Family Pyxicephalidae

Cacosternum nanum parvum Poynton, 1963

Mountain Caco, Mountain Dainty Frog, Berg Blikslanertjie (A)

By E. Scott

Currently accepted name: Cacosternum parvum
Red listing status: Least Concern (2013)

Photo by Allison Sharp; Vaughan Jessnitz, 2012. URL: FrogMAP: 142402

Distribution

This taxon is treated as a subspecies of C. nanum in this atlas, pending its formal elevation to full species status (E. Scott in prep.; see C. n. nanum account). There has been much confusion in the literature surrounding the separation and distribution of C. n. nanum and C. n. parvum, because the key in Poynton (1964) provides inadequate characters to separate these subspecies. Poynton (1964) and Lambiris (1989a) listed grid localities where both species are supposedly present, but these were based on some specimens being identified as both nanum and parvum (Bates 1995). Material examined from all of these contested localities was found to be referable to C. n. parvum (E. Scott in prep.), and no specimens of C. n. nanum have been obtained from any of these localities.

C. n. parvum occurs in high-altitude habitats above 1200 m along the Drakensberg escarpment. It is known from the northern parts of Eastern Cape Province but appears to have its stronghold in KwaZulu-Natal, with an apparent gap between populations in this province and those farther north, in Swaziland and Mpumalanga Province. The identity of the isolated specimen from near Louis Trichardt (2330AB), mentioned by Poynton (1964), has not been confirmed.

C. n. parvum has been recorded in sympatry with C. n. nanum at Malolotja Nature Reserve (2631AA) in Swaziland (R.C. Boycott pers. comm.), and in the Maclear (3128AB) and Mount Frere (3028DD) districts in the Eastern Cape Province (M. Burger pers. comm.).

The advertisement calls of C. n. nanum and C. n. parvum are sufficiently different to allow recognition in the field and were used to identify populations during the atlas period. The distribution map for C. n. parvum presented here is based mainly on aural records. The atlas data are accurate but incomplete.

Habitat

C. n. parvum appears to be restricted to high-altitude grassland habitats above 1200 m. It breeds in well-vegetated (grassy) ponds, marshes and streams, and inundated grassland.

This species vies with C. striatum for the title of the smallest frog in South Africa. Its small size reflects a marked trend in the genus towards size reduction in high-altitude forms.

Life history

Very little is known of the life history of C. n. parvum. Specimens recorded near Graskop, Mpumalanga Province, were calling from beneath grass at the edge of shallow puddles in inundated grassland, while another population was breeding at a seep on a grassy slope. Advertisement and (presumably) agonistic calls were recorded (L.R. Minter pers. comm.).

Conservation

C. n. parvum has been recorded from the Royal Natal National Park and the Giants Castle and Cathedral Peak nature reserves in KwaZulu-Natal Province, as well as Malolotja Nature Reserve in Swaziland. The species is locally abundant, and is not threatened or in immediate need of conservation action.

Current distribution map

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