Family

Afrana Dubois, 1992

river frogs, rivierpaddas (A)

By A. Channing

Currently accepted name:
Red listing status:

Description

The genus name is derived from Latin: Afr = Africa and rana = frog.

Afrana was separated from the widespread genus Rana by Dubois (1992), on the basis of differences in morphology of the tadpoles. The adults are usually >55 mm in body length, with long, muscular legs and extensive webbing between the toes. Most species are green or brown with darker markings. Stripes, particularly vertebral stripes, are a common feature.

Afrana males lack external vocal apparatus, whereas males in the morphologically similar genus Ptychadena have bilateral, external vocal sacs. Another similar genus, Strongylopus, may be distinguished from Afrana by its relatively longer foot that is at least as long as the distance from the tip of the urostyle to the tympanum (Channing 2001).

Distribution

The genus Afrana comprises 10 species and is distributed throughout sub-Saharan Africa, excluding West Africa. Three of the four species that occur in the atlas region are endemic to this region. Although certain members of the genus are morphologically similar, all species may be easily identified by their calls. The atlas data are generally reliable, but a few misidentifications may have been made in areas where congeners occur (see species accounts).

Habitat

The species inhabit all biomes where they are associated with permanent water, from small springs to slow-flowing streams, large rivers, garden ponds and farm dams (Channing 1979). They usually breed in slow-flowing, shallow water. Adults remain in the same habitat throughout the year.

Life history

Breeding takes place throughout the year in warmer parts, but is restricted to the wet season elsewhere. In southwestern Western Cape Province, breeding peaks after the winter rains have started, while in the rest of the country it peaks during the summer rainy season. However, calling may be heard throughout the year in all habitats.

Eggs are laid in shallow water, in a mass that soon sinks to the bottom and becomes covered with debris. The tadpoles are solitary, and may take more than two years to reach metamorphosis.

These frogs prey on both flying and crawling insects. In turn, they are eaten by large birds, other frogs, terrapins, snakes and small mammals. In many parts of Africa, large specimens are eaten by humans.

Conservation

The genus is widespread and abundant, and is only locally threatened by habitat loss and pollution. Some species adapt tp human habitation by taking up residence in established gardens where water features are present. The members of this genus are not in need of special conservation action.