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Frog hind foot Toad front foot Tree frog front foot
Three types of feet: A bullfrog's hind foot (left), a toad's front foot (middle), and a tree frog's round-toed front foot (right.) [Click each picture for a larger image.] Photos by Amy Snyder.  

  A  frog's two front legs have four toes each, while the back legs have five toes each. Aquatic frogs are likely to have long, strong legs with webbed back feet to help them swim. Frogs that live on land tend to have shorter legs for walking and climbing. Tree frogs have large, round toe pads that help them cling to branches. These toe pads work like suction cups to help the frog cling on to wet leaves and other smooth surfaces.

The Costa Rican flying tree frog soars from branch to branch with the help of its feet. Webbing between the frog's toes puffs up with air like a parachute, holding the frog aloft as it sails from tree to tree.

American bullfrog
American bullfrog ( Rana catesbiana ); not to be confused with a toad. [ Click for a larger image.] Photo by Amy Snyder.

Frogs and Toads:
What's the difference?

Technically speaking, toads are frogs. Both are members of the order Anura, a group that experts usually refer to simply as frogs. Within this large group, the name "toad" is given to those with dry, warty skin and short hind legs for walking instead jumping. Meanwhile, those with smooth, moist skin and long, strong, webbed hind legs for swimming and jumping are called frogs. In general, frogs live in moist climates and lay their eggs in clusters, while toads live in drier climates and lay their eggs in long chains. But be warned: drawing the line between frogs and toads can be tricky. For example, there are frogs with warty skin, and toads with slimy skin. Many species fit equally well into both categories.

RealVideo Exploratorium staff frogkeeper Ned McAllister discusses the feeding habits of frogs, toads, and tadpoles. [Need Help ?]

Spadefoot toads have hard, horn-like growths on their hind feet. These claw-like "spades" help them dig cool underground burrows in the dry climates where they live. Unlike most animals, spadefoot toads dig backwards. While digging with their hind feet, they move in a backward spiral and gradually disappear into the earth.

Finding Food
Frogs eat almost any live prey they can find, including insects, snails, spiders, and worms, or small fish. Some larger frogs eat even larger prey: The ornate horned frog of Argentina can gulp up a mouse in one mouthful. All prey gets swallowed whole, because frogs can't chew. If they have teeth at all, they are usually only on the upper jaw, used for holding onto prey and not for biting or chewing.

Some frogs catch insects with a long sticky tongue. It takes less than a second for a frog's tongue to roll out, adhere to prey, and roll back into the frog's mouth. High-speed photography has revealed that frog's eyes shut completely as the tongue is shot out. Since frogs can't see while they're striking, they can only make a catch by taking careful aim in advance. Meanwhile, not all frogs have tongues. Tongueless frogs use their fingers to catch prey and stuff it into their mouths.

Catching fast-moving insects requires good eyesight. Frogs' large eyes see a wide range of colors and also see well in dim light. It's nearly impossible to sneak up on a frog, because their bulging eyes help it to see in all different directions without moving its head. The positioning of the eyes -- on top of head -- allows a frog to sit in the water with only its eyes and nose above the surface.

Frogs' eyes have a surprising auxiliary function: they help in swallowing. As a frog swallows its prey, the eyes sink through openings in the skull and help force the food down the throat. This is why frogs seem to blink as they eat.


Frog and Toad Skin
Two types of skin: Moist, slimy frog skin, and drier, wartier toad skin. [ Click to for a larger image.] Photos by Amy Snyder.  

Serious Skin
Frogs' skin is critical to their survival. Through it, they both drink and breathe. Frogs don't swallow water; they get all the moisture they need through their skin. And though frogs have lungs, they rely on the extra oxygen they absorb through their skin, especially when they're underwater.

Frogs must keep their skin moist. Otherwise, oxygen can't pass easily through it and the frog suffocates. Frog skin secretes a mucus that helps keep it moist. Even so, their skin tends to dry out easily, which is why they usually stay near bodies of water. Toads' skin doesn't lose moisture as quickly, so they can live farther from water than most frogs. In a pinch, frogs and toads can rely on dew for moisture, or burrow underground into moist soil.

About once a week, frogs shed their skin. The process begins with the frog doing a lot of twisting, bending, and stretching to loosen the old skin. Then the frog pulls the skin over its head like a sweater and -- usually -- eats it.

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