129 Fun Facts About Frogs

What feature gives glass frogs their name?

See-through belly skin shows a glass frog's heart, liver and gut; a sleeping frog turns two to three times more transparent by packing about 89% of its red blood cells into its liver.

In the Brothers Grimm tale The Frog Prince, what does the frog fetch from a well for the princess?

A golden ball: in the Grimms' telling no kiss breaks the spell, because the princess hurls the frog against her bedroom wall in a fury and he lands as a prince.

Which body part does a frog use to help push swallowed food down its throat?

Its eyeballs: a frog's eyes sink through gaps in the skull as it gulps and press the meal toward the gullet, and leopard frogs that could not retract them needed about three-quarters more swallows per cricket.

In everyday usage, what most often marks an animal out as a toad rather than a frog?

Dry, warty skin is the everyday marker, but the labels are informal: the smooth-skinned Panamanian golden frog belongs to the true toad family, and every toad is, strictly speaking, a frog.

Which puppeteer built the first Kermit in 1955 from his mother's old coat and a ping-pong ball?

Jim Henson made the puppet for a local Washington TV show, Sam and Friends, and at first Kermit was a vague lizard-like creature: he only became a frog later.

Which frog from Cameroon and Equatorial Guinea is the largest in the world?

The goliath frog can top 3 kg and 30 cm, yet it starts out ordinary: its tadpoles are no bigger than other frogs'.

Unlike a human's, a frog's tongue is attached at which part of its mouth?

The front: hinged at the tip of the jaw, the tongue flips out faster than a blink, and its saliva turns watery on impact, then thicker than honey to hold the insect on the way back.

Which North American species can spend the winter frozen solid, with no heartbeat or breathing?

Wood frogs flood their organs with glucose as antifreeze while ice forms under the skin and the heart stops; in Alaska they stayed frozen for about 193 days in a row, and every one thawed out alive.

Which fungal disease, first described in 1998, has devastated frog populations around the world?

Chytridiomycosis attacks the keratin in a frog's skin and upsets its salt and water balance; genetic detective work has traced the pandemic strain back to the Korean peninsula.

Which country imported cane toads from Hawaii in 1935 to eat sugar-cane beetles, with disastrous results?

Australia's toads bred fast and kept spreading, and their poison kills the native predators that try to eat them: northern quolls and water monitors crash wherever the toads arrive.

How do frogs drink water?

They absorb it through their skin, mostly at a thin 'drinking patch' on the belly and the underside of the thighs, so a frog drinks by sitting in water rather than swallowing it.

What is a group of frogs called?

An army is the traditional collective noun, and it fits in spring, when frogs and toads migrate back to the ponds where they hatched, sometimes thousands at a time.

Which order, named from the Greek for 'without a tail', contains frogs and toads?

Anura joins the Greek an-, 'without', and oura, 'tail', because adult frogs lose the tail they swam with as tadpoles; salamanders, which keep theirs, sit in the order Caudata.

Wallace's flying frog of Southeast Asia glides from tree to tree using what?

Its huge webbed feet: the frog spreads the webbing between its long fingers and toes into four small parachutes and can steer a glide of up to 15 metres to a lower branch.

About how long is Paedophryne amauensis, the Papua New Guinea frog named the world's smallest vertebrate in 2012?

About 8 mm: adults average 7.7 mm, and the frog was found only because researchers tracked an insect-like call into the leaf litter and bagged handfuls of it; a Brazilian flea toad has since measured even smaller.

What special adaptation allows tree frogs to climb smooth vertical surfaces?

Sticky toe pads are kept wet with watery mucus that seeps from channels between their six-sided surface cells; the film is so thin that the pad also grips by direct friction, even on glass.

Which Colombian frog is often called the most poisonous animal in the world?

The golden poison frog is so toxic that Colombia's Emberá hunters poison their blowgun darts with its skin secretions; its scientific name, Phyllobates terribilis, says the rest.

What happens to a tadpole's tail during metamorphosis?

It is reabsorbed by the body, cell by cell, through programmed cell death; in most tadpoles the tail holds no bone, only soft tissue, which is thought to be why it can be absorbed so quickly.

What is the term for a frog's egg mass laid in water?

Frogspawn floats in jelly-coated clumps, whereas toads lay long strings of eggs that swell as their jelly soaks up water and tangle around the stalks of pond plants.

