Natal Cascade Frog (Hadromophryne natalensis)

View the above photo record (by Tyrone Ping) in FrogMAP here.

Find the Natal Cascade Frog in the FBIS database (Freshwater Biodiversity Information System) here.

Family Heleophrynidae

NATAL CASCADE FROG – Hadromophryne natalensis

Hewitt, 1913

Habitat

H. natalensis inhabits clear, swift-flowing streams in mountainous terrain; these waters flow through wooded and forested habitat and have headwaters in montane grassland. Annual rainfall in these habitats is 800–2700 mm. Adults often frequent waterfalls and cascades, where they may be found beneath submerged rocks, in rock cracks, in caves, or sometimes in exposed positions on wet rock faces. Tadpoles live on rocky substrates in swift-flowing streams; when disturbed they take cover beneath rocks or in cracks (Boycott in prep.).

This species occupies both Forest and Grassland biomes. Vegetation types include Afromontane Forest, Wet Cold Highveld Grassland, Moist Upland Grassland, North-eastern Mountain Grassland, Afro Mountain Grassland and Short Mistbelt Grassland.

Behaviour

Young frogs have been collected under stones and on moss covered boulders in shallow headwater streams in May and August in the Woodbush Forest and the Wonderwoud. Three adult female specimens were found in a wet rocky recess at the base of a waterfall in October in Malolotja Nature Reserve, Swaziland. These observations indicate that at least some individuals in the population remain in the vicinity of the breeding habitat after the presumed breeding period has passed. In the KwaZulu-Natal Drakensberg, adults were found in a soil pit and in a hole in a road cutting in grassland, some distance from the nearest streams and forests (Bourquin and Channing 1980; Channing 2001).

Breeding usually takes place in late summer (March–May) when stream flow is reduced, and before winter temperatures become severe (pers. obs.). Males usually call from hidden sites beneath clusters of boulders in stream beds, under the roots of large trees growing in streams, amongst boulders that have created a cascade of rushing water, in rock cracks and crevices in waterfalls, and on cliff faces and rocks located close to waterfalls and cascades. The species has not been heard calling while submerged and males do not call in close proximity to one another, even during peak breeding periods (Boycott in prep.).

The eggs and oviposition sites of H. natalensis have not been described, but it is unlikely that its breeding biology differs greatly from that of the related Heleophryne species.

Status and Conservation

The forested ravines and high altitude montane grasslands, which are the natural habitat of H. natalensis, are mostly protected within remote wilderness areas. However, afforestation with exotic trees, particularly in Mpumalanga and Limpopo provinces, has substantially reduced the non-breeding habitat and caused perennial streams to dry up, effectively eliminating entire breeding populations in the process (L.R. Minter pers. obs.). Additional threats to certain isolated populations comprise the damming of mountain rivers as has occurred in the Lesotho Highlands Project, water extraction and the introduction of alien fish species into the habitat. Nonetheless, owing to the wide distribution of this species, it is not considered to be a conservation priority. It occurs in several private and public protected areas, including Ukahlamba-Drakensberg Park, a World Heritage Site.

Distribution

H. natalensis is endemic to the atlas region. It occurs throughout the Drakensberg and Maluti mountains and along the great escarpment of South Africa, Swaziland and Lesotho. The recorded altitudinal range is 580–2675 m (Boycott in prep.).

The atlas records are reliable but incomplete, especially for most of Lesotho. This species should be easy to detect since the tadpoles are easily identified and are present in streams throughout the year. Channing (2001) expressed the opinion that this taxon contains a number of cryptic species and that field and laboratory investigations should be undertaken to explore this possibility.

Further Resources

Virtual Museum (FrogMAP > Search VM > By Scientific or Common Name)

More common names: Natal Ghost Frog (Alternative English Name); Natalse Snelstroompadda (Afrikaans)

Recommended citation format for this species text:

Boycott RC, Tippett RM.  Natal Cascade Frog Hadromophryne natalensis. BDI, Cape Town.
Available online at http://thebdi.org/2021/12/20/natal-cascade-frog-hadromophryne-natalensis/

Recommended citation format: 

This species text has been updated and expanded from the text in the
2004 frog atlas. The reference to the text and the book are as follows:

Boycott RC 2004 Hadromophryne natalensis Natal Cascade Frog. In Minter LR
et al 2004.

Minter LR, Burger M, Harrison JA, Braack HH, Bishop PJ, Kloepfer D (eds)
2004. Atlas and Red Data Book of  the Frogs of South Africa, Lesotho and
Swaziland. Smithsonian Institution, Washington, and Avian Demography
Unit, Cape Town.