Family Pyxicephalidae

Strongylopus springbokensis Channing, 1986

Namaqua Stream Frog, Springbok Frog, Namakwa Langtoonpadda (A)

By A. Channing

Currently accepted name: Strongylopus springbokensis
Red listing status: Vulnerable

Photo by Grundlingh Felicity, 2012. URL: FrogMAP: 936

RED LIST SPECIES

Status: Vulnerable (VU) Criteria: B1ab(iii)+2ab(iii)

Identification

S. springbokensis resembles S. grayii in overall shape, but in profile it has a sharper snout. In S. springbokensis, the foot length is less than twice the head width, whereas in S. grayii it is more than twice the head width. The dorsum is yellowish brown with darker markings edged in dark brown. A narrow vertebral stripe is often present. Breeding males have small spines along the back of their legs and webbing develops along the margins of their fingers, making them broad and paddle-shaped (Channing 2001).

The advertisement call of S. springbokensis consists of a series of 2–7 notes with a total duration of 1.17 s (7 notes; Channing 2001). The call is easily distinguishable from the short clicking call of S. grayii. Aggression and male release calls are also produced.

Distribution

S. springbokensis is endemic to the Northern Cape Province of South Africa. It is distributed from the Gariep (Orange) River valley southward through Namaqualand to Garies (3018CA), and as far east as Aggenys (2918BD). Altitude ranges from 200–1600 m. Distribution data are difficult to collect as the breeding sites are not obvious and are often inaccessible. The atlas data are reliable but probably incomplete.

Habitat

In relatively low-lying areas, S. springbokensis inhabits Upland Succulent Karoo vegetation in the Succulent Karoo Biome, while on the mountains it occurs in North-western Mountain Renosterveld of the Fynbos Biome. These areas receive annual rainfall of <60 mm. In this arid environment, these frogs are restricted to the proximity of springs, seeps, small permanent and non-permanent streams and artificial impoundments.

Life history

At the start of the winter rains, males begin calling from well-concealed call sites, usually some distance from water. The eggs are laid out of water, in the vicinity of the calling male. They are deposited under rocks or in rock crevices, tunnels in vegetation, or rodent burrows. Development is arrested after the tadpole’s eyes and tail are well formed. Tadpoles remain at this stage until rain floods the nest and then emerge from the egg capsules to continue their development in the water (Channing 1986).

Conservation

Status

S. springbokensis was assigned to the category Data Deficient (Harrison et al. 2001) but was subsequently re-assessed and raised to Vulnerable (this publication). This decision was based on the results of additional atlas surveys that confirmed the limited and fragmented nature of the species’ distribution and the threats to its habitat. The species is distributed among at least four subpopulations (sensu IUCN criteria): Springbok, Richtersveld, Ghaamsberg and Kammiesberg. The habitat of each subpopulation is fragmented.

S. springbokensis occurs in Richtersveld National Park.

Threats

S. springbokensis is threatened by habitat loss which is expected to continue at the rate of <20% over the next 30 years. Increased grazing pressure, destruction of vegetation around breeding sites, siltation of streams, and pollution were identified as specific threats. A local threat in Springbok (the town for which this species is named) is the conversion of the type locality, an old reservoir in the town, to a duck pond, with the subsequent disappearance of this species from the site.

Recommended conservation actions

Additional distribution surveys and monitoring of populations at known breeding sites are recommended. Research aimed at identifying limiting factors should be conducted so that the habitat can be managed appropriately.

Current distribution map

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