Because they live both in water and on land, scientists treat frogs as what?

Bioindicators of ecosystem health: frogs sit in the middle of food chains, eating insects and feeding birds and snakes, so when a pond's frogs vanish it flags trouble above and below them.

When a frog fires its tongue at prey, what is it mainly reacting to?

Its movement: a frog's retina has 'bug detector' cells that fire when a small dark object moves across its view, and it must line the target up first because it shuts its eyes as the tongue shoots out.

What is the inflatable sac on a male frog's throat used for?

Amplifying mating calls: the sac is a resonating throat pouch, and because the frog shuttles the same air back and forth instead of breathing it out, it can call with its mouth and nostrils shut.

Which continent's first frog fossils were reported in 2020?

Antarctica has no frogs today, but a hip bone and a piece of skull about 40 million years old show helmeted frogs lived there when it was warm and wet; their living relatives survive in Chile.

Why do many frogs have brightly colored skin?

To warn predators that they are toxic: the signal works so well that one harmless frog, Allobates zaparo, copies the colours of its poisonous neighbours and is left alone too.

Which branch of zoology covers frogs and the rest of the amphibians, plus reptiles?

Herpetology takes its name from the Greek herpeton, 'creeping thing': the science lumps frogs in with snakes and lizards because early naturalists filed all crawling animals together.

In which classic video game does the player help a frog cross a busy road and river?

Frogger outlived the arcades: in a 1998 Seinfeld episode, George wheels a Frogger cabinet across a busy street to save his old high score, dodging cars just like the frog.

What is the primary way frogs breathe as adults?

Adult frogs breathe through both lungs and skin: the thin, moist skin lets oxygen pass straight into the blood, so a frog wintering at the bottom of a pond can get by on its skin alone.

Which Madagascan species puffs itself up and oozes a sticky white gum when threatened?

The tomato frog's white gum is among the stickiest secretions of any amphibian: it clogs a predator's eyes and mouth until the attacker lets the bright red frog go.

What do tadpoles primarily eat before they become frogs?

Algae and plant matter: most tadpoles scrape it off surfaces with horny tooth ridges and digest it in a long, coiled gut, which shortens as they switch to a frog's diet of live prey.

The African clawed frog (Xenopus laevis) was historically used for what unexpected purpose?

Pregnancy testing in humans: injected with a pregnant woman's urine, the frog laid eggs within hours; when chemical tests took over, labs let their frogs go, and the species is now invasive in many countries.

In frog reproduction, what is 'amplexus'?

The male's mating clasp, from the Latin for 'embrace': he can grip the female for days, helped by horny pads on his thumbs, and fertilises the eggs as she lays them.

In an American bullfrog, an eardrum noticeably larger than the eye tells you what?

It is a male: his eardrums outgrow his eyes while a female's stay about eye-sized, and experiments suggest the big drums help broadcast his booming call as well as hear rivals.

Which amphibian, unseen since 1955 and declared extinct, was found alive in Israel in 2011?

The Hula painted frog vanished when Israel drained the Hula marshes in the 1950s; after a ranger found one in 2011, it proved to be the last survivor of Latonia, a genus known only from fossils.

Queensland's extinct gastric-brooding frog raised its young in its stomach, then gave birth how?

Through its mouth: the mother swallowed her fertilised eggs, switched off her stomach acid and went without food for about six weeks, then opened wide and let fully formed froglets out.

Which hormone is responsible for triggering metamorphosis in tadpoles?

Thyroxine comes from the thyroid gland: tadpoles fed powdered thyroid in a 1912 experiment turned into tiny frogs ahead of time, while tadpoles whose thyroid was removed never changed and grew into giants.

Captive-bred poison dart frogs are harmless because their toxins come from where?

Their diet of ants, mites and termites supplies the poison: the frogs store alkaloids made by their prey instead of making their own, so a frog raised on captive food never becomes toxic.

The 'crucifer' in the spring peeper's scientific name refers to what?

A cross-shaped mark on its back earns the peeper the Latin name 'cross-bearer'; males peep about 20 times a minute, and the faster and louder singers win the mates.

How does the female Surinam toad carry her developing young?

Embedded in the skin of her back: the eggs sink in and skin grows over each one, and months later fully formed little toads push their way out, with no free-swimming tadpole stage.

