FIRE-BELLIED TOADS AND BARBOURULAS: Bombinatoridae

PHYSICAL CHARACTERISTICS

Fire-bellied toads are best known for the striking red, orange, or yellow colors that many species have on their throats, bellies, and even the undersides of the forelegs. They are named for these flame-like colors, which have black or gray spots, blotches, and patterns running through them. When seen from the top, the frogs show no hint of the bright colors underneath, and the brown, gray, and/or green of their backs and heads blend in with the environment. Some have patterns on their backs, but these also camouflage the frog rather than make it more noticeable. The barbourulas are also colored in muddy greens and browns, but they do not have the flashy undersides of the fire-bellied toads.

Members of this family have skin on their backs that is covered with warts and sometimes with pointy warts that look like tiny spikes. The belly skin, in contrast, is much smoother and in most cases has no warts at all. The head has a rounded snout and two large eyes with triangular pupils, and the sides of the head do not have the round eardrums, or tympanums (tim-PAN-umz) seen in many other frogs.

The frogs are small- to medium-sized. Adults grow from 1.6 to 3.9 inches (4 to 10 centimeters) long from the tip of the snout to the rump. Males and females look alike, except that the males have leathery pads on their front feet. The males use these pads to clutch onto the females during the mating season.

Even though the fire-bellied toads and barbourulas are often listed as being in their own family, some people prefer to group them into another family that also contains the midwife toads and painted frogs. Other scientists like to split them into still different arrangements. Scientists are not sure which is best, but most lean toward the family as it is described here.

GEOGRAPHIC RANGE

Fire-bellied toads and barbourulas can be found in Europe and Asia, including parts of eastern and western Russia, Ukraine, Turkey, China, and Korea. Some species also live farther south in Vietnam, Borneo, and the Philippines.

HABITAT

The members of this family live mostly in the water. The fire-bellied toads prefer marshy areas, or small, often shallow ponds, where the water has little if any current. The barbourulas, on the other hand, like the faster-moving water of mountain streams and small pools of water that have plenty of rocks to provide hiding places.

DIET

Adults generally eat invertebrates (in-VER-teh-brehts), which are animals without backbones. These can include worms and snails, as well as beetles and other insects. The tadpoles of many species will eat insects, too, but usually fill their stomachs mostly with algae (AL-jee), plants, and fungi. Unlike many other types of frogs and toads, the members of this family do not have tongues they can flip out of their mouths to capture prey. Instead, they must lunge at prey and grab their meals with their mouths. This means that a fire-bellied toad, for example, must get close to its prey so it can leap and catch the insect before it can run or fly away. The camouflage pattern on the toad's back helps to hide it from prey and makes this type of hunting more successful.

BEHAVIOR AND REPRODUCTION

The fire-bellied toads are best known for the rather unusual way they defend themselves. The frogs have glands in the warts down their backs that can release a bad-tasting, white and foamy ooze that is also slightly poisonous. When the frog feels threatened, possibly by a predator that comes too close, it flips over, arches its back, stretches out its back legs, and reaches its forelegs up. Sometimes, the frog stays on its belly, but arches its back and spreads its legs. Both of these unusual displays show off the frog's bright red, orange, or yellow underside to the predator. Scientists call this odd back bend an unken (OONK-en) reflex. The unken reflex and the colors it displays remind the predator that this frog does not make a good snack. Despite the frog's best efforts, the defense tactic is not always successful, and many of these frogs become meals for attackers. For example, a shorebird known as a night heron may get as much as one-quarter of its diet from fire-bellied toads.

The two main types of frogs in this family—the fire-bellied toads and the barbourulas—lead very different lives. The fire-bellied toads are very active during the day, often hopping about on land in open areas, like meadows. Compared to the fire-bellied toads, the barbourulas are very shy. These frogs stay out of sight, usually hiding among rocks in the water. When barbourulas do wander onto land, their gray and brown backs help them blend into the colors of this habitat, too. This camouflage, their secretive behavior, and the small numbers of this species that exist have made barbourulas difficult to study, and scientists still know little about them.

