Family Bufonidae

Schismaderma carens (Smith, 1848)

Red Toad, Red-backed Toad, African Split-skin Toad, Rooiskurwepadda (A)

By J. Theron and L.R. Minter

Currently accepted name: Schismaderma carens
Red listing status: Least Concern

Photo by Diedericks G., 2008. URL: FrogMAP: 18

Distribution

The Red Toad occurs from southeastern Democratic Republic of Congo and Tanzania, southward to Botswana, Zimbabwe and Mozambique. In the atlas region, S. carens is found from Vryburg (2624DC) in North West Province, eastward through the northern Free State, Gauteng, Limpopo Province, northern and eastern Mpumalanga and Swaziland, and southward throughout KwaZulu-Natal to Port Edward (3130AA). Within this area the species appears to be absent from the relatively cool highveld grasslands between Wakkerstroom and Dullstroom in Mpumalanga, and the relatively hot and dry Limpopo River valley.

The species cannot be confused with any other toad species and has a particularly characteristic call. The atlas data are reliable.

Habitat

This species inhabits a wide variety of vegetation types, primarily in the Savanna biome, but is also found in Grassland vegetation types, such as Rocky Highveld Grassland in Gauteng (Poynton and Broadley 1988; Lambiris 1989a). It breeds in deep, muddy pools or dams in these habitats.

Life history

When not breeding, S. carens has been found in caves, mine adits, burrows, and under stones, logs and piles of dead vegetation. It often enters houses, taking shelter in cupboards, plant pots, drawers and other unexpected places (Poynton and Broadley 1988; Jacobsen 1989; Lambiris 1989a). Individuals have even been found 2 m from the ground in trees. This toad seems to emerge earlier in spring and remains active later in autumn than most other summer-breeding species (Jacobsen 1989).

Breeding occurs in summer, usually at the peak of the rainy season. Calling has been recorded October–January in the Suikerbosrand Nature Reserve in Gauteng (Carruthers and Carruthers 1979). The low, booming call is produced while floating in water with limbs outstretched. Calling usually occurs at night but also on overcast, humid days. A large breeding aggregation at Hans Merensky Nature Reserve called throughout the night, laying their eggs in the early hours of the morning. By dawn, amplexing pairs were still present at the site but no egg-laying was observed (L.R.M. pers. obs.). Eggs are laid in double strings (cf. Stewart 1967) entwined around submerged vegetation. Estimates of egg numbers vary from about 2500 to 20 000 (Rose 1962; Stewart 1967; Passmore and Carruthers 1995; Channing 2001).

Tadpoles exhibit shoaling behaviour, forming dense clusters, 10–15 cm in diameter, that slowly move through the water, possibly aiding feeding by stirring up the substrate and creating a suspension of food particles (Wager 1965; Pienaar et al. 1976; Passmore and Carruthers 1995). This shoaling behaviour does not appear to deter predators as there are many records of fish, terrapins, birds and aquatic insects and their nymphs or larvae feeding avidly on these swarms (Pienaar et al. 1976; Channing 2001.). An interesting feature of the tadpole is the horseshoe-shaped fold of skin that extends backwards from behind the eyes to the middle of the body. This structure has a respiratory function, demonstrated by the fact that it is larger in tadpoles that are reared in polluted water with a low oxygen content. Under these conditions the tadpoles swim close to the surface (Charter and MacMurray 1939; Channing 2001).

Amplexus between S. carens and Bufo poweri has been observed in the wild (Power 1926a), but Blair (1972) was unable to induce artificial fertilization between these species. Given the great phylogenetic divergence between Schismaderma and Bufo, it seems unlikely that successful hybridization actually occurs and museum specimens identified as hybrids are probably anomalous individuals.

Conservation

S. carens is not threatened. It occurs in numerous protected areas, including the Kruger National Park and adjacent private nature reserves, the Sandveld and Suikerbosrand nature reserves, and the Greater St Lucia World Heritage Area. Even in disturbed areas it adapts well to human habitation, occurring commonly in suburban gardens and homes. The ability of the tadpole to survive in polluted water favours its survival in human settlements, but adults and juveniles are often killed by traffic on roads.

Current distribution map

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