Which Ecuadorian species can switch its skin from spiny to nearly smooth within minutes?

The mutable rain frog fooled its finders: they caught a spiny frog, left it in a cup overnight, found a smooth one the next day and assumed they had picked up the wrong animal.

Which North American species, a resident of cold mountain streams, makes no calls at all?

The coastal tailed frog has no voice and no eardrums; its 'tail' is a mating organ that places sperm inside the female, so the fast current of its mountain streams cannot wash it away.

The Argentine horned frog is nicknamed after which arcade character?

Pac-Man lends his name because the frog is nearly all mouth: it sits motionless waiting for prey and will try to swallow anything that fits, and some things that do not.

Besides calling, how does the Panamanian golden frog signal to rivals and mates?

By waving a hand, like semaphore: the frogs live beside fast, noisy streams that can drown out a call, so males wave a forelimb at rivals and at females, who may wave back.

How does Central Africa's hairy frog produce the 'claws' it uses in defence?

By breaking its own toe bones: the sharp tip of the last bone snaps free of its anchor and slices out through the skin of the toe, a claw with no keratin, unlike any other in living vertebrates.

India's pig-nosed purple frog, formally described only in 2003, spends most of its life where?

Underground: the purple frog burrows in the Western Ghats and surfaces only briefly each monsoon to breed, which is how it went without a formal description until 2003.

The baggy-skinned Titicaca water frog is jokingly nicknamed after which body part?

Telmatobius culeus is nicknamed the 'scrotum frog' for its baggy skin folds, which boost oxygen uptake in the cold, high-altitude Lake Titicaca shared by Bolivia and Peru.

What sound does the desert rain frog of Namibia and South Africa make when threatened?

A high-pitched squeak, from a frog that never needs open water to breed: its young skip the tadpole stage and hatch straight from the egg as tiny frogs.

Florida's largest tree frog, an invader, is named after which island?

Cuba's tree frog, the largest in the United States, spreads by hitchhiking on plant shipments and vehicles; in Florida it eats smaller native tree frogs and even causes power cuts by getting into electrical equipment.

The coquí, named for its two-note night call, is native to which island?

The common coquí (Eleutherodactylus coqui) is Puerto Rico's unofficial symbol; the 'co' note warns off rival males, the 'quí' attracts females, and the species skips the tadpole stage entirely.

Why is the giant frog of Dominica and Montserrat called the 'mountain chicken'?

Its meat tastes like chicken, islanders say, and it was long hunted as a delicacy; then a frog-killing disease reached Dominica in 2002 and wiped out over 85% of the frogs in under 18 months.

How does the male midwife toad earn its name?

He carries the eggs on his legs: after mating he winds the egg strings around his back legs and keeps them moist for weeks, taking them to water only when they are ready to hatch.

What does the male African bullfrog occasionally do while guarding his tadpoles?

Eats some of them, yet he is a devoted guard: he attacks anything that comes near the brood and, if their pool starts to dry up, digs a channel to lead the tadpoles to deeper water.

As of 2014, which country was the world's largest exporter of frog legs?

Indonesia led the trade; many of the frogs are caught wild, mostly for European dinner tables, and researchers warn that the harvest is depleting wild frog populations.

Who wrote and illustrated the Frog and Toad easy-reader books?

Arnold Lobel wrote that 'Frog and Toad are really two aspects of myself'; the pair grew out of the animals he drew as a sick, lonely second-grader to win over his classmates.

Which American author made his name in 1865 with a tale about a jumping frog in Calaveras County?

Mark Twain's tale has the gambler Jim Smiley bet forty dollars on his frog Dan'l Webster, only for a stranger to fill the frog with quail shot so that it cannot leave the ground.

Disney's The Princess and the Frog (2009) is set in which city?

New Orleans gives the film its jazz and its bayou: Tiana dreams of opening a restaurant there until a kiss with frog-prince Naveen turns her into a frog too.

In Exodus, the plague of frogs came straight after the Nile turned to blood, making it which of the ten?

Second: the frogs swarmed into Egypt's bedrooms, ovens and kneading troughs, Pharaoh's magicians conjured still more, and when the plague lifted the dead frogs lay in reeking heaps.

In Aristophanes' comedy The Frogs, which god of theatre visits the underworld?

