Amphibians are an odd group of animals. They were the first vertebrates or animals with backbones to climb out of the water and live on land for part of their life cycles. They also never left the water.
Whether the amphibians are frogs, salamanders, or caecilians, they make the most of where water and land meet. Some amphibians look like what you expect and have predictable, carnivorous lifestyles. Others look like dinosaurs or leaves and have unique adaptations.
Here is a guide on the biology and ecology shared among amphibians and a survey of 30+ species spread across six continents.
What are Amphibians
Amphibians spend their youth with gills living in the water and then live as adults with air-breathing skin on land. They earned the name “amphibian,” from the Greek “amphibios,” meaning “double life.”
Like fish and reptiles, they are cold-blooded and need the environment to warm them. Unlike fish and reptiles, amphibians lack scales. They have bare, moist skin with glands that produce mucus that coats the skin. Some species shed their skin.
Amphibian Biology
Amphibians perceive the world with the same five senses that humans do. Besides sight, sound, touch, smell, and taste, some amphibians have other senses. They may detect geomagnetic fields and infrared and ultraviolet light.
Glands lie beneath the skin. These glands in some species release a substance that tastes bad to predators.
In other species and specific locations, neurotoxins pass through the skin. These locations are:
- Frogs: on the back
- Toads: behind the ears
- Salamanders: behind the eyes
- Caecilians: upper surface
Evolution of Amphibians
Amphibians have something interesting in common with humans: juvenilization.
This process is when an animal favors maintaining juvenile body traits over its adult counterparts. Juvenilization also comes with slower growth and development rates.
Humans kept larger heads. Amphibians retained fewer and smaller bones. Some larger salamander species didn’t metamorphose. They had their childhood feathery gills and didn’t use lungs or breathe through their skin.
Amphibian Life Cycle
Early Life
Most amphibians breed in the spring and lay gooey eggs, called spawn, among aquatic plants. These plants protect the eggs until the young, also known as larvae, hatch. Since the larvae breathe through gills, they need to be in the water when they hatch.
Many amphibian parents guard the eggs. Father frogs and toads protect their nests, and mother salamanders, newts, and caecilians do the protecting. Some species employ both parents while others don’t bother.
Reproduction
Yet, some amphibians don’t lay eggs or are oviparous. Instead, they retain the eggs until they hatch or metamorphose into miniature adults. Live birth is called viviparous. Live birthing occurs in half of the caecilians, occasionally in salamanders, and rarely in frogs.
As the young grow, their feathery gills and tails will shrink while their legs and often lungs develop. The animal will slowly spend more time exploring the land.
When this metamorphosis or transition is complete, they will live in damp habitats on land but breed in the water. But there are exceptions favoring water and other dry habitats.
Amphibian Ecology
Food and Water
Adult amphibians are carnivores. The smaller ones eat aquatic insects, spiders, worms, and other amphibian larvae. Yet larger adult frogs and toads may hunt small vertebrates like rodents, birds, and lizards. Larvae tend to be herbivores.
Their permeable skin not only lets oxygen pass so the animal can breathe. It also lets water through so the animal can drink.
Adaptations
Amphibians live on six continents, the exception being Antarctica. As a rule, amphibians don’t tolerate extreme cold, dry heat, wind, or saltwater. These conditions dry their skin. So they also haven’t colonized oceanic islands, interior deserts, or exposed landforms.
When amphibians do get cold, they hibernate. They dive underwater into the mud, or if on land, they will wedge between rocks or logs. As cold-blooded or ectotherm animals, amphibians also need to regulate their temperature. To cool, they swim, and to warm, they sunbathe.
Conservation
Environmental contamination is detrimental to amphibians. They breathe through their skin and need constant access to clean water. So when toxins end up in the water, they “breathe” it in.
Amphibians are seeing a significant die-off. In part, this comes from herbicides upstream from their habitat. But a fungal disease has also spread in Central and South America.
Chytridiomycosis
Chytridiomycosis is a worldwide infection caused by Batrachochytrium dendrobatidis. For short, scientists call it chytrid or Bd. The disease infects one-third of amphibian species and has been detrimental to several hundred species.
