Family Ptychadenidae

Ptychadena porosissima (Steindachner, 1867)

Striped Grass Frog, Grassland Ridged Frog, Gestreepte Graspadda (A)

By L.R. Minter and N.I. Passmore

Currently accepted name: Ptychadena porosissima
Red listing status: Least Concern

Photo by Evans Nick, 2014. URL: FrogMAP: 2017

Distribution

P. porosissima is distributed from Ethiopia, southern Zaire and Angola, southward throughout East Africa to Zambia, Zimbabwe and southern Mozambique (Stewart 1967; Poynton and Broadley 1985b; Channing 2001). In the atlas region it is recorded from a few scattered localities in Limpopo and Gauteng provinces, but is more widely distributed in Mpumalanga, western Swaziland, KwaZulu-Natal, and the northeastern part of Eastern Cape Province, almost reaching East London in the south (3227DD).

Poynton (1964) suggested that P. poyntoni Guibé 1960 from Inhluzane, KwaZulu-Natal, was based on a hybrid population of P. uzungwensis and P. porosissima, and placed P. poyntoni in the synonymy of P. porosissima. Jacobsen (1989) was of the opinion that the Inhluzane population probably reflected the range in variation within P. porosissima, rather than a hybrid population involving P. uzungwensis.

The atlas data are reliable as this species is easily identified by its call and by diagnostic morphological characters. The distribution range shown in the map is reasonably accurate although the coverage is incomplete. More intensive surveys are required in order to clearly demarcate the distribution pattern of this species.

Habitat

P. porosissima has adapted to a wider range of habitats than the other Ptychadena species in the atlas region: from the sub-tropical coastal environment of KwaZulu-Natal, to temperate grassland along the crest of the great escarpment and the highveld and, occasionally, wooded grassland (Passmore 1978; Jacobsen 1989). It is also widely distributed at high elevations in Malawi and other parts of Africa (Stewart 1967).

In the atlas region, this species inhabits a variety of vegetation types in the Grassland Biome (Jacobsen 1989). In these habitats the altitude ranges from sea level to 2300 m.

The breeding habitat includes vleis, inundated grassland and sedge pans.

Life history

Adults have been recorded throughout the year in moist depressions and seepage areas, and occasionally along streams, but may move as far as 500 m from water (Stewart 1967; Jacobsen 1989). They probably survive dry conditions in the same way as other Ptychadena species, for example, by retreating into deep mud-cracks, although no specific instances are recorded in the literature.

Males usually call from concealed positions amongst emergent vegetation within the water, supporting themselves on emergent plants, with the hind third of their bodies submerged (Passmore 1978). Calling peaks between 23:00 and 02:30, at which time temperatures are usually substantially lower; this may represent a pre-adaptation that has allowed this species to invade temperate habitats (Passmore 1978).

Less intense calling continues throughout sporadic dry periods in summer, that is, calling is not dependent on rain, perhaps due to an association with relatively permanent bodies of water (Passmore 1978). In wet weather, choruses may develop during the day (Stewart 1967).

Eggs are laid in shallow water with silty or sandy substrates, and float at the surface (Lambiris 1989a; Channing 2001).

Adults feed opportunistically on terrestrial arthropods (Inger and Marx 1961), as well as earthworms, snails and other frogs (Channing 2001).

Conservation

Although P. porosissima is widespread and occurs in a few protected areas, its distribution is patchy and its conservation status is uncertain. Surveys of populations in conservation areas are needed (Jacobsen 1989).

Current distribution map

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