Dionysus sets out to bring back Euripides but, after judging a contest between two dead poets, takes Aeschylus home instead; the frogs are a chorus that croaks at him as he rows across the lake on the way down.

Heqet, depicted as a frog, was the ancient Egyptian goddess of what?

Heqet was the frog-headed goddess of fertility and childbirth: frogs appeared in great numbers around the yearly Nile flood, which is probably why Egyptians tied them to abundance and new life.

In Chinese feng shui, the three-legged toad Jin Chan is kept to attract what?

Wealth: the 'money toad' squats on a pile of old Chinese cash with a coin in its mouth, and it is the companion of the Daoist immortal Liu Haichan, himself honoured as a form of the god of wealth.

Which cartoonist created Pepe the Frog in the 2005 webcomic Boy's Club?

Matt Furie created Pepe the Frog in his 2005 comic Boy's Club, where the catchphrase 'Feels Good Man' first appeared; Furie later fought the character's co-option as a hate symbol.

The Crazy Frog's chart-topping 2005 single was a cover of the theme from which film?

Beverly Hills Cop's theme, 'Axel F', gave Crazy Frog a UK number one that kept Coldplay off the top; the ringtone mascot's 'voice' began as a Swedish teenager imitating a two-stroke engine.

In the 1780s, Luigi Galvani noticed that a dead frog's legs did what when struck by a spark?

Twitched: Galvani put it down to 'animal electricity', but Alessandro Volta argued the metals were responsible and, to prove it, built the voltaic pile, an early battery.

Central America's túngara frog lays its eggs in what kind of structure?

A floating foam nest: during mating the male whips a fluid released by the female into froth, and the tough foam shields the eggs for the four days or so until the tadpoles swim out.

The painkilling alkaloid epibatidine was first isolated from a frog from which country?

John Daly isolated epibatidine in 1974 from the skin of Epipedobates anthonyi, a poison frog from Ecuador, but its structure was not worked out until 1992.

Mantella frogs, the Old World lookalikes of South America's poison frogs, are found only on which large island?

Madagascar's mantellas look so much like the unrelated poison frogs of the Americas that the first ones described, around 1870, were filed in the same genus: a textbook case of convergent evolution.

In Matsuo Bashō's most famous haiku, a frog jumps into what?

An old pond: the 1686 verse ends on nothing more than 'the sound of water', and that spring Edo's poets met at Bashō's hut for a frog-poem contest, apparently in tribute to it.

What happens when a dormant Outback frog, Cyclorana platycephala, is gently squeezed?

It releases stored water, held in its bladder and in pockets of skin; Aboriginal Australians dug the buried frogs up in dry times, squeezed out a fresh drink and let them go unharmed.

Which TV network used Michigan J. Frog as its mascot from 1995 to 2005?

The WB took Michigan J. Frog, the singing star of a 1955 Chuck Jones cartoon, as its mascot at launch; in 2005 its chairman declared 'the frog is dead and buried' because he made the network look too young.

In The Wind in the Willows, Mr. Toad becomes obsessed with what?

Motor cars hooked Toad the moment one ran his horse-drawn caravan into a ditch: he sat in the road murmuring 'Poop-poop!', went on to crash car after car and landed in prison for stealing one.

Which pop star recorded the 1984 hit 'We All Stand Together' with the Frog Chorus for a Rupert Bear cartoon?

Paul McCartney bought the film rights to Rupert Bear in 1970, the day after announcing he was leaving the Beatles, but the animated short this song comes from took until 1984 to appear.

In which 1995 Super Nintendo role-playing game is a cursed knight called Frog a playable hero?

Chrono Trigger's Frog was a human named Glenn until the wizard Magus killed his friend, the knight Cyrus, and cursed him into a frog's body; he fights on with the legendary sword Masamune.

In Super Mario Bros. 3, what does the Frog Suit mainly improve?

Underwater speed: the suit lets Mario swim fast and hold his own against currents, but back on dry land he can only hop about clumsily.

The three Battletoads heroes are named after what?

Rash, Zitz and Pimple are named after skin conditions — a rash, a zit and a pimple; Rare created the trio in 1991 to rival the Teenage Mutant Ninja Turtles games.

Sitting alone on a log in the swamp, Kermit opens The Muppet Movie singing 'Rainbow Connection' on which instrument?

