AFRICAN BURROWING SNAKES: Atractaspididae

PHYSICAL CHARACTERISTICS

The African burrowing snakes have small heads, rounded at the front. Their heads are no larger in diameter than their necks. Only the quill-snouted snake has a head that comes to a point. The members of this family have small, sometimes very tiny, eyes with round pupils. Most have fangs, or long, pointed teeth, at the rear of the mouth, but some have hollow fangs at the front of the mouth. These front fangs swing out to inject venom, or poison, into their prey, animals that they hunt for food, or their predators (PREH-duh-ters), the animals that hunt them for food.

These small to medium-sized snakes are long and thin; adults range in length from about 12 to 40 inches (30 to 102 centimeters), from head to tail tip. Most are black or brown with a different-colored ring around the neck. A few have bright stripes. All have smooth scales, instead of the ridged scales seen in many other snakes.

GEOGRAPHIC RANGE

Most African burrowing snakes live in the central and southern regions of Africa, known as sub-Saharan Africa, but a few make their homes in Israel or in Jordan.

HABITAT

Just as their name suggests, this group of snakes likes to live in burrows, or tunnels, underground. They are especially fond of sandy soils. Some like the damp soil of lowland forests, but others can live quite well in the drier sands of grasslands and areas that are almost desertlike.

DIET

African burrowing snakes typically eat other animals that like to live underground. Depending on the species, or type, of snake, the meals may include lizards, blind snakes, worm lizards, centipedes (sen-tuh-PEEDS), and frogs. The larger African burrowing snakes will also eat rodents, a group of animals that includes mice. Some species will eat a variety of different animals, but some are very particular. One kind of quill-snouted snake, for example, eats only large worm lizards. Although scientists are unsure how the snakes successfully attack and kill such a large animal, they suspect that this snake stabs the lizard to death with its hard and pointed head. Other picky diners are the "centipede eaters," which rarely make a meal out of anything except the small, many-legged animals called centipedes. The snake grabs the centipede and chews it with its rear fangs to inject venom. When the venom knocks out or kills the centipede, the snake turns it around to swallow it head first.

BEHAVIOR AND REPRODUCTION

Also known as mole vipers or burrowing asps, members of this family are known best for their underground lifestyles. Some African burrowing snakes only crawl through tunnels that other animals make, but some can force their heads through loose sand and "dig" their own tunnels. Most of these snakes (except the burrowing asp) have fangs at the rear of the mouth, and so they must take a full bite to get any benefit from their fangs.

A TAIL OF DISGUISE

Among the African burrowing snakes, the yellow and black burrowing snakes have an unusual color pattern that helps them survive. An attacking animal could end the life of one of these snakes with a well-aimed bite to its head, but the snake is able to persuade the attacker to bite its tail instead. The snake does it by curling up its body into a coil and hiding its bright yellow head inside the coil. Then it raises its tail, which is also colored yellow, and waves it back and forth. When the attacker takes a bite of the snake, all it gets is the tail. The snake can often slither off, injured but still alive.

A burrowing asp, on the other hand, has two long, hollow fangs at the front of the mouth that it uses to inject venom into a prey animal or to protect itself from a predator. This unusual snake holds just one of its two backward-curving fangs outside its mouth and, keeping its mouth closed, stabs sideways and backward with its head to hook the bare fang into the prey or predator. This unusual backward-curved fang can make the snake quite dangerous to humans who mistakenly believe that they can safely hold the snake behind the head. With a quick backward flick of the head, the snake can force its fang into a human's hand. This unique venom-delivery system has given several other common names to the burrowing asp, including side-stabbing snake and stiletto snake. A stiletto is a type of thin, sharp knife.

During breeding time, many species come out of their underground tunnels to find mates. The females of all except one species of African burrowing snake lay eggs. Typically, the female will lay two to fifteen oblong-shaped eggs, either in moist soil or inside an old and unused termite nest. The eggs hatch in six to eight weeks into young snakes that are about 6 to 8 inches (15 to 20 centimeters) long. The exception is the Jackson's centipede eater, which gives birth to two or three live young that are about 4 inches (10 centimeters) long.

AFRICAN BURROWING SNAKES AND PEOPLE

Most African burrowing snakes are not dangerous to humans, but some have venom powerful enough to make people sick and sometimes kill them. Bites typically occur at night, when people accidentally step on a snake or turn over in bed and roll onto a snake that has crawled under the covers. For the most part, however, African burrowing snakes are gentle animals that rarely bite humans. The burrowing asps are different. When humans even slightly bother a burrowing asp, it will strike again and again.

CONSERVATION STATUS

A few species of African burrowing snake live in very small areas, but no species is endangered or threatened.

SOUTHERN BURROWING ASP (Atractaspis bibronii): SPECIES ACCOUNT

Physical characteristics: Also known as Bibron's burrowing asp or the side-stabbing snake, the southern burrowing asp has backward-curved fangs at the front of its mouth. This snake has a thick body, with smooth, purplish-brown to black scales down its back and, usually, a dark-gray belly. A few have dark blotches on a whitish to cream-colored belly. Females can reach 24.4 inches (62 centimeters) in length, and males can grow to about 26 inches (66 centimeters).

Geographic range: This snake is found in the southern half of Africa.

Habitat: These snakes spend much of their lives underground in savannas, flat plains covered with grass and a few trees. They also live in dry, nearly desert habitats and near the coast in thick, brushy areas.

Diet: The southern burrowing asp eats other reptiles, rodents, and frogs.

Behavior and reproduction: True to their name, these snakes can dig through the soil. Much of their digging is done to make hollow compartments under rocks. They usually remain underground, but sometimes they come to the surface at night after a rainstorm. They have an unusual smell, but scientists still are unsure if that smell has any purpose, such as attracting mates or scaring off attackers. In the summer female southern burrowing asps each lay four to eleven oblong eggs, which hatch into 6-inch-long (15-centimeter-long) young snakes.

Southern burrowing asps and people: When people and burrowing asps live in the same area, snakebites are somewhat common. A bite can lead to pain and swelling, but it will not kill humans.

Conservation status: This species is not endangered or threatened. ∎

FOR MORE INFORMATION

Books:

Branch, Bill. Field Guide to Snakes and Other Reptiles of Southern Africa. Sanibel Island, FL: Ralph Curtis Books, 1998.

Lovett, Sarah. Extremely Weird Snakes. Santa Fe, NM: John Muir Publications, 1999.

Mattison, Chris. The Encyclopedia of Snakes. New York: Facts on File, 1995.

Montgomery, Sy. The Snake Scientist. Boston: Houghton Mifflin, 2001.

Spawls, Stephen, and Bill Branch. The Dangerous Snakes of Africa: Natural History, Species Directory, Venoms, and Snakebite. Sanibel Island, FL: Ralph Curtis Books, 1995.

Spawls, Stephen, et al. A Field Guide to the Reptiles of East Africa: Kenya, Tanzania, Uganda, Rwanda, and Burundi. San Diego: Academic Press, 2002.

Web sites:

"Ecoviews: Africa Really Does Have Some Dangerous Snakes." University of Georgia Savannah River Ecology Laboratory. http://www.uga.edu/srelherp/ecoview/Eco16.htm (accessed on August 26, 2004).