WARNING STRETCH

The fire-bellied toads warn predators to stay away by bending up their bodies to show off their brightly colored undersides. The bright colors are an advertisement to the predators that the frog has a nasty taste. Many other bad-flavored frogs and salamanders also bend in this way. Scientists call this type of strange stretch an unken reflex, because unken is the German word for fire-bellied toad. A reflex is an automatic action. People have reflexes, too, such as blinking or twitching at sudden noises.

The mating season for many of the fire-bellied toads starts in late spring and continues into the middle of summer, and some may breed two or three times a year. Unlike the males of other types of frogs, which call only during certain times of the day, male fire-bellied frogs sing at any time, even though they only mate with the females in the evening hours. Males mate with females by grabbing onto their back so they look as if they are riding them piggyback. This puts the male in the right position to fertilize (FUR-teh-lyze) her eggs as she releases them. During the mating season, a male will sometimes mistakenly grab onto a second male instead of a female. The second male frantically tries to squirm away, sometimes making a croaking squeal, known as a release call. People sometimes use this mating behavior as a quick way to tell the males from the females: During the mating season, those toads that climb onto the backs of others are likely to be males, and those who do not try to squirm away when another grips them are likely females. Just because a toad tries to get away does not necessarily mean that it is a male, however, because females who are not ready to mate will also try to escape the clutch of a male toad.

Each female can lay up to 200 eggs a year, although many lay only a few to a couple of dozen at a time. She usually drops them in the water, either on underwater plants or down on the bottom. Some frogs lay their eggs in permanent bodies of water, like streams or ponds that never dry up, but others lay their eggs in temporary pools of water that disappear in dry summer months. In about a week, sometimes longer, the eggs hatch into tadpoles. In another six weeks or so, the tadpoles turn into baby frogs. The timing is very important to those that are born in temporary pools of water. If they cannot change into toadlets before the water disappears, they may dry up and die.

The female barbourula is a bit different than the fire-bellied toad. She lays her eggs— about 80 large eggs at a time—beneath underwater stones. Little more about this species's reproduction is known.

FIRE-BELLIED TOADS, BARBOURULAS, AND PEOPLE

People often buy and sell fire-bellied toads as pets, partly for their beautiful coloration, partly for their display of the unken reflex, and partly because they are quite easy to keep. Many of these frogs can live more than ten years in captivity. Sometimes pet owners find that the flashy colors on a pet fire-bellied toad's underside fades, but they can brighten up the belly again if they feed the toad the right types of foods. The species in this family also sometimes wind up in laboratories where scientists study how they develop from eggs to adults or learn how the animals' bodies work.

PREDATOR LEARNING

The fire-bellied toads use their colors to advertise to predators that they taste bad. This can only work, however, if the predators learn what the colors mean. How does a predator learn? When a young predator finds one of these frogs for the first time, it only sees what it thinks is an easy meal. When it takes the frog into its mouth, however, the frog oozes an unpleasant-tasting poison from its skin, and the surprised predator quickly spits it out. Sometimes the frog dies from the attack, but often it survives. In either case, the predator has learned a lesson to stay away from these frogs and anything that looks like them. This is why many poisonous animals have bright colors, especially red. Scientists call such warning colors aposematic (ay-POE-sem-AT-ik) coloration.

CONSERVATION STATUS

Half of the ten species in this family are at risk, according to the World Conservation Union (IUCN). Four are Vulnerable, which means they face a high risk of extinction in the wild. These are the Philippine barbourula, the large-spined bell toad (also known as the Guangxi fire-bellied toad), the Lichuan bell toad, and the small-webbed bell toad (also known as the Hubei fire-bellied toad). The biggest threats to these frogs include pollution, habitat destruction, and collection for the pet trade. In addition, some are extremely rare. The large-spined bell toad, for example, is so uncommon that scientists have only found a few individuals and only in a small part of China. Fortunately, most of this area is protected inside a national nature reserve. Likewise, the Lichuan bell toad only appears to live in ten locations inside two Chinese provinces, and the habitat in many of these areas is being destroyed as new farms and homes move in. At least one of these populations, which makes its home inside a nature reserve, is protected.

