AUSTRALIAN TOADLETS AND WATER FROGS: Myobatrachidae

PHYSICAL CHARACTERISTICS

Most of the Australian toadlets and water frogs are either small, slender creatures with long hind legs or tiny toads with short hind legs. Those members of the family that burrow head first, like the turtle frog, usually have powerful front legs and snouts that are tough, like the callous on a person's hand, while those that burrow hind end first, such as the northern toadlet, typically have hard bumps, called tubercles (TOO-ber-kulz), on their back feet to help them dig.

Overall, the Australian toadlets and water frogs range from 0.6 to 3.1 inches (1.6 to 7.9 centimeters) long from snout to rump, but the majority are on the smaller side. Typically, the frogs in this family are gray or brown, but often have brighter colored patches of skin that appear when they lift their front or back legs. Some, however, have bold colors all over their bodies. The Corroboree frog, for instance, is black and vivid yellow or green, while the sunset frog is covered in orange, red, and blue.

GEOGRAPHIC RANGE

Most of the species in this family live only in Australia, but at least two also are found in southern New Guinea.

HABITAT

Depending on the species, a frog in this family may live in a rainforest stream, a mountain meadow, a forest, a grassland that is dry much of the year, or in desert-like sand dunes near oceans. Many of them burrow into the soil or disappear under moss, leaf piles, or logs during the daytime. Even the tadpoles live in many habitats. Eggs and tadpoles may develop in a stream that flows all year, in a pond that will dry up later in the year, in a nest on land, or under the ground. In a few species, the eggs and/or tadpoles actually develop into frogs inside pockets on their fathers' hips, or inside their mothers' stomachs.

DIET

The Australian toadlets and water frogs eat arthropods (AR-thro-pawds), which are insects, spiders, and other invertebrates that have jointed legs. An invertebrate (in-VER-teh-breht) is an animal that does not have a backbone. Some species eat mainly one type of arthropod. The sandhill frog, for instance, eats mostly ants, even sometimes poking its head inside ant hills. In many cases, however, scientists do not know exactly which types of arthropods these species eat because they have not yet done thorough studies of the frogs.

BEHAVIOR AND REPRODUCTION

Most of the frogs in this family hide themselves away during the day. Some stay under damp leaves, moss, logs, or rocks on the ground, and others burrow. Burrowers may use their front legs to dig head first, or they may use their hind legs to scramble into the ground back end first. The turtle frog, which has a body with the shape of a turtle but without the shell, is a head-first burrower. It uses its short, but thick and strong front legs to scrape aside the sand and pushes its hard snout forward. A few species, such as Eungella torrent frog, may be active day or night. Some species that stay above ground for much of the year will burrow during the dry season and only return to the surface after the rainy weather returns.

In the breeding season, the males of some species set up and defend territories. For instance, male stonemason toadlets will get into wrestling matches over a good calling place. In other species, such as the quacking froglet, the males do not set up territories and instead chase after females. As many as five males may try to mate with a single female at the same time.

Most of the frogs in this family mate only at certain times of the year. For those that live in areas with dry and rainy seasons, the mating period usually happens in the rainy time of year. Usually, the males call only or mainly during the breeding season, although the males of some species call almost year-round. Different species have different calls. For instance, the smooth toadlet makes a buzzy, creaking sound, the eastern sign-bearing froglet gives a loud "eeek," and the Victorian smooth froglet has a repeating call that starts with a short quacking noise and follows with a repeated "tik-tik-tik-tik-tik-tik-tik." Most males call only at night, but those species that are active during the day also call sometimes in broad daylight. The moss frog, for example, makes its knocking call in the daytime from a hiding spot among plants on the floor of its mountain rainforests. Depending on the species, the males may call from underground, from a stream, pond or other watering hole, or from a hiding place on land, as the moss frog does.

