Amphibians in Tennessee include salamanders and frogs. Amphibian means “two-lived” because they live both on land and in water. At Radnor, they rely on the fishless ponds and streams for a place to live, mate, and lay eggs. During certain life stages, amphibians can breathe through their skin! Water and water particles can pass through the skin into their bodies. This makes them very sensitive to pollution and to changes in the environment. Keeping Radnor Lake healthy helps ensure that its amphibian population is healthy. They also are ectothermic meaning they use their environment to regulate body temperature much like reptiles.
Amphibians utilize several defense mechanisms to evade predators. Some have slippery skin to make it difficult for a predator to keep a good grasp, while others use camouflage to hide. Some even use bright colors to warn predators of unpalatable or toxic prey. More than 200 toxins have been found in only a small sample of the world’s amphibians. Most use their sticky tongues to capture prey, which includes mosquito larva.
Salamanders have moist, porous skin, lay jelly-like eggs, and have a long tail. Unlike lizards, they do not have scales, claws, and cannot survive far from water. They are nocturnal and hunt for invertebrates. In some habitats, they are the most abundant creature in the forest. Salamanders also are one of the most important pieces of the forest floor ecosystem. In many forest habitats, salamanders are the main controller of insect populations.
The southeastern Unites States has the greatest diversity of salamanders in the world. Most salamanders begin life in an aquatic larval stage and move to a terrestrial adult stage. Exceptions include the Mudpuppy which lives completely in water and the Zigzag Salamander which lives completely on land.
In addition to monitoring environmental health, salamanders make valuable contributions to fields such as animal behavior, genetics, and medicine. Major human borne dangers to amphibians are timber harvest, agriculture, draining wetlands, urbanization, and the introduction of exotic predators. At Radnor Lake, the problem lies in siltation from watersheds outside the park boundaries and habitat loss in the surrounding community.
Frogs and toads are the other type of amphibians. Frogs are tailless vertebrates that have skin with no feathers, hair, or scales. Tennessee has 21 native species of frogs and toads. Frogs have smooth, moist skin with large hind legs while toads (a specialized frog) have rough, dry skin with smaller hind legs.
Frogs communicate vocally and were the first animals on land with vocal chords. Males call to attract a mate. They sing mostly at night, which means most people only hear frogs as sound effects in the movies. After mating, female frogs can lay thousands of jelly-coated eggs in water. They undergo metamorphosis, hatching out of eggs as tadpoles and as adults move onto land and change shape.
So why are amphibians like salamanders and frogs important? In most environments, amphibians are the main predator of insects. They are also a major source of food for reptiles, birds, fish, and mammals. Scientists worldwide study amphibians to find treatments for illnesses such as Alzheimer’s and for pain relief.
Frogs and salamanders, because of their sensitivity to pollution, are subject to biomagnifications – the effects of chemical contamination in the food web. Studying their populations in a specific area indicates the health of the environment. Unfortunately, amphibian numbers are declining worldwide. There have been no official studies on amphibian health inside Radnor Lake State Natural Area, but there are indications of pollution inside the park and habitat loss in the surrounding communities.
Educating people about amphibians helps remove the stigma of being gross or ugly and supports efforts to protect them and the health of the park.