Description
Hadromophryne natalensis males measure up to 45 mm and females to 63 mm SVL (Wager 1986). The eyes of H. natalensis are large and protruding and have vertically elliptical pupils (Burton 2002). The head is somewhat flat (Burton 2002). The body is also flattened, with expanded triangular discs on the fingers and toes (Wager 1986). Toes are half-webbed (Wager 1986). Breeding males have spines on the dorsal surfaces of Fingers I-III, as well as around the shoulders (Channing 2001).

This frog varies in color from brown to dark blue-black, with blotches of yellow or green (Channing 2001; Wager 1986). Limbs are barred (Wager 1986). The underside is whitish and the throat is marbled with light brown (Wager 1986).

Hadromophryne natalensis tadpoles reach 85 mm in total length, with the body 32 mm and the tail 53 mm (Wager 1986). The tadpole has a modified mouth, with only a lower beak (Channing 2001). Teeth of young tadpoles have been described as "fanglike", replaced by regular denticles as the larvae mature (Channing 2001). Tadpoles have four upper rows and generally 14 lower rows (range 12-17) of labial teeth (Wager 1986). The mouth is encircled by papillae, with two rows of papillae above the mouth and four rows below (for a drawing of the mouth, see Wager 1986). The oral disc is “suckerlike", allowing it to cling to rocks in fast-flowing streams (Channing 2001). A long, laterally flattened, and muscular tail is present (Burton 2002), with narrow fins that begin 1/3 of the way down the tail (Wager 1986). The coloration is brown with darker mottling and sometimes a black tail tip (Wager 1986).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Lesotho, South Africa, Swaziland

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (3 records).

Hadromophryne natalensis is found along the eastern scarp of South Africa, in the Maluti and Drakensberg Mountains, from Lesotho along the KwaZulu/Natal monocline to western Swaziland, and then north along the Drakensberg escarpment to Limpopo Province (Grobler et al. 2003; IUCN 2008). It occurs in montane primary forest with high rainfall (800-2700 mm) and clear, shaded, perennial, highly oxygenated fast-flowing streams (Grobler et al. 2003; Boycott 2004; Wager 1986), and kloofs (gorges) (Wager 1986). The elevational range is 580-2,675m asl (Boycott 2004). The habitat requirements coupled with a preference for high elevation result in highly localized distributions (Grobler et al. 2003).

Life History, Abundance, Activity, and Special Behaviors
Hadromophryne natalensis is not commonly observed and consequently its biology is still poorly known (Grobler et al. 2003). Tadpoles are present in the streams year-round and are much easier to find than the adult frogs (Wager 1986). Natal Ghost Frogs are nocturnal, generally concealing themselves under streambed rocks throughout the day but emerging at night to climb over the rocks and even into the trees (Burton 2002). Sometimes they are observed during the day, waiting for prey in the splash zone of waterfalls (Lambiris 1989). These frogs live and reproduce around fast flowing mountain streams, although adults may also be found up to a kilometer from streams, under stones or piles of debris (Wager 1986), or in cliffside and bank holes (Channing 2001). The holes are sometimes a very tight fit, and often only the snout of the frog shows (Wager 1986).

These frogs breed in late summer (March-May), when stream flow is lower (Boycott 2004). When breeding season begins, males begin to call from concealed spots under large boulders in streambeds, the splash zones of waterfalls, rock crevieces in waterfalls, rock ledges near waterfalls or cascades, or from under roots of trees growing in the stream (Channing 2001; Boycott 2004). Males do not call in close proximity to one another (Boycott 2004). The call has been described as similar to a faint ringing bell (Boycott 2004) or to the call of the Egyptian fruit bat Rousettus aegyptiacus (Channing 2001). A melodious "ting" is sounded around two times a second, lasting 140ms with a dominant frequency of 1.5 kHz, and repeated slowly about ten times (Channing 2001; Boycott 2004). Sometimes a "currick" sound precedes the series of bell-like "tings" (Boycott 2004). Amplexus is inguinal (Burton 2002). Heleophrynid females are oviparous, attaching clutches of 50-200 eggs to the underside of submerged rocks, with the eggs hatching in 4-5 days (Boycott 2004).

The tadpoles are algae-feeders, and leave a characteristic cleared grazing trail on algae-covered streambed rocks. Young H. natalensis tadpoles have fanglike teeth, which are replaced by regular denticles over time (Channing 2001). To effectively deal with swift flowing water, tadpoles are equipped with ventral, oral suction discs, which are used as an anchor (Channing 2003). The tadpoles can also use the ventral sucker in locomotion. By alternating movements of the upper and lower lips, the larvae can "walk" along rock surfaces both forwards and backwards, and even climb up out of the water along a wet rock face (Wager 1986). Adhesion is strong enough that it is very difficult to pry the tadpole loose (Wager 1986).

