Spring 1998

[TEXT ARCHIVE WEB-PUBLISHED FEBRUARY 2002.
ORIGINAL PRINT PUBLICATION DATE: SPRING 1998.]

Tiger Salamander:
The Secret Life of an Amphibian

By Sheryl De Vore

In spring when the warm rains come, a male salamander awakens and slithers to a shallow pond where many more males have congregated to begin a miniature ballet. The only ones invited to the dance are the females. The males greet them nose-to-nose, pushing the other males aside, as they engage in a primreview ritual.

Thus begins another part of the double life of the secretive salamander, an animal that looks and sometimes behaves like a reptile, but is actually an amphibian.

The salamander sheds its skin as reptiles do, but would dry out if it basked in the sun as a snake does. It looks like a lizard, but it has smooth, moist skin, whereas a lizard has dry, scaly skin.

Salamanders are more secretive than other amphibians. Unlike frogs, salamanders don't sign loud, raucous mating choruses in spring, but pursue their mates quietly. They are a vital part of the food web in woodland ephemeral ponds, seldom betraying their presence to human searchers.

The salamander's ancestors appeared 350 million years ago when Earth consisted of one large landmass surrounded by a vast ocean. Some small fish evolved into creatures that developed legs in place of fins, allowing them to live on land and sea. Thus amphibians lead double lives.

The largest group of amphibians is the Anura, which consists of nearly 4,000 species of frogs and toads. Salamanders belong to a smaller group in the order Urodela. Some 350 kinds of salamanders exist in the world, 160 of those in the United States.

A salamander needs a dark, moist environment in which to live. Indeed, it must remain wet if it is to breathe absorbing needed moisture through its skin. This may explain why the salamander is most active on wet evenings.

The most common and largest salamander in the Chicago Wilderness region is the tiger salamander (Ambystoma tigrinum). As an adult, this dark-colored amphibian, sporting yellow spots, measures between seven and eight inches long. It swallows various prey whole including earthworms, insects, fish, frogs, other salamanders, and even baby mice.

The tiger salamander emerges from hibernation early in the Chicago region, often in March if spring is warm, sometimes as late as April, to court and mate. The female lays 23 to 100 eggs loosely clustered on twigs or stems a foot or more below the water's surface.

In an hour, the eggs quadruple in size, and in two weeks, the eggs hatch into creatures with flat heads and wide mouths that trap hundreds of microscopic plants and animals. The young have no arms or legs, just fin-like tails to help them swim. Unlike adults, they breathe through gills.

As the water-bound young mature, their front and hind legs begin to grow. The gills disappear, and lungs form, at which time the adolescent salamanders must come to the surface to breathe. Finally they leave their watery home heading for cover on land, burrowing into loose soil or leaf mold to keep wet and camouflaged during the day.

Salamanders can be a tasty meal for birds, snakes, shrews, voles, fish, frogs, even spiders. That's why a salamander is built to run so swiftly. Some salamander species secrete a chemical that makes them distasteful to a would-be predator.

When autumn approaches, salamanders retreat beneath the ground to hibernate until spring. Within the last 50 years, the populations of many species of amphibians including frogs, toads, salamanders, and newts have declined markedly.

An international group of scientists — The Declining Amphibians Population Task Force — has been studying the causes of this decline. Preliminary data show that the decrease could be due to human activities such as habitat destruction and pollution.

For more information on the status of salamander populations, contact The Terrestrial Salamander Monitoring Program, Patuxent Wildlife Research Center, 12100 Beech Forest Drive Laurel, MD 20708-4038, or send e-mail to frog@usgs.gov.