Chytrid has been around for a long time, but the fungus has spread across the globe. This spread happened because of a new strain developing in the 20th century and the commercial trade of amphibians.
The disease attacks skin tissue with keratin. Larvae lack keratin except around the mouth, but adult amphibians have keratin throughout. The fungal spores then attach to the keratin and thicken it.
Because amphibians breathe and drink through their skin, thickened skin causes problems. It blocks oxygen and electrolytes from reaching their blood. If the animal gets sick enough, it has a heart attack and dies.
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Types of Amphibians
Amphibians fall into three classifications called orders.
- Anura: Frogs and Toads
- Urodela: Salamanders and Newts
- Gymnophiona: The relatively unknown snake-like caecilians
These orders together have 73 families and 7,292 species. About 90 percent of these species are frogs.
Anura
The name “anura” refers to the Greek “an-” for “without” and “oura” meaning “tail.” Which, when you think about a frog, sounds suitable.
The largest frog is the Goliath frog (Conraua goliath) and grows to 32 cm (12 inches) and 3 kg (6.6 lbs). The smallest amphibian is also a frog, Paedophryne amauensis,at 7.7 mm (0.3 inch).
What Defines a Frog
Frogs and toads have distinctive shapes. They have wide, flat heads with large eyes. Their broad bodies have short forelegs and long, folded back legs built for jumping. Often their toes have stick bulbs at the ends and webbing between each toe.
Though they have no claws and toads have no teeth, frogs have a top row of teeth. Another difference is that frogs have smooth skin, and toads have “warty” skin, though there are some exceptions.
Frogs and toads have adapted to living on trees, in water, or underground in different kinds of ecosystems from deserts to tropical rainforests. They have radiated and diversified far more than other amphibians. Despite that adaptability, 75 percent stick to tropical rainforests.
Urodela
Sometimes scientists call salamanders Order Caudata, where the Greek “cauda” means “tail.” Scientists also use Order Urodela, which has French influence from the Greek “oura” for “tail” and “delos” for “evident.”
The largest salamander is also the largest amphibian. It is the Chinese giant salamander (Andrias davidianus) at 1.8 m (5’-10”0) from nose to tail and weighing 11.3 kg (24.9 lbs). The smallest salamander is the arboreal minute salamander (Thorius arboreus) at 15 mm (0.6 inches).
What Defines a Salamander
Salamanders contrast to frogs and toads. Salamanders have long backs and narrow torsos. They have long tails, and their small legs prop out to the side. Though they are amphibians, they resemble lizards.
Newts are a strictly aquatic category of salamander. To help with swimming, newts have rudder-like flattened tails.
Salamanders, like frogs, lack claws and tend to have smooth skin. Unlike frogs, salamanders live in damp habitats in the northern hemisphere instead of the tropics. And many of the species in the tropics are descended from migrants from the north.
Salamanders spend much of their lives and sometimes all underwater. When on land, they seek shelter under rocks and logs during the day and hunt small invertebrates at night.
Gymnophiona
Caecilians are the amphibians that most of us have never heard of. They look like oversized worms, lacking any appendages. They use their torso muscles and folded skin with belly scales to haul along the surfaces. Yet, they are amphibians.
The order’s name comes from the Greek “gymnos” meaning “naked” and “ophis” for “serpent”.
The largest caecilian is the Thompson’s caecilian (Caecilia thompsoni) at 1.5 m (4’-11”). The smallest caecilian is Grandisonia brevis at 11.2 cm (4.4 inches).
What Defines a Caecilian
Like mammals with their whiskers, caecilians have extensions on their faces to feel their environment. These extensions are fleshy, with one on each side between the eye and nostril. They smell for prey.
As fitting for wormlike creatures, caecilians mostly live underground. They love the moist soil, rotting wood, and plant debris of forest floors. Some also live in water.
Unlike salamanders, caecilians mostly live in the southern continents around the equator.
What Makes Caecilians Oddities in the Animal Kingdom
Many caecilians give birth to live young. The larvae have jaws with teeth that scratch a milky substance from the mother’s uterus for nutrition.
