MIDWIFE TOADS AND PAINTED FROGS: Discoglossidae

PHYSICAL CHARACTERISTICS

Midwife toads and painted frogs are medium-sized frogs that reach about 1.6 to 3 inches (40 to 75 millimeters) long from the snout to the rump. From the outside, the four species of midwife toads look quite different compared to the six painted frog species. The midwife toads have the typical pudgy-looking, warty body and rounded snout of a toad. The painted frogs, on the other hand, look much like the average frog with a trimmer body and a snout that narrows down almost to a point. Sometimes, the painted frogs are quite warty, but even so, they look more like a frog that happens to have warts than like a toad.

The two groups in this family do share several characteristics. Their bodies sit low to the ground, which gives them a squat look. Most of the midwife toads and the painted frogs have warts that are small but noticeable. Some, such as the Iberian midwife toads, even have warts on their eyelids. Both have a thick, disk-shaped tongue that resembles a small, round saucer instead of the long, thin tongue of most other species of frogs. They have large eyes, which may have vertical pupils that look like top-to-bottom slits, or somewhat heart-shaped pupils that are wider at the top than at the bottom.

The skeletons of the midwife toads and painted frogs also have some similar features. For example, the adults have just three ribs. Frogs, including the members of this family, have small, spiky ribs that attach to the backbone but not to the breastbone. Humans, on the other hand, have a full rib cage that is attached to the breastbone in the front and the backbone, or spine, in the back. Different species of frogs have different numbers of ribs, and they are attached to different places in the backbone. The midwife toads and painted frogs have three ribs attached to the second, third, and fourth bones in the spine (counted from the neck down).

The color of these frogs varies from species to species. Many have gray, brown, and black patterns that blend into the background. The midwife toads typically have reddish spots on the tops of their warts, which sometimes form noticeable rows down each side of the body. They are often a lighter color, sometimes white, on the underside. Many painted frogs have obvious dark bands on all four legs and spots and blotches on the back. The now-extinct Hula painted frog had an unusual dark belly that was speckled with white. Its scientific species name is nigriventer, which means a dark underside.

In some cases, members of the same species in this family look quite different. The Corsican painted frog is one such frog. In this species, some individuals are all mostly one color, usually a shade of brown or dark gray, but others are covered with obvious dark spots. In both the midwife toads and painted frogs, the males and females generally look much alike. In some species, such as the Iberian and Mallorcan midwife toads, the male is a bit smaller but otherwise looks very much like the female.

The family as it is listed here includes only the midwife toads and painted frogs. Some people, however, add fire-bellied toads and barbourulas to this family. This book lists them under their own family, called Bombinatoridae.

GEOGRAPHIC RANGE

These frogs are mainly European, living in both central and southern Europe. Some also live in northwestern Africa and Israel.

HABITAT

Besides looking different, midwife toads and painted frogs spend their time in different habitats. The painted frogs stay nearer—and often in—the water and are particularly fond of rocky-bottomed, swift-flowing streams, although some live very well in small ponds that may dry up during part of the year. Many will only go into freshwater areas, but some, such as the Tyrrhenian painted frogs, survive in somewhat salty water. When the painted frogs hop onto land, they stay along the shoreline or in areas where the ground is at least somewhat moist. The midwife toads prefer drier areas, like forests and meadows, but they never stray too far from a stream or pond. Both the midwife toads and the painted frogs stay out of sight during the day by crawling under rocks and logs or hiding in burrows that they dig.

DIET

Their diets may include beetles, caterpillars, grasshoppers, flies, and other insects, as well as other types of invertebrates (in-VER-teh-brehts), which are animals without backbones. These invertebrates may include spiders, pillbugs, and snails. Although their tongues do not flick out of their mouths, as do the long tongues of many other species of frogs, they have no trouble snapping up prey right into their mouths.

BEHAVIOR AND REPRODUCTION

Midwife toads and painted frogs are mainly active at night, which is when they hunt for food. During the day, they remain hidden under logs and rocks or in burrows. Not all of the members of this family dig their own burrows, but those that do, like the species that is known simply as a painted frog, use their front legs and toes to scrape their way into sandy ground head-first. They may pat firm the top of the burrow as they dig by butting the head up against it. Sometimes the frog digs only shallow burrows that go little farther than the length of its body, but at other times, the frog may dig a deeper, longer system with side tunnels. When the frogs leave their hiding spots at night, they tend to stay in fairly moist areas to look for food.