The banjo scene was shot with Kermit's puppeteer sealed in a metal tank sunk beneath the swamp water, working the frog through a rubber sleeve and breathing through an air hose.

Three Dog Night's 'Joy to the World' opens with a bullfrog that shares its name with which Old Testament prophet?

Jeremiah was a bullfrog only because Hoyt Axton needed placeholder nonsense to pitch the melody; Three Dog Night took it to the top of the charts.

Guenther's marsupial frog alone has regained what feature, lost by frogs over 200 million years ago?

True teeth in its lower jaw came back after frogs had gone without them for more than 200 million years, a rare breach of Dollo's law, the rule that evolution never rebuilds a complex trait once it is lost.

Which Shakespeare play's witches drop 'eye of newt and toe of frog' into their cauldron?

Macbeth's three witches start the pot with a toad that has sweated venom under a cold stone for thirty-one days, chanting 'Double, double, toil and trouble' as they stir.

In Aesop's fable, a frog bursts while trying to puff itself up as big as which animal?

An ox: in most tellings the frog keeps swelling and asking 'Was it as big as this?' until it bursts, and Roman poets such as Horace borrowed the fable to mock people living beyond their station.

Which West Coast frog's call became the stock 'ribbit' of Hollywood film soundtracks?

The Pacific tree frog's two-part call was dubbed into so many films as night-time background that 'ribbit' became the frog sound everywhere; the Los Angeles frogs are now often split off as a species with the same call.

In 2019, scientists found that pumpkin toadlets glow under UV light because of what?

Fluorescent skeletons: bony plates in the head and back shine through unusually thin skin; the toadlets cannot hear their own calls, so the glow may be a signal to each other, though that is unproven.

Why is South America's Pseudis paradoxa called the 'shrinking frog'?

Its tadpole is far larger than the adult: up to 27 cm long, it becomes a frog only a quarter to a third of that length, perhaps because the tadpole stays under growth hormones for unusually long.

What dried up the waterfall mist that Tanzania's Kihansi spray toad lived in?

A hydroelectric dam cut the flow over the falls by 90 percent and the toad went extinct in the wild; it survives because zoos in the Bronx and Toledo learned to breed the few hundred rescued in time.

Costa Rica's golden toad, last seen in 1989, lived only in which cloud forest reserve?

Monteverde's golden toads still gathered by the hundred at rain pools in the spring of 1987; two years later searchers found a single male, and none has been seen since.

In Aesop's fable of the frogs who asked for a king, what does Zeus first drop into their pond?

A log: once the splash died down the frogs sat on King Log and jeered at him, so they begged for a real ruler and were sent one that ate them, a water snake in the oldest version.

Gardiner's Seychelles frog, which lacks a middle ear, hears using which body part?

Its mouth cavity: a 2013 X-ray study found that the mouth works as a resonator and bone carries the sound on to the inner ear, letting the 11 mm frog hear without a middle ear.

The Bornean flat-headed frog was long believed to be the only frog lacking what?

Lungs: researchers who dissected the frog in 2008 found none and announced the first lungless frog, but micro-CT scans later showed it has lungs after all, and the paper was retracted in 2024.

Which chocolate maker has sold Freddo, the frog created in Melbourne in 1930, since buying its inventor's firm in 1967?

Cadbury inherited Freddo when it bought MacRobertson's; the frog exists because 18-year-old Harry Melbourne talked the firm out of a chocolate mouse, arguing that women and children were scared of mice.

The mink frog of North America's northern lakes gets its name from what?

Its musky smell: handle or frighten the frog and its skin gives off an odour like a mink's, though people who have never met a mink say it is closer to rotting onions.

In English, 'frog' became a derogatory nickname for people of which nationality, thanks to a famous dish?

The French were 'frog-eaters' in English by the 1760s, after their taste for cuisses de grenouille; a century before, a 'frog' could just as well mean a Dutchman, a dig at his marshy country.

A frog regularly sheds its outer skin; what does it usually do with the old layer?

A frog eats it within moments: the skin splits down the back and the underside, the frog pulls its limbs free and works the loose slough forward to gulp it down.

Where is a frog's tongue attached to its jaw?

At the front: the tongue lies folded with its free end pointing down the throat, so it can be flipped out and pulled back at great speed with prey stuck to it.

Which transparent layer does a frog draw across each eye for protection while it is swimming?