Caecilians survive on egg yolk before being born, and they mature after three years. They breed similarly to mammals, particularly marsupials. Both have a cloaca, a cavity used for reproduction, urination, and defecation.
Those who lay eggs will deposit them in a sheltered area near the water. Some will nestle with the eggs, and the young will develop into miniature metamorphosed adults before hatching. When the young hatch, as larvae or adults, they travel to the water by themselves.
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Amphibians of Africa
1. Algerian ribbed newt (Pleurodeles nebulosus)
The Algerian ribbed newt (Pleurodeles nebulosus) is among the few salamander species in Africa. As its name suggests, it lives in northeastern Algeria, though also western Tunisia.
It grows to 23 cm (9.0”) long from nose to tail. It has a flattened skull and body but a rounded nose. During the breeding season, the tails grow fins.
Algerian ribbed newts reside in rivers, swamps, ponds, and drainage areas. It lives where it can find enough water for breeding and feeding. Their gray, green, and brown colors help them blend into their surroundings.
2. Lake Tanganyika caecilian (Scolecomorphus kirkii)
The Lake Tanganyika caecilian (Scolecomporphous kirkii) grows to 21.5–46.3 cm (8.4”- 18”) long and has 130–150 folded rings along that length. They have a gray-lavender color, darker on top, lighter below, and the light becoming cream-colored by the mouth.
The tentacles extend below, and the eyes are visible in the base of the tentacles.
Like its namesake, this caecilian resides in eastern Africa, including Tanzania. It also lives around Lake Malawi and farther south in Malawi and Mozambique.
These areas are rainforest, agricultural, and mountainous. Either way, the caecilian goes about life under loose materials on the surface.
This species gives birth to live young, burrows and eats arthropods like insects and spiders. Snakes have been found in the region with caecilians in their stomachs.
While, in general, we know little about how caecilians live, it doesn’t mean they are rare. This species is abundant in its home region.
3. Western clawed frog (Xenopus tropicalis)
The Western clawed frog (Xenopus tropicalis) has extraordinarily thick legs and waist compared to its head. It grows from nose to rump or “snout-vent” between 3.8 cm and 5.5 cm (1.4”-2.1”) and has notable black claws on its hind webbed feet. They tend to be dirty orange to gray.
It prefers tropical rainforests, savannas, wetlands, and even agricultural ponds. The frogs range across western central Africa from Cameroon to Senegal.
During the dry season, western clawed frogs stay close to streams. There they can hide among roots, logs, and rocks. Then in the rainy season, they wander across the forest for new water habitats. In any season, the frog eats worms, insects, and tadpoles.
Mothers lay eggs among vegetation, and the eggs often stick to the plant. Tadpoles will eat zooplankton, filtering them through tissue in their mouth rather than eating with teeth.
4. Kihansi spray toad (Nectophrynoides asperginis)
The Kihansi spray toad (Nectophrynoides asperginis) comes from Tanzania and is one of the few frogs that give live birth. It grows to 2–3 cm (0.7-1.1”) and has a golden-orange color.
When the toad still had its natural habitat, it lived only on a few acres at the Kihansi River waterfall deep in a gorge. It had access to constant water spray and rocky outcrops with vegetation like grass, moss, and ferns.
Kihansi toads no longer survive in the wild. They had a population peak in 1999, people built a dam upstream, and the toad population crashed by 2004. But private collections still raise them. These institutions have to mimic this specific environment.
They need internal fertilization, and you can see larvae inside the females because of the toad’s translucent skin. When ready, the mother births 5-13 larvae.
5. Malagasy rainbow frog (Scaphiophryne gottlebei)
The Malagasy rainbow frog (Scaphiophryne gottlebei) is a species with black, white, orange, and green colors. They reach 2–4 cm (0.7-1.2”) from nose to rump and were popular for the pet trade, but now it’s endangered.
Malagasy rainbow frogs like various lifestyles and live burrowing underground or climbing trees. They live on Isalo Massif in altitudes between 700 m and 1,000 m (2,296-3,280 ft). In that area, the frog will live in narrow canyons and the sandy banks at the base of the streams that form these canyons.
