Salamander

I

Introduction

Salamander, shy, elusive animal that resembles a lizard but has smooth, delicate skin instead of scales. Salamanders are amphibians, a group of moist-skinned animals that also includes frogs, toads, and wormlike creatures called caecilians. All amphibians are cold-blooded, or more correctly, ectotherms—animals whose body temperature depends on their environment. Salamanders display a wide diversity of lifestyles. Some live all of their lives on land, whereas others live entirely in water, and still others live part of their lives on water and part on land.

Descendants of the first animals with backbones to live on land, salamanders are one of the oldest groups of existing terrestrial vertebrates. The earliest known true salamanders lived about 150 million years ago during the Jurassic Period. Today there are about 380 different species of salamanders belonging to 10 different families.

Even in places where salamanders are plentiful, humans are often unaware of their presence because they are typically inactive during the day and are virtually silent. Perhaps because they are so mysterious, salamanders are the subject of numerous myths and legends. The name salamander comes from Greek words meaning fire-lizards. Ancient peoples linked salamanders to fire because salamanders often crawled out from logs that had been thrown onto fires, leading people to believe that these animals could walk through fire.

II

Range and Habitat

Salamanders are found throughout much of the world at altitudes up to 4,000 m (13,000 ft). In the western hemisphere their range spreads across the United States and Canada and extends south through Central America to the northern portion of South America. Salamanders also live in Europe, the Mediterranean area, Africa, and Asia, including the islands of Japan and Taiwan.

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Many salamanders inhabit moist, forested areas, sheltering in shallow burrows or amidst fallen leaves, logs, and other ground debris. Some salamanders, including all members of a subgroup called newts, divide their time between land and watery environments such as the edges of streams and small springs. Others are totally aquatic. For instance, giant salamanders such as the hellbender spend their entire lives in rivers, streams, or bodies of water inside underground caves. On the other hand, some tropical salamanders never live in the water, making their homes in bushes and trees instead.

III

Physical Characteristics

An adult salamander has a slender, elongated body with a long tail, and in most cases, two pairs of legs roughly equal in size. Most salamanders are drab in color, but some, such as fire salamanders, have brilliant yellow, orange, or red markings. The majority of salamanders measure 10 to 15 cm (4 to 6 in) in length, but the smallest known salamander reaches just 2.7 cm (1.1 in), and the Japanese giant salamander grows to 1.5 m (5 ft).

Those salamanders that spend all or part of their lives on land tend to be slight, with small heads, slender bodies, and a sprawling gait that comes from moving the two legs that are diagonally opposite one another at the same time. Aquatic salamanders, such as the amphiuma, are usually larger, and they often have reduced limbs. Some aquatic salamanders, such as the greater siren, have no hind legs at all. The front limbs of most species end in four fingers, and the rear limbs typically end in five toes. Like other amphibians, salamanders do not have claws.

Salamanders are the only amphibians that have long tails as adults. They use these tails, which are often as long as their bodies, for balance in walking and propulsion in swimming. Many salamanders can shed their tails if a predator threatens them. Once shed, the tail reflexively flails about on the ground and distracts the would-be predator while the salamander slips away and later regenerates a new tail.

Like all amphibians, salamanders have delicate, permeable skin through which water and gases, such as oxygen and carbon dioxide, can enter and leave the body. Most adult salamanders have saclike lungs for breathing air and use their permeable skin only as a source of supplemental oxygen. Some species never develop lungs and instead obtain oxygen through gills or through their skin and the mucous membranes of their mouths and throats. Salamanders also have glands in the skin that secrete a thick layer of mucus. On land, this mucus prevents the skin from drying out, and in water, it helps maintain the correct balance of salt and water in salamanders’ body fluids. Other glands in salamander skin secrete toxic poisons. Salamanders equipped with poison-producing skin glands often display bright colors and conspicuous markings, possibly to warn predators that they are poisonous to the touch. Male salamanders commonly have skin glands that produce scent-emitting chemicals called pheromones that play a role in courtship and mating.

Most salamanders have well-developed eyes. They also have nasal sensory organs capable of detecting chemical changes in the environment. These nasal organs serve an important function in feeding, courtship, and locating breeding sites. Their sense of hearing is poor, and salamanders rarely make noise, although some species are known to make faint squeaks or yelps when excited or disturbed.

IV

Diet

Most salamanders are carnivorous—that is, they eat other animals rather than plants. Adult salamanders that live in water prey on the larvae of frogs, known as tadpoles, and various invertebrates, including snails and worms. Some also eat small fish. These salamanders locate prey by smell and ingest it by opening their mouths in the water and sucking in their prey.

Terrestrial salamanders rely on vision to find food. Most are solitary, sit-and-wait opportunists that eat soft-bodied invertebrates, including insects, slugs, and worms. When one of these prey animals unwittingly comes within reach, the salamander rolls its fleshy, sticky tongue out of its mouth to snatch it up. Some tropical salamanders have projectile tongues that they can extrude from their mouths for distances equal to 40 to 80 percent of their total body length to snap up unsuspecting prey.

Many salamanders are nocturnal—that is, they do most of their hunting in the cool, dark hours of night and remain inactive during the day. Those that are active during daylight retreat to the cool depths of bushes and other ground cover during the hottest period of the day. Some groups are active only during certain seasons. When conditions are too cold or too dry for them to muster the energy necessary to find food, these salamanders enter a resting state similar to hibernation. The siren spends much of its time burrowed in the muddy bottom of seasonal ponds and ditches that dry up in the heat of the summer. When the mud and sand starts to dry, the mucous coating on its skin hardens to form a protective cocoon, which enables the siren to survive out of water for many weeks.

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