The nictitating membrane takes its name from the Latin for 'to blink'. Because it is see-through, a frog can shield and moisten its eye without losing sight of prey or danger.

In a frog's digestive system, which large organ makes the bile that is stored in the gallbladder?

The liver makes bile, which waits in the gallbladder until a meal leaves the stomach, then joins pancreatic juice to digest the food so that the nutrients can be absorbed.

Across frog species, the amount of webbing between the toes mainly reflects what about its lifestyle?

Time in water decides it: fully aquatic African dwarf frogs have completely webbed toes, while White's tree frog, a climber, is only a quarter to half webbed.

A frog's three-chambered heart has two atria but only one of which chamber, where the blood streams meet?

The ventricle is single in frogs, a layout they share with lizards. Oxygen-rich and oxygen-poor blood arrive through separate atria, then a spiral valve steers each stream to the correct vessel.

Which part of a frog's brain keeps its jumps on target by controlling muscular coordination and posture?

The cerebellum handles coordination and posture. A frog's brain has many of the same parts as a human's, though its cerebrum is relatively far smaller.

Which single opening at a frog's rear end serves for waste, urine, eggs and sperm alike?

The cloaca takes its name from the Latin for a sewer or drain. Birds and reptiles share the arrangement, whereas most placental mammals have separate openings for each job.

In a frog's skeleton, the tail vertebrae are fused into which single rod tucked inside the pelvis?

The urostyle lets a frog pass force from its legs to its body during a leap. It forms from the base of the tail as a tadpole turns into an adult.

For jumping strength, which two leg bones, separate in humans, are fused into one in a frog?

The tibia and fibula form one strong bone in a frog's leg. The forearm bones are fused in the same way, because the front limbs must absorb the impact of every landing.

The swellings on a toad's neck and shoulders that ooze milky toxins to deter predators have which name?

Parotoid glands are healthy organs, but their lumpy look is the reason behind the mistaken belief that touching a toad gives you warts.

Which part of a frog's brain regulates breathing, digestion and other automatic body functions?

The medulla oblongata runs the automatic jobs. Ten pairs of cranial nerves feed a frog's brain directly, two fewer than mammals, birds and reptiles have.

Otto Loewi's 1921 experiment on two beating frog hearts revealed which chemical messenger of the nerves?

Acetylcholine was first named Vagusstoff, after the vagus nerve. Fluid from a heart slowed by that nerve also slowed another heart, proving that nerves signal with chemicals.

A frog's light-sensing 'third eye', found by Nils Holmgren in 1918, is linked to which part of the brain?

The pineal body regulates daily rhythms, and the spot above it carries sensory cells that look like the cone cells of a retina. Tuataras and most lizards have one too.

Which fish-like sense organ lets tadpoles feel ripples and currents but is lost in land-living adult frogs?

The lateral line detects vibration and pressure changes in water, so it is useless in air. Fully aquatic frogs such as Xenopus keep theirs for life, visible as a stitch-like pattern.

What are the rough swellings that a male frog grows on his thumbs each breeding season to hold a partner?

Nuptial pads swell and gain pigment as the breeding season starts, giving the male a firm hold on his partner. They are one of the easiest ways to tell the sexes apart.

Unlike the red blood cells of humans and other mammals, a frog's red blood cells keep which structure?

A nucleus stays in the red cells of nearly all vertebrates except mammals, whose cells push theirs out as they mature to leave more room for haemoglobin.

Which pigment-containing cells in a frog's skin expand or contract to change its shade between night and day?

Chromatophores produce the pigment of frogs, fish, reptiles and cephalopods such as squid. Mammals and birds rely instead on a different class of cell, the melanocyte.

The word 'tadpole' comes from two Middle English words that together meant what?

Toad head is the literal meaning, from tadde and pol. Polliwog was built the same way, joining the word for a head to one meaning to wiggle.

As a tadpole grows into a frog, which of these does it develop first?

Back legs come first. The front pair grow hidden inside the gill pouch and only show once the pouch disappears, which is why they seem to arrive so suddenly.

A frog's egg has no shell; each one is instead wrapped in a protective coat of what?

Jelly does more than protect: the inside of a globular egg cluster has been measured up to 6 °C warmer than the surrounding water, which speeds up the growth of the young.

Common frogs lay their eggs in clumps; in what form does the common toad lay its eggs?

