Seychelles Frogs: Sooglossidae
Seychelles Frogs: Sooglossidae
SEYCHELLES FROGS: SooglossidaeSEYCHELLES FROG (Sooglossus sechellensis): SPECIES ACCOUNT
A small family, the Seychelles frogs include only four species. They are Gardiner's frog, which is one of the tiniest frogs in the world; a species known simply as Seychelles frog; Thomasset's frog; and the family's newest member, Seychelles palm frog, which scientists named in 2002. The frogs have a typical frog appearance with hind legs that are longer than the front legs, long toes on the hind feet and shorter ones on the front feet, and large, bulging eyes on the head. They also have a somewhat pointy snout and horizontal pupils in their eyes.
The four species come in different colors. The upper body of the Seychelles frog is usually yellowish brown with black spots and blotches. The Gardiner's frog may be reddish brown or tan with or without spots or stripes and sometimes with noticeable, small warts. The newly named Seychelles palm frog is light brown with a dark, diamond-shaped pattern in the middle of its back and faded dark patterns on its hind legs. Finally, Thomasset's frog is dark brown to reddish brown with a thin, light stripe running from its snout down the middle of its slightly warty back to its rump. The back also sometimes has small light-colored specks on either side of the line. Whatever their color or pattern, however, the four species blend in quite well with their habitat. Males and females look alike.
Depending on the species, the adults may be very small or medium-sized. The Gardiner's frog, which is tiny enough to completely fit on a U.S. dime, only reaches about 0.4 to 0.5 inch (1.0 to 1.3 centimeters) long from the tip of its slightly pointy snout to the end of its rump. The largest member of the family is Thomasset's frog. This species usually grows to 1.8 inches (4.5 centimeters) in length. As in many other types of frogs, the females of each species are a bit larger than the males. For example, a female Gardiner's frog usually grows to 0.47 inch (1.19 centimeters) long and sometimes reaches 0.5 inch (1.3 centimeters) long, while the male typically grows to 0.4 inch (1 centimeter) long with a maximum length of 0.43 inch (1.1 centimeters).
In 2003, scientists announced the discovery of a new species of frog, known only by its scientific name—Nasikabatrachus sahyadrensis. They placed this species in its own family, but have since decided that its nearest relatives are the Seychelles frogs. In other words, the new species and the Seychelles frogs have the same ancestors. Nasikabatrachus sahyadrensis is a very odd-looking purple frog that apparently stays underground for all but two weeks a year, when it comes out to mate. The World Conservation Union (IUCN) considers it to be Endangered, or facing a very high risk of extinction in the wild, because it lives in a small area of mountain forests, and its habitat is disappearing as the forest is turned into farmland. As of 2004, scientists had only found 135 individuals, and only three of those were females.
Seychelles frogs live only in the country called Seychelles, which is a group of islands in the western Indian Ocean about 580 miles (930 kilometers) northeast of Madagascar. Scientists believe that these islands may have been part of India far in the past, but about 55 to 65 million years ago, India began to slowly move away to its current location, about 1,800 miles (2,900 kilometers) north and now part of Asia. Like many other islands, the Seychelles islands are actually the tops of mountains that are mostly underwater. Scientists believe that the common ancestor of the Seychelles frogs and the new species of Nasikabatrachus sahyadrensis, lived more than 130 million years ago when Seychelles and India were still connected. As of yet, they have found no fossils of any of the four Seychelles frogs or of the new purple species.
Within Seychelles, these frogs live only on Mahé and Silhouette islands, and usually more than 656 feet (200 meters) above sea level, although a single Thomasset's frog was found lower on the mountain, at about 312 feet (95 meters) above sea level. Rainforests are home for all four species. The Seychelles palm frog only lives in those areas that have plenty of palms, and Thomasset's frog likes to remain in forests near rocky streams.
They will eat mosquitoes, fruit flies, and other small insects, as well as mites and other invertebrates (in-VER-teh-brehts), which are animals without backbones, that they find in the forest. Thomasset's frog also hunts for insects alongside streams.
BEHAVIOR AND REPRODUCTION
The four Seychelles frogs usually stay out of sight under piles of leaves lying on the rainforest floor, inside cracks in rocks, and even within hollow plant stems or on the base of a leaf where it attaches to a stem. The Seychelles palm frog, for example, hunkers down in the leaves of palm and sometimes banana trees. Usually, only rains will bring the Seychelles frogs out of their hiding places. During these wet periods, the frogs will hop about day or night looking for food. Thomasset's frog often settles on a streamside rock after sunset and waits for flying insects to zip by closely enough for it to capture and eat them.
The mating season occurs during the rainy season. Males may call during the day or at night from under leaves or from one of their other hiding spots. Unlike the males of many other types of frogs, males in the Seychelles frog family do their calling alone and from their own personal, on-land location. In other frogs, the males often group together in one place—usually in the water—and all call at the same time.
NEW PURPLE FROG!
In 2003, scientists announced the discovery of a new, red-eyed, purple frog that is so unusual, they even created a separate family for it. The frog, which is only known by its scientific name—Nasikabatrachus sahyadrensis—was described in National Geographic News as "a bloated doughnut with stubby legs and a pointy snout." Villagers in a small village in western India found the odd frog while digging a well and turned the purple creature over to scientists. After studying it, the scientists agreed that it was not only a new species, but was so different that it needed its own family, which is now known as Nasikabatrachidae. Of all the other frogs in the world, they think it is most closely related to the Seychelles frogs, which live 1,900 miles (3,000 kilometers) away on an island country in the Indian Ocean.
