DO GIANT SALAMANDERS REALLY EXIST?

by Whit Gibbons

May 22, 2011

By my calculation, if all the salamanders Tom Luhring caught during his research project for his master's degree from the University of Georgia were laid end to end, they would be longer than three football fields. That has to be a world record.

Tom, who is now a doctoral student at the University of Missouri, conducted his research at the Savannah River Ecology Laboratory in South Carolina on a group of amphibians known as the giant salamanders. These secretive creatures inhabit swamps and lowlands, spending their entire lives in the mud and waters of places where few people ever go. His studies of one species, the greater siren, have revealed more about their population ecology, movement patterns and behavior than had ever been known before. The species, which has been known to science for more than two centuries, is one of the heaviest salamanders in the Western Hemisphere. Yet little was known of certain aspects of its biology before Tom's research.

The largest salamanders in North America are aquatic species that live in the East. The greater siren reaches lengths of more than three feet. Another giant salamander of the Southeast, the amphiuma, has a record length of almost four feet. Like sirens, amphiumas are seldom seen by people despite their large size. That their scientific name (Amphiuma) is used as their common name in most places is indicative of their rarity, although they are called lamper eels or Congo eels in some regions.

Two other salamanders, the hellbender and the mudpuppy, or waterdog, also qualify as giants, although neither gets as long as the biggest amphiumas and sirens. The mudpuppy, reaching a length of a foot and a half, is primarily a northern species, found in lakes, ponds and rivers. Hellbenders are bulky creatures that can reach two and half feet long. They live in cold mountain streams and rivers from Alabama to New York. The world's largest salamander, from Japan, is closely related to the hellbender; it can be more than five feet long.

Sirens and amphiumas, despite their enormous size relative to other amphibians, have minuscule legs with toes. An amphiuma more than a yard in length will have legs less than an inch long and no thicker than a toothpick. Amphiumas and sirens are short-legged, dark-colored, slippery creatures, but distinguishing one from the other is easy: sirens have only two of the seemingly useless legs, whereas amphiumas have four. In addition, sirens have external, visible gills; amphiumas have an opening alongside the head that leads to internal gills.

Sirens and amphiumas are slimy animals that seldom leave the water; they would soon dehydrate if left on dry ground. But both live in aquatic habitats that can dry up completely during long-term droughts. What do great big water-dwelling salamanders do then? First, as their lake home dries up, they burrow into the remaining mud. Then they secrete a slimy body covering, which hardens into a cocoon that can keep them moist for a few months to more than a year. When the rains return and the cocoon is exposed to water, the siren or amphiuma emerges to begin feeding on aquatic insects and other invertebrates that have also survived the drought.

Sirens and amphiumas kept in aquariums as pets have been known to live for decades, but no one knows how long they can live in the wild. Their courtship and mating behavior are also still a mystery, even for specimens kept in captivity. Amphibian biologists are not sure how closely related sirens are to other salamanders, and some even argue that sirens are not salamanders at all, but some other type of amphibian.

America's giant salamanders bring to the fore two ecological insights. One, scientists know relatively little about the biology of some of the largest animals in our midst, which means we still have much to learn about the world around us. Second is the realization that some of our local creatures are as fascinating in their own way as any exotic species with a starring role in a nature show.

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