Family Microhylidae

Phrynomantis annectens (Werner, 1910)

Marbled Rubber Frog, Gemarmerde Rubberpadda (A)

By A. Channing

Currently accepted name: Phrynomantis annectens
Red listing status: Least Concern

Photo by Wingate G., 2013. URL: FrogMAP: 1705

Distribution

P. annectens is endemic to the larger Namib region, from Angola southward through western Namibia, reaching South Africa in the extreme northern parts of Northern Cape Province. In the atlas region, it is known from the Augrabies Falls, the Richtersveld around the Vandersterrberg Mountains, and the rocky areas between Aggenys/Pofadder and the Gariep (Orange) River. These areas range from 600 to 1200 m in altitude.

The atlas survey added several new Bushmanland localities for P. annectens. The species probably occurs in other localities with suitable habitat in the Richtersveld and in Bushmanland south of the Gariep (Orange) River. The atlas data are reliable but likely to be incomplete.

Habitat

In the atlas region, P. annectens occurs in the far-northern parts of the Succulent Karoo and Nama Karoo biomes where it is associated with inselbergs and other rock exposures. The pools of rainwater trapped in these outcrops provide breeding habitat. The average annual rainfall in this region is <60 mm, falling mainly in winter in the west (Richtersveld) and in summer in the east (Bushmanland).

Life history

Breeding takes place immediately after the first rains of spring or summer. Males call from the edges of small pools formed by the runoff from sheets of rock, or in the deeper rock pools remaining in drainages after the rains. Females lay 80–100 eggs in groups of 2–8 and attach them to submerged rock surfaces or vegetation (Channing 1976, 2001). These develop quickly and free-swimming tadpoles hatch within 18–36 hours. Older tadpoles are large and transparent with flattened heads and conspicuous fins, flecked with silver and gold. They are gregarious, forming schools that hang in the water column and filter out unicellular algae and diatoms (Channing 2001). The tadpole stage lasts at least eight weeks before metamorphosis is completed. During the dry season the adults aestivate in deep rock cracks.

Predators of the adults have not been recorded, but dragonfly nymphs are known to prey on the tadpoles.

Conservation

The distribution of P. annectens is mainly extralimital and it occurs in many protected areas in Namibia and Angola. In South Africa, it occurs in Richtersveld and Augrabies Falls national parks, and is protected by provincial (Northern Cape) conservation regulations. In the atlas region, the habitat occupied by P. annectens is not heavily exploited, hence the species is not classified as threatened. However, quarrying and mining lead to the pollution of surface water by fuels and lubricants used to run and maintain heavy machinery, and this will affect local populations.

Current distribution map

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