Usually, the males and females pair and mate at the calling site. To mate, the male must climb onto the female's back as she lays her eggs. In a few species, however, the male calls not from the watering hole where he will mate, but from land a distance away. When a female approaches him, he climbs onto her back and she carries him to the water. The floodplain toadlet does things a little differently. Instead of the male climbing onto the female's back, she squirms underneath him while he is calling. Once she is fully beneath him, he stops calling, holds onto her, and they move to the water to mate.

THAT'S A MOUTHFUL!

The female gastric brooding frog of Australia takes very good care of her young. After she lays up to two dozen eggs, she puts them in an especially safe place where they can develop and grow, and that place is inside her stomach. Normally, the stomach acids digest things that animals eat, but the acid in these frogs' bellies turns off so the eggs can safely turn into tadpoles and then froglets inside the female's stomach. When the froglets are finally born, they leave her body the same way they came in: through her mouth. Scientists had just begun studying these unusual animals for use in controlling stomach acid in humans when the frogs disappeared. One of the two gastric brooding frog species vanished in 1983, and the second species, which was just discovered in 1983, disappeared in 1985. The IUCN now considers both to be Extinct. The same method that the frog used to turn off its stomach acid is now used in medicines to help people who have stomach ulcers. An ulcer is a sore on the wall of the stomach.

The females of some of the species in this family, like the tinkling frog, mate in the water and lay their eggs there. Their eggs hatch into tadpoles that swim off in the water and eventually turn into froglets. Others, such as the red-backed toadlet, lay their eggs on land. When rains drench the land, the eggs hatch into tadpoles that float in the rainwater or squirm on the wet soil to get to a pond or other watering hole, where they eventually change into froglets. Moss frogs also lay their eggs on land, but their tadpoles survive without a pond or even a puddle. Moss frog eggs are large and coated with jelly. When the tadpoles are born, they live in the leftover jelly for more than a year, even surviving under a layer of winter snow. After about 13 months, they finally turn into froglets. Female sandhill frogs and a few other species lay their gel-covered eggs underground. These eggs hatch into froglets, skipping the tadpole stage.

Perhaps oddest of all are the hip pocket frogs and the gastric brooding frogs. Female hip pocket frogs lay their eggs in and/or under damp leaves on the ground. The female stays with her eggs until they are ready to hatch. The male then takes over. He rests the front part of his body on the hatching eggs, and up to a dozen newborn tadpoles squirm up the sides of his body and into his two pouches, one of which is on each hip. In about two months, froglets crawl out of the pockets to face the world. In the gastric brooding frogs, on the other hand, the female takes charge. After she lays her eggs, she swallows them. The eggs turn into tadpoles and then froglets in her stomach and leave her body through her mouth. While the eggs are in her stomach, she stops eating.

AUSTRALIAN TOADLETS, WATER FROGS, AND PEOPLE

For the most part, people do not see these mostly night-active frogs in the wild. They are also uncommon in the pet trade. Scientists are interested in the skin of many of these frogs, because it oozes a gooey fluid that may one day be useful in making medicines.

TANGLED FAMILY LINES

Organizing the species of gastric brooding frogs, Australian toadlets and water frogs, and Australian ground frogs has been a confusing chore. Some people lump them all together into one family, while others separate them into three families. Scientists have been studying bones, fossils, and other characteristics to sort it out. For now, however, this book takes the middle ground with two families: the Limnodynastidae for the Australian ground frogs and the Myobatrachidae for the Australian toadlets and water frogs as well as the two recently extinct species of gastric brooding frogs.

CONSERVATION STATUS

According to the World Conservation Union (IUCN), three species are Extinct and are no longer in existence, and six are Critically Endangered, which means that they face an extremely high risk of extinction in the wild. In addition, two are Endangered and face a very high risk of extinction in the wild; four are Vulnerable and face a high risk of extinction in the wild; and three are Near Threatened and at risk of becoming threatened with extinction in the future. The IUCN also lists six as Data Deficient, which means that there is not enough information to make a judgment about their threat of extinction.