As tadpoles, this species filter feeds dead tissue and plankton. Before growing up, some will get washed downstream by a storm from where they hatched.
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Amphibians of Asia
6. Hula painted frog (Latonia nigriventer)
The Hula painted frog (Latonia nigriventer) of Israel was thought to be extinct in the 1950s, but scientists rediscovered it in 2011. Four individuals were found in the 40s and one in the 50s, so it was always a rare find. Today, about a dozen have been found in a 1.25-hectare area.
The region drained the wetlands in the 50s to temper malaria cases and add more farming land. Surviving frogs live in the remaining wetland that’s now a designated conservation area. A few others were found in other parts of the Hula Valley, and the range might extend into Syria.
This species also belongs to a frog family that diverged from other amphibians in the Jurassic Period and has few close modern relatives. For comparison, humans diverged from marsupials like kangaroos that far back.
Hula painted frogs grow 4–13 cm (1.5-5cm). They often have some orange blotches, but some are mostly black.
7. Chinese giant salamander (Andrias davidianus)
The Chinese giant salamander (Andrias davidianus) is the largest amphibian in the world. It grows over 1.0 m long (3 ft) from nose to tail and is 11 kg (24 lbs). The tail makes up almost 60 percent of the body length. One of the largest specimens collected was 1.8 m (5’-10”) long.
They have puny eyes and chubby, flat bodies with a fin going down the back. As creatures of rivers, their skin has a rocky, marbled texture and a mostly dark, grayish color.
Giant salamanders love temperate mountain waters. They stick to fast, meter-deep water where they can hide in vegetation and crevices big enough for them.
Like reptiles of similar size, giant salamanders take many years to reach maturity and live for decades. On average, they change from larvae to adult in three years and reach sexual maturity in seven years.
Giant salamanders breed every year, grow all their lives, and die after 60 years. The males “sand-push,” where they spend a week clearing their den to attract a female.
8. Oriental fire-bellied toad (Bombina orientalis)
The Oriental fire-bellied toad (Bombina orientalis) prefers in the calm water of temperate forests. It lives in northeastern China, Korea, Japan, and even northeastern Russia.
They are common throughout their range, and people find they make easy pets. Scientists also like to study them for their unusual vocalizations and learning abilities. Most frogs croak through vibrating instruments like eardrums or resonators. But this species does it by inhaling.
Like other colorful frogs and toads, they have bright colors to warn of their toxicity. But in their case, they need to show their stomachs to show those colors. They have orange or red bellies with black spots, but the rest of their bodies are dark green.
This species is a frog but gets referred to as a toad because of its subdued body color. It grows 3.8–5.1 cm (1.5-2.0 inches).
9. Common yellow-banded or Ceylon caecilian (Ichthyophis glutinosus)
The common yellow-banded caecilian (Ichthyophis glutinosus) is the most-studied egg-laying caecilian. They grow to 23–41 cm (9-16 inches) and have 340–390 folded rings along that length.
Like many caecilians, this species is a dark purplish-gray on top. But for the belly, it has a bright yellow. Also known as the Ceylon caecilian, and as indicated by that, this species lives on the island once known as Ceylon, now called Sri Lanka.
It lives in swamps and on mountainous rainforests and farmland. Specifically, it likes decomposing materials like compost, organic-rich and moist soils, and manure.
Ceylon caecilians eat worms and occasionally other animals of similar size. It will twist and back up to split their prey.
Mothers lay 30 eggs at a time and huddle around until they hatch. When they hatch, larvae are 8–11 cm long. They will reach maturity after 280 days.
10. Crab-eating frog (Fejervarya cancrivora)
The crab-eating frog (Fejervarya cancrivora) is green to brown and gray with large eyes. It grows between 8.0 cm and 10.7 cm, (3.0-4.2 inches) with females larger than males.
This species prefers coastal wetlands like marshes, mangroves, and rice paddies. It is a rare example of a frog that tolerates brackish, or part fresh and part sea, water.
In their brackish habitats, the frog will eat crustaceans like crabs. But when they live in freshwater ecosystems, they target insects.
Crab-eating frogs live in southern Thailand and neighboring countries like Malaysia and Borneo. Sometimes people local to these regions catch and eat the frogs.
