True Toads, Harlequin Frogs, and Relatives: Bufonidae
TRUE TOADS, HARLEQUIN FROGS, AND RELATIVES: BufonidaeLONG-FINGERED SLENDER TOAD (Ansonia longidigita): SPECIES ACCOUNTS
HARLEQUIN FROG (Atelopus varius): SPECIES ACCOUNTS
MARINE TOAD (Bufo marinus): SPECIES ACCOUNTS
GOLDEN TOAD (Bufo periglenes): SPECIES ACCOUNTS
The toads in this family are known as the "true" toads. All other frogs that are called toads are not really toads. They may have a toad's body shape or have numerous warts, but they are not true toads. One of the features true toads have that no other type of frog has is a Bidder's organ. A Bidder's organ is a female body part that is found inside a male toad. This organ does not appear to do anything in a healthy male toad. It does, however, help to tell a true toad apart from all other species of frogs that exist on Earth.
True toads have other hidden features, too. They have an odd joint between their lower backbone, or spine, and their hip bones that makes it difficult for the toads to jump well. They can walk or hop short distances, but they cannot leap several feet like some of the other species of frogs. They have only seven bones in their spines instead of the eight that most other frogs have; they have fewer bones in their front and back feet, and they have shorter toes than other frogs typically have. In addition, the pair of shoulder blades, which are usually separate in other frogs, are fused together in toads into one big shoulder blade that stretches across the whole upper back. Their lack of teeth also sets the true toads apart. None of the true toads have teeth on the upper jaw, while almost all other frogs do.
The most noticeable feature of true toads is their warty skin, especially the huge "wart" on the back of the head. The big "wart" is called a paratoid (pair-RAH-toyd) gland and makes a white, liquid poison that looks like milk. Not all true toads have paratoid glands, but the glands are usually very noticeable in the toads that do have them. The pair of paratoid glands on the American toad, for example, looks like large, flat water balloons that extend from behind the eye to the front of the back. Some species of frogs that are not true toads also have paratoid glands, so just seeing a paratoid gland is not enough to identify a frog as a true toad.
Many toads have plump bodies, short heads with rounded snouts and large mouths, eardrums that are visible on the sides of the head, short legs, and numerous warts on their backs and legs. The Houston toad is a good example. It has a fat-looking, round body that is covered with many small warts. Its head is short with a wide mouth and visible eardrums. Its front legs are thick but rather short, and its hind legs are much shorter than the legs of a leaping frog. Some of the toads in this family, however, look little like this typical toad. The harlequin frog, which is actually one of the true toads, has long and thin front legs, long hind legs, a thin body, no eardrums, and quite smooth skin.
In general, true toads are shades of brown, green, and/or gray, which allows these rather slow creatures to blend in with the background. The Chirinda toad, for instance, has a light brown back and legs and dark brown sides. When it sits still, it almost disappears against the dead leaves of its habitat. The green toad, which lives in Europe, Asia, and northern Africa, is brown with green blotches, a pattern that blends in with the ground where it lives. A few species, however, have very bright colors. The Yungas redbelly toad has a black and sometimes green back, but a bright red belly, and the male golden toad, which is now extinct, or no longer in existence, was vivid orange.
True toads also come in many different sizes. The Roraima bush toad, which lives in South America, grows to only 0.8 inches (2 centimeters) long from the tip of the snout to the end of the rump, while the marine toad can reach 9 inches (23 centimeters) in length. The Rococo or Cururu toad, can grow even larger, sometimes reaching nearly 10 inches (25.4 centimeters) long.
Members of this family live throughout much of the world, including all continents except Antarctica. They do not naturally live in Australia, but people have introduced them there, and the toads are doing well.