Long double strings, each 3 to 4.5 metres from end to end and holding 1,500 to 6,000 small black eggs, get tangled round plant stalks as the pair wander the shallows.

As a tadpole turns into a frog, which digestive organ is rebuilt far shorter?

The intestine of a tadpole is a long spiral suited to a diet of plants; a meat-eating frog needs far less gut, so it is rebuilt much shorter during the change.

Most frogs release eggs and sperm into the water at the same moment, a method known by what name?

External fertilisation is the rule in frogs: the male has no penis, so he sheds sperm straight onto the eggs as the female lays them.

Which feature, missing in tadpoles, do a frog's eyes gain as it takes on its adult form?

Eyelids and their glands form only during the change. The eyes also shift higher up the skull, letting a submerged frog keep watch with little more than its eyes showing.

Which process of controlled cell death removes the fins and other tadpole organs an adult frog no longer needs?

Apoptosis is cell death on command: once a tadpole's swimming and feeding gear is redundant, the cells dismantle themselves and the body recycles the material.

Some frogs hatch from the egg as tiny adults, skipping the free-swimming tadpole stage; what is this called?

Direct development means the whole tadpole phase is completed inside the egg. Every species of the genus Eleutherodactylus does it, which may explain the group's success.

Which small opening lets the water that a tadpole has passed over its internal gills flow back out?

The spiracle vents the chamber that skin forms over the gills in a tadpole's first days. Depending on the species there may be one on the left side, one underneath or a pair.

Which toad of North America's deserts can go from laid egg to tiny toadlet in as little as nine days?

Couch's spadefoot breeds in pools left by summer thunderstorms, so its young must be out before the puddle dries. The sun-warmed water speeds their growth.

Which British biologist won a Nobel Prize for cloning a frog from the cell nuclei of a tadpole?

John Gurdon did it at Oxford in 1958, showing that a specialised cell still carries the instructions for a whole animal. The Nobel came in 2012, shared with Shinya Yamanaka.

The dark upper half of a frog's egg is called the animal hemisphere; what is the pale, yolky lower half named?

The vegetal pole holds large, yolky cells that divide very slowly. The dark top divides fast, and the spot where the sperm enters it decides which side becomes the frog's back.

After repeated cell divisions, a frog embryo becomes a hollow ball of cells known by which name?

The blastula is a hollow sphere of cells around a fluid-filled space. In the next stage, gastrulation, cells move inward to form the three layers from which all the frog's organs are built.

A tadpole feeds with a horny beak and rows of tiny scrapers made of which tough material?

Keratin forms rows of tiny scrapers called keradonts, and because their number and layout differ from one species to the next, biologists use them to identify tadpoles.

A tadpole's swimming tail has almost no bone or cartilage; which flexible rod stiffens it instead?

The notochord is all the support the tail gets, apart from a few vertebrae at its base that later become part of the adult skeleton.

The oldest known fossil tadpole, a 2024 find of the species Notobatrachus degiustoi, lived during which period?

The Jurassic tadpole, some 161 to 168 million years old, already filter-fed like many modern ones. Its adults were among the largest known frogs of the age of dinosaurs.

Tadpoles excrete waste nitrogen as ammonia; most land-living adult frogs switch to which less toxic compound?

Urea is the less toxic choice for life out of the water. A few tree frogs with little access to water go a step further and excrete uric acid.

Frog embryos can sense the vibrations of an attacking snake or wasp and respond by doing what?

Hatching early lets the young escape being eaten. Left alone, an egg laid in water normally hatches within a week, when enzymes released by the larva split the capsule.

To help control its temperature, a frog's skin typically turns which way in cool, damp weather?

Darker is the cool-weather setting, because frogs use the shade of their skin to regulate temperature. One tree frog, Chiromantis xerampelina, can even turn white to avoid overheating.

Extra legs on a wild frog can be caused by which parasite digging into the tadpole's limb buds?

A flatworm called Ribeiroia ondatrae digs into the rear of a tadpole and scrambles the limb bud cells. Losing a leg bud to a dragonfly nymph can instead leave a frog with three.

In a male frog, semen from the testes passes through which paired organs on its way out?

The kidneys also serve as plumbing in a male frog: the testes are attached to them, and semen travels through them and on down the same ducts that carry urine.