Amphibians of Australia
11. Turtle frog (Myobatrachus gouldii)
The turtle frog (Myobatrachus gouldii) has an odd body shape for a frog. It has a narrow head but a broad body like a turtle. Even its legs share the heavy-set look of a turtle.
Turtle frogs like to burrow up to 1.2 m (3ft-11”) into the sands of Western Australia’s deserts. The species grows to 5 cm (1.9 inches) and has a pink to brown color.
Because of the unpredictable moisture in the desert, turtle frogs time their mating to when the rain comes. They share the burrow for months before they mate and lay eggs.
The eggs are large for frogs, measuring 7.5 mm across. The young metamorphose inside the eggs and hatch as frogs. This transition and not needing standing water for reproduction are rare in frogs.
12. Hamilton’s frog (Leiopelma hamiltoni)
The Hamilton’s frog (Leiopelma hamiltoni) is a surviving member of a primitive frog family in New Zealand. They grow 4.3–5.2 cm (1.6-2.0 inches), lack webbing between their toes, and tend to have light and dark brown patterns.
Hamilton’s frog lives in rocky and mossy zones on the small Stephens Island between New Zealand’s North and South main islands. This species and others survive on such islands because invasive mammals haven’t had a chance to take over.
The young hatch as miniature frogs and climb onto the father frog, who stays close to eggs and hatchlings. Adults and the young eat insects like springtails and flies. The tuatara, a native lizard that survives from a Triassic lineage 250 million years ago, hunts this frog.
13. Paedophryne amauensis
The Paedophryne amauensis is the smallest amphibian and lacks a common name. It grows 7–8 mm from nose to rear, has a wide head, and short snout. For color, it has bronze with black splotches and white flecks.
Scientists know little about the frog. They discovered it in 2012 among damp leaf litter in central Papua New Guinea. Only males have been found and described for samples.
P. amauensis are crepuscular or active at dawn and dusk. Researchers have caught the males because they sing during their active hours to attract mates. The voice has a high pitch, lasts for minutes, and cycles after 3–41 seconds for a break.
As tiny as they are, the food that frogs usually eat can eat P. amauensis. They avoid lowland and water habitats, which have more biodiversity and predators.
14. Pouched frog (Assa darlingtoni)
The pouched frog (Assa darlingtoni) is a species where the father carries his tadpoles in a pouch until they metamorphose. It also crawls instead of hops in its habitat.
Pouched frogs live in southeastern Australia. They prefer moist hideouts under logs and rocks in rainforests and the sclerophyll forests. Sclerophylls are a hard-leafed type of tree. They are common in chaparral regions like southern California, the Mediterranean, and Australia.
They grow to 2.5 cm (.09”) long and have a red and brown color with a lighter tone for their side stripes. Both parents guard the eggs until they hatch and move into the father’s pouch.
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Amphibians of Europe
15. Danube crested newt (Triturus dobrogicus)
The Danube crested newt (Triturus dobrogicus) looks like a cross between a creature from the Age of the Dinosaurs and a fish. An adult male has a sail on its back and tail and mottling of various colors with black and white spots. The young look more like standard dark salamanders.
This species lives in central and eastern Europe in the Danube river and its tributaries. The newt favors calm water for breeding where the males use their sails for a courtship dance. Females lay eggs on aquatic plants.
The larvae will also grow up in this environment and reach 13–15 cm (5.1-5.9 inches). But adults return to shady land habitats like rocks, abandoned burrows, and forests.
16. Western spadefoot (Pelobates cultripes)
The western spadefoot (Pelobates cultripes) is a vocal frog that will enlarge and squeal at animals that threaten it. It looks gold-gray with black blotches, including spade-shaped ones, and grows to 12 cm (4.7 inches) and can live 10–15 years.
The toad lives in southwestern Europe, namely Portugal, Spain, and France.
It favors sandy soil and adapts well to the north and southern latitudes and lower and higher altitudes. Individuals up north may hibernate, while those in the south might estivate or hibernate in the summer to avoid heat.