True toads, harlequin frogs, and their relatives make their homes for most of the year in a variety of habitats from wet or dry forests to fields, and even some dry deserts. They can survive in very warm, tropical areas, as well as cooler places with snowy winter seasons. They do not live in far northern North America or northern Asia, but some exist without problem high on windswept or snow-capped mountains that are up to 16,400 feet (5,000 meters) above sea level. The vast majority of toads are terrestrial (te-REH-stree-uhl), which means they live on land. Examples of terrestrial toads include the American toad, the marine toad, and the Houston toad.
Only a few true toads climb and live in trees or spend most of their time in the water. One of the toads that is arboreal (ar-BOR-ee-ul), which means that it lives in trees, is the brown tree toad of Borneo, Sumatra, Malaysia, and Thailand, which are all in southeastern Asia. Using the wide pads on the tips of its toes to help it cling to twigs and branches, this toad usually stays in the trees except during mating season, when it enters streams. The aquatic swamp toad, on the other hand, is aquatic (uh-QUOT-ik), which means that it usually remains in the water. This large toad, which also lives in parts of southeastern Asia, has full webbing between its toes to help it swim.
Most toads eat insects, spiders, and other arthropods (AR-throe-pawds). Arthropods are animals that do not have backbones, but have jointed legs. Those that live in rainforests eat quite a few ants, which are plentiful there. Some, like the American toad, will also eat an occasional earthworm. The larger species, including the marine toads, eat a great many insects, but they can and sometimes do eat larger animals, including mice, other frogs, and lizards.
BEHAVIOR AND REPRODUCTION
Many true toads are mainly active at night, when they come out of hiding to hunt for food. One of these, the Colorado river toad, lives in the deserts of the western United States. It avoids the hot daytime sun by staying underground and comes out at night to search the sand for beetles, snails, and other invertebrates (in-VER-teh-brehts). Invertebrates are arthropods and other animals without backbones. A few toads, including the Yungas redbelly toad, are active during the day.
Like most other frogs, toads have small poison glands in their skin. In many toads, some of the poison glands group together to form the paratoid glands, one of which is located behind each eye. When the toad feels threatened, it can ooze and sometimes squirt the milky poison from these glands. To some predators the poison tastes bad, but it can make others sick or even cause them to die if they swallow enough. Some toads, like the harlequin frog, do not have paratoid glands, but still are able to ooze enough poison through their other skin glands to ward off predators. This is an important defense tactic in the toads, many of which can only hop short distances and often cannot escape a predator by running away. Some toads, like the American toad, will even turn to face a predator, which puts the paratoid glands in the attacker's face. Not all predators are bothered by a toad's poison. The hog-nosed snake, for instance, makes toads a regular part of its diet.
Some toads, like the Yungas redbelly toad, do something different when they feel threatened. They strike a stiff pose, called the unken (OONK-en) reflex. In this position, they arch the back while holding up their red-bottomed feet and showing off the red of the belly. This display and the flash of color probably helps to remind predators that the toads have poisonous skin.
Many true toads mate during wet times of the year, often in the spring rainy season. In many species, a heavy rain will bring hundreds of males to ponds, streams, or newly filled pools of water where they begin calling. Toads often mate in the small pools that are only filled with water part of the year. These pools do not contain fish, which might eat the toads and/or their young. The typical male true toad has a balloonlike bit of flesh on its throat that inflates and deflates. This flesh, called a vocal sac, allows the toad to call. The males of most other types of frogs also have vocal sacs. Most of the true toads call with a steady trill. The American toad, for example, has a beautiful, long trill that lasts several seconds. Others, like the brown tree toad, have voices that are more like squawks than trills.
True toads usually call in choruses, which means that the males of a species group together and call all at once. The females hear the calls and follow them to the males. They mate when the male grasps the female from behind and holds on near her front legs, while the female lays her eggs in the water. In some species, like the Houston toad, the male may have to cling to the female's back for several hours before the female is ready to lay her eggs. Malcolm's Ethiopian toad mates differently than other true toads. Instead of the piggyback position that other toads and the vast majority of frogs use, the male and female of this species mate belly to belly.
