GHOST FROGS: Heleophrynidae

PHYSICAL CHARACTERISTICS

With colors and patterns that almost perfectly match the forest floor where they live, the ghost frogs live up to their name and, when they are very still, seem to vanish into the background. The Cape ghost frog, also known as Purcell's ghost frog, has a brown back and head that are covered with black blotches—almost as if someone had shaken out a wet paintbrush and splattered black paint on the frog. When in its habitat where the green mosses and plants and dark clumps of dirt and pebbles form a patterned blanket on the ground, the frog blends in well enough almost to disappear. People and predators can walk within a few feet of this frog and never notice it.

The other five species of ghost frog also have such camouflage, or cryptic (CRIP-tik) coloration. The frogs may be tan, brown, purplish brown, gray, or green, usually have darker blotches on the back and head, and may have dark bands around the front and back legs. The blotches may be purple, brown, or nearly black. The Natal ghost frog has the opposite coloration with a brown to black head and back and yellowish to green markings. The ghost frogs' undersides are typically lighter colored and almost see-through, giving them another ghost-like quality. Sometimes they have dark markings on the throat.

All ghost frogs have front and back toes that end in large, triangle-shaped pads. They have long, thin hind legs and shorter front legs on bodies that are slightly flattened. Their back toes are webbed, sometimes all the way to the tips. Their large, bulging eyes have catlike, vertical pupils, and their snouts are rounded in front and somewhat flattened overall. In their mouths, the tongue is disk-shaped, and small teeth line only the upper jaw.

Ghost frogs are small- to medium-sized frogs, reaching 1.4 to at least 2.6 inches (3.5 to 6.5 centimeters) long from the tip of the snout to the rump. Males and females look mostly alike, but the females usually are larger. Females of the largest species sometimes reach lengths a bit longer than 2.6 inches (6.5 centimeters). Males of the species called Rose's ghost frog also have small black spines on their lower front and rear legs, back, and thighs, and male Natal ghost frogs develop pads on the lower front legs and little spines on the toes of their front feet during breeding season.

The ghost frogs were once grouped in another family that includes the Surinam horned frog and other leptodactylid frogs, but they now have their own family. Although scientists believe that the ghost frogs are a very ancient group, they have not yet found any fossils of species in this family.

GEOGRAPHIC RANGE

Ghost frogs live in and around South Africa's Drakensberg Mountains, where some of the world's highest waterfalls are found.

HABITAT

The ghost frogs may make their homes among the forests and sometimes grasslands of the Drakensberg mountain range, which are the highest mountains in South Africa. They can be found from sea level up the mountains' steep slopes to 9,843 feet (3,000 meters), but usually in an area with a swift, rocky river or stream, which is where they mate and have their young.

DIET

The adult diet includes various insects, snails, and other invertebrates (in-VER-teh-brehts), or animals with no backbone, as well as smaller frogs. They apparently are not cannibalistic (can-ih-bull-ISS-tik), which means that they do not eat members of their own species. The tadpoles are vegetarians and eat algae (AL-jee) that they scrape off underwater rocks. Algae are plantlike growths that live in water but have no true roots, leaves, or stems.

BEHAVIOR AND REPRODUCTION

During the day, they hide from sight under or between rocks, or in cracks within rocks. Their flattened bodies help them to squeeze into even small openings. At night, they hop out to look for food. Their sticky, wide front and back toe tips help them to climb easily up even the wet and slippery sides of streamside rocks. Predators often do not see these camouflaged frogs, but even when they do, they often leave them alone, because the frog's skin contains a mild poison that many predators learn to avoid.

In the breeding season, the skin on these frogs becomes baggy. They usually breed from spring to mid-summer after the heavy storms of the rainy season. Male ghost frogs group together at waterfalls or at a river or stream with a fast current and begin calling from a hiding place under a rock or in a rock crack or from a spot that is sprinkled with water from a waterfall. Some species call both day and night, but others call mostly at night. Depending on the species, the call may be quite loud or so quiet that it can only be heard from about 10 feet (3 meters) away. Some calls, like those of the Cape ghost frogs and Natal ghost frogs, are repeating ringing sounds. Male and female ghost frogs are excellent swimmers and spend much of the breeding season in the water.

YEAR-ROUND WATER

Often, a tadpole's life depends on the water where it lives. Because tadpoles do most of their breathing through their gills, they have to remain in the water until they change into froglets, which can then breathe through their skin or with their lungs on land. In many species, the tadpoles are born into small watering holes and even puddles that dry up quickly. To survive, they must make the change into froglets while they are still only weeks or months old. In some species, like the ghost frogs, however, the tadpoles do not turn into froglets for 12 to 24 months. The adults must lay their eggs in lakes, ponds, rivers, streams, and/or wetlands that stay filled with water all year. Ghost frogs usually have their young in rivers and streams. Such waterways are called "permanent" because they are always, or permanently, filled with water. Those that dry up for part of the year are known as "temporary" watering holes, because they are only filled for a while, or temporarily.

The females lay their 50 to 200 eggs one at a time either in a slow part of the stream or river or in a puddle or other wet area alongside the river or stream. Some species attach their large and gel-covered eggs to the bottom of an underwater rock. After the eggs are deposited, the female and male leave, and the eggs and tadpoles develop on their own. Usually within a week, the eggs hatch into tadpoles, which may stay in the quiet water or move into faster flowing water. They use their suction-cup-shaped mouths to grab onto rocks, while they scrape algae from them with tiny teeth. The tadpoles typically change into froglets when they are 1 to 2 years old.

