How do scientists sort the animals that people call frogs and toads, and where do the two names come from? Frogs and toads belong to a group of amphibians called Anura, and there are thousands of species of them. They are sorted into families, including Ranidae (true frogs), Hylidae (treefrogs) and Bufonidae (toads). True frogs, such as bullfrogs and pickerel frogs, are the largest of these, and unlike treefrogs, their front toes are not as webbed. Technically, a toad is a kind of frog, and scientists do not draw a firm line between the two: there is no scientific distinction between the names, although most frogs and toads are usually called one or the other.

What does a frog's skin do besides cover its body, and why does it matter so much to where the frog can live? A frog's skin does more than cover it. Frogs breathe with lungs and also through their moist skin, and the skin has to stay moist, which is why most frogs live in or near water. Frogs take in water by absorbing it through their skin instead of drinking it, while a toad's thicker skin loses moisture more slowly, so toads can live farther from water than most frogs. Amphibians that have no lungs absorb all the oxygen they need through their moist skin. As of November 2026, the only lungless frog species known is the Bornean flat-headed frog, Barbourula kalimantanensis.

How does a frog use color, and how can the same skin hide it or make it stand out? Some frogs can change their color, like chameleons, according to light, temperature, humidity, or even mood. A frog that changes color does it with pigment grains inside its cells. When the grains are packed together in the center of each cell the frog is light colored, and when they spread out the frog's color darkens. Other colors work as hiding places: a red-eyed tree frog is green, which helps it blend in with leaves, and it is active at night and sleeps during the day, while a toad's bumpy skin helps it blend into its surroundings.

Some colors on a frog stay out of sight until they are needed. Many dull-looking frogs have hidden flash colors, bright patches on the belly, groin or backs of the thighs. A fire-bellied toad's plain brown back matches the ground, but when threatened it shows its red underside, which can startle predators or buy the toad time to escape. Bright colors can also be a warning, and certain frogs of Central and South America have especially strong poisons in their skin, and poison dart frogs have bright colors that warn predators they are poisonous. In the wild, they are too toxic to touch.

Golden poison frogs do not act aggressively toward people; the danger lies in their very toxic skin. Captive ones tend to lose their toxicity without the wild prey that are the source of the toxin, so the poison comes from what the frogs eat in the wild. Toads have poison too, because a toad's skin has glands that make a poison, and the large glands behind the eyes are called parotoid glands. The poison is called bufotoxin, and it can kill small animals and cause allergic reactions in people. Because the poison can irritate people, it is best not to handle a toad, and nobody should lick or eat one, and although you may have heard that touching a toad gives you warts, in fact, touching a toad does not give you warts.

In a study of how frogs catch insects, a frog's tongue captured an insect in under 0.07 seconds, five times faster than a human eye blink. A frog cannot see while its tongue is striking, so it can only make a catch by taking careful aim in advance. A frog's saliva is viscoelastic, which means it has properties of both a fluid and a solid. A frog's eyes help it swallow. As the 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.

Calls are the loudest part of a frog's life, and they begin inside the body. Frogs make their calls with the help of one or two pouches of skin called vocal sacs. Male frogs and toads call by breathing in air with their lungs and then bouncing the air between their vocal sacs and their lungs, and the vocal sacs work like echo chambers to amplify the sound of the call. Male bullfrogs croak to attract mates and to claim their territory, and during breeding, female frogs and toads listen carefully and hop closer to males with a deeper or more powerful call, which signals a larger size and a greater ability to survive and reproduce.

Where do young frogs grow up, and how do they get there? Most frogs and toads start life in the water, but some frogs raise their young in other ways. A strawberry poison dart frog lays eggs on land, not in a pond. When the tadpoles are ready to hatch, the mother carries them on her back to water-filled bromeliads in the trees. The tadpoles finish growing in these tiny, predator-free pools, and she feeds them unfertilized eggs. Baby Surinam toads grow up on their mother's back and do not swim around as tadpoles, while a bullfrog tadpole can take two winters, or almost three years, to turn into a frog.

How can an animal live through a winter by freezing? Wood frogs spend the winter frozen and thaw out when the weather warms, although when blood freezes in most animals, nothing delivers oxygen and nutrients to the organs, so extreme metabolic damage occurs. At the start of a wood frog's freeze, its liver makes large amounts of glucose that flush into every cell in its body. A frozen wood frog thaws from the inside outward, and wood frogs and spring peepers can freeze completely in winter, so they can start breeding much earlier than other amphibians. As of November 2026, scientists do not yet understand what starts a wood frog's heart again after it has been frozen for the winter.

What do frogs and toads do for the places where they live, and what is happening to them? Frogs and toads eat so many insects that they help keep a large part of the world's insect numbers down. As of November 2026, most scientists agree that there is a worldwide decline in frog numbers. As of November 2026, habitat loss and invasive species are among the biggest threats to frogs and toads, and bullfrogs that people have introduced may be driving native frogs to extinction in some areas. As of November 2026, a fungus disease called chytrid is causing severe declines in many frog populations. Amphibians react strongly to changes in their surroundings, so scientists use them as signs of how healthy a place is.

Words to know

• pigment: color material
• amplify: make louder
• toxic: poisonous
• lungless: without lungs