Usually, the female lays her eggs, often hundreds of them, in a long string. The egg string may wrap around underwater plants, but sometimes it simply floats in the water. Most toads leave their eggs after they are laid. Toad eggs commonly hatch in a week or two into tiny tadpoles. American toad tadpoles, including their tails, are often no longer than a person's fingernail. The tadpole stage is also quite short, and they can turn into toadlets in just a few weeks. The toadlets are typically very small. People walking through the forest are frequently surprised at toadlets' tiny size. Baby American toads are also no bigger than a fingernail. Even the enormous marine toad has small toadlets.
A few toads, like the Roraima bush toad, probably have eggs that turn into toadlets instead of changing into tadpoles first. Scientists are not sure about the bush toad, however, because they have never watched an egg hatch.
TRUE TOADS, HARLEQUIN FROGS, THEIR RELATIVES, AND PEOPLE
People have been interested in toads for many, many years, and they have written about toads in many, many books, especially make-believe children's books. Children find living toads interesting, in part because usually the toads are quite simple to catch. People should, however, be careful not to put their hands into their mouths after touching a toad until they have washed their hands. This is good practice after handling any animal. Toads are not hunted for food, but some toads are common in the pet trade.
BELLY TO BELLY
Most toads, as well as other frogs, mate with the male on the female's back in a piggyback position. The female lays her eggs at the same time that the male releases a fluid that contains microscopic cells called sperm. The sperm and eggs mix, and the eggs start to grow. Malcolm's Ethiopian toads have their own style. The male and female mate belly to belly. Instead of the sperm mixing with the eggs after they leave the female's body, the sperm mixes with them while they are still inside her body. She lays the eggs later, long after the male has left.
The World Conservation Union (IUCN) lists five species in this family as Extinct, which means that they are no longer in existence. These include the golden toad, the last of which was seen in 1989; the jambato toad, last seen in 1988; the longnose stubfoot toad, last seen in 1989; and two other species known only by their scientific names: Adenomus kandianus, last seen more than one hundred years ago; and Atelopus vogli, the only individuals of which were seen only during a 1933 expedition and in just one spot in the world. Scientists are especially concerned about the species that disappeared in the late 1980s. Although they are not certain, they believe that the frogs may have died off because of infection with a fungus, known as chytrid (KIT-rid) fungus, which has harmed many different species around the world. Global warming, which has changed the world's weather patterns, pollution, the introduction of fish that eat frogs, and loss of habitat may also have played a role in some of the species' extinctions.
In addition, the IUCN lists the Wyoming toad as Extinct in the wild. This means that the frog is no longer alive except in captivity or through the aid of humans. The Wyoming has a typical toad appearance: chubby body, numerous warts on its back and legs, large paratoid glands, and a short, round-snouted face. It once lived in a larger part of Wyoming and was quite common in the 1950s, but began to disappear in the 1960s. Scientists had thought that it had already become extinct by the 1980s, but a small population turned up in 1987. The toad now only exists within a national wildlife refuge. Currently, ecologists are keeping a watchful eye on the population and are raising toadlets in captivity to release into the refuge. Without this help, scientists believe the toads would likely have already become extinct. They are unsure why the frogs are disappearing, but think that the chytrid fungus may have been a cause.
ROCK AND ROLL
The Roraima bush toad defends itself from predators in a bizarre way. The toad, which grows to barely 0.8 inches long (2 centimeters), cannot leap or even take small hops. Instead, it slowly walks over the rocks in its habitat. When it feels threatened, this toad tucks itself into a little ball and rolls down the side of the rock, giving it the look of just another tiny stone falling away.
Other frogs noted by the IUCN include eighty-two species that are Critically Endangered and face an extremely high risk of extinction in the wild; seventy species that are Endangered and face a very high risk of extinction in the wild; forty-nine that are Vulnerable and face a high risk of extinction in the wild; twenty-six that are Near Threatened and at risk of becoming threatened with extinction in the future; and sixty that are Data Deficient, which means that scientists do not have enough information to make a judgment about the threat of extinction.
