SALAMANDERS AND NEWTS: Caudata

PHYSICAL CHARACTERISTICS

Caudata (kaw-DAY-tuh) is the group of animals most people call salamanders but that also includes newts, sirens, hellbenders, olms, mudpuppies, and amphiumas (AM-fee-yoo-muhs). Salamanders are four-legged amphibians that have a long tail and short legs. Amphibians (am-FIB-ee-uhns) are vertebrates (VER-teh-brehts), or animals with a backbone, that have moist, smooth skin; are cold-blooded, meaning their body temperature is the same as the temperature of their surroundings; and, in most instances, have a two-stage life cycle. The word "amphibian" comes from a Greek word that means "having a double life." One of the life stages is a larva (LAR-vuh) that lives in water and has gills, and the other is an adult that lives on land and has lungs. Larvae (LAR-vee, the plural of larva) are animals in an early stage that go through metamorphosis (meh-tuh-MOR-foh-sus), or a change in body form, before becoming adults. Other amphibians are frogs, toads, and caecilians (sih-SILL-yuhns).

The head of a salamander is the same width as or narrower than the trunk. The trunk has twelve to eighteen vertebrae (ver-teh-BREE), which are the bones that make up the spinal column, also called the backbone even though it is made up of more than one bone. The tail of a salamander usually is about the same length as the head and body combined. Most salamanders are 1.5 to 8 inches (4 to 20 centimeters) long, but some can be as long as 5 feet (1.5 meters). Sirens and amphiumas look different from other salamanders in that they have a long, snakelike body, a short tail, and tiny legs.

The moist skin of a salamander contains many glands. Some of these glands make mucus, and some make poison. Most salamanders have camouflage coloring, but some are brightly colored. The brightly colored ones are poisonous or look like the poisonous ones in order to trick predators. Salamander skin is thick and tightly attached to the bone and muscle under it. Salamanders get 90 percent of their oxygen through their skin and also drink through their skin. Salamanders cannot survive if their skin dries out.

Salamanders have a long, fast tongue that contains as many as eleven bones. The tongue shoots from the mouth through the action of specialized muscles. The muscles that bring the tongue back into the mouth are extremely long, being anchored on the animal's hip bones. Salamanders have large eyes they use mainly for finding prey and watching out for predators. Salamanders also have an excellent sense of smell. Although they can hear, salamanders have no outer ears, and sound appears to play little role in their lives.

GEOGRAPHIC RANGE

Almost all salamanders live in the Northern Hemisphere. One species even lives north of the Arctic Circle. Only a few species of salamanders live south of the equator, and those live in North and South America as far south as Bolivia.

HABITAT

Salamanders live in cool, damp places. Most live on land, some live in water, and some move between water and land. Salamanders live in areas ranging from northern forests to tropical rainforests and from sea level to high mountains. Some salamanders live in trees, and some live in caves. Salamanders that live on land often spend long periods in underground burrows, especially when they are not breeding and during cold winters and dry summers.

IS IT A SALAMANDER OR A LIZARD?

Many people confuse salamanders and lizards. In the southern parts of the United States, salamanders often are called "spring lizards." Salamanders are amphibians, but lizards are reptiles. Salamanders have smooth, moist skin, but lizards have dry, scaly skin. Salamanders have rounded toes, but lizards have claws.

DIET

Adult salamanders eat spiders, insects, worms, crustaceans such as crayfish, mollusks such as slugs and snails, fish and fish eggs, tadpoles, other salamanders, and even small rodents. Crustaceans (krus-TAY-shuns) are water-dwelling animals that have jointed legs and a hard shell but no backbone. Mollusks (MAH-lusks) are animals with a soft, unsegmented body that may or may not have a shell.

BEHAVIOR AND REPRODUCTION

Adult salamanders live alone rather than in groups. They hide during the day under leaves, rocks, or logs and are active at night but sometimes come out on rainy days. Salamanders hunt mainly by sight but also by smell. They sit and wait for prey to come close and then capture it with an explosive motion of their tongues. The tongue action is so fast it cannot be seen by human eyes.

WORLD CONSERVATION UNION CATEGORIES

Extinct No longer in existence.

Extinct in the Wild No longer alive except in captivity or through the aid of humans.

Critically Endangered Facing extremely high risk of extinction in the wild.

Endangered Facing very high risk of extinction in the wild.

Vulnerable Facing high risk of extinction in the wild.