The males of all species call during the breeding season either from the water or from shoreline spots on land. In some species, the call sounds like chiming bells, and in others it sounds more like a series of high-pitched "poo" or "pie" noises. Unlike most other species of frogs, some females in this family also call. The Iberian midwife toad, for example, calls back when the male calls. Her call is similar, but quieter than his. Studies of the Iberian midwife toads show that females respond better to males who make faster but lower-pitched calls. Both male and female Mallorcan midwife toads also call. Some scientists believe that their calls do more than bring males and females together to mate. Their studies suggest that the toads, especially the youngest froglets—those that have just made the change from tadpoles—may listen to the calls simply to find out where other toads are, so they can join them in a safe place.

When a male and female mate, the male climbs onto her back and hangs on just above her back legs. From this position, she releases her eggs, and he releases sperm, which unite to start development. Here again, the painted frogs do things differently from the midwife toads. The female painted frogs may mate many times a night, laying up to 1,000 eggs in a single 24-hour period, and she may have more than one mating day in a year. The Iberian painted frog, for example, may mate on six separate days a year and lay a total of 1,500 eggs in a year. Females drop their eggs into the water, where they either stay on the surface or sink to the bottom. The eggs hatch into tadpoles several days later. The exact timing of the hatch depends on the temperature of the water. In Iberian midwife toads, for example, eggs in warm water can hatch in just two days, but eggs in cold water may need six days before they are ready to hatch. The young then remain in the tadpole stage until the next spring or summer, when they change into froglets. When they reach 3 to 5 years old, the young are adults and old enough to mate themselves.

The midwife toads are very unusual in the way their eggs develop. The process starts when the female lays strings of eggs, one string at a time. After 10 minutes or so, the male collects the strings and wraps them around his ankles, one after the other. By the time he is done twirling them around his legs, the male is wearing what looks like a skirt of beads. A single male may mate with several females, and some, like the Iberian midwife toad, may carry up to 180 eggs from four different females. The eggs of the Mallorcan midwife toad are larger, but fewer in number. The Iberian midwife toad's eggs are about one-tenth of an inch (2.6 to 3.5 millimeters) in diameter, and the female may lay 40 to 50 eggs at a time. The female Mallorcan midwife toad typically lays only a dozen or fewer eggs, but her eggs are twice the size at about two-tenths of an inch (5.4 to 7 millimeters) in diameter.

Regardless of the size or number of eggs, the male continues to wear and protect them until they are ready to hatch. At that time, he hops over to the water to allow the newly hatched tadpoles to swim off on their own. This unusual behavior of the male gives the toads their name: midwife toads. A midwife is a person who helps a woman deliver her baby. Although the male toad doesn't help the female bear her eggs, he does help make sure they hatch. Tadpoles of the midwife toads can grow quite quickly. Those of the Mallorcan midwife toad, for instance, can double their size and double it again in just a few weeks. Tadpoles make the change to toadlets, a process called metamorphosis (MEH-tuh-MORE-feh-sis), early the following spring and generally are old enough to mate when they reach their second year.

MIDWIFE TOADS, PAINTED FROGS, AND PEOPLE

People rarely see these toads and frogs in the wild. Scientists, however, are especially interested in the midwife toads for the unusual way the males care for the eggs. In most frogs, neither the male nor the female play any part in guarding the eggs or rearing the young.

CONSERVATION STATUS

Of the 10 species in this family, the World Conservation Union (IUCN) considers one as already Extinct, or no longer living, and three others as Vulnerable, which means that they face a high risk of extinction in the wild. It also ranks two others as Near Threatened, which means that they are likely to qualify for a threatened category in the near future.

The Extinct species is the Hula painted frog, which once lived in Israel and possibly Syria. Scientists know about this species from just five specimens, the last of which was collected in 1955. Since then, no other specimens have been found. It probably disappeared as a result of damage to its habitat, especially when people drained the wetlands where it lived in an attempt to wipe out mosquitoes and to turn the swamp into farmland.

HUMAN-CAUSED EXTINCTION

One of the Earth's frogs disappeared in the 1950s at the hands of humans. At that time, people in Israel were trying to fight a dangerous, fever-causing disease called malaria (muh-LAIR-ee-uh). The disease spreads through the bites of infected mosquitoes. One of the people's answers was to drain the swamps where the mosquitoes lived. Without water, the mosquitoes would die out, and the disease would vanish, too. The water disappeared, but the mosquitoes were not the only animals affected. The swamps were also home to other animals, including the Hula painted frog. Unlike the mosquitoes, which exist in Israel to this day, the Hula painted frog could not survive the destruction of its home and is now extinct.