The U.S. Fish and Wildlife Service lists three U.S. species as being Endangered and one as Threatened. The Endangered species are the Wyoming toad, which was described above, the Houston toad, and the arroyo or southwestern toad. The Threatened species is the Puerto Rican crested toad.
The Houston toad, which the IUCN also considers to be Endangered, once lived in Texas along the coast of the Gulf of Mexico. It became less common in the last half of the twentieth century when the city of Houston became bigger and people began building in what had been the toad's habitat. In addition, the area had a spell of extremely dry weather, which also hurt the toads. The toads now live in a much smaller area.
Half of the arroyo toads, listed by both the U.S. Fish and Wildlife Service and the IUCN as Threatened, disappeared between 1994 and 2004. The toads make their homes in parts of northwestern Mexico and California. The drop in their numbers probably happened as the result of several things, including the construction of roads, dams, and buildings; too much cattle grazing, which is hurting the plants in the frog's habitat, and the introduction of frog-eating fish to the toads' habitat.
Only twenty percent of the Puerto Rican crested toads that lived on Earth in 1994 were left by 2004. As of 2004, fewer than 250 adult toads remained in the wild. The species is listed as Threatened by the U.S. Fish and Wildlife Service and Critically Endangered by the IUCN. The toad, which is native to Puerto Rico and the British Virgin Islands, probably disappeared because people began cutting down and building in the forest where the toads lived so people could move into and live in the area. According to the IUCN, people drained the pools of water where the toads once mated and laid their eggs to make the area into parking lots. Scientists have been able to raise baby crested toads in captivity, but when they are set free, these young toads die. One small population of toads still survives in the wild. It lives inside a national forest and appears to be safe from further habitat destruction.
Physical characteristics: Also known as the long-fingered stream toad, the long-fingered slender toad has very long and thin front and back legs. Its front legs are about as long as its body. The front legs and back legs also have very long, thin toes. The toad's body is rather slender, and its back is covered with small warts. It has a small head, but it has large, brown eyes and a large mouth. The snout hangs a bit beyond the lower jaw, making the frog look as if it has a slight overbite.
Unlike many other toads, it does not have the large poison "warts," called paratoid glands, behind its head. The frog is dark brown to reddish brown, sometimes with faded black bands noticeable on its hind legs. Males and females look similar, but the females are a bit bigger. Males typically grow to 1.4 to 2 inches (3.5 to 5 centimeters) long from snout to rump, while females usually reach about 1.8 to 2.8 inches (4.5 to 7 centimeters) in length.
Geographic range: The long-fingered slender toad is native to Borneo.
Habitat: The long-fingered slender toad lives among forests from the bottoms of mountains up to about 7,220 feet (2,200 meters). It breeds near fast-flowing streams and in steep places.
Diet: Adults eat small insects, especially ants, of the rainforest. Tadpoles eat plants that they find growing on rocks in the streams where they live.
Behavior and reproduction: Scientists know little about the behavior of these toads outside of their mating time. To breed, males group together next to rocky streams and call females with high-pitched trills. Eggs hatch into tadpoles, which have a sucking mouth on the underside. This helps the tadpole hang onto plants or rocks in the fast water of the stream in which they live until they change into toadlets.
Long-fingered slender toads and people: People very rarely see this toad in the wild, and scientists know little about it.
Conservation status: The World Conservation Union (IUCN) has listed this toad as Near Threatened, which means that it is at risk of becoming threatened with extinction in the future. It lives in areas around streams, and these areas are changing as the forests are cut. Logging not only removes trees, but allows soil to flow into the streams, muddying them and making them unsuitable for the tadpoles. Scientists fear that the number of frogs will soon drop as their habitat is destroyed. Fortunately, some populations of this species live in areas where logging is not allowed. ∎
Physical characteristics: Also known as the harlequin toad, the harlequin frog may come in several different colors, always with a bright pattern of blotches on a dark, usually black, background. The bright pattern is often yellow, but may also be another color like green, orange, or red. The frog gets its common name from these colors. A harlequin is a court jester, a person who hundreds of years ago wore gaudy, colorful costumes to entertain an audience.