17. Fire salamander (Salamandra salamandra)
The fire salamander (Salamandra salamandra) resembles a wet ember. Black patches mix with bright red or yellow ones. Like with frogs, this bright coloration means the amphibian is poisonous. The alkaloid toxin called samandarin causes convulsions and high blood pressure.
Fire salamanders grow to 15–25 cm (5.9-9.8 inches) from nose to tail tip. They live in deciduous forests in the hills of central Europe. There, the salamanders hide under fallen leaves and among protected moss when they aren’t in a stream. They also tolerate elevations up to 1,000 m (3,280 ft).
18. Common midwife toad (Alytes obstetricans)
The common midwife toad (Alytes obstetricans) is a species where the father carries eggs around his legs. He dips them in water for moisture until ready to hatch. He gets the eggs by squeezing the female during mating, the jelly string attaches to him, and he fertilizes them.
This midwife toad lives in western Europe. It’s not picky about habitat and will inhabit forests, lakes, rivers, shrublands, deserts, pastures, and cities. It also lives in low elevations and those up to 2,400 m (7874 ft)
Midwife toads resort to many defensive mechanisms when they feel threatened. They will buff up to look big or extend their legs to look taller. They grow to 5.5 cm (2.1 inches) and have a light silver-gold color.
19. Olm or proteus (Proteus anguinus)
The olm or proteus (Proteus anguinus) is one of the few salamanders that will breed in a juvenile state if conditions are poor enough. They can also live longer than any amphibian, often reaching 70 years in captivity.
Olms have an impressive yellow and pink color on their lanky bodies and long faces. If you imagine how East Asian countries depict dragons, olms fit that well. Yet they only grow to 25 cm (9.8 inches).
This salamander lives around the Adriatic Sea in countries like Italy and Croatia. It prefers underground freshwater like that in karst or limestone caves. The water here is calm, at a constant cool temperature, and has high oxygen concentration.
Olms will find cave insects, mollusks, and shrimp-like amphipods to live off. They catch them using their extra-sensitive senses that compensate for the lack of visibility in caves.
The cooler the temperature, the longer eggs take to hatch and larvae to mature. Even as adults, olms have a slower metabolism and lower oxygen use that befits the cold, cavernous habitat.
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Amphibians of North America
20. Three-toed amphiuma (Amphiuma tridactylum)
The three-toed amphiuma (Amphiuma tridactylum) belongs to an eel-like category of salamanders. They are exclusive to the wetlands of the U.S.’s Deep South. The three amphibians each have a set number of toes and are named for that distinction.
This dark gray animal has an exaggerated long body and small, vestigial legs compared to other salamanders. The largest specimen grew to 1.06 m (3’-6”), but 45.7–76.0 cm (17-29 inches) is the standard size range. Even in adulthood, they keep gills.
Amphiumas live at wetland bottoms. Sometimes they reside in hillside creeks, but usually, they prefer the stale water of bayous, lakes, and marshes. They hunt at night and eat the typical amphibian diet of worms and small varieties of fish, crustaceans, and insects.
21. Mexican burrowing caecilian (Dermophis mexicanus)
The Mexican burrowing caecilian (Dermophis mexicanus) reaches 60 cm (23.6 inches). The Guatemalan variety grows larger than the Pacific. It’s dark gray with a pale gray body and has 110 annuli or skin ring folds.
This species also has secondary annuli, which not all caecilians have. It has between 35 and 85 secondary annuli. The tentacles protrude from each side, between an eye and a nostril.
Despite often being called the “Mexican” burrowing caecilian, it also lives elsewhere. It inhabits other Central American countries like Guatemala, Honduras, and Nicaragua.
It likes both lowlands and mountains. Because the highlands run like a spine down the region, the same species evolved different lengths on either side of the mountains.
The Mexican burrowing caecilian spends much time in shallow, loose soil burrows and creating burrows. But it scouts for ambush sites from on top of the forest debris and will also surface during rain. Once it finds a good site, it waits for prey to come to it.
22. Axolotl (Ambystoma mexicanum)
The axolotl (Ambystoma mexicanum) is a well-known example of neoteny or juvenilization. This salamander has pronounced red, feathery gills all its life and grows to 30 cm. In the wild, it has a dark, gravelly color. But captive varieties are sometimes albino.
