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African Treefrogs: Hyperoliidae

African Wart Frog (acanthixalus Spinosus): Species Accounts

Physical characteristics: The African wart frog is covered with warts on its head, back, and the tops of its legs. It is an olive green, gray, or brown frog with dark bands—sometimes broken bands—that run from one side of its back to the other. It has thin legs, some webbing between the toes of its front and hind feet, and round pads on the tips of its toes. It has large brownish eyes and a rather long snout that narrows toward the front. This frog has an orange tongue. It can grow to 1.4 inches (3.6 centimeters) long from its snout to its rump. Young frogs are orange and maroon.

The African wart frog is active at night. During the day, it typically sits in a puddle of water that has formed inside a tree hole or a pocket on a branch. (Illustration by Emily Damstra. Reproduced by permission.)

Geographic range: It lives in west-central Africa, including Cameroon and the Democratic Republic of the Congo.

Habitat: This frog makes its home in rainforests that are thick with trees and plants. It spends most of its time in water-filled holes of either living or dead trees, sometimes in holes of large branches.

Diet: Although scientists are not sure what they eat, they suspect that these frogs probably eat arthropods, as do many other species in this family.

Behavior and reproduction: The African wart frog is active at night. During the day, it typically sits in a puddle of water that has formed inside a tree hole or a pocket on a branch. Usually, the frog floats underwater with just its nostrils sticking out into the air. The frog may hop out of the water at night to find food. Its body colors and patterns help to hide it from predators, but if a predator does see the frog and comes too close, the African wart frog closes its eyes, tucks its legs in tight against its body, and thrusts out its tongue. This may startle a predator enough that it leaves the frog alone.

This frog mates near the water of its tree hole or branch. Unlike other frogs, the male African wart frog does not have a vocal sac and does not make a call, so a female cannot find him by hearing him. Instead, scientists think the male and female locate each other by smell. The pair mate above the water, and the female lays eight to ten yellow-colored eggs that attach with a sticky gel to the wall of the tree or branch hole barely above the water. The eggs hatch into tadpoles, and the tadpoles drop down into the water, where they live and grow for about three months. During that time, they eat little bits of food that they find in the water, such as pieces of plants. They then turn into froglets.

African wart frogs and people: People rarely see this frog. Since the males make no calls, people never hear them either.

Conservation status: The IUCN lists this species in the category of "least concern," which means that it is under no known threat of extinction and the animal does not qualify for any of the Threatened categories. With many species of frogs, scientists estimate the size of the population during the mating season when the males are calling and the frogs are easiest to find. Since the males in this species of frog are quiet, scientists have not been able to make good estimates about the frogs' numbers. Nonetheless, they believe the frogs are quite common. Since the frogs mate and lay their eggs in the holes of trees, the logging of these trees may cause a problem for the frogs in the future. ∎



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

Lovett, Sarah. Extremely Weird Frogs. Santa Fe, NM: John Muir Publications, 1991.

Mattison, Chris. Frogs and Toads of the World. New York: Facts On File Publications, 1987.

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

Schiotz, Arne. Treefrogs of Africa. Frankfort am Main, Germany: Edition Chimaira, 1999.

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Web sites:

"African Tree Frogs (Hyperoliidae): Herpetology." Chemistry Biology Pharmacy Information Center. http://www.infochembio.ethz.ch/links/en/zool_kriecht_froesche_laub_afrikan.html (accessed on May 10, 2005).

"Family Hyperoliidae (African tree frogs)." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/pictures/Hyperoliidae.html (accessed on May 10, 2005).

Heying, H. "Family Hyperoliidae (African tree frogs)." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Hyperoliidae.html (accessed on May 10, 2005).

Opisthothylax immaculatus. AmphibiaWeb. http://elib.cs.berkeley.edu/cgi-bin/amphib_query?query_src=aw_lists_alpha_&where-genus=Opisthothylax&where-species=immaculatus (accessed on May 10, 2005).

Razzetti, Edoardo R., and Charles Andekia Msuya. Field Guide to the Amphibians and Reptiles of Arusha National Park (Tanzania). http://www.gli.cas.cz/SEH/files/tanzie2002.pdf (accessed on May 16, 2005).

Additional topics

Animal Life ResourceAmphibiansAfrican Treefrogs: Hyperoliidae - Physical Characteristics, Habitat, Diet, Behavior And Reproduction, Conservation Status, Bubbling Kassina (kassina Senegalensis): Species Accounts - GEOGRAPHIC RANGE, AFRICAN TREEFROGS AND PEOPLE