Let's hear three croaks for frogs 

What, you didn't know they were in trouble? One-third to one-half of all amphibian species are threatened with extinction, the conservation group Amphibian Ark says. Loss of habitat is the major threat, affecting the most species, but a disease called chytrid fungus is also proving deadly.

Frogs and toads make up one of three main groups of amphibians. There are about 3,500 known species of frogs and 300 kinds of toads. They can be found on every continent except Antarctica.

All toads are frogs, but not all frogs are toads.

Like all amphibians, frogs and toads begin their lives in the water, breathing with gills; as adults on land, they breathe with lungs.

You are most likely to see a toad in your yard or garden; frogs prefer ponds and other still waters. Both animals must return to water to lay their eggs.

"Frogs tend to lay eggs in clumps: a single egg surrounded by other eggs, like a ball of eggs," said Matt Evans, a biologist and herpetologist (an expert in reptiles and amphibians) at the National Zoo in Washington, D.C. "A lot of toads lay their eggs in a single line, so it's like a string of eggs."

A lot can be learned about frogs and toads by observing them. For example, if a toad feels threatened, it will lean forward on its front legs and pump its lungs full of air to appear larger. A frog will tend to flee, using its powerful legs to hop to safety.

Evans reveals a little-known fact about frogs and toads: "They actually use the inside of their eyes to push food down into their throats."

You can see this more clearly in frogs, Evans says: "Frogs have big eyes. You always see a frog blink when it's swallowing. The eye socket goes down into their mouth, so when they swallow, their eyes push down and help push food that's in their mouth back into their throat."

Frogs and toads generally do not use their front legs to grab food or assist them in eating. They have a long, sticky tongue that's hinged at the front of the mouth so it can rapidly flip out and capture insects. And the frog's teeth aren't used for chewing.

"They're bringing a food item in that's alive when it comes to their mouth; they have to swallow it immediately," Evans says.

If you encounter a frog or toad this summer, Evans has some advice.

"It is an age-old myth that toads cause warts. That is not true," he says.

But do beware of frogs and toads, especially if they are secreting toxins.

"If you get it on your hands and rub your eyes, it could cause some stinging and some burning," he says. "I'd say, after you handle them, just wash your hands."