Family Hyperoliidae

Hyperolius pickersgilli Raw, 1982

Pickersgill’s Reed Frog, Avoca Reed Frog, Pickersgill se Rietpadda (A)

By P.J. Bishop

Currently accepted name: Hyperolius pickersgilli
Red listing status: Endangered

Photo by Evans Nick, 2013. URL: FrogMAP: 1147

RED LIST SPECIES

Status: Endangered (EN) Criteria: B1ab(ii,iii,iv)+2ab(ii,iii,iv)

Identification

H. pickersgilli is a small- to medium-sized Hyperolius species that reaches a snout–vent length of 22.3 mm in males and 28.5 mm in females (Raw 1982). The sexes are morphologically distinct.

Males and juveniles are light to dark brown, often with small black spots on the dorsum, and a dark-edged, white to silver, dorsolateral stripe extending from the tip of the snout, over the eye, to the groin. The lower surfaces of the limbs are yellow, while the abdomen and throat are yellowish to white. Adult males have a bright yellow gular sac.

As females mature, the dorsal colouration becomes a brilliant light to yellowish green and the dorsolateral stripe disappears, although a dark canthal streak from nostril to eye is sometimes present. The flanks are off-white to brownish white, and are distinctly demarcated from the dorsal colouration by an irregular margin. The ventrum is light yellow to white.

The males of H. argus, a sympatric species, possess a similar dark-edged, dorsolateral stripe, but the snout is less pointed and the thighs and concealed portions of the hands and feet are brown to orange or orange-red. H. pickersgilli females can be distinguished from H. tuberilinguis by the distinct border that separates the dorsal and lateral colouration in the former. H. pickersgilli is also substantially smaller than both H. tuberilinguis and H. argus (Raw 1982; Lambiris 1989a; Passmore and Carruthers 1995; Channing 2001).

Male H. pickersgilli produce unusually soft, cricket-like calls at irregular intervals. The call structure, with reference to published calls, is as follows: emphasized frequency: 3–3.3 kHz; duration: 0.1–0.7 s; number of pulses: 5–30; pulse rate: 50–100/s (Raw 1982; Passmore and Carruthers 1995). This variation may be partly due to a difference in the temperature at which the recordings were made (not indicated by the authors). A larger call sample, corrected to a common temperature, is required before a satisfactory description of the advertisement call can be given.

Distribution

H. pickersgilli is endemic to KwaZulu-Natal, ranging from west of Kingsburgh (3030BB) in the south, along the coastal lowlands to St Lucia (2832AD) in the north. At least eight subpopulations (sensu IUCN criteria) are known (Harrison et al. 2001). The species is secretive, inconspicuous and easily overlooked: for example, at Twinstreams-Mtunzini Natural Heritage Site (2831DD), an area where frogs have been extensively studied for the past 25 years, this species escaped notice until fairly recently. Thus, although the area of suitable breeding habitat is relatively small, surveys may reveal additional populations.

It is interesting to note that this species is seldom found at the same breeding sites as H. marmoratus.

The atlas data may be regarded as reliable, but incomplete.

Habitat

H. pickersgilli inhabits Coastal Bushveld-Grassland, where it breeds in marshy areas containing dense stands of Saw Grass Cyperus immensus. The water at breeding sites is stagnant and rarely exceeds 50 cm in depth.

Life history

The behavioural ecology of H. pickersgilli in the non-breeding season is unknown. Calling takes place August–March, and froglets have been collected from late January to early March. Males call from elevated positions, well concealed in dense stands of sedges Cyperus spp.

A gelatinous mass of about 50 eggs is attached to vegetation, several centimetres above the water (Raw 1982). About one week later, tadpoles drop out of the egg mass into the water.

Raw (1982) noted that this species often occurs in sympatry with several other hyperoliids that also lay their eggs out of water, and speculated that this choice of oviposition site represents an adaptation to breeding in stagnant water with a low oxygen content.

Conservation

Status

H. pickersgilli has been listed as Rare (Branch 1988) and as Vulnerable (IUCN 2000). Its status was raised to Endangered in view of its small area of occupancy (<500 km²), severe fragmentation of its habitat, and evidence of a continuing decline in the area of occupancy, extent and quality of habitat, and number of locations (Harrison et al. 2001; this publication).

H. pickersgilli occurs in the following protected areas: Greater St Lucia Wetland Park, Umlalazi Game Reserve and Twinstreams-Mtunzini Natural Heritage Site. Outside of these areas it is protected by the KwaZulu-Natal Nature Conservation Ordinance, No. 15 of 1974, as amended. It is listed as a species of importance in KwaZulu-Natal (Goodman 2000).

Threats

The major threats to H. pickersgilli are ongoing habitat loss and fragmentation as a result of drainage for agricultural and urban development. The pollution of breeding sites in the vicinity of human settlements by DDT, which has been re-introduced to control malaria vectors, also poses a serious threat. Increase in human habitation and changes in land use are likely to have additional negative effects on the habitat, including the spread of alien vegetation.

Recommended conservation actions

A thorough distribution survey and a study of the life history and habitat requirements of this species are recommended. Known breeding habitats should be protected and monitored (Harrison et al. 2001).

Management recommendations include habitat management, limiting factor management, public education and monitoring programmes. This species often occurs in relatively small, stagnant ponds, which are more likely to be drained by landowners and municipalities than are larger wetlands. The public should be made aware of the importance of preserving these small pockets of breeding habitat.

Current distribution map

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