The frog has very thin but long front legs. Its back legs are a bit thicker and still longer. Its eardrum is not visible. Males grow to about 1.1 to 1.6 inches (2.7 to 4 centimeters) long from snout to rump. The females are larger, reaching 1.3 to 1.9 inches (3.4 to 4.8 centimeters) in length. In some populations, the females and males look much alike, but in others, the males and females come in different colors.
Habitat: Harlequin frogs live in moist forests in valleys and partway up the sides of mountains. Scientists have not seen the frogs mating in the wild, but they believe these frogs do so in rocky streams, because this is where they have found harlequin frog tadpoles.
Diet: They eat small arthropods, including spiders and insects, like caterpillars, flies, and ants.
Behavior and reproduction: At night, harlequin frogs sleep on top of large leaves above streams. They are active during the day, hopping about in plain view. Their bright colors help remind predators that the frogs can ooze a very poisonous and bad-tasting liquid from their skin. The poison in the liquid is the same as that found in the very dangerous puffer fish. Males set up territories and make short buzzing sounds to tell other males to stay away. Sometimes, the males will fight by jumping on or chasing one another. They may also circle a front foot in the air before or after a fight. Unlike the males of other frogs, harlequin frog males do not call females for breeding. They do, however, mate like most other frogs with males climbing onto the backs of females. A harlequin frog female may carry a male on her back for several days until she has finished laying her eggs.
Harlequin frogs and people: Humans almost never see this extremely rare frog.
Conservation status: The World Conservation Union (IUCN) has listed this frog as Critically Endangered and facing an extremely high risk of extinction in the wild, because most of them have disappeared since 1988. In 1996, in fact, scientists feared that all of the more than one hundred populations known to exist in Costa Rica were already gone. Seven years later, however, a tiny population was discovered there. Some populations still live in Panama, but their numbers appear to be dropping. Scientists believe that the frogs are mainly disappearing because of infection with a fungus, called chytrid fungus, which is also killing many other frogs worldwide. In addition, people have introduced trout, a popular game fish, to some of the waterways in which the frogs breed. The trout eat harlequin frogs. ∎
Physical characteristics: The marine toad is an enormous toad that can grow to as much as 9 inches (23 centimeters) long from snout to rump and weigh up to 2.2 pounds (1.5 kilograms). Sometimes it is called the giant toad, and in Belize, its nickname is the spring chicken. It is a dark-colored toad, often gray to brown, and sometimes reddish brown. Frequently, it has darker brown blotches and sometimes white spots on its back. It has large paratoid glands spreading from the back of its head to the front legs. It has a short, rounded snout, large eyes, and a noticeable eardrum on each side of its head.
Geographic range: The marine toad naturally occurs in Mexico, Central America, South America, and southern Texas in the United States, but people have introduced it to many other places around the world, including Hawaii, Japan, the Philippines, Australia, and numerous islands of the West Indies. It is now a pest species in many countries.
Habitat: In its native areas within South, Central, and North America, the marine toad prefers to make its home in fields and open forests that have at one time lost their trees, perhaps to logging or to fires. It naturally breeds in ponds, at the edges of lakes, and in small pools that form in rainy parts of the year and dry up later on. This toad, however, is very adaptable. This means that it can adjust to live in other places, too. This has helped the toad move into new areas, including villages and towns, and make its home there.
Diet: The marine toad has a good appetite. It eats a wide variety of arthropods. It will sit down at night near a light in a town and spend hours flipping out its tongue to snap up insects that fly toward the light. It will also devour ants, cockroaches, and many other types of insects wherever it can find them. Besides arthropods, marine toads have a reputation for gobbling down cat food and dog food from the feeding dishes of family pets. They are also known to sometimes eat snakes, frogs, and even small mammals, like mice.