The three extinct species are the northern gastric brooding frog, which is sometimes known as the Eungella gastric brooding frog; the southern gastric brooding frog, also called the Conondale or platypus gastric brooding frog; and the Mount Glorious day frog, which also goes by the names Mount Glorious torrent frog or southern day frog. The northern and southern gastric brooding frogs vanished in 1983–1985, and although the Mount Glorious day frog was quite common in the early 1970s, it disappeared in 1979. Scientists do not know what caused the three species to die out, but they suspect that changes to their habitats, including the loss of trees and native plants, and infection with a fungus may be at least partly to blame.

Scientists are also unsure why the numbers of many other at-risk species are dropping. The Corroboree frog, which is Critically Endangered, is an example. This small species lives in mountain grasslands and forests. It is a beautiful, shiny black frog, with bright yellow or green stripes. In just 10 years, the number of adults living in the wild dropped from about 2,000 to fewer than 250 in 2004. Some scientists believe that differences in the weather, fungus infections, or habitat changes may be playing a role in the disappearance of the frogs, but they do not know for sure.

Studies of other at-risk frogs, however, have revealed why they are vanishing. The white-bellied frog, which is Critically Endangered, has become less and less common. As of 2004, it only lived in a few areas of the southwestern edge of Western Australia. Scientists believe that this burrowing frog has suffered because of habitat loss. According to the IUCN, about 70 percent of the habitat where this frog might live and breed has been logged or otherwise cleared since humans arrived in this part of Australia. The frogs now live in small groups here and there where the habitat is still in good shape.

SANDHILL FROG (Arenophryne rotunda): SPECIES ACCOUNTS

Physical characteristics: The sandhill frog, which also goes by the name of round frog, is a chubby little creature with toad-like features. It has a round, somewhat flat body with small hind legs and short, but strong front legs. The first toe on each of the unusually wide front feet is very small. The tiny head has a short, rounded snout with a hard, callous-like tip. Sandhill frogs are usually very light gray with darker gray and sometimes rust-colored speckles on the warty head, back, and legs. They also have a narrow, light-colored, sometimes hard-to-see, stripe down the middle of the back. Males and females look alike. Females grow to 1.1 to 1.3 inches (2.8 to 3.3 centimeters) long from snout to rump, and males usually reach 1 to 1.3 inches (2.6 to 3.3 centimeters) in length.

Geographic range: Sandhill frogs live along the ocean in far western Australia from Kalbarri to Shark Bay and Dirk Hartog Island.

Habitat: Sandhill frogs live in desert-like sand dunes along the ocean's coast and stay underground during the day. At night, when the air is more humid, they look for food on land. Unlike most other frogs, this unusual species does not need any ponds, streams, or even puddles of water to survive. Instead, it gets most of its moisture from the damp sand underground.

Diet: Their diet includes ants, beetles, spiders, and other arthropods.

Behavior and reproduction: A sandhill frog digs head first into the sand, making good use of its hard snout and strong front legs. It stays underground during the day, digging deep enough to reach damp sand. At night, it crawls out of the sand and starts looking for food. It does not hop, instead walking across the dunes and leaving tiny, wide-spaced footprints behind. The males call from April to July, which is late fall in Australia, but do it underground. The males and females pair up, sometimes with several pairs in the same place, and the females lay their eggs from September to December, also underground and usually about 31.5 inches (80 centimeters) deep. The young skip the tadpole stage, and froglets hatch out of the eggs.

Sandhill frogs and people: Most people only see this animal's footprints, rarely the frog.

Conservation status: This frog is quite common in the sand dunes where it lives and is not considered to be at risk. ∎

HIP POCKET FROG (Assa darlingtoni): SPECIES ACCOUNTS

Physical characteristics: Also called a pouched frog or marsupial frog, the hip pocket frog is best known for the pouch above each hind leg of the male. Each of his pouches is large enough to hold several eggs, but unless they are filled, the pockets are difficult to see and only visible as small slits. Hip pocket frogs have a rather wide body, which may be brown, pinkish brown, gray, or red. They commonly have a dark brown stripe that starts behind the eye, carries over the shoulder and onto the side of the frog behind its front leg. Their legs may have dark or faded brown bands, and all four feet end in pad-tipped toes. The underside of the frog is white. Females usually grow to 0.7 to 0.8 inches (18 to 21 centimeters) long, and males are usually about 0.1 inches shorter.

