Student Research Page
Amphibians are a group of animals that includes salamanders, frogs and toads (called anurans), and the worm-looking caecilians. The two most common groups of amphibians are those that have tails (salamanders, newts, and mudpuppies) and those that do not have tails (frogs and toads).
Amphibians are special. Most begin life as an egg laid in the water then transform into land animals. They hatch from jelly-like eggs into larva. Tadpoles are an example of frog larva. The larva breathes through gills, like a fish. Then an amazing change takes place. The larva go through metamorphosis and grow into a frog. "Meta" means change and "morph" means shape.
During metamorphosis, they become air breathers. Frogs and toads loose their tails. Their intestines change from being able to digest plants and being able to digest animal matter. They develop lungs that can breathe air, legs that can better move on the land, and wide mouths that can swallow prey.
Built for Action
Both frogs and toads have strong hind legs. These legs allow them to make a series of small hops (toads) or incredible leaps (frogs) to escape enemies or to capture food.
Frogs and toads have very long tongues to gather food. They eat bugs, spiders, worms and even smaller reptiles and amphibians, including their own kind. Some species are large enough to eat smaller mice and even small birds. Many species eat anything they can fit into their mouths! When prey is detected, the frog or toad shoots its tongue in the direction of the prey. The sticky tongues catches the food, then it "reels" its tongue back into its mouth. When swallowing food, amphibians have to blink their eyes. Their eye balls help push food down their throat!
Amphibians' moist skin is used for breathing! If frogs or salamanders become too dry they begin to have trouble breathing and may die.
Some amphibians, like the Poison Dart Frog of Central and South America, can secrete poisons through their skin. Should a predator attack them they get a mouthful of poison, sometimes enough to kill them.
The Slimy Salamander of Central Texas lives in caves, ravines, and cliffs. They can secrete a substance that acts like glue. The predator’s jaws stick together and giving the amphibian time to escape.
Toad skin is an exception in the world of amphibians. It is dry to the touch and feels something like leather. It is covered in small wart-like bumps. Toads also have bean-shaped warts on the back of the head that will give off a milky-white liquid, called Bufotoxin, when another animal tries to eat them.
Most salamanders look like small lizards, but they are not lizards. Salamanders have smooth skin and do not have claws on the end of their toes. Some salamanders look like a larva even as adults.
Temperature and rainfall affects when amphibians reproduce. Frogs and toads in Texas generally breed from late winter through spring, with some species breeding throughout the spring and summer. The male frogs and toads arrive at breeding pools during the wet season.
Male frogs and toads “sing to their ladies;” although the human ear may not recognize their calls as music. The males inflate their throats with air and blow it out. The sound of their voice depends on their species. Some sound like clicks (Cricket Frogs), a buzz (Narrowmouth Toads), peeps and chirps (Tree Frogs), trills and bleats (Toads), or the deep bellow of the American Bullfrog. Listen to their calls.
Male anurans tend to call at night from flooded ditches, swamps, ponds, lakes, streams, and rivers. Females select males based on the volume and length of their calls.
Females lay eggs in a clear jelly-like substance. Most frogs lay their eggs in bunches around aquatic plants while most toads lay their eggs in long stings. After hatching, most larva are on their own. But, the male African Bullfrog guards its eggs and developing young against all predators and have been known to take on lions.
Some amphibian species never experience the larval stage and complete development while within the egg.
The First Amphibians
After fish, amphibians were the first vertebrates on Earth. The earliest forms were really fish with club-shaped fins that allowed them to crawl across the mudflats of low tides. Amphibians developed almost 400 million years ago, long before the dinosaurs. Despite the fact that they still must return to the water in order to bear young, they were the first animals to live on land.
Today, there are approximately 6,000 species of frogs, toads, and salamanders world wide. The smallest amphibian is the Brazilian Golden Frog at less than half an inch to the Chinese Giant Salamander at close to six feet long. Texas has over 40 species of amphibians.
Why Should I Care About Amphibians?
Amphibians have much to offer us. They consume large amounts of agricultural and other pests. Amphibians are also food for many species of birds, reptiles and mammals. Tadpoles can fall victim to larger invertebrates, fish, amphibians, reptiles, birds, and mammals.
They also serve as an indicator species. The health and number of amphibians helps identify or indicate the health of the local environment. Amphibian skin can quickly absorb pesticides and pollution in water. They may be one of the first species harmed by polluted water in a habitat. When biologists observe problems with amphibians, they let others know. Scientists study eary signs of water pollution so people can take action to help habitats for the health of wildlife and people.
Amphibians may help people in another way. The skin secretions of some amphibians may prove to be useful as medicine. Scientists are currently studying these skin secretions in hopes of developing new medicines and pain-killers.
Amphibians are in trouble world-wide and their populations are declining.
Household chemicals are causing them serious problems. Pesticides can be absorbed by their sensitive skin or get into their food. Unused medicines flushed down the toilet have resulted in male frogs turning into females.
As lf these problems weren’t enough, there is now a fungus affecting amphibians across the globe. Chritid is deadly with no known cause, nor cure. It has already led to the extinction to a number of frog species.
In some places of the world, amphibians that have been released into parts of the world where they are not native have caused problems themselves. The Cane Toad was introduced to southern Florida and Australia with the hopes that they might control beetles that feed on the sugar cane. The powerful skin secretions can cause death to predators that attack them. Without a predator that can withstand its Bufotoxins, the Cane Toad has over-run Australia and has now become the problem.
What can you do to help amphibians in Texas?
- Become familiar with the kinds of amphibians that live in your area. Learn about their habits, habitats and life-histories.
- Learn to recognize potential threats to amphibian populations and work to help prevent them. If you own land with native wetlands, maintain some in their natural state.
- Provide sources of shallow water.
- Don't dump trash, chemicals, unused medicine or even aquarium plants and animals into streams, down storm sewers of in wet caves or sinkholes. Don't flush them down the toilet, either!
- If you live in an urban or suburban setting, create a "toad house" by knocking a hole in a flower pot and turning it upside down near your water faucet.
- Join Texas Amphibian Watch. Keep a map and field guide handy and watch for amphibians wherever you go. Pick a favorite pond or wetland and start counting the kinds and numbers of each species that use it.
- Follow these rules to keep you and the amphibians safe.
- Develop your skills and join the national North American Amphibian Monitoring Program.