The Vulnerable species are the Betic midwife toad and the Mallorcan midwife toad of Spain and the Corsican midwife toad of France. Habitat loss and destruction have hurt the Betic and Corsican toads, while the Mallorcan midwife toad faces threats from new species that have come into its habitat. These new animals, known as introduced species, include a snake and a frog. The snake, called a viperine snake, eats both adult Mallorcan midwife toads and their tadpoles. The new frog, known as the Iberian green frog or Iberian water frog, is taking away food and space from the Mallorcan midwife toad and causing the toad's numbers to drop. By the mid-1980s, conservationists had begun taking steps to protect the toad. In one effort, they have captured some toads so they could breed them in captivity and return the newborn toads to some areas where they had once lived but have since disappeared. This has been very successful, and soon three populations of these reintroduced toads had begun breeding in the wild. Conservationists are now trying to create new watering holes so they can raise and release additional toads in places that are free of animals that might eat them or compete with them for available food.

The toads are doing much better since these efforts began. In 1996, the IUCN considered the species to be Critically Endangered, which meant that it faced an extremely high risk of extinction in the wild. Just eight years later, in 2004, the IUCN saw such improvement in the toad's numbers that it took the species off the Critically Endangered list and now considers it to be Vulnerable, which means that it is at a lower risk of becoming extinct. The Mallorcan midwife toad is unusual for another reason. Until the late 1900s, scientists thought that it had become extinct 2,000 years ago, and all they would ever see were its fossils. They were stunned in 1980, when they learned of a living population that had turned up in a remote, mountainous area. Shortly after this discovery, however, the invading viperine snakes and Iberian green frogs were already taking their toll on the toads and lowering their numbers.

MIDWIFE TOAD (Alytes obstetricans): SPECIES ACCOUNTS

Physical characteristics: The midwife toad is a small, plump toad that sits low to the ground. Its tan to gray skin is spotted in black, brown, and greenish colors and is covered with tiny warts. These warts, which often sit in the middle of a dark spot, give the toad a rough look. In addition, a single row of red-tipped warts runs down each side of its back from behind the eardrum and over two larger warts to the hind leg. The two warts, each of which forms almost a ridge behind the eardrum, are called paratoid (pair-RAH-toyd) glands. These glands and the other warts on its back contain poison and help protect the toad from predators, which find that the poison tastes bad. The toad's large head has a rounded snout and big, copper-colored eyes with vertical slits for pupils. Its underside is off-white, often with gray speckles toward the front. The midwife toad has chubby legs and no webbing between its toes. Unlike many other frogs that have small, somewhat weak front legs, the midwife toad's forelegs are quite strong. The soles of its front feet have bumps, called tubercles (TOO-ber-kulz). It usually grows to 2.2 inches (5.5 centimeters) long from the tip of its snout to the end of its rump. The males are usually a bit smaller than the females.

Geographic range: The midwife toad is a European species, living in a small area in the Netherlands, in all but the coastal region of Belgium, and in much of Portugal and Spain, as well as France, Germany, Luxembourg, and Switzerland.

Habitat: The midwife toad lives in mountain ponds and slow-moving streams that are filled with water all year long and in nearby hiding places on land. Sometimes, they crawl into mostly bare, sandy soils; beneath small stones as well as large slabs of stone; and inside cracks in walls. All of these spots provide a moist, and at least somewhat warm, shelter for the toads.

Diet: The adults eat various invertebrates, including pillbugs, snails, and different insects.

Behavior and reproduction: During the day, these toads remain out of sight under stones, inside the cracks in stone walls, and in other hideaways where they are shielded from the drying wind and temperature swings. They are also able to use their forelegs to dig head-first into loose gravel and make burrows that they use as shelter. They become active as the sun sets and spend their nights looking for things to eat. They spend the winter in their hideaways, but come out in the early spring to begin mating. The mating season for these toads may begin as early as February in some areas, and it continues through the summer. At night, the male performs his mating call, which is a "poo" sound that he makes once every second or so. He may further prepare a female for mating by tickling her with his toes. They mate with the male on her back and clinging to her waist.

