Amphibians: Frog & Toad

Range: almost everywhere on Earth except Antarctica, the Arctic, and Greenland Habitat: nearly every kind of habitat except polar regions and very dry deserts

Frog or toad?

Frogs have long legs that are good for hopping, skin that is smooth and moist, and special pads on their toes that help them climb. Toads, on the other hand, are more heavyset with shorter legs, and usually have drier skin, often with warty-looking bumps. Frogs are more likely to live in or near water than toads. The word "frogs" can include both frogs and toads, as some frogs may not live near water and some toads have smooth skin. Can you get warts from holding a toad? No! But you can die from holding a frog—if it's a poison dart frog! Some of these bright little South American frogs are so toxic that one drop of their skin secretions can kill an adult human.

No necks

When you look at a frog or a toad, you'll notice that it doesn't seem to have a neck. Practically speaking, this is true. Most frog and toad species have large, protruding eyes so they can see in most directions. They can also hop around to look in another direction. But they can't turn their heads like we can, since their necks are almost non-existent.

When is a fish not a fish?

When it's a tadpole! Most frogs and toads start life out in the water. The mother lays her eggs in water, or at least in a moist place like a dew-collecting leaf or plant. The eggs hatch into tadpoles (also known as pollywogs or froglets) that look like funny, big-headed fish. Then they gradually grow legs, absorb their tails, lose their gills, and eventually turn into frogs and toads that start breathing air and hopping.

It's all a matter of survival

Adult frogs and toads have two main color schemes. Each one signals a different survival technique. Those with bright colors (like poison dart frogs) are easy to see and warn potential predators that the frog is toxic. The hoppers with mottled green or brown colors are camouflaged so predators have a hard time finding them. Toads have additional survival techniques as well. If a predator is after them, they puff themselves up so they look too big to swallow. Most toads can also secrete a burning milky toxin from a gland behind their eyes!

What's for dinner?

Most frogs and toads eat insects, spiders, worms, and slugs. Some of the larger species will go for mice and other small rodents, and even other small reptiles and amphibians. At the San Diego Zoo they are fed crickets, worms, fruit flies, or mice.

Hoppers are responsible for keeping a large part of the world's insect population under control. In some cases, however, their appetites can be a problem. Latin American cane toads Bufo marinus were introduced to Australia in 1935 to kill sugarcane beetles. But instead of beetles, the toads preferred to eat native frogs, small marsupials, and snakes. Not only that, but they poisoned everything that tried to eat them, including rare animals like Tasmanian devils and pet dogs! Since they lay more than 50,000 eggs at a time, they turned into bigger pests than the beetles they were supposed to get rid of.

A ribbeting chorus

Have you ever walked past a pond or creek at night and heard lots of frogs croaking and ribbeting like a giant froggy chorus? It's likely you're hearing a bunch of male frogs making calls to attract females. Each frog species has a different call that is used to attract mates and warn off rivals. When a female picks a male whose call she likes, the male grabs her and she lets out all her eggs. Then he fertilizes the eggs and in some species also guards them.

Dad takes the lead

In many species of hoppers it is the dad that cares for the eggs. He may transport the eggs to a safe, wet place by putting them on his back, in a pouch on his belly, or even in his mouth. Or he may wait until the eggs hatch into tadpoles before he transports them from a wet place on land to actual water. Although the dad is more likely to perform these tasks, the moms often do too. Sometimes both parents do the babysitting—it depends on the species. The highly endangered Australian gastric-brooding frog Rheobatrachus silus has one of the weirdest ways to care for eggs. The female eats as many as 20 eggs after the male fertilizes them. Then she stops eating regular food, because the eggs are developing in her stomach! When they've begun to turn into tadpoles, she vomits them up and starts eating again!

What does the future hold?

It's hard to get a handle on the world's frog and toad populations, because there are so many of them in so many hard-to-find places. But there is enough information to suggest that we should be worried. In the 1980s, scientists began getting reports from all over the world about disappearing amphibian populations, even in protected areas! The loss of wetlands and other frog habitat because of industry and human population growth is one of the biggest causes. Also the increase of roads has been hard on migrating frogs. When hoppers try to cross a highway to get to their breeding pools, they get squashed by cars. Then there are non-native species like trout and even other frogs that humans introduce. The non-natives often eat all the local native frogs. There are also pollutants that get into the rivers and ponds and kill the frogs and tadpoles.