The fifth of the five at-risk species is the Bornean flat-headed frog. This species is Endangered and faces a very high risk of extinction in the wild. The Bornean flat-headed frog lives in a single, tiny area that measures less than 300 miles by 300 miles (500 kilometers²), and scientists know about it from just two individuals collected from forest rivers. Unfortunately, human activity near the rivers, including illegal gold mining, is making the rivers muddy and polluted, which may hurt the frogs that still live there.

Although the other five species in this family are not listed as being at risk, scientists are watching them closely because some groups of these frogs are disappearing. Human development in the habitat of the fire-bellied toad is wiping out entire populations of this animal.

FIRE-BELLIED TOAD (Bombina bombina): SPECIES ACCOUNTS

Physical characteristics: When seen from above, fire-bellied toads (also known as European fire-bellied toads) are usually dark gray or black with large black markings. When they live in places with green, leafy areas, they typically have dazzling lime-colored backs that are decorated with black spots. In both cases, their bellies are the same colors: red or orange with big black areas and small white dots. Sometimes, individuals have much more black on their bellies than red or orange. The fire-bellied toads have a rounded snout and eyes with a triangular pupil, but they do not have a flat, circular eardrum showing on each side of the head, as many other frogs do. The warts on their backs are rather tall with rounded tips. Their front feet do not have webs, but the hind feet do. Fire-bellied toads usually grow to about 1.6 inches (4 centimeters) long from snout to rump but occasionally can reach 2 inches (5 centimeters) long. Males and females look similar, except that the male has a slightly bigger head. In addition, the males develop pads on two of the toes on each front foot and on the inside of the forelegs throughout the breeding season. A male uses these pads to help him cling to the female during mating.

Geographic range: Fire-bellied toads live in central and eastern Europe, including Denmark, Austria, Germany, Poland, Greece, Turkey, and other nations. Sweden and the United Kingdom are home to some fire-bellied toads, but the toads did not get to these countries on their own. Rather, people probably brought them into the countries and released them. When a frog comes to a new place in this manner, it is said to be introduced. Sometimes, people introduce new species on purpose, perhaps thinking that they would be good additions to the area. Other times, people set free their old pets. In many cases, these pets die, but sometimes they do quite well and begin breeding. Overall, however, conservationists warn people not to introduce new species, because they may hurt the other species that are already there, perhaps by eating their food or by bringing in new and dangerous diseases.

Habitat: Fire-bellied toads live in just about any watering hole they can find. Some populations, especially those in northern areas, prefer clean waters, but those in more southern areas can survive in somewhat polluted waters. These may include lakes and ponds, rivers and streams with slow currents, marshes, and small pools of water, sometimes located in forests and sometimes in more open habitats. The toads do not live high up in the mountains, as some other members of this family do. They spend most of their time either in the water or on land near the water's edge. Summer weather can dry up the small pools of water where some of the toads live, but they are able to survive by crawling into the wet, muddy gaps that remain.

Diet: Adult fire-bellied toads are mainly insect-eaters, often gobbling up mosquitoes. They will also eat many other land insects, like beetles, ants, and flies, as well as water-living insects and other invertebrates. The tadpoles eat a few insects they find in the water, but they are mostly vegetarian and eat algae and plants.

Behavior and reproduction: These frogs are active during the daytime and spend the warm, sunlit hours swimming or hopping about on shore looking for things to eat. They are more sluggish when the temperature drops below about 60°F (15°C) and often remain hidden until the weather warms up again. On warm, humid nights, they will wander farther away from their watering holes to find food. In the water, they can usually escape predators by taking a quick, deep dive. On land, these frogs have back colors that blend into the environment. When a predator does see one and comes too close, this toad will arch its back, displaying the unken reflex, to show off its bright belly-side colors.