Geographic range: Hip pocket frogs live in mountains along the border of New South Wales and Queensland and in northeastern Australia.

Habitat: Hip pocket frogs make their home in the mountain rainforests that are thick with trees and plants. They usually stay out of view in deep piles of leaves, under rocks, or in other hiding places on the forest floor.

Diet: They eat various arthropods.

Behavior and reproduction: Scientists know little about their behavior outside of breeding and reproduction. The breeding season begins when the males start to make their calls, which are fast, repeated, buzzy sounds. The females follow the calls to the male's hiding spot under a log or in the leaves on the ground. When a female gets closer, the male calls even more. The male climbs onto her back and mates with her as she lays her eggs, which fall onto the damp dirt and rotting leaves. The female stays with her eggs for several days until they are ready to hatch. The male then moves in and covers the hatching eggs with the front part of his body. Tadpoles wiggle out of the eggs, up his sides, and into his hip pouches. A single male can have as many as six tadpoles in each of his two pockets. The tadpoles stay inside. Each has yolk left over from its egg that it can eat and so does not need to find any other food. In 48 to 69 days, the tadpoles change into froglets and crawl out of the male's pockets to live life on their own.

Hip pocket frogs and people: People rarely see this small frog.

Conservation status: The hip pocket frog is not considered endangered or threatened. ∎

EUNGELLA TORRENT FROG (Taudactylus eungellensis): SPECIES ACCOUNTS

Physical characteristics: Also known as the Eungella day frog, the Eungella torrent frog is a light brown or gray frog with dark brown markings on its head, back, and legs. The markings on its head include one wide blotch that stretches between its two large eyes. The markings on its hind legs may look like bands. Its body is rather long and thin, and it also has slender front and hind legs. The toes on each of its four feet widen out at the end into pads, and the bones inside the tips of the toes are T-shaped. The hind legs are much longer that the front pair. Its throat and belly are creamy white with a touch of yellow on the thighs and lower belly. Some have smooth backs, but others have scattered, small bumps. Males and females look similar, but the males are usually a bit smaller. Males grow to 1 to 1.1 inches (2.5 to 2.8 centimeters) long from the tip of the snout to the end of the rump, while females normally reach 1.1 to 1.4 inches (2.8 to 3.6 centimeters) in length.

Geographic range: Eungella torrent frogs live in a small mountainous area of mid-eastern Queensland, Australia.

Habitat: The frogs spend their days in small or large, swift mountain streams located at 490 to 3,280 feet (150 to 1,000 meters) above sea level or in the thick plants of the surrounding rainforest.

Diet: Scientists are unsure, but they think Eungella torrent frogs eat different types of arthropods.

Behavior and reproduction: Eungella torrent frogs may be active day and night, often sitting on or under rocks along the river or near waterfalls where they can feel the splash of the crashing water. They often bob their heads or wave their hind legs, apparently a way to communicate. The males may call year-round, although they tend to do more calling and mating from January to May, which is the summer and fall in Australia. The call is a soft rattle. The females lay 30 to 50 eggs at a time, and these hatch into tadpoles. The tadpoles, which have suction cups around their mouths, usually move about at the bottom of the stream until they change into froglets in November, December, and January.

Eungella torrent frogs and people: Very few people have seen this rare frog.

Conservation status: According to the World Conservation Union (IUCN), this species is Critically Endangered, which means that it faces an extremely high risk of extinction in the wild. This was a common species until 1985, when scientists began noticing that the torrent frogs were quickly disappearing. In the late 1980s, they feared the frogs might be extinct, but the frogs turned up again in 1992. They now live in nine spots inside Eungella National Park, and their numbers seem to be climbing very slowly. Scientists do not know what caused the frogs to decline in the 1980s and are watching this species closely. ∎

FOR MORE INFORMATION

Books:

Anstis, M. Tadpoles of South-eastern Australia: A Guide with Keys. Sydney: Reed New Holland, 2002.

