Family Hemisotidae

Hemisus guttatus Rapp, 1842

Spotted Shovel-nosed Frog, Spotted Snout-burrower, Gespikkelde Graafneuspadda (A)

By G.J. Alexander

Currently accepted name: Hemisus guttatus
Red listing status: Vulnerable

Photo by Dickinson R, 2010. URL: FrogMAP: 257

RED LIST SPECIES

Status: Vulnerable (VU) Criteria: B2ab(ii,iii,iv)

Identification

This striking species is quite unmistakable. The largest of its genus, H. guttatus reaches 80 mm in body length. The dorsum is uniform olive to dark brown with scattered, small yellow spots; the ventrum is white (Lambiris 1989a). It resembles other Hemisus species in having a small head, small eyes and a pointed snout with a hard tip. Other adaptations to its burrowing lifestyle include a lack of webbing between the toes, muscular legs and arms, and thick, strong fingers.

The advertisement call is a cricket-like trill, approximately 2 s in duration, with an emphasized frequency of just over 2 kHz. By contrast, the call of H. marmoratus is twice as long and has a frequency of about 3.5 kHz (Passmore and Carruthers 1995; L.R. Minter pers. comm).

Distribution

H.guttatus is endemic to the atlas region, occurring in southern Mpumalanga and central and eastern KwaZulu-Natal. Along the coast it has been recorded from Hluhluwe (2832BA) in the north, to Durban (2930DD, 2931CC) in the south. It also occurs as far inland as Dundee (2830AA, AB), Newcastle (2729DB) and Piet Retief (2630DD). In 1993, this species was unexpectedly discovered on the summit of the Lebombo Mountains (2732AA; W.R. Branch pers. comm.).

Although H. guttatus may be locally abundant, its fossorial habitat ensures that it is rarely observed and few locality records exist. The apparently patchy distribution may be the result of an inadequate data set rather than an indication of a fragmented population. The atlas data are accurate but incomplete and inadequate for a reliable description of the distribution range.

Habitat

Along the coast, H. guttatus inhabits Coastal Bushveld/Grassland, while in the interior it occurs in North-eastern Mountain Grassland and Natal Central Bushveld. It has also been collected in pitfall traps in the Dukuduku Forest Reserve (T. Bodbijl pers. comm.).

It breeds on the edges of pans or swampy areas, and along rivers, especially where the gradient is slight and alluvial deposits are present (Alexander 1990; Passmore and Carruthers 1995). More adequate data may show that this species is restricted to particular river catchments.

Life history

Males call October–December during rain or light drizzle (Alexander 1987). Calling males are notoriously difficult to find. Calling may initially take place underground, with males emerging onto the surface as the chorus intensity increases, as is the case in H. marmoratus. A calling H. guttatus male was unearthed at the onset of a heavy downpour, in its burrow on the edge of a grassy pan (L.R. Minter pers. comm.).

As is usual for Hemisus, amplexus appears to be initiated on the surface and the female then burrows down to form the brood chamber. The female remains with the eggs during their development. Wager (1986) reported that females lay c.2000 eggs (cf. Channing 2001: 200 eggs), which form a circular compact mass c.63 mm in diameter and 18 mm deep. The nest cavity is located c.200 mm below the surface and has a diameter of c.75 mm.

Data on breeding imply a similar sequence of maternal care as has been recorded for H. marmoratus (Kaminsky et al. 1999). However, the postulation that females escort tadpoles to water needs verification (Van Dijk 1997), as direct observations of this behaviour have not been published.

Conservation

Status

H. guttatus was not listed in earlier South African Red Data books (McLachlan 1978; Branch 1988). However, in view of its small area of occupancy (501–2000 km), severely fragmented distribution, the rate of habitat loss (>20% in the past 50 years), a decrease in the quality of habitat and predicted population decline (rate unknown), it was accorded Near Threatened status (Harrison et al. 2001), subsequently changed to Vulnerable (this publication).

This species is known to occur in the Greater St Lucia Wetland Park (World Heritage Site), Umlalazi and Bluff nature reserves, Hluhluwe-Umfolozi Park and Bonamanzi Private Nature Reserve. Of concern is the fact that breeding populations appear to be relatively small, with <10 individuals heard calling at any one site during the atlas survey.

Threats

The long-term survival of H. guttatus is threatened by rapid and extensive urban development, forestry and other agricultural practices, particularly along the KwaZulu-Natal north coast. These activities result in the continuing loss, fragmentation and alteration of its habitat through the draining, impoundment and eutrophication of wetlands in the vicinity of residential areas and agricultural lands. Impounded wetlands are often stocked with alien fish species, which may result in the local extinction of frog populations, while plantations of exotic trees reduce the availability of surface water and lead to the disappearance of natural pans.

Recommended conservation actions

There is an urgent need for baseline studies to measure sizes of populations and to determine the extent of occurrence and area of occupancy so that this species’ conservation status can be properly assessed (Harrison et al. 2001). In particular, the presence of H. guttatus in protected areas needs to be documented and monitored. The basic biology of this species, its life history and limiting factors, also await description.

This little-known and charismatic species should be brought to the attention of the public, and private landowners should be encouraged to participate in its protection.

Current distribution map

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