Once the weather begins to cool off in the fall, usually September or October, but sometimes as late as November, the fire-bellied toads begin their hibernation (high-bur-NAY-shun), which is a state of deep sleep. To survive the cold of winter, the toads bury themselves in the mud either on land or underwater on the bottom of their watering holes. Hibernation usually lasts from about October to April. In May, after they wake up and become active again, the males start calling. Although they may call during the day, they begin to call even more as the sun sets. They flatten out their bodies and call from their watery homes, sometimes with their heads above the water's surface and sometimes from underwater. To make the call, the male blows up a single vocal sac that looks like a bubble under his chin when it is inflated. When the male is not calling, the vocal sac shrinks back down and is not noticeable. The call is somewhat like a chicken's cluck. During mating, the male climbs onto the female's back and grips her in front of her hind legs. His front foot pads help him to hang on.

Each year, females can lay 80 to 300 eggs, which they lay in small groups. The eggs hatch into tadpoles about one to two weeks later, and the tadpoles turn into toadlets between July and September, but always before the next hibernation. Although they now have legs, the toadlets stay in the water for this first year. When they reach about 2 to 4 years old, they are adults and ready to become parents themselves. In the wild, fire-bellied toads can live to be about 12 years old, but in captivity they sometimes reach as much as 30 years old.

Sometimes, this species of toad will mate with yellow-bellied toads and have young. These young are called hybrids (HIGH-brihdz). Scientists have compared these hybrids to young that have parents of the same species and found that the hybrid eggs and tadpoles are ten times more likely to die before they reach three weeks old.

Fire-bellied toads and people: Its bright belly colors have helped to make this toad very popular in the pet trade.

Conservation status: This species is not considered to be at risk. ∎

ORIENTAL FIRE-BELLIED TOAD (Bombina orientalis): SPECIES ACCOUNTS

Physical characteristics: Also known as an Oriental bell toad, the Oriental fire-bellied toad has a bright red to orange underside that is marked with large, dark blotches. Its back is brownish to greenish gray or bright green, usually has black and shiny spots, and is covered with pointy warts. Each of the two large eyes on its head, which is colored like the back, has a triangular pupil. Some people think the pupil looks more like a heart than a triangle. The front and back toes look as if their tips were dipped in bright orange or yellow paint. The front toes have no webbing between them, but the back toes are webbed.

Oriental fire-bellied toads usually grow to about 1.5 to 2 inches (3.8 to 5 centimeters) long from the tip of their snout to the end of the rump. Males and females look alike, except that males have slightly thicker forelegs. In addition, during breeding season, the males develop black pads on their front legs and toes. The male uses these pads, which are called nuptial (NUHP-shul) pads, to grip onto the female during mating.

Geographic range: The Oriental fire-bellied toad lives in Korea, on two Japanese islands called Tsushima and Kyushu, in northeastern China, and in parts of nearby Russia.

Habitat: Oriental fire-bellied toads usually are found in or near ponds, lakes, swamps, and slow-moving streams. They may also be found in ditches and other temporary ponds, which typically dry up during the summer. These water bodies may be in forests or meadows.

Diet: Young tadpoles are vegetarians but begin to eat insects as they grow larger. Once they become toadlets, they switch to a diet of small invertebrates. The adults eat beetles, ants, flies, and other insects that they find on land or in the water. They also eat worms and snails.

Behavior and reproduction: Like many other members of this family, Oriental fire-bellied toads display their brightly colored underside as a way to scare off predators. Often, this toad will remain on its belly, lift its legs, and stretch its forelegs over its head to provide a good look at its throat and belly colors. Sometimes, it will flip over onto its back while holding out its forelegs, a display that shows off its underside even more. It also releases a bad-tasting poison from its warts. The combination of poison and the display helps the toad avoid becoming a predator's next meal.

These toads are more active when temperatures are higher and the weather is not too dry. On these warm days, they will hop about in search of food. During especially dry spells in the summer, they sometimes take shelter under rocks or logs until a rain wets the land again. When the weather cools, usually in October, they find shelter either on the bottom of a stream or on land and hibernate for as long as seven or eight months. When they take their winter's sleep on land, they usually find a hiding spot under a pile of leaves or stones or inside a dead and rotting log or tree stump. Sometimes, up to six of these toads will spend the winter huddled together.

