MADAGASCARAN TOADLETS: Scaphiophrynidae

PHYSICAL CHARACTERISTICS

The Madagascaran toadlets are small frogs that look like toads. Many come in shades of brown or green, as do many toads. One of the toadlets is called the green burrowing frog. It, for instance, is green with brown blotches on its back, head, and legs. The red rain frog, however, is a more brightly colored member of this family. This species, which is also known as the rainbow burrowing frog, is red, orange red, or pink on its back and the top of its head, but white or light yellow green on its sides, legs, lower face, and underside. It also has considerable black markings on its body, along with a few yellow or whitish blotches on the back and head. Many of the toadlets have detailed, darker brown patterns on their backs. From one side of the back to the other, the patterns are usually mirror images of each other. This type of mirror-image pattern is known as a symmetrical (sim-MET-rih-kul) pattern.

Most Madagascaran toadlets have small warts. In some species, like Mocquard's rain frog, the warts may be as little as grains of sand, if they are there at all. The red rain frog has no warts on its back. Madagascaran toadlets have short back legs, but both their front and back legs have rather long toes. Each of the back feet has a noticeable bump, or tubercle (TOO-ber-kul). Their toes are either unwebbed or barely webbed. A few species, like the red rain frog and green burrowing frog have large pads on the tips of their front toes. The undersides of the frogs may be light or dark-colored. Mocquard's rain frog is a species with a white underside. It does, however, have red or dark purple patches on the undersides of its upper legs. The red rain frog, on the other hand, has a dark underside that is usually a dark grayish purple.

The web-foot frog, also known as the narrow-headed frog, looks different from the other eight species of Madagascaran toadlets. This frog has a teardrop-shaped, pudgy-looking body with a snout that comes to a point. Its hind legs are rather long. It has very small eyes that only barely bulge from the sides of the head. The toes on the back feet are fully webbed.

Males and females look much alike, although the males in some species may have darker throats and be a bit smaller than females. Depending on the species, adults may be 0.8 to 2.4 inches (2 to 6 centimeters) long from the tip of the snout to the end of the rump. Red rain frogs can grow to 1.4 inches (3.6 centimeters) long as adults. Mocquard's rain frogs are a bit smaller, and the males are even smaller than the females. Female Mocquard's rain frogs grow to 1.1 to 1.3 inches (2.8 to 3.3 centimeters) long, while males only reach 0.8 to 1.1 inches (2 to 2.7 centimeters) long. Adult web-foot frogs reach to 0.8 to 1 inches (2 to 2.4 centimeters) long. In this species males are a bit larger than females.

This family contains about nine species. Some scientists count more, mostly by splitting one or more of these nine species into two, or count fewer by grouping two into one species. Although this volume lists the Madagascaran toadlets in their own separate family, some scientists believe they should be grouped with the family of narrow-mouthed frogs.

GEOGRAPHIC RANGE

All of the species in this family live in Madagascar, a large island nation in the Indian Ocean off southern Africa.

HABITAT

Madagascaran toadlets live in many areas of Madagascar from low areas at sea level to slopes up to 6,600 feet (2,000 meters) above sea level. Although the tadpoles of all species are found in the still waters of swamps and pools of water that dry up later in the year, the adults live in a variety of different habitats. Some, like the brown rain frog and the red rain frog, prefer hot, dry places in the western and southern regions of the country. The red rain frog spends the daytime hours under stones scattered along the ground of rather humid forests that cover slopes and canyons in the dry area. Other members of this family live in much colder places high on mountains where even the trees do not survive. These frogs, including the Madagascar rain frog, which is also known as the green rain frog, exist in grassland habitats. Rainforests, on the other hand, are the surroundings for the green burrowing frog and the web-foot frog. The web-foot frog, for instance, usually stays among fallen, rotting, and damp leaves lying on the forest floor.

DIET

Scientists know very little about the diet of Madagascaran toadlets, but they believe the frogs are mainly insect-eaters. Although toadlets, like the red rain frog, will eat crickets in captivity, this does not necessarily mean that they normally eat crickets in the wild. The tadpoles are filter-feeders, which means that they strain out tiny bits of food from the water.

BEHAVIOR AND REPRODUCTION

The Madagascaran toadlets usually remain hidden during the day, staying out of sight underground, often beneath stones or logs. The green burrowing frog sometimes comes out during the day. This frog's color and pattern help it to blend in as it wanders about on leaves along the ground or climbs up green moss-covered trees. The color and pattern of the web-foot frog is also an excellent camouflage. Unless the frog moves, most people cannot see the brown and yellowish frog against the muddy ground, plants, and trees of its habitat.

Scientists have learned most of the information about this family during the frogs' mating seasons and believe that the frogs bury themselves underground and rest for much of the rest of the year. This resting period is known as estivation (es-tih-VAY-shun).

AN ANCIENT LINK

Scientists are interested in the Madagascaran toadlets because they think the toadlets may be a link between two major groups of frogs. One group, called the Ranoidea, includes the true frogs of the family Ranidae and others. The second group, called the Microhyloidea, includes the narrow-mouthed frogs and others. The skeletons of the adult Madagascaran toadlets include some bones that are like those found in both of these two groups. Madagascaran toadlet tadpoles also have a few features of each group. Because of the similarities between Madagascaran toadlets and the two major groups, scientists believe that both the Ranoidea and Microhyloidea probably had the same ancestor—one that, like the Madagascaran toadlets, had a combination of their characteristics. The species in Ranoidea kept some of those characteristics, and the species in Microhyloidea kept others.