Barker, John, Gordon C. Grigg, and Michael J. Tyler. A Field Guide to Australian Frogs. Chipping Norton, Australia: Surrey Beatty, 1995.

Campbell, A., ed. Declines and Disappearances of Australian Frogs. Canberra, Australia: Environment Australia, 1999.

Cogger, H. G. Reptiles and Amphibians of Australia. 6th edition. Sydney: Reed New Holland, 2001.

Cogger, Harold G., and Richard G. Zweifel. Encyclopedia of Reptiles and Amphibians. San Diego, CA: Academic Press, 1998.

Cogger, H. G., E. E. Cameron, and H. M. Cogger. Zoological Catalogue of Australia. Vol. 1, Amphibia and Reptilia. Canberra, Australia: Australian Government Publishing Service, 1983.

Cronin, Leonard. Key Guide to the Reptiles and Amphibians of Australia. Sydney: Envirobooks, 2001.

Ehmann, H., and G. Swan. "Reproduction and Development in the Marsupial Frog Assa darlingtoni (Leptodactylidae: Anura)." In Biology of Australasian Frogs and Reptiles, edited by G. Grigg, R. Shine, and H. Ehmann. Chipping Norton, Australia: Surrey Beatty and Sons, 1985.

Halliday, Tim, and Kraig Adler, eds. The Encyclopedia of Reptiles and Amphibians (Smithsonian Handbooks). New York: Facts on File, 1991.

Littlejohn, M. J., M. Davies, J. D. Roberts, and G. F. Watson. "Family Myobatrachidae." In Fauna of Australia. Vol. 2A, Amphibia and Reptilia, edited by C. J. Glasby, G. J. B. Ross, and P. Beesley. Canberra, Australia: AGPS, 1993.

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

Roberts, J. D. "The Biology of Arenophryne rotunda (Anura: Myobatrachidae): A Burrowing Frog from Shark Bay, Western Australia."

In Research in Shark Bay, Report of the France-Australe Bicentennary Expedition Committee, edited by P. F. Berry, S. D. Bradshaw, and B. R. Wilson. Perth, Australia: West Australian Museum, 1990.

Robinson, Martyn. Field Guide to the Frogs of Australia. Sydney: Reed New Holland, 1993.

Swan, Gerry. Green Guide to Frogs of Australia. Sydney: New Holland, 2001.

Tyler, Michael J. Australian Frogs: A Natural History. Ithaca, NY: Cornell University Press, 1994.

Tyler, M. J., ed. The Gastric Brooding Frog. London and Canberra: Croom Helm, 1983.

Periodicals:

Sunquist, Fiona. "Really Weird, Really Wild!" National Geographic World (February 1999): 3.

Web sites:

"Corroboree Frog." Kidcyber.http://www.kidcyber.com.au/topics/frog_corrob.htm (accessed on March 1, 2005).

"Frogs — Amphibia." Wildlife of Sydney.http://faunanet.gov.au/wos/group.cfm?Group_ID=36 (accessed on February 24, 2005).

"Frogs of Australia." Amphibian Research Centre.http://frogs.org.au/frogs/index.html (accessed on February 24, 2005).

"The Frogs of NSW Wetlands - Other Frogs." NSW Department of Land and Water Conservation.http://www.dlwc.nsw.gov.au/care/wetlands/facts/paa/frogs/other_frogs.html (accessed on February 24, 2005).

"Information on Protecting Australian Frogs." ASX Frog Focus.http://www.asxfrogfocus.com/ (accessed on March 1, 2005).

Jamal, Rina Abdul. "Marsupial (Pouched) Frog." AnimalFact.com.http://www.animalfact.com/article1020.htm (accessed on March 2, 2005).

"Useful Links and Frog Resources." NSW National Parks and Wildlife Service.http://www.nationalparks.nsw.gov.au/npws.nsf/Content/Useful+links+and+frog+resources (accessed on February 24, 2005).