SUNBEAM SNAKES: Xenopeltidae

PHYSICAL CHARACTERISTICS

The two species of sunbeam snakes—the common sunbeam snake and the Hainan sunbeam snake—are among the world's most beautiful snakes. Their metallic-looking bodies shine different colors depending on how light bounces off them. When a sunbeam snake is in the shade, its back looks dark purplish brown or black, but when it slithers out into the sun, the large scales on its back and head erupt into a wave of color. Like a raindrop can bend sunlight to create a rainbow, this snake has scales that reflect sunlight into many colors. This property is called iridescence (IH-rih-DEH-sense). In fact, another common name for this snake is the iridescent earth snake. Young snakes, which are also iridescent, often have a white patch, or collar, on the upper neck.

Adults have slightly flattened bodies that are white, light gray, or light yellow on the bottom. The light color also extends up onto the lip scales. Sunbeam snakes have very small eyes on a head that is about the same diameter as the neck, so the head is not as obvious as it is in vipers, pythons, and many other snakes. The head flattens out toward the snout, giving it a wedge shape suited for digging. The skeleton also has some interesting features. The bone in the front of the upper jaw has teeth where most snakes do not. The snake's teeth are also all hinged at the base, rather than more firmly attached to the jaw bone, so they can wiggle back and forth a bit without falling out.

Adults usually reach about 2 to 3 feet (0.6 to 0.9 meters) in length. The tail makes up about one-tenth of the body's total length. In snakes, the tail begins at the vent, a slitlike opening on the belly side.

GEOGRAPHIC RANGE

Sunbeam snakes live in southern China and Southeast Asia from the Nicobar and Andaman islands west of Thailand to the Philippines and south through much of Indonesia.

HABITAT

Sunbeam snakes spend at least part of their time underground, hidden in leaves or under trash. They live in humid forests, as well as rice paddies, farm fields, parks, and gardens next to the woods. People rarely see them deep in the forests, which may mean they do not travel there, but it may also simply mean people usually overlook them in that habitat.

DIET

Scientists have only studied the diet of the common sunbeam snake, which eats lizards, frogs, and snakes, as well as small mammals and birds. The snake is a very fast eater, swallowing its prey more quickly than most other snakes can. Scientists have not studied the other species.

"OLD" SPECIES

Scientists sometimes refer to some species, such as the sunbeam snakes, as being relicts (REH-lihkts). Relict species are those that now live in a much smaller area than they once did. Typically, they have been on Earth for a very long time compared to other similar animals and have a set of features—usually something in the skeleton—that is similar to that seen in ancient animals, many of which are known only from their fossils. In some cases, relicts now live in widely separated areas, because the species in between died out over the years.

BEHAVIOR AND REPRODUCTION

These snakes are nonvenomous (nahn-VEH-nuh-mus), or not poisonous. They stay out of sight most of the day, remaining underground in burrows. A sunbeam snake uses its wedge-shaped head to push through leaves, litter, and loose soil. Although it is capable of digging, it usually uses burrows made by other animals rather than making them itself. The snakes become more active at night and leave the burrows to hunt. They seem to keep up their guards when out at night, moving quickly with the head pressed against the ground and the tongue flicking about again and again to pick up any scents of other animals in the air. When they feel threatened, sunbeam snakes will shake the tail like a rattlesnake does, but the sunbeam snakes have no rattles, so the tail makes no noise. Nonetheless, scientists believe that the motion alone is enough to make an attacker, also known as a predator (PREH-duh-ter), think twice about approaching the snake. Predators that come too close are greeted by a very bad-smelling material that oozes from the snake's vent area. If the predator actually touches the sunbeam snake, the snake will stiffen its body and jerk about wildly. Again, while this poses no danger to the attacker, the motion may be enough to cause the predator to leave the snake alone.

Female sunbeam snakes lay up to seventeen eggs at a time. Scientists know little else about their reproduction.

SUNBEAM SNAKES AND PEOPLE

Sunbeam snakes and people leave one another alone for the most part, but the snakes are starting to become more popular in the pet trade as more people become familiar with their color-changing scales. They make poor pets, however, because they remain underground most of the time and usually give off a bad odor when handled. They also are very nervous, and the stress is likely one reason they often die soon after they are purchased. In addition, the snakes do not reproduce well in captivity, which means that people must hunt them in the wild to supply the pet trade, rather than raise babies from already captured snakes.

CONSERVATION STATUS

These snakes are not listed as endangered or threatened.

COMMON SUNBEAM SNAKE (Xenopeltis unicolor): SPECIES ACCOUNT

Physical characteristics: The common sunbeam snake has a dark purplish brown back, but its smooth scales shine in blues, greens, reds, and yellows when the animal slithers out on a bright, sunny day. Its belly is whitish. That whitish color extends into a collar around the back of the head and front of the neck in juveniles. The snakes have wedged-shaped heads that help them to dig into the soil. Adults usually reach less than 3 feet (0.9 meters) in length, but some can grow to 49 inches (1.25 meters).

Geographic range: The common sunbeam snake lives in southern China and Southeast Asia.

Habitat: The common sunbeam snake is semifossorial (SEM-ee-faw-SOR-ee-ul). "Fossorial" means it lives below ground, and the term "semi" means they only spend part of their time there. They are most often seen at the edges of forests or in the farm fields and neighborhoods nearby.

Diet: In the wild, they eat lizards, especially skinks, as well as frogs, snakes, small mammals, and small birds. Captive snakes will eat mice.

Behavior and reproduction: This snake stays underground much of the day and comes out at night to hunt. In captivity, it kills mice by constriction (kun-STRIK-shun), which is the ability to squeeze a prey animal until it cannot breathe and therefore dies. When threatened, the common sunbeam snake will shake its tail and, if touched, will jerk its body. Females lay up to seventeen eggs at a time, and eggs reportedly hatch in about seven to eight weeks, but scientists know little else about its reproduction.

Common sunbeam snakes and people: The common sunbeam snake and people leave one another alone.

Conservation status: This snake is not listed as endangered or threatened. ∎

FOR MORE INFORMATION

Books

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

Campden-Main, S. M. A Field Guide to the Snakes of South Vietnam. Washington, DC: Smithsonian Institution, 1970.

Cox, M. J. The Snakes of Thailand and Their Husbandry. Malabar, FL: Krieger Publishing Company, 1991.

Deuve, J. Serpents du Laos. Paris: ORSTOM, 1970.

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

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

Taylor, Barbara. Snakes. New York: Lorenz, 1998.

Zug, G. R., L. J. Vitt, and J. P. Caldwell. Herpetology: An Introductory Biology of Amphibians and Reptiles, 2nd ed. San Diego: Academic Press, 2001.

Web sites

"Sunbeam Snake (Iridescent Earth Snake)." Ecology Asia. http://www.ecologyasia.com/Vertebrates/sunbeam_snake.htm (accessed on September 21, 2004).

"Sunbeam Snake (Xenopeltis unicolor)." Science Museums of China. http://smc.kisti.re.kr/animal/class/cls310.html (accessed on September 21, 2004).

"Sunbeam Snake or Iridescent Earth Snake." Wild Singapore. http://www.wildsingapore.per.sg/discovery/factsheet/snakesunbeam.htm (accessed on September 21, 2004).