Say you are thirsty. Can you put
your hand in a glass of water and drink it through your skin? Of course you
can’t! But some animals can absorb water this way. These animals are called
amphibians.
Amphibians are very interesting
creatures. They live a kind of double life. They spend the first part of their
life in water and the second part on land. In fact, the word amphibian
comes from two Greek words that mean “both” and “lives.” Amphibians are 
ectothermic, tetrapod vertebrates of the class Amphibia. Modern amphibians are all Lissamphibia. Amphibians also have special skin glands that produce useful proteins. Some transport water, oxygen, and carbon dioxide either into or out of the animal.
KINDS OF AMPHIBIANS
An amphibian is an animal that has
moist, hairless skin. Amphibians are cold-blooded, which means they cannot make
their own body heat. They get warm in the sun and cool off in the shade. The
three main groups of amphibians are frogs and toads, salamanders, and
caecilians. All amphibians have backbones.
The three kinds of amphibians look
very different from each other. Frogs and toads have legs but do not have tails.
Salamanders have short legs and long bodies ending in tails. Caecilians do not
have any legs. They look a lot like big earthworms.
There are more than 4,000
different species (kinds) of amphibians in the world. Nearly all
amphibian species are frogs or toads. Toads differ from frogs in the roughness
of their skin. Toads have bumpy skin, and frogs have smooth skin. Toads also
have shorter legs than frogs.
The biggest amphibian found on
Earth is the Japanese giant salamander. It can grow to be longer than 5 feet
(1.5 meters). Tiny frogs, such as the gold frog, are only about 0.4 inch (about
1 centimeter) long.
THE DOUBLE LIFE
Most amphibians start out as
larvae. Larvae look totally different from adult amphibians. Frog and toad
larvae are sometimes called pollywogs or tadpoles. These larvae look more like
fish. They live underwater and have a tail that they use for swimming. They
breathe through gills to get oxygen from the water.
An amphibian’s body changes
completely when it goes from a larva to a grown-up. This kind of change is
called metamorphosis. Most grown-up amphibians have lungs for breathing instead
of gills. Some have both lungs and gills.
Full-grown amphibians have legs
for moving about on land. Frogs and toads have strong hind (back) legs for
jumping. Most salamanders have four short legs and a long, strong tail. The tail
helps them keep their balance while walking and pushes them forward while
swimming. Caecilians never grow legs. They use their hard heads as battering
rams when they burrow in the soil. In water, they swim as eels do, by wiggling
their wormlike bodies back and forth.
AMAZING SKIN
Amphibians can “drink” through
their skin. The skin of an adult amphibian is able to absorb water from its
surroundings. Most amphibians do not even swallow water. Their skin soaks up as
much as they need.
Amphibians also breathe through
their skin. Their skin takes in oxygen as well as water. Most grown-up
amphibians get oxygen through both their lungs and their skin. But some
salamanders get all their oxygen through their skin. They do not even have lungs
or gills.
Slimy stuff called mucus covers an
amphibian’s skin. The mucus keeps just the right amount of salt and water in the
amphibian. In some species the mucus is poisonous, which helps keep predators
from eating the amphibian.
SENSING THE WORLD
Some amphibians have good eyesight
and hearing, and some do not. Most frogs and toads can hear well. Salamanders,
caecilians, and some frogs can only sense vibrations in the ground or
water.
Frogs have great eyesight. They see
through two bulging eyes that stick out from their heads. Most caecilians are
totally blind.
All amphibians can smell and taste
pretty well. Caecilians use feelers on their heads. Amphibians have a place in
their mouths called Jacobson’s organ that helps them smell and taste the world
around them.
AN AMPHIBIAN’S LIFE
Amphibians that live in cold
places spend most of their time trying to keep wet and warm. In hot places, they
try to keep wet and cool and usually come out only at night. During the day,
they stay under rocks or logs or in the ground.
Amphibians hibernate (become inactive) during cold winters. They
become inactive in hot places during the summer.
Almost all grown-up amphibians are
meat eaters. Frogs and salamanders have sticky tongues. They flick out their
tongues to catch insects, spiders, and other animals. Caecilians have sharp
teeth for grabbing their prey.
Amphibians mate when it is rainy
outside. They gather in groups to find mates. Some male salamanders show bright
colors to get the attention of females. Male frogs call out to females. Their
call sounds like this: “ribbet.” Female amphibians lay eggs in water or wet
places on land. Larvae hatch out of the eggs.
No one knows how long amphibians
live in the wild. Some captured toads have lived 30 years.
WHERE AMPHIBIANS LIVE
Amphibians live everywhere except
Antarctica. They can be found in grasslands, rain forests, evergreen forests,
deserts, and mountain areas. Caecilians live only in the tropics.
Amphibians need water to breed
and have babies. So most of them live near ponds, swamps, or streams. A few
species can even find water in deserts. Some burrowing frogs live in a dry part
of Australia called the outback. They breed and feed only when it rains, which
is not very often.
DISAPPEARING AMPHIBIANS
Amphibians have lived on Earth
for more than 300 million years. But recently, something scary has been
happening to them. Amphibians are disappearing. There are fewer and fewer
amphibians in many parts of the world, including North America, South America,
and Australia. No one knows why.
Some amphibians have also been
found with extra legs or other strange problems. Scientists are working hard to
find out what is happening to the amphibians.
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