Lower Risk/Conservation Dependent If the conservation program were to end, the animal would be placed in one of the threatened categories.

Low Risk/Near Threatened At risk of becoming threatened with extinction in the future.

Least Concern There is no known threat of extinction, and the animal does not qualify for any of the threatened categories.

Data Deficient There is not enough information to make a judgment about the threat of extinction.

Not Evaluated The species has not been evaluated for the threat of extinction.

Salamanders live as long as thirty years in the wild. The type of life cycle and method of development vary from species to species. In many species female salamanders lay eggs in the water, and the male releases sperm on them. Fertilization (FUR-teh-lih-ZAY-shun), or the uniting of egg and sperm to start development, takes place outside the female's body. The eggs hatch into larvae that have gills and live in the water, sometimes for years, before going through metamorphosis. During the transformation the larvae lose their gills, develop lungs, grow legs, and crawl onto land. After metamorphosis, the adult salamanders spend all or most of their time on land. In some species, female salamanders guard their nests of eggs in order to protect them from predators and to keep them from drying out.

About one-half of salamander species do not have a water-dwelling larva stage. When they hatch from eggs laid on land, the young salamanders have the same body form as adults and continue to live the rest of their lives on land. In some species of salamanders, larvae that hatch from eggs laid on land wriggle to nearby water or are caught up by rising waters in the spring. They live in water for a while and then undergo metamorphosis. Still other species of salamanders live their entire lives in water with their bodies in the larva body form. Their reproductive organs do mature, however, and these salamanders do produce young.

Some male salamanders do not spread sperm on eggs but deposit a sperm packet in or near the water. The female takes the sperm into her body, and fertilization takes place inside her. In a few species of salamanders, the developing larvae stay inside the female for one or two years or even longer. These larvae go through metamorphosis inside the female. The young animals are quite large when they are born, having received their nourishment first by eating their siblings and later by eating secretions in the female.

Most salamander larvae can be classified as the pond type or the stream type. The pond type usually change form in one season and have large, feathery gills and a large tail fin. Stream-type larvae have a small tail fin, very short gills, and a flat body with short, fat legs and hard toes. These larvae may live for several seasons before going through metamorphosis.

U.S. FISH AND WILDLIFE SERVICE CONSERVATION CATEGORIES

Endangered In danger of extinction throughout all or a significant portion of its range.

Threatened Likely to become endangered in the near future.

SALAMANDERS, NEWTS, AND PEOPLE

Some people keep salamanders as pets. Salamanders also have been the subjects of myth, folklore, and literature. According to Aztec myth in Mexico, a god trying to escape from his enemies dove into water and changed himself into a salamander. From at least the time of the ancient Romans people have believed that salamanders cannot be harmed by fire. This belief arose because salamanders were seen crawling out of the flames after people placed logs on a fire. People also once believed that salamanders had magical powers. In the play Macbeth by William Shakespeare, three witches brew a potion using "eye of newt."

CONSERVATION STATUS

The World Conservation Union (IUCN) lists two species of salamanders as Extinct, forty-six as Critically Endangered, 105 as Endangered, eighty-one as Vulnerable, and fifty-six as Near Threatened. Extinct means no longer in existence. The U.S. Fish and Wildlife Service lists six species of salamanders and newts as Endangered and five as Threatened.

FOR MORE INFORMATION

Books:

Bernhard, Emery. Salamanders. New York: Holiday House, 1995.

Lawlor, Elizabeth P. Discover Nature in Water and Wetlands. Mechanicsburg, PA: Stackpole, 2000.

Llamas Ruiz, Andres. Reptiles and Amphibians: Birth and Growth. New York: Sterling, 1996.

Petranka, J. W. Salamanders of the United States and Canada. Washington, DC: Smithsonian Institution Press, 1998.

Web sites:

Hawes, Ales. "On Waterdogs, Mudpuppies, and the Occasional Hellbender." Zoogoer.http://nationalzoo.si.edu/Publications/ZooGoer/2000/2/waterdogsmudpuppieshellbender.cfm (accessed on March 28, 2005).

"Order Caudata (Salamanders)." Animal Diversity Web.http://animaldiversity.ummz.umich.edu/site/accounts/classification/Caudata.html (accessed on March 28, 2005).

"Order Caudata: Salamanders." Northern Prairie Wildlife Research Center. http://www.npwrc.usgs.gov/narcam/idguide/index.htm#ambystom (accessed on March 28, 2005).