Amphibians
Amphibian eggs are laid in freshwater, and larval stages, such as the frog’s tadpoles, live only in freshwater. Some amphibians, such as the large eel-like sirens, are completely aquatic for their entire life cycles. Others, such as toads and tree frogs, live on land or on vegetation as adults and are able to move from one stream system to another more easily than freshwater fishes.
The importance of amphibians in the Everglades ecosystem is inadequately documented and in need of research. However, while the list of species is short, amphibian populations are often so large that they obviously play a major role in the food chains.
Amphiuma and Sirens
Both are wetland inhabitants and reach a very large size, slightly over 3 feet, and are predators primarily on clams, snails, crayfish, and other amphibians such as tadpoles. Sirens have red external gills on each side of the head and small forelegs with fingers, and often swim in open water where they are occasionally seen. The amphiuma lacks such gills and has four thin vestigial, filament-like legs, each with a tiny pair of toes. It is secretive, moving slowly through dense aquatic vegetation and through soft sediments. When their wetland habitat dries, both species will aestivate in the mud. Burrowing through bottom sediments allows them to find crayfish and clams.
A green treefrog (above) in temporary brown coloration, and a squirrel treefrog. Where treefrogs are abundant, sometimes several assemble in a location protected from the sun during the heat of the day. Photo by Tom Lodge
Treefrogs and Toads
A green treefrog (above) in temporary brown coloration, and a squirrel treefrog. Where treefrogs are abundant, sometimes several assemble in a location protected from the sun during the heat of the day. (Photo by T. Lodge.)
The squirrel treefrog may be the most commonly encountered amphibian for visitors to the Everglades, known for its coloring and occasional loud, scratchy outbursts. Like the somewhat larger green treefrog, it can change color from green to brown. Once common in Miami, both species have almost completely disappeared, most likely due to predation by the introduced Cuban treefrog
A similar situation has resulted in the elimination of the southern toad from urban areas. The much larger cane toad was introduced in the area and preyed on the southern toad. Large poison glands on the sides of the neck area exude a white, milky toxin when the toad is disturbed, making them poisonous to dogs.
True Frogs
Pig frogs are common, but not easily seen because of their cryptic coloration and their tendency to stay away from shore; they remain dispersed throughout the deeper freshwater marshes. The pig frog grows very large, its body length sometimes reaching just over 6 inches. They are voracious predators and will eat almost any moving prey that can be swallowed whole, including young water snakes that, as adults, will eat pig frogs. Frog legs served in southern Florida are usually those of pig frogs, and they have been hunted extensively in the Everglades.
Lodge, Thomas E.. The Everglades Handbook. CRC Press. Kindle Edition.