Asiatic Giant Salamanders and Hellbenders: Cryptobranchidae

Physical characteristics: Most hellbenders are 11 to 20 inches (28 to 51 centimeters) long and weigh 4 to 5 pounds (1.8 to 2.3 kilograms). The record length is 29 inches (74 centimeters). Male hellbenders are smaller than females. Hellbenders have a broad, flat body and head, like those of a catfish. The tail, however, is flat from side to side, looking like an eel's tail, and has a ridge along the top and the bottom to help in steering. Hellbenders are brown or gray, but during the breeding season some of them change from greenish brown or yellowish brown during the day to orange at night. The toes have rough pads that help the salamanders keep their traction on slippery rocks. Other names for hellbenders are devil dogs, water dogs, mud devils, mountain alligators, and walking catfish.

Hellbenders have floppy folds of skin along the sides of their bodies and on their legs. This skin is filled with many tiny blood vessels that absorb oxygen from the water flowing over the salamander. The larvae of Hokkaido salamanders eat small water-dwelling invertebrates. Adults eat insects, crustaceans, water worms, and, sometimes, fish. (© Dr. Paul A. Zahl/Photo Researchers, Inc.) Hellbenders get about 95 percent of their oxygen this way. They have lungs and can gulp air through them if necessary, but they rarely come to the surface. The lungs are used mainly as internal balloons to help keep the hellbender light enough to walk along the bottom. Hellbenders are very slimy. The slime is made in glands in the skin and tastes bad to predators.

Geographic range: Hellbenders live only in North America. Their range is southern New York south to northeastern Mississippi and west to eastern Missouri and Arkansas. The hellbenders that live in this region are called eastern hellbenders. Other hellbenders live only in south central Missouri and a few rivers in north central Arkansas. These are called Ozark hellbenders.

Habitat: Hellbenders live in clear, fast-moving, rocky streams and rivers less than 2,500 feet (750 meters) above sea level. The riffling movement over rocks keeps the water full of oxygen, and the rocks give the hellbenders places to hide and breed.

Diet: Crayfish are the main prey of hellbenders, but these salamanders also eat insects, snails, fish eggs, and worms. Hellbenders eat by sucking in their prey with a rush of water.

Behavior and reproduction: Hellbenders spend their entire lives in the water. They never make the change to land the way many salamanders do. When they are not breeding, hellbenders live alone. They hide during the day, sometimes with their head sticking out from under a rock. Even though they have an eel-like tail, hellbenders almost never swim. They walk slowly along the river or stream bottom on their short legs. When they are too hot or when there is not enough oxygen in the water, hellbenders rock their bodies from side to side to get more water on their loose flaps of skin.

Hellbenders breed in the late summer to early fall. At breeding time, male hellbenders dig nests under rocks or logs and lure in one or more females. The males sometimes fight one another for the best rocks. Each female lays two strands of 150 to 750 round eggs, which end up in clusters in the nest. Because more than one female may breed with the same male, some nests have almost two thousand eggs, which expand to the size of Ping-Pong balls. The larger a female, the larger are her eggs. The male releases a cloud of sperm over the eggs. Fertilization and development take place outside the body. After they lay their eggs, the male forces the females out of the nest. The males then guard their nests from predators until after the larvae hatch.

Larvae hatch in two to three months, when they are about 1 inch (2.5 centimeters) long. When they start eating small invertebrates, the larvae turn dark brown or black. Newly hatched hellbender larvae have gills that stick up behind their heads. These gills disappear when the larvae are 1.5 to two years old and are 4 to 5 inches (10 to 13 centimeters) long. Over the next five to six years the young hellbenders grow about 0.8 inches (2 centimeters) per year while their heads and bodies flatten. Hellbenders can reproduce when they are about seven years old. Hellbenders live more than thirty years.

Hellbenders and people: Hellbenders are harmless to people. Because they can live only in very clean water, the presence of hellbenders is a sign of good water quality. Some people believe hellbenders interfere with fishing, but they are wrong. Some people try to trap hellbenders to sell as pets, but removing these salamanders from the wild is illegal. In Pennsylvania scientists have found evidence of huge piles of hellbender skeletons that date back ten million years. The scientists believe these fossils are evidence that early people used hellbenders for food and in tribal ceremonies.

Conservation status: The World Conservation Union (IUCN) lists hellbenders as Low Risk/Near Threatened, which means they are at risk of becoming threatened with extinction in the future. The main danger to hellbenders is damage to their habitat through silt buildup, which smothers eggs and the animals the hellbender need for food; loss of trees, which allows silt to wash into the water and removes the shade hellbenders need to keep cool; and pollution of river water by chemicals used on crops and from old mines. Hellbenders absorb the chemicals in polluted water through their skin the same way they absorb oxygen. Some scientists believe too many hellbenders are being collected. They are researching the best conditions for breeding hellbenders so that someday these salamanders can be returned to the wild. ∎