Axolotls live only in two lakes near Mexico City: Lake Chalco and Lake Xochimilco. The region drained and developed over other lakes centuries ago, and the issue persists in the modern lakes.
The area has many drainage channels, and the salamander will live in those. The water quality can be questionable in any of these locations.
They eat algae in all stages of life. But they will expand into aquatic insects as adults, especially during dry seasons. It is also only during dry periods that the juvenilized adult might transition into a true adult salamander to breed out of water.
23. Hellbender (Cryptobranchus alleganiensis)
The hellbender (Cryptobranchus alleganiensis) can be an alarming salamander to come across and has the name to match. It resembles a flat rock but with skinfolds that add a monstrous quality to the animal. Settlers thought it was a creature from the fires of hell, bent on returning.
Hellbenders are strictly aquatic and live in the central and eastern United States. One subspecies inhabits the Ozark Mountains of northern Arkansas and southern Missouri. The other subspecies live across the rest of the species range.
They are the largest salamanders on the continent. They grow between 30-74 cm (11.8-29 inches) from snout to tail tip and weigh 1.5–2.5 kg (3.3-5.5 lbs). Hellbenders have inhabited the waters in this region for 65 million years.
This species breathes through the folds in its skin and specializes in water that has enough dissolved oxygen. Lower temperatures and turbulent flow from large rocks hold more oxygen.
24. Greater siren (Siren lacertina)
The greater siren (Siren lacertina) belongs to a salamander group unique to North America. Sirens are long and juvenile ized, their gills intact and legs small. But amphibians, another North American group, also have these traits. Sirens, though, have lost their hind vestigial legs.
All three siren species live in the eastern United States. The greater siren prefers the coastal plains of the southeast. They grow between 18-97 cm (7-38 inches) and weigh anywhere from 55 g to 1 kg (1.9 oz-2.2lbs). Sirens have grayish tones of green and yellow.
Like fish, sirens have a lateral line organ or a line of pressure-sensitive tissue that can detect water flow. Scientists also speculate that sirens can sense electromagnetic fields.
25. Wood frog (Rana sylvatica)
The wood frog (Rana sylvatica) is known for the proteins in its blood that have anti-freeze traits. They grow between 5 cm and 7 cm nose to rump with females larger than males. This species can be light or dark brown with yellow or green tinges.
This frog lives from Alaska, across Canada, to the southern Appalachians. It tends to migrate between local formations for different seasons.
Compared to many amphibians, the wood frog likes uplands including bogs, damp ravines, and vernal pools. These pools are seasonal, yet this species requires them for breeding. It will retreat to the uplands during the winter.
Larvae will eat decomposing plants in the water. But adult frogs have that classic feeding behavior where they react to movement and launch their sticky tongues at small insects.
26. Cuban tree frog (Osteopilus septentrionalis)
The Cuban tree frog (Osteopilus septentrionalis) is a cannibalistic species. It grows between 5 cm and 12.7 cm and can be gold, green, gray, or brown. Depending on their environment, they will shift their color like a chameleon.
It originates from the Caribbean on islands such as Cuba, the Bahamas, and the Cayman Islands. But it has also invaded other islands and Florida.
Like many invasive species, it is successful because it has a flexible diet and habitat preference. They will live in cities, estuaries, and on farms.
Cuban tree frogs can be nuisances. Even in their native territories, they eat anything that can fit into their mouths, including smaller Cuban tree frogs. While they hunt, they will climb over utilities and can compromise them.
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Amphibians of South America
27. Nauta Mushroom-tongue Salamander (Bolitoglossa altamazonica)
The Nauta mushroom-tongue salamander (Bolitoglossa altamazonica) is a small, montane salamander. It has webbed feet and can appear from dark brown to a dull purple on the bottom and rusty orange on top.
Nauta mushroom-tongued salamanders live in dry sections of the Amazon Tropical Rainforest. They tolerate between 100-1500 m (328-492 ft) in elevation up against the east side of the Andes Mountains but prefer between 200-600 m (656-1968 ft).
