Mole Salamanders: Ambystomatidae
MOLE SALAMANDERS: AmbystomatidaeTIGER SALAMANDER (Ambystoma tigrinum): SPECIES ACCOUNT
Mole salamanders are small to large, stocky salamanders that live in water as larvae and on land as adults. Larvae (LAR-vee) are animals in an early stage that change form in a process called metamorphosis (MEH-tuh-MORE-feh-sis) before becoming adults. Mole salamanders are 3.5 to 14 inches (9 to 35 centimeters) long from the tip of the snout to the tip of the tail. They have a broad head, small eyes that stick out from the head, deep grooves along the sides of the body, and a long tail that is flat from side to side. Mole salamanders often have bold patterns as adults. Many species are brightly colored with yellow, orange, or silver spots, bars, and frosted patterns on a black background. Some mole salamanders have large poison glands on the head and along the body. All mole salamanders have lungs after metamorphosis.
Mole salamander larvae live in the water and have filmy gills that stick out behind their heads. Gills are organs for obtaining oxygen from water.
The larvae have a large tail fin that extends onto the body. Their small eyes do not have moveable eyelids. Many species of mole salamanders in Mexico and the United States do not go through metamorphosis; as adults they keep the body form they have as larvae. However, their reproductive organs mature, and they can breed.
Mole salamanders live in woodlands and grasslands, including partially dry pine and juniper woodland with vernal pools, ponds, or streams for breeding. A vernal (VUHR-nehl) pool is one that forms in the spring but then dries up for the rest of the year. Species that do not go through metamorphosis live in large lakes, as long as there are no predatory fish around.
Mole salamanders are predators as both larvae and adults. They eat insects, earthworms, crustaceans, frog tadpoles, and even baby rodents. Crustaceans (krus-TAY-shuns), such as crayfish, are water-dwelling animals that have jointed legs and a hard shell but no backbone.
BEHAVIOR AND REPRODUCTION
Mole salamanders spend most of the year in underground burrows and tunnels made by small mammals and come out only on rainy nights to feed or to travel to breeding sites, where they stay for several weeks. This behavior gives these salamanders their name. Moles are small mammals that spend almost all their time in tunnels searching for insects to eat.
Two key types of behavior of mole salamanders are their defenses from predators and their traveling. Many mole salamanders that have gone through metamorphosis take a head-down position and lash their tails when threatened. Both behaviors show predators parts of the salamander's body that are full of poison glands. Mole salamanders are famous for their travels to breeding ponds. In some species hundreds of salamanders may travel on a single rainy night to a breeding site, giving a spectacular display of salamanders crossing the landscape, including roads. In other species the travels take as long as many weeks rather than one night. In general, males travel before females do and stay for a longer time in the breeding pond.
Axolotls (ACK-suh-lah-tehls) are a species of mole salamanders that never go through metamorphosis and never leave the water. According to Aztec legend a god named Xolotl escaped from his enemies by diving deep into a lake and changing himself into a salamander. Mexico City was later built on that lake.
Most mole salamanders breed in the winter or spring, although mountain salamanders breed in the summer. Landdwelling adults move into vernal pools, ponds, or, more rarely, streams to breed. Two species mate and lay eggs on land. Males often compete for females. The males deposit bags of sperm on the ground, and females take the bags into their bodies, where sperm and egg unite. One male may deposit more than thirty sperm bags in a single night. Females lay the eggs either one at a time or in large clusters. The eggs attach to the pond bottom or to plants. After hatching, larvae spend several months to several years in the water before going through metamorphosis and starting a land-dwelling lifestyle.
MOLE SALAMANDERS AND PEOPLE
People in Mexico eat mole salamanders. Everywhere they live, mole salamanders give important clues about the health of the environment.
The World Conservation Union (IUCN) lists eight species of mole salamanders as Critically Endangered, two as Endangered, three as Vulnerable, and one as Low Risk/Near Threatened. Critically Endangered means facing extremely high risk of extinction in the wild. Endangered means facing very high risk of extinction in the wild. Vulnerable means facing high risk of extinction in the wild. Low Risk/Near Threatened means at risk of becoming threatened with extinction in the future.
The U.S. Fish and Wildlife Service lists two species of mole salamanders as Endangered and two species as Threatened. Endangered means in danger of extinction throughout all or a significant portion of its range. Threatened means likely to become endangered in the near future.
In 2004 the eastern tiger salamander was chosen by schoolchildren to be the official state amphibian of Illinois.
Large numbers of mole salamanders crossing roads to and from their breeding ponds sometimes are killed by cars. In New York State an underpass was built to help these salamanders. The main dangers to mole salamanders are loss of their land and water habitats, the introduction of predatory fish that eat the salamander larvae, and, possibly, a fungus disease. Mole salamander species that do not go through metamorphosis are especially at risk because they spend their entire lives in a single lake, where introduced fish, pollution, and draining can endanger an entire species.
Physical characteristics: Tiger salamanders are about 14 inches (35 centimeters) long from the tip of the snout to the tip of the tail, making them the largest land-dwelling salamanders. Tiger salamanders are large, strong salamanders. Adults have many color patterns depending on where they live. The most common pattern is the one that gives them their name: black with bright yellow stripes, spots, or bars. Some tiger salamanders have blurry gold blotches or yellow flecks on a black background. Others are solid olive green, brown, or black. In the central part of the United States and in the Rocky Mountains, some tiger salamanders do not go through metamorphosis.
Geographic range: Tiger salamanders have the widest geographic range of any other salamander in North America. The range extends from southern Canada south roughly to the border between Mexico and the United States.
Habitat: Tiger salamanders live mainly in grasslands in prairie and open, dry woodland, from sea level to a height of more than 11,000 feet (3,350 meters).
Diet: Fearsome predators, tiger salamanders eat just about any animal. As larvae, they eat prey ranging from microscopic plants and animals drifting in the water to tadpoles and even one another. As adults on land, tiger salamanders eat all kinds of invertebrate and small vertebrate prey, including animals almost as large as they are. Invertebrates (in-VER-teh-brehts) are animals without backbones, and vertebrates are animals with backbones.
Behavior and reproduction: Adult tiger salamanders spend almost all of their lives in underground rodent burrows. They come out and travel to breeding ponds during spring rains and sometimes can be found on the surface at night during heavy rains. Tiger salamander larvae are often the top predators in the vernal pools and ponds where they live. To reproduce, male salamanders deposit sperm sacs, and female salamanders take them up into their bodies, where sperm and egg unite. The female then lays the eggs. After hatching, some of the larvae go through metamorphosis, and some do not.
Tiger salamanders and people: In many parts of the United States, tiger salamander larvae are sold as fish bait. Throughout their range tiger salamanders cannot live in the same bodies of water as predatory fish. When people stock these waters with bass, catfish, and other species, tiger salamanders are at risk.
Conservation status: Tiger salamanders are not considered threatened or endangered. ∎
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