Family Pyxicephalidae

Arthroleptella

By P.J. Bishop

Currently accepted name: Anhydrophryne ngongoniensis
Red listing status: Critically Endangered



Photo by Rollinson D P; Andre Bernon, Patrick Rollinson, 2010. URL: FrogMAP: 309

Identification

The small size of the adult frog (16–22 mm), coupled with the softness of its call, probably explain why this species remained undetected until fairly recently. Males produce a soft, trilled, cricket-like call, repeated three or four times with an interval of about one second between calls. The call consists of 8–10 pulses with a duration of 55 ms, and the frequency at the midpoint is 4.5 kHz (Bishop and Passmore 1993; Passmore and Carruthers 1995). Males call in bouts of up to seven calls, often alternating with an adjacent male.

The dorsal colouration is fairly consistent with no sexual dimorphism, being a sandy to golden brown background with four indistinct stripes composed of small dark brown spots. A broad, dark brown stripe (bordered ventrally and dorsally by a thin white/silvery stripe) begins at the tip of the snout and passes through the nostril, eye and tympanum to end at the axilla. The belly is white, while the ventral surfaces of the limbs and throat are pale yellow.

Distribution

A. ngongoniensis is endemic to a small area of mistbelt on the eastern escarpment in KwaZulu-Natal and the Eastern Cape where it occurs at altitudes in excess of 1000 m. At the time of the species’ description (Bishop and Passmore 1993), it was known from only three localities in the Ixopo region, all within a single quarter-degree grid cell (3030AA). Although another three localities in three different grid cells were discovered during the atlas period, the species’ area of occupancy still appears to be restricted to less than 10 km2. The new localities are Ngele Forest Reserve near Weza (3029DA), Poortjie in the Mpur forestry area east of Franklin (3029BC), and south of Donnybrook (2929DD). Even the predicted distribution of this species does not extend its range significantly (Armstrong 2001). The atlas data are reliable.

Habitat

The breeding and non-breeding habitat is in Short Mistbelt Grassland, Moist Upland Grassland, and Afromontane Forest. Preferred sites are located on fairly steep slopes (30–40°) on either side of seepage channels, covered with a dense growth of indigenous grasses, but at Ngele the species occurs in Afromontane Forest. Most of the known sites are surrounded by exotic tree plantations. The frogs are usually found at the bases of grass and sedge tussocks amongst a network of loose tunnels in the humus layer.

Life history

In misty weather, males call throughout the day and night, but only during the night in less humid conditions. During the day males call from well concealed positions at the bases of grass tussocks, while at night they climb to calling positions about 20 cm below the tips of the grass stems and are easily seen. Males do not possess a vocal sac and produce a quiet call. Eleven to 14 unpigmented eggs are laid on damp soil or vegetation at the bases of grass tussocks. The tadpoles undergo direct development, emerging as fully formed froglets approximately 27 days after egg laying (Bishop and Passmore 1993).

Although there are no documented accounts of predators, these are likely to include snakes, other frog species and invertebrates, while prey includes ants, termites, insect larvae, and other small invertebrates characteristic of the grassland leaf litter.

Conservation

Status

In the description of this species, the authors (Bishop and Passmore 1993) recommended that it be classified Vulnerable. Harrison et al. (2001) and this publication list it as Critically Endangered in view of its small area of occupancy (<10km2), rapid rate of habitat loss (>50% over the past 50 years) and an estimated global population size of less than 2500 individuals in six fragmented and isolated sub-populations.

A. ngongoniensis occurs in the Ngele Forest Reserve and is protected by the KwaZulu-Natal Nature Conservation Ordinance, No. 15 of 1974, as amended.

The population at Poortjie, east of Franklin, occurs on land under management of Singisi Forest Products. The conservation importance of the site was brought to the attention of this tree-farming company, that has responded positively by appointing a consultant to draw up a management plan and monitoring protocol. The largest known population of Leptopelis xenodactylus (Endangered) also occurs at this site, which was therefore highlighted as one of the most important frog localities in the Eastern Cape/KwaZulu-Natal region (cf. Burger and Harrison 2002). Efforts were underway as of January 2003 to obtain permanent protection for the site, the first initiative in South Africa to establish a nature reserve specifically for the protection of frogs.

Threats

The major threat to A. ngongoniensis is habitat loss and fragmentation due to afforestation and other agricultural practices. The ongoing encroachment of alien trees and plantations is likely to alter moisture regimes, and the presence of quantities of woody vegetation can cause lethally hot fires, presenting a potential threat. Timber harvesting, which can drastically alter habitat over a short period of time, also presents a potential future threat.

In addition, all the grassland types in which this species occurs are poorly conserved, and in the absence of fire, Afromontane forest and grassy fynbos may invade these grasslands (Bredenkamp et al. 1996).

Recommended conservation actions

Urgent conservation action was recommended by Harrison et al. (2001) as rapid deterioration or loss of its habitat could easily lead to the extinction of this species. A population and habitat viability assessment was recommended. In addition, the remaining protected areas of moist upland grasslands, such as the Coleford and Himeville nature reserves, should be intensively searched for new populations of this species.

Management recommendations include the establishment of a monitoring programme, and management of wild populations, habitat and limiting factors. In view of an extremely restricted and fragmented distribution, priority should be given to the conservation and management of the remaining habitat of this species before it becomes extinct.

Current distribution map



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

Citation:

  • Web:
    FrogMAP. 2017. Arthroleptella. Animal Demography Unit. Acceesed from http://frogmap.adu.org.za/?sp=110; on 2017-11-22 11:11:17.
  • Book:
    Minter L.R., Burger M., Harrison J.A., Braack H.H., Bishop P.J. & Kloepfer D. (eds). 2004. Atlas and Red Data book of the frogs of South Africa, Lesotho and Swaziland. SI/MAB Series no. 9. Smithsonian Institution, Washington, D.C. Published by the Smithsonian Institution and the Avian Demography Unit (now Animal Demography Unit).