When the toads come out of hibernation in the spring, the males float on the surface of the water and start making their mating call. Depending on how close a person is to the calling toads, the mating call may sound like a duck quacking or more like a small bell. Males and females continue to mate throughout the summer. The female lays up to 250 large eggs a year, but only about six to 30 at a time, and places them beneath underwater rocks. Within one to two weeks, sometimes longer, the eggs hatch into tadpoles. The tadpoles change into toadlets in about two months and before hibernation. Overall, the Oriental fire-bellied toads can grow to a ripe old age. In the wild, they may live for as long as 20 years.

Oriental fire-bellied toads and people: Many people keep this toad as a pet.

Conservation status: This species is not considered to be at risk. ∎

YELLOW-BELLIED TOAD (Bombina variegata): SPECIES ACCOUNTS

Physical characteristics: The yellow-bellied toad is most known for its bright yellow to yellow-orange underside, which is marked with black. The amount of black differs from individual to individual. Some may have an almost completely black belly, and others may be almost completely yellow. From a top view, however, this toad is olive-green with black speckles. These colors and the pattern on the head and back match the colors and pattern of the toad's habitat and help to hide it from predators. Compared to other members of this family, it has more warts, and its belly even has a few. This toad's warts are also different from other species because those on the back are very pointy and almost make the toad look as if it is covered with small spines. The tips of its front and back toes are yellow or yellow-orange like the belly. This species can grow to about 2 inches (5 centimeters) long from snout to rump. The males and females look much alike, except that the males have pads on their front toes. During the breeding season, the males also develop pads on their forelegs. They use the pads to hold onto the female's back during mating.

Geographic range: Yellow-bellied toads live throughout much of central and southern Europe, including Austria, Greece, Hungary, Italy, Switzerland, the United Kingdom, and many other countries.

Habitat: These toads live in ponds, lakes, slow- and fast-moving streams and rivers, and pools of water in the hills and on mountainsides. They also do well near humans and can even survive in very polluted waters that would kill other types of frogs. They also spend much of their time on land in forests and/or meadows. In many places, this toad is quite common, and a person can see several toads within three feet (91 centimeters) of each other.

Diet: Unlike many other members of this family, the adult yellow-bellied toad finds almost all of its food on land. Its diet is made up of beetles, flies, ants, spiders, and other invertebrates.

Behavior and reproduction: This toad likes warmer weather and is most active during the daytime. Its schedule on a typical warm day includes time spent looking for food to eat and time resting in the water or sunbathing on land. Many cold-blooded animals, including frogs, warm themselves by such sunbathing, or basking. Like the other fire-bellied toads, the yellow-bellied toad will display the unken reflex when threatened. When the weather cools in October, it leaves the water and begins its hibernation in underground burrows or holes beneath rocks. When it awakens again the next spring, the males begin calling. Those higher in the mountains awaken last because the weather stays cold longer.

When the males and females come together, a male will climb onto a female's back and hang on just in front of her hind legs. Mating can continue off and on throughout the summer, even lasting until August. Often, a heavy rain will trigger many toads to mate at once. The female lays 45 to 100 eggs over the entire summer, but only about two dozen at a time. The eggs hatch 12 days later into tiny tadpoles. Some of the tadpoles turn into toadlets before the fall hibernation, but others wait until the following spring to make the change.

Yellow-bellied toads and people: Some people keep these toads as pets, although they are not as popular as some other species. The poison from the toad's skin, although it is not especially strong, can cause some stinging to humans who handle them.