From the "wrracck toc toc toc toc" of the Thomasset's frog to the high "peep" of the Gardiner's frog, each species has its own call. To mate, the male climbs onto the female's back and uses his front legs to hang just in front of her hind legs. Although scientists do not know how some of these frogs lay their eggs or how those eggs develop into frogs, they do have details about Gardiner's frog and the Seychelles frog species. The female Gardiner's frog lays her eight to 15 eggs in a hiding place on the ground and stays with them. Instead of hatching into tadpoles, these eggs hatch in three to four weeks right into tiny froglets, each one about 0.12 inch (3 millimeters) long—no bigger than a grain of rice. As the froglets hop away, the female's job is done and she leaves. In the Seychelles frog species, the female lays her eggs on land and stays with them just as the Gardiner's frog does, but her eggs hatch in two to three weeks into tadpoles. Without water to swim in, the tadpoles instead wiggle up and cling to the mother's back. They stay there until a short while after they turn into froglets, and finally hop off to live on their own.
As yet, scientists are not sure how Thomasset's frogs or the Seychelles palm frogs mate, where the females lay their eggs, whether their eggs develop into tadpoles or right into froglets, and if the adult female or adult male watch over their young. They do know, however, that the female Thomasset's frog lays large eggs, and they think this may mean that her eggs skip the tadpole stage and hatch right into froglets. All frog species with eggs that hatch into tadpoles go through what is known as indirect development. Those whose eggs skip the tadpole phase and develop directly into froglets go through direct development.
SEYCHELLES FROGS AND PEOPLE
People rarely see these secretive frogs.
According to the World Conservation Union (IUCN), all four species are Vulnerable, which means that they face a high risk of extinction in the wild. Because all these frogs live in small areas, and some have small populations, changes to their habitat could possibly be dangerous to them. Fortunately, many live in Morne Seychellois National Park or inside the boundaries of a conservation project on Silhouette Island, and some seem to be able to survive in newly growing forests that were once cut down.
Physical characteristics: The Seychelles frog is yellowish-brown with black spots and blotches on its head, legs, and back. The blotches on its back legs may look like bands. It usually has a triangular-shaped, dark spot that runs from one of its rather large eyes across its forehead to the other eye. Its snout is somewhat pointed. The toes on its long hind legs and shorter, thinner front legs have no webbing between them. The females usually grow to about 0.8 inch (2 cen-timeters) long from the tip of the snout to the end of the rump, while the typical size of the males is about 0.6 inch (1.5 centimeters).
Geographic range: Seychelles frogs live on Mahé and Silhouette Islands in Seychelles, a country in the Indian Ocean.
Habitat: They make their homes in the rainforests of the island mountains at least 660 feet (200 meters) above sea level. They usually hide in leaf piles on the ground, often in areas where cinnamon grows.
Diet: Seychelles frogs' diet includes small insects and other invertebrates that the frogs find on the forest floor.
Behavior and reproduction: They usually remain hidden, except on wet days and nights. During these rainy periods, they hop out of their hiding spots to search for food. To mate, the males begin calling from under the leaves at any hour of the day or night. A male climbs onto the back of a female and mates with her while hanging onto her body just above her hind limbs. She lays her eggs on land, and her six to 15 eggs hatch into tadpoles, which scramble onto her back. The tadpoles stay on her back and soon turn into froglets. The froglets leave her back to grow up on their own. At one time, scientists thought that the tadpoles rode on the back of an adult male. A closer look, however, showed that it was the female who was the caretaker of her young.
Seychelles frogs and people: People rarely see these frogs.
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. The frog lives in a small area on only two islands, but it is quite common there. Some of the frogs live in Morne Seychellois National Park and others within the boundaries of a conservation project on Silhouette Island. While it is doing quite well, a change to its habitat could possibly hurt some populations or the entire species. As people move closer to its habitat, conservationists are keeping a watchful eye on this species. ∎
FOR MORE INFORMATION
Halliday, Tim, and Kraig Adler, eds. The Encyclopedia of Reptiles and Amphibians (Smithsonian Handbooks). New York: Facts on File, 1991.
Noble, Gladwyn K. The Biology of the Amphibia. New York: McGraw-Hill, 1931.
Nussbaum, R. A. "Amphibians of the Seychelles." In Biogeography and Ecology of the Seychelles Islands, edited by D. R. Stoddart. Hague: Dr. W. Junk, 1984.
"'Weird stuff' found in India." Current Science January 16, 2004 (89): 12.
"Amphibians." Silhouette Island.http://www.silhouette-island.com/public/amphibians.htm (accessed on February 22, 2005).
"The Animal Life." Virtual Seychelles, Republic of Seychelles.http://www.virtualseychelles.sc/envi/envi_nathis_frm.htm?nathis_body=envi_nathis_amph.htm (accessed on February 22, 2005).
"Pictures of Seychellfrogs (Sooglossidae)." Swiss Herp.http://www.swissherp.org/Amphibians/Sooglossidae/Sooglossidae.html (accessed on February 22, 2005).