Generally tadpoles are found in very shaded sections of the stream, but at higher elevations they may sometimes be found in sunlit parts of the stream (Wager 1986). Metamorphosis takes up to two years, and thus perennial streams are required (Wager 1986; Boycott 2004).

Front legs appear at about 30 mm, at which stage the tail is still present but the suctorial mouth disappears; the froglet hides in partially submerged stream vegetation or in rock crevices until metamorphosis is complete (Wager 1986).

As adults, Natal Ghost Frogs consume insects, spiders, and other arthropods (Channing 2003).

This species has somewhat toxic skin secretions, with one component similar to a toxin in the wasp Vespa mandarina (Channing 2001).

Trends and Threats
Hadromophryne natalensis is listed as “Least Concern” as a species (Minter et al. 2008). At least two populations occur in protected areas (Grobler et al. 2003), including Ukahlamba-Drakensberg Park, which is a World Heritage site (Boycott 2004). However, this species requires clear, highly oxygenated streams with algae-covered rocks for tadpole development (Grobler et al. 2003). Some populations face localized threats, such as pollution, silting due to overgrazing, and habitat degradation due to proximity to urbanization (Grobler et al. 2003). Others face habitat loss due to planting with exotic trees and subsequent drying up of streams, or damming of mountain rivers, or predation due to introduction of exotic fish (Boycott 2004). In addition, larval populations have been reported to have a high level of chytrid infection (68% of tadpoles in preliminary surveys), although no chytrid-related mortality has yet been observed in H. natalensis (Smith et al. 2007).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Urbanization
Drainage of habitat
Dams changing river flow and/or covering habitat
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Predators (natural or introduced)
Disease
Loss of genetic diversity from small population phenomena

Comments
Hadromophryne natalensis may actually be a species complex (Channing 2001). Separated by areas of lower elevation, populations are often restricted to their mountainous habitats. These geographical boundaries are barricades to gene flow; genetic variation is low within populations but high amongst populations (Grobler et al. 2003).

This species was formerly known as Heleophryne natalensis, but has recently been separated out into a new genus (van Dijk 2008). A complete, annotated 3D model of this species can be found on Sketchfab, a result of the NSF oVert Digitization project.

References

Boycott, R. C. (2004). ''Heleophryne natalensis Hewitt, 1913.'' Atlas and Red Data Book of the Frogs of South Africa, Lesotho, and Swaziland. SI/MAB Series #9. L. R. Minter, M. Burger, J. A. Harrison, H. H. Braack, P. J. Bishop, and D. Kloepfer, eds., Smithsonian Institution, Washington, D. C..

Burton, M., and Burton, R. (2002). ''Ghost Frog.'' International Wildlife Encyclopedia. M. Burton and R. Burton, eds., Marshall Cavendish Corporation, New York.

Channing, A. (2001). Amphibians of Central and Southern Africa. Cornell University Press, Ithaca.

Channing, A. (2003). ''Natal ghost frog.'' Grzimek's Animal Life Encyclopedia, 2nd edition. Volume 6, Amphibians. M. Hutchins, W. E. Duellman, and N. Schlager, eds., Gale Group, Farmington Hills, Michigan.

Grobler, J. P., Mafumo, H. B., and Minter, L. R. (2003). ''Genetic differentiation among five populations of the South African ghost frog Heleophryne natalensis.'' Biochemical Systematics and Ecology, 31(9), 1023-1032.

Lambiris, A. J. L. (1989). ''A review of the amphibians of Natal.'' Lammergeyer, 39, 1-210.

Phaka, F.M., Netherlands, E.C., Kruger, D.J.D., Du Preez, L.H. (2019). Folk taxonomy and indigenous names for frogs in Zululand, South Africa. J Ethnobiology Ethnomedicine 15, 17. [link]

Smith, K. G., Weldon, C., Meyer, L., and du Preez, L. (2007). ''COS 59-1: Patterns of amphibian chytrid prevalence and mortality in the Drakensberg Mountains of South Africa and Lesotho.'' Conference abstract, Ecological Society of America/Society for Ecological Restoration, 2007 meeting, San Jose.

Wager, V. A. (1986). Frogs of South Africa: Their Fascinating Life Stories. Delta Books, Craighall.

van Dijk, D. E. (2008). ''Clades in heleophrynid salientia.'' South African Journal of Herpetology, 57, 43-58.

Species Account Citation: AmphibiaWeb 2023 Hadromophryne natalensis: Natal Ghost Frog <https://amphibiaweb.org/species/2053> University of California, Berkeley, CA, USA. Accessed Nov 22, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Nov 2024.

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