Behavior and reproduction: Marine toads often spend their days grouped together in an out-of-the-way spot. They become active at night, which is when they do the bulk of their hunting. Sometimes, they travel quite a distance at night. Scientists are not sure how they do it, but the toads are always able to find their way back home. In the spring mating season, male marine toads move to water, sometimes even swimming pools, and begin calling for females. They usually prefer a shallow spot on the shore of a pond or small lake, or at the edge of a marsh. Here, a male pushes up on his front legs and makes his call, which is a long, low trill that may last ten or twenty seconds. When many of them call at once, the sound is something like a tractor engine. When a female approaches a male, he climbs onto her back, and grasps her behind her front legs. The two toads may swim about with the male still riding on the female's back until she finishes laying her eggs. One female may lay a string of twenty-five thousand eggs, sometimes more, and a single string may stretch nearly 10 feet long. In about two weeks, the eggs hatch into small, black tadpoles. The tadpoles may group together in schools, just as fish do, until they turn into toadlets.
Marine toads and people: In 1935, people brought the toad to Australia with the hopes that it would eat a type of beetle that was destroying the sugar cane crop. The toads, which got the nickname cane toad, found plenty to eat besides the beetles. The toads bred quickly, and since they had very few predators, soon became pests themselves. The toads are still very common in Australia. One of the reasons that people in that country dislike the toads is that pet dogs sometimes try to eat them. The poison in the toad's skin can cause illness and sometimes death.
Conservation status: The World Conservation Union (IUCN) does not list this species as being at risk, but rather notes that it is becoming more numerous and spreading to more places around the world. The toad's skin poison can make other organisms sick and even kill the eggs and tadpoles of other frogs that share water with marine toads and their tadpoles. ∎
Physical characteristics: Only male golden toads are golden, and they actually are more orange than gold. Some people even call them orange toads instead. The females are very dark green, almost black, with red markings. Both males and females have thin, bony-looking bodies, much different than many of the plump toads in this family. Their front and hind legs are quite thin. Besides their colors, males and females are different in size. The females are the larger of the two, growing to 1.7 to 2.2 inches (4.2 to 5.6 centimeters) long from snout to rump. The males usually reach 1.5 to 1.9 inches (3.9 to 4.8 centimeters) in length.
Geographic range: Now extinct, golden toads once lived along a mountain ridge in the Monteverde Cloud Forest Preserve of northwestern Costa Rica. For this reason, some people call it the Monteverde toad.
Habitat: Golden toads lived in mountain rainforests 4,920 to 5,250 feet (1,500 to 1,600 meters) above sea level.
Diet: Scientists had not yet learned about its diet before it became extinct in 1989.
Behavior and reproduction: The studies of this toad were mainly done during the breeding season, so very little is known about its behavior outside of mating and egg-laying. When heavy rains fell in the rainforest where this toad lived, hundreds of males would appear in groups. Scientists are not sure whether the males called. They did, however, notice that the number of males always outnumbered the females at a breeding site. Often, when a male would climb onto the back of a female to mate, one or more other males would begin wrestling with the first for the chance to push him off. If they were successful, one of these males would hop on the female, which would start yet another battle. The females laid their eggs in strings, and the eggs hatched into 1.2-inch (3-centimeter) tadpoles.
Golden toads and people: Following the extinction of this species, scientists became very concerned about the disappearance of frogs and toads around the world. The golden toad now serves as a symbol for amphibian conservation efforts.
Conservation status: Although scientists had seen large mating populations of the golden toad until 1987, its numbers dropped greatly in 1988 when only two females and eight males appeared at their normal breeding site. In 1989, a single, lone male arrived for mating season. He was the last golden toad ever seen. Although scientists do not know for sure, they think that infection with the chytrid fungus, pollution, and/or global warming, combined with the very small area in which they lived, may have caused the species to die out. ∎
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