Conservation status: This species is not considered to be at risk, but it may still be in some danger. More than a dozen populations of this toad have disappeared from the Ukraine alone, and others may soon vanish as people continue to move into and destroy their habitat. ∎

PHILIPPINE BARBOURULA (Barbourula busuangensis): SPECIES ACCOUNTS

Physical characteristics: The Philippine barbourula is also known as the Busuanga jungle toad, the Philippine discoglossid frog, and the Philippine flat-headed frog. It is larger than any of the fire-bellied toads and typically can grow to about 3 inches (7.6 centimeters) long from its rounded snout to its rump. Like the other barbourula species, the Philippine barbourula has camouflage colors and patterns. Its back is drab brown or greenish brown with dark markings, a combination that hides the frog against the background of its water habitat. It has large eyes and a rounded snout. Both its front and back toes are webbed, which allows its feet to work like paddles as it swims through the water. Its hind legs, which are much larger and more powerful than its front legs, also give it swimming power.

Geographic range: Three western Philippine islands, called Busuanga, Culion, and Palawan, are home to this species.

Habitat: A fast-flowing, clean and clear, rocky or stony mountain stream or river is the best place to find one of these frogs. Within the three Philippine islands where this species lives, it is split into small populations that are often separated quite a distance from one another.

Diet: Scientists suspect that these frogs mainly eat insects that they find in the water, although they may sometimes venture onto land to find a meal. More studies are needed to learn about their diet.

Behavior and reproduction: Philippine barbourulas spend much of their time floating at the top of the water, but people rarely see them because the frogs frighten easily and quickly dive out of sight to hide underneath stones or inside cracks in rocks, especially near the shoreline. The females even lay their large eggs beneath underwater stones. They may lay as many as 80 eggs, which possibly skip the tadpole stage and develop right into froglets. Additional studies are needed to provide more information about this secretive species.

Philippine barbourulas and people: People rarely see this species.

Conservation status: According to the World Conservation Union (IUCN), this species is Vulnerable, which means that it faces a high risk of extinction in the wild. Part of the reason the species are at risk is that people continue to damage the frogs' habitat by cutting down trees and/or by polluting the streams and rivers through such activities as mining and farming. Some people also collect these rare frogs to sell as pets. Many of the frogs on Palawan are safe from these dangers, because they live in rainforest that has been set aside as protected land. ∎

FOR MORE INFORMATION

Books:

Arnold, E. Nicholas. Reptiles and Amphibians of Europe (Princeton Field Guides). Princeton, NJ: Princeton University Press, 2003.

Arnold, E. N., J. A. Burton, and D. W. Ovenden. Reptiles and Amphibians of Britain & Europe (Collins Field Guide). London: HarperCollins Publishing Limited, 1999.

Duellman, William E., and Linda Trueb. Biology of Amphibians. Baltimore: Johns Hopkins University Press, 1994.

Garcia Paris, Mario. Los Anfibios de España. Madrid: Ministerio de Agricultura, Pesca y Alimentación, 1985.

Gasc, Jean-Pierre, A. Cabela, J. Crnobrnja-Isailovic, et al., eds. Atlas of Amphibians and Reptiles in Europe. Paris: Societas Europaea Herpetologica and Muséum National d'Histoire Naturelle, 1997.

Herrmann, Hans-Joachim. Terrarien Atlas. Vol. 1, Kulturgeschichte, Biologie, und Terrarienhaltung von Amphibien, Schleichenlurche, Schwanzlurche, Froschlurche. Melle, Germany: Mergus Verlag, 2001.

Miller, Sara Swan. "Fire-Bellied Toads." Frogs and Toads: The Leggy Leapers. New York: Franklin Watts, 2000.

Zug, George R., Laurie J. Vitt, and Janalee P. Caldwell. Herpetology: An Introductory Biology of Amphibians and Reptiles. 2nd edition. San Diego: Academic Press, 2001.

Web sites:

"Fire-Bellied Toad." The Sacramento Zoological Society.www.saczoo.com/1_about/_animals/fact_sheets/firebellied_toad2.pdf (accessed on February 6, 2005).

"The Oriental Fire-Bellied Toad." Utah's Hogle Zoo.http://hoglezoo.org/animals/view.php?id=201 (accessed on February 6, 2005).

"Frogs: A Chorus of Colors." American Museum of Natural History.http://www.amnh.org/exhibitions/frogs/featured/flashers.php (accessed on February 6, 2005).