uropeltid Snakes. Madurai, India: Madurai Kamaraj University Publications, 1985.

Smith, M. A. The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-Region. Reptilia and Amphibia. Vol. 3, Serpentes. London: Taylor and Francis, 1943.

Web sites

"Family Uropeltidae (shield-tailed snakes and short-tail snakes)." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/pictures/Uropeltidae.html (accessed on September 22, 2004).