The species ranges from Venezuela to Bolivia. In their local areas, they are common and crawl on low-lying vegetation.
28. Cane toad (Rhinella marina)
The cane toad (Rhinella marina) is most well known for its presence in Australia. But they originate from South America. This massive toad grows 10–15 cm (3.9-5.9 inches) long with the record reaching 24 cm and has a tan color.
It was introduced to Australia to outcompete resources against invasive, overpopulated hares. Instead, the cane toads became a new menace and remain so. The same error happened in various Oceania and Caribbean islands.
Cane toads resemble fossils found in Columbia dating from the late Miocene Epoch, which was 5–23 million years ago. Those specimens even shared the same open, coastal terrain modern cane toads like.
These toads have been successful across time and geographic regions. They achieve this by eating anything that will fit into their mouths, even dead animals. They also breed like the hares. For good measure, they have poison glands to protect them from predators.
29. Dyeing poison dart frog (Dendrobates tinctorius)
The dyeing poison dart frog (Dendrobates tinctorius) is born on the rainforest floor. Then carried on a parent’s back to the canopy to drop off the tadpoles in the water pools of leaf junctions in rosettes and bromeliads. They grow to 5 cm and have rich yellow and blue with black colors.
These large plants provide sheltered water until the tadpoles grow up. For food, the mother will lay unfertilized eggs into the pools for the tadpoles.
The species lives in northern South America along a bedrock formation called the Guiana Shield. This region covers forests from Venezuela to Brazil.
Bright colors show that the frog is poisonous. If a predator eats it, the predator will discover a bad taste, pain, and muscle spasms. People who handle these frogs will also develop symptoms by touching the skin.
30. Cayenne caecilian (Typhlonectes compressicauda)
The Cayenne caecilian (Typhlonectes compressicauda) is a large caecilian of 52 cm (20.4 inches) with 85 skinfold rings. Toward the back, the body flattens and has a length-wise bottom ridge, like what ships have. They also have four rows of teeth.
Gills on larvae fit on top rather than on the sides but only last for a few days after birth. The larvae eat insects, worms, frog eggs, and tadpoles. Adults will also eat dead fish and shrimp.
This caecilian lives along the northern arc of South America from Peru to French Guiana to Brazil. It likes pushing itself into barely submerged mud in swamps and river banks. When they hunt, they sway side to side like snakes.
Unusual among caecilians, the Cayenne caecilian has two lungs and a tracheal or throat lung. As a mud dweller, it might encounter low-oxygen and high-carbon situations. So this creature also has a high concentration of hemoglobin compared to other amphibians.
31. Túngara frog (Engystomops pustulosus)
The Túngara frog (Engystomops pustulosus) is the only amphibian that engineers floating foam nests for their eggs. The mother secretes proteins like soap, and once she creates the raft, she lays the eggs in the middle and the raft among protective vegetation.
Túngara frogs grow to 3–3.6 cm (1.1-1.2 inches) and are brown with warts, resembling a toad. Its range goes from Mexico in the north, Venezuela in the south, islands like Trinidad and Tobago. The species are adaptable and live in marshes, tropical forests, and grasslands.
Larvae eat ants and termites while adults eat those and snails and insects. As small as they are, other frogs, insect larvae, and bats might eat them.
32. Common Surinam toad or star-fingered toad (Pipa pipa)
The common Surinam toad (Pipa pipa) looks like a dead brown leaf or a toad run over by a vehicle. But it lives well in most types of wetlands and in most countries that border the Amazon Rainforest.
Besides being flat, the Surinam toad also had broad, webbed feet and a triangular head, both of which resemble the lobes of a leaf. Its eyes are so small they aren’t easily seen by observers, and the toad lacks teeth and a tongue. It also grows between 15.4 cm and 17.1 cm (6-6.7 inches).
These toads don’t croak to attract a mate. They instead make metallic clicking sounds by snapping a bone in the throat called the hyoid. The pair meets on the water floor and flips in arcs. The fertilized eggs then get embedded in the mother’s back.
Her skin will form a honeycomb and provide home and transport for the young, which hatch as metamorphosed toads. The mother will then shed that shaped skin to return to normal skin.