The frogs mate during the summer's rainy season, which usually begins in Madagascar in December, January, or February. After heavy rains soak the ground and fill pools and swamps with water, males will group together at the watering holes and begin calling together. Group calling is known as a chorus. The sound of the loud choruses can carry over long distances and attract females. Each male calls by using his body and his vocal sac, which is extra flesh on his throat. He sucks in air, blows up both his body and his vocal sac, and lets out the air to make his call. This can be a dangerous time for the male frogs, which not only call in females with their calls, but may call in predators. While the males are calling and their bodies are full of air, the frogs cannot dive down into the water to escape, and this makes them easy targets for predators.

Mating in each of these frog species typically occurs all at once and over a very short time. A frog species that mates together and over a short time is known as an explosive breeder. To mate, the male holds onto the female's back by grasping her near her front legs. From this position, she lays her eggs. Many species, including the web-foot frog and Mocquard's rain frog, lay several hundred tiny eggs measuring just 0.04 inches (1 millimeter) in diameter. Usually, the eggs float together and form a film on the water surface. The eggs hatch into tadpoles. The warmer the temperature outside, the faster the tadpoles turn into froglets.

MADAGASCARAN TOADLETS AND PEOPLE

The more colorful Madagascaran toadlets are common in the pet trade.

CONSERVATION STATUS

The World Conservation Union (IUCN) considers one species in this family to be Critically Endangered, which means that it is facing an extremely high risk of extinction in the wild. All of the members of this species, the red rain frog, live in two tiny spots in south-central Madagascar. One of these spots is inside a national park. People sometimes collect this beautiful species to sell in the pet trade, but this could be hurting the species because its numbers are so low.

According to the IUCN, other species in this family are at risk. It lists the species known only by its scientific name of Scaphiophryne boribory as Endangered and facing a very high risk of extinction in the wild; the green burrowing frog as Vulnerable and facing a high risk of extinction in the wild; and the Madagascar rain frog as Near Threatened and at risk of becoming threatened with extinction in the future. Two other species known by the scientific names of Scaphiophryne obscura and Scaphiophryne verrucosa are Data Deficient, which means that too little information is available to make a judgment about the threat of extinction. Some scientists think that these two species are actually one and the same and often list them both as Scaphiophryne verrucosa.

MOCQUARD'S RAIN FROG (Scaphiophryne calcarata): SPECIES ACCOUNT

Physical characteristics: Mocquard's rain frog is a tiny species with small legs, a slightly pointy snout, and smooth to slightly warty skin on its back. Its back and head may be brown, gray, or green, often with a dark brown and symmetrical pattern on its back. Many also have a light-colored stripe running from head to rump down the middle of the back. Their legs are brown, usually with noticeable dark brown bands. Their sides are dark brown, the belly is white, and the undersides of the thighs are red or purple. The back toes have very little webbing between them, and the front toes have none at all. Males have a black throat, while females' throats are white with brown markings. Males and females are also a bit different in size. Males grow to 00.8 to 1.1 inches (2 to 2.7 centimeters) long from snout to rump, and females reach 1.1 to 1.3 inches (2.8 to 3.3 centimeters) in length. This species, along with the web-foot frog at 0.8 to 1.0 inches (2 to 2.4 centimeters) long, are the smallest Madagascaran toadlets.

Geographic range: They live in western and southern Madagascar.

Habitat: Mocquard's rain frogs live in dry areas up to 1,000 feet (300 meters) above sea level. They can survive in forests, shrubby or grassy spots, and even farmland.

Diet: Scientists know little about the frog's diet, but the stomach of one captured frog was filled with large ants.

Behavior and reproduction: Like other Madagascaran toadlets, Mocquard's rain frog is active at night during the rainy season and likely spends the dry season buried underground. Heavy rains soak the earth during the summer in Madagascar, and males of this species group together at newly water-filled pools and swamps. The males begin calling in choruses for females and create quite a racket. When a female approaches a male, he calls even faster before climbing onto her back to mate. He holds on near her front legs as she lays several hundred small eggs. The eggs hatch into tadpoles. The tadpoles, which are almost completely see-through, sift food out of the water or pick small particles out of the water to eat. The tadpoles change into froglets in a few weeks, not long before their watering hole dries up for another year. The tiny newborn froglets are just 0.2 to 0.3 inches (5.5 to 7.5 millimeters) long from snout to rump.

Mocquard's rain frogs and people: This frog disappears underground in all but the rainy season, when some may hop into people's homes.

Conservation status: The World Conservation Union (IUCN) does not consider this species to be at risk. Mocquard's rain frog is quite common in its habitat, some of which is located in protected areas. ∎

FOR MORE INFORMATION

Books:

Glaw, Frank, and Miguel Vences. A Fieldguide to the Amphibians and Reptiles of Madagascar. 2nd ed. Köln: Vences & Glaw Verlag, 1994.

Web sites:

"How Animal Camouflage Works." How Stuff Works.http://science.howstuffworks.com/animal-camouflage.htm (accessed on April 15, 2005).

"Narrow-headed frog." Madagascar Biodiversity and Conservation.http://www.mobot.org/mobot/madagascar/image.asp?relation=A56 (accessed on April 15, 2005).

"Paradoxophyla palmata." AmphibiaWeb. http://elib.cs.berkeley.edu/cgi-bin/amphib_query?query_src=aw_lists_alpha_&where-genus=Paradoxophyla&where-species=palmata (accessed on April 15, 2005).

"Species: Scaphiophryne marmorata." Naturalia.http://www.naturalia.org/ZOO/ANFIBI/e_39.html (accessed on April 15, 2005).

Staniszewski, Marc. "Madagascan Burrowing Frogs FAQ." Marc Staniszewski's Amphibian Information Centre.http://www.amphibian.co.uk/scaphiophryne.html (accessed on April 15, 2005).