Family Hyperoliidae

Afrixalus delicatus Pickersgill, 1984

Delicate Leaf-folding Frog, Delicate Spiny Reed Frog, Delikate Blaarvouendepadda (A)

By M. Pickersgill and P.J. Bishop

Currently accepted name: Afrixalus delicatus Pickersgill, 1984
Red listing status: Least Concern (2013)

Photo by Evans Nick, 2012. URL: FrogMAP: 606

Distribution

A. delicatus is distributed along the coastal plain of Mozambique (Pickersgill 1984; Poynton and Broadley 1987), and is also known to occur in southern Malawi, ranging northward along the East African coast to southern Somalia (M.P. unpubl. data). In the atlas region, ubiquitous populations of A. delicatus occur along the coastal belt of northern KwaZulu-Natal, reaching Mount Edgecombe (2931CA) in the south. This species is syntopic with A. s. spinifrons at many localities where the ranges of these two species overlap (M.P. pers. obs.).

A. delicatus is also similar, morphologically, to A. aureus, and is sympatric with that species over part of its range. However, the latter seems to prefer drier habitat and does not usually utilize the same breeding sites (Pickersgill 1984; M.P. pers. obs.). Also, the advertisement call of A. aureus lacks a “zip” component and cannot be confused with A. delicatus.

The accurate identification of A. delicatus and A. s. spinifrons requires careful morphological examination and recording of the advertisement call. However, most of the atlas data were obtained from identified museum material or from field workers familiar with these species, and may therefore be regarded as reasonably accurate and complete.

Habitat

A. delicatus inhabits Coastal Bushveld-Grassland: a mosaic of forest patches, evergreen thicket and secondary woody vegetation set in a grassy matrix, that extends along the KwaZulu-Natal coast from sea level to an altitude of 300 m. The annual rainfall exceeds 1000 mm and there is an abundance of surface water that collects in a variety of natural wetlands and artificial impoundments. When breeding, this species seems to show a preference for relatively permanent bodies of water such as ponds, vleis and marshes, particularly those with emergent vegetation that includes Polygonum pulchrum and Ludwigia stolonifera used during oviposition. (Telford 1982; Backwell 1991).

Life history

A favourite retreat in winter is the leaf axils of Strelitzia and bananas; little else is known about the behavioural ecology of A. delicatus during the non-breeding season.

Breeding takes place September–February in South Africa. Males congregate on emergent vegetation at their breeding sites in the evening and call until about 00:30, although calling activity is more subdued after midnight or once most of the males have paired. In South Africa, calling males within a chorus form groups of about eight individuals with a density of 2–3.2 males/m² (Backwell and Passmore 1991), and about 25% of males are satellites (Backwell 1991). In Kenya, choruses consist of many hundreds of males with aggregation densities of 15–>40/m² (M.P. pers. obs.).

The eggs are white, enveloped in vertically folded leaves of grasses and herbs, up to 15 cm above the water. The mean clutch size is 93 (Wager 1965; Telford 1982; Pickersgill 1984; Backwell and Passmore 1991).

During the day, both sexes retire to leaf axils of vegetation in or near standing water, although some individuals may be found in exposed positions on the shaded sides of Cyperus or Typha leaves (M.P. pers. obs.). A. delicatus is believed to feed largely on mosquitoes (Wager 1965) and other small insects. The predators of this species are unknown.

Conservation

A. delicatus occurs in a number of reserves, particularly in northern KwaZulu-Natal, such as those at Kosi Bay, St Lucia, Dukuduku and Mtunzini. However, further south its survival is threatened by sugar farming that has resulted in extensive habitat loss, draining of wetlands, and burning. Urban sprawl places additional pressure on breeding populations. In urban areas, A. delicatus survives as isolated populations largely associated with well-vegetated water hazards on golf courses and stagnant seepages at the fringes of farmland.

Current distribution map

Undated records;  pre-1996;  1996 to 2002;  2003 to present