GHOST FROGS AND PEOPLE

People rarely see these frogs.

CONSERVATION STATUS

According to the World Conservation Union (IUCN), two of the six species are Critically Endangered, which means that they face an extremely high risk of extinction in the wild. One is Hewitt's ghost frog, which lives in and around four streams about 1,310 to 1,805 feet (400 to 550 meters) above sea level in the Elandsberg mountains of South Africa's Eastern Cape Province. The frog breeds in the streams, but spends the rest of the year in the surrounding areas that have scattered trees and shrubs. Fires and human activity, like the logging of the few trees and the building of roads are destroying the frog's nonbreeding habitat and also allowing more dirt to drain into the streams where the frog has its young. In addition, new fish species that eat the frogs have been added to the streams, and in some places, the streams have dried up.

The other Critically Endangered species is Rose's ghost frog, which is also known as the Table Mountain ghost frog or thumbed ghost frog. This species makes its home in mountain forests, shrubby areas, and even inside caves on the sides of Table Mountain between 785 and 3,480 feet (240 to 1,060 meters) above sea level. The entire area where it lives is inside the Cape Peninsula National Park. New plants in the park, numerous park visitors, and a high number of fires are changing the frog's habitat and making it difficult for this species to survive. In addition, people have built holding areas for some of the mountain water, which is taking some away from the streams where the frogs' eggs and tadpoles develop. Since the tadpoles need more than a year before they turn into frogs and can leave the streams, they may die if too much water is sidetracked for the holding areas.

To learn more about the frogs of South Africa and how well they are surviving, scientists are now collecting information about them through the Southern African Frog Atlas Project (SAFAP).

NATAL GHOST FROG (Heleophryne natalensis): SPECIES ACCOUNT

Physical characteristics: The Natal ghost frog has a brown to black head and back with yellowish to green blotches, and a lighter colored underside with markings on its throat. Like other ghost frogs, its body is flattened a bit, and it has small triangular-shaped pads on the tips of its front and back toes. Its large, bulging eyes have vertical, cat-like pupils.

Geographic range: It lives in the Drakensberg and Maluti moun-tains of South Africa, Lesotho, and Swaziland from 1,900 to 8,776 feet (580 to 2,675 meters) above sea level.

Habitat: The forests and sometimes the grasslands of the eastern mountains of southern Africa are home to these frogs. As the breed-ing season draws near, they travel 0.6 miles (1 kilometer) or more to reach a fast-moving stream where they mate and have their young.

Diet: Tadpoles are vegetarian and scrape algae from rocks with their small teeth. As adults, Natal ghost frogs eat spiders, small insects, and other invertebrates.

Behavior and reproduction: These frogs usually hide in holes along stream banks and cliffs during the daytime, but sometimes venture out to waterfalls, where they sit in water-splashed areas and look for things to eat. They are most active at night, however, and do the bulk of their hunting then. Their breeding season begins after the heavy spring rains. During this time, the males begin calling from hideaways under rocks, or in plants near a stream, or in the splashing water from a nearby waterfall. Their call sounds like the repeated ringing of a small, quiet bell. The females arrive, mate with the males, and lay their eggs beneath underwater rocks. In about four or five days, the eggs hatch into tadpoles. The tadpoles turn into froglets when they are 2 years old.

Natal ghost frogs and people: People rarely see this frog.

Conservation status: While the World Conservation Union (IUCN) does not list this rather common frog as being at risk, it does note that the frog's numbers are slowly dropping. It believes several things are to blame. First, loggers and/or farmers are cutting down the forests that are home to this species. The removal of the trees can also muddy up the streams and rivers and make it difficult for the frogs to breed there. This muddying happens because plants, including trees, help keep rain from quickly washing down hills and slopes and taking the soil with it into the water. In addition, people are draining away water from under the ground. People are also putting barriers, or dams, in the rivers. Both activities can cause the levels of the rivers and streams to fall. If too much water disappears, the tadpoles, which need water to survive, could die. Another threat comes from fish, such as trout, that people put in the rivers. People may add trout to a waterway for sport fishing or for food. The problem is that the trout eat many other animals, including tadpoles and frogs. ∎

FOR MORE INFORMATION

Books:

Channing, A. Amphibians of Central and Southern Africa. Ithaca, NY: Cornell University Press, 2001.

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

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

Web sites:

"Cape Ghost Frog." Cape Nature Conservation. http://www.capenature.org.za/cederbergproject/html/capeghost.html (accessed on February 17, 2005).

"The Ghost Family: Six Amphibians Exclusive to Southern Africa." The World Conservation Union (IUCN).http://www.iucnrosa.org.zw/news/ghost_frogs.html (accessed on February 17, 2005).

Heying, H. "Heleophrynidae." Animal Diversity Web.http://animaldiversity.ummz.umich.edu/site/accounts/information/Heleophrynidae.html (accessed on February 17, 2005).

"Table Mountain Ghost Frog." University of the Western Cape.http://www.botany.uwc.ac.za/envfacts/fynbos/ghost_frog.htm (accessed on February 17, 2005).

"UCT (University of Cape Town) scientists join project." Amphibian Conservation Alliance. http://www.frogs.org/news/article.asp?CategoryID=46&InfoResourceID=939 (accessed on February 17, 2005).