Amphibians are animals that live part of their lives in water and part on land. They are vertebrates and are also ectothermic; they cannot regulate their own body heat, so they depend on sunlight to become warm and active. Amphibians also can't cool down on their own, so if they get too hot, they have to find a burrow or some other shade. In cold weather, amphibians tend to be sluggish and do not move around much.
Young amphibians do not look like their parents. Generally called larvae, they change in body shape, diet, and lifestyle as they develop, a process called metamorphosis. A frog is a good example, starting out as a tadpole with gills to breathe underwater and a tail to swim with. As the young frog gets older, it develops lungs, legs, and a different mouth. Its eyes also change position, and it loses its tail. At this point it is an adult frog and spends most of its time hopping on land rather than swimming like a fish in the water.
Most amphibians have soft, moist skin that is protected by a slippery secretion of mucus. They also tend to live in moist places or near water to keep their bodies from drying out. Many adult amphibians also have poison-producing glands in their skin, which make them taste bad to predators and might even poison a predator that bites or swallows them. Some of these amphibians, like poison frogs, are brightly colored as a warning: Don't eat me, or you'll be sorry!
There are about 5,500 known amphibian species, divided into 3 main groups: salamanders, newts, and mudpuppies; caecilians; and frogs and toads. The largest amphibian is the Japanese giant salamander at 6 feet long (1.8 meters) and 140 pounds (63 kilograms), and the smallest is the gold frog at 0.39 inches (1 centimeter) long.
In an effort to help save amphibians, San Diego Zoo Global has been active in several areas of amphibian conservation. The most obvious is our remarkable live collection, which you can see when you visit the San Diego Zoo. We have joined with other organizations to help save endangered frogs and donate money and staff time to support amphibian conservation programs.