Family Rhacophoridae

Chiromantis Peters, 1854

foam nest frogs, skuimnespaddas (A)

By R.C. Boycott and J. Theron

Currently accepted name: Chiromantis sp.
Red listing status:

Description

The genus name is derived from the Greek: chiro = hand; mantis = leaf (foliage) frog. Most rhacophorids are arboreal frogs that possess enlarged toe pads. In some species, extensive webbing on the hands and feet is used for parachuting (Duellman and Trueb 1986).

In Chiromantis, the outer two fingers are widely separated from and lie almost at right angles to the inner pair, enabling the hand to effectively grasp branches or twigs. The species possess a horizontal pupil and an internal, median, subgular vocal sac. The fingers and toes are webbed and end in large, marginally grooved, adhesive discs; cartilages are present between the penultimate and terminal phalanges of the digits (Stewart 1967; Poynton and Broadley 1987; Lambiris 1989a).

These large, grey to brown tree frogs attain a maximum length of 80 mm in C. xerampelina. They have an elongated shape and a hunchbacked appearance due to the presence of large projections of the sacrum to which the pelvic girdle is attached. Their ability to change colour enables them to camouflage themselves against bark and other substrates on which they sit.

Distribution

The family Rhacophoridae, containing the genus Chiromantis, occurs in Africa, Madagascar and Asia. The genus Chiromantis comprises four species that are restricted to tropical Africa, from Sierra Leone to northern Somalia and south to southern Africa. The most widespread of the four, C. xerampelina, is the only one found within the atlas region.

Habitat

Chiromantis species inhabit Forest and Savanna biomes. In the atlas region, C. xerampelina occurs most commonly in arid bushveld and savanna habitats.

Life history

Foam nest frogs, as their name implies, construct foam nests in which eggs are laid. The foam is produced by the beating action of the hindlimbs of the female during mating, as is the case in the other four genera of rhacophorids that build foam nests (Jennions et al. 1992). In other families that have foam-nesting species, both sexes may cooperate in nest building, and forelimbs as well as hindlimbs may be used to beat the foam.

The nests are constructed on natural objects overhanging water, such as the branches of trees and shrubs, grass tussocks and rocks, as well as artificial structures such as dam walls, bridges and buildings, and the near-vertical rock walls of flooded quarries.

During nest construction, the female’s eggs are fertilized by more than one male. This breeding strategy (polyandry) is known in only one other species of southern African frog, Afrixalus delicatus (Backwell and Passmore 1991).

Once the eggs hatch, the tadpoles remain within the foam nest for several days before dropping into the water below. The nest offers protection from aquatic predators during the early stages of development.

Conservation

As far as is known, none of the species in this genus is threatened or requires conservation action. The proliferation of farm dams in savanna habitats has probably increased the number of potential breeding sites considerably.