About 10 to 15 minutes after the female lays her strings of eggs, the male scoops them up and wraps them around his legs. He carries them there until they hatch. He may mate with more than one female and sometimes carries as many as 150 eggs at a time. As the eggs grow and become bigger, they look like large dark beads. The male stops now and then to soak the eggs in water. This keeps the eggs moist. When they are ready to hatch in about three to six weeks, the male again hops to the water. There, the tadpoles squirm out of the eggs and into the water. The tadpoles wait until the next spring when they are about 2 to 3.1 inches (5 to 8 centimeters) long to change into toadlets. Over the winter, they usually remain in the water. They are mature enough to mate when they are about 2 years old.

Midwife toads and people: Because of their secretive habits, people rarely see these toads in the wild. Scientists still find them to be fascinating creatures and are especially interested in the male's care of the young.

Conservation status: This species is not considered to be at risk. Conservationists are still watching it closely, however, because some populations of this toad have vanished or are losing numbers. The cause may be habitat destruction and possibly the introduction to the streams of fish that prey on the toads. ∎

PAINTED FROG (Discoglossus pictus): SPECIES ACCOUNTS

Physical characteristics: The painted frog is a rather wide, little frog with long hind limbs and shorter, but stocky forelegs. Its front feet have no webs between the toes, but the back toes are webbed. It is yellowish to greenish brown with long, dark, greenish brown markings. The markings may be bands or oval spots and are sometimes outlined in a lighter color. They usually have a brown band between the eyes. Often, just behind the barely noticeable eardrum, they have a thin paratoid gland that reaches back like a little ridge. The frog has a wide head with a rather pointy snout and big eyes centered with pupils that have shapes described as either hearts or upside down teardrops. Its back has scattered warts. The typical painted frog grows to 2.8 to 3.1 inches (7 to 8 centimeters) long.

Geographic range: Painted frogs live along the Mediterranean Sea in the northeastern African countries of Tunisia, Algeria, and Morocco; in Sicily, which is a southern island of Italy; and on the small Mediterranean islands of Malta and Gozo. Some have also been introduced to areas in France and Spain.

Habitat: Painted frogs live in freshwater and sometimes somewhat salty waters, usually preferring streams or small puddles. People often see them at night in the water filling tire ruts or the hoof prints of cattle. They frequently live near humans, making their homes in orchards or other farm fields, in wells and canals, or in campgrounds.

Diet: Their diet includes insects and other invertebrates.

Behavior and reproduction: Painted frogs use their strong front legs to dig burrows under stones, where they hide during the daytime. At night, they become active and begin looking for food. Their mating season runs almost all year—from January to early November. The males go to the water and give a call that sounds somewhat like the hushed chuckle a person might make in a library. To mate, a male climbs onto the female's back, grabbing her above her hind legs. Over the next half hour to two hours, she lays as many as 50 eggs while the male clings to her back. Afterward and on that same night, she may mate with many other males. The busiest of females may mate with about 20 different males and lay one thousand eggs in a single night. She drops her eggs one by one. They either clump together on the water surface or sink. In about six days, the eggs hatch into tadpoles, which change into froglets one to three months later. The froglets continue to grow and are mature enough to mate the following year.

Painted frogs and people: Because the females can lay so many eggs over a very short time, scientists sometimes use them in laboratory experiments, which may study how eggs develop.

Conservation status: This species is not considered to be at risk. In some places, however, farmlands have disappeared, and the frogs have vanished with them. ∎

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.

Gasc, Jean-Pierre, et al., eds. Atlas of Amphibians and Reptiles in Europe. Paris: Societas Europea Herpetologica and Muséum National d'Histoire, 1997.

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

Zug, George R., Laurie J. Vitt, and Janalee P. Caldwell. Herpetology. 2nd edition. San Diego: Academic Press, 2001.

Web sites:

"Discoglossidae." AmphibiaWeb.http://elib.cs.berkeley.edu/aw/lists/Discoglossidae.shtml (accessed on February 7, 2005).

"Discoglossus nigriventer." Recently Extinct Animals. http://home.hetnet.nl/harrie.maas/speciesinfo/palestinianpaintedfrog.htm (accessed on February 7, 2005).

"Mallorcan Midwife Toad Saved from Extinction." Durrell Wildlife Conservation Trust.http://www.durrellwildlife.org/index.cfm?p=295 (accessed on February 7, 2005).

"The Mallorcan Midwife Toad." Durrell Wildlife Conservation Trust.http://www.durrellwildlife.org/index.cfm?p=60 (accessed on February 7, 2005).