Cover photo by Jean-Paul Brouard.

Find the Common Caco in the FBIS database (Freshwater Biodiversity Information System) here.

Family Pyxicephalidae

Identification

The Common or Boettger’s Caco is a small species that attains 23mm in length. The body is somewhat elongate and widest in the belly region, with a narrow head and a long neck. The dorsal colouration varies from green to light and dark brown or sometimes greyish. Individuals may be spotted, striped or uniform in colour. There is a dark band running from the snout, through the eye, to the base of the forelimbs. Below this there is a pale band along the upper lip from the snout to the base of the forelegs. The undersides are smooth with small grey to black spots. The limbs are relatively long and thin.

Habitat

The Common or Boettger’s Caco inhabits a wide variety of vegetation types in the Nama Karoo, Succulent Karoo, Savanna, Grassland, Fynbos and Thicket biomes. This species is usually absent from forests, although it is sometimes found in forest clearings. Within these biomes, it favours open areas with short vegetation and is especially abundant in grassy areas. The Common Caco can tolerate drier habitats than C. nanum, but also occurs in high-rainfall areas (Van Dijk 1977). In the Nama Karoo and Kalahari, C. boettgeri occurs naturally only in pans or along river courses, but can also be found in artificially created water bodies. The Common Caco breeds in any small, temporary water body, such as pools in flooded grasslands, culverts and other rain-filled depressions.

Behaviour

During the dry season, the Common Caco aestivates in mudbanks, mudcracks, the burrows of other animals, disused termitaria, and under stones.

This species appears to have an extended breeding season. During the rainy season, males usually start calling in the late afternoon and call incessantly after dark, continuing until around midnight. Large choruses are common.

Call bouts are usually initiated by the same individual in the group (Channing 2001). Males normally call from concealed positions under vegetation or other cover, at water level, but have also been observed calling from totally exposed positions. A short territorial call is sometimes uttered by individual males prior to their regular advertisement call. In addition to the advertisement and territorial calls, several other vocalizations are known from the males of C. boettgeri, but their function is not well understood.

Clutches of c.250 eggs are attached to vegetation below the surface of the water (Channing 2001). The tadpoles usually hatch two days later, and metamorphosis is completed within approximately two weeks (Pienaar et al. 1976; Wager 1986).

The Common Caco is known to feed on termites (Passmore and Carruthers 1995) but probably takes any small insect. Like its congeners, it is probably a major predator of mosquitoes (Wager 1986). The Intermediate Egret Egretta intermedia, Spotted Skaapsteker Psammophylax rhombeatus (Channing 2001) and Giant Bullfrog Pyxicephalus adspersus (W.R. Branch pers. comm.) are known to prey on this frog.

Status and Conservation

The Common Caco is known from various nature reserves and protected areas throughout its range and is not threatened. The species is a supreme generalist, adapting well to disturbance. It appears to be unaffected by moderate eutrophication of its water through organic pollution such as bovine (or other) excrement and fertilisers. No conservation actions are necessary for this species.

Distribution

The Common Caco is one of the most widespread and abundant frog species in the atlas region, occurring in most suitable habitats throughout its range at both high and low elevations. The species is absent from Namaqualand, the highlands of Lesotho, the top of the Soutpansberg and along much of the Mpumalanga escarpment.

The lack of records from south-eastern KwaZulu-Natal, the Buffalo River and the Lower Tugela River basin may reflect a genuine absence of this species (Lambiris 1989a). Conversely, the paucity of records from the arid Northern Cape Province and parts of Eastern Cape Province is probably the result of inadequate sampling effort.

The range of the Common Caco may have increased in the last century due to human activity, particularly where bush and reeds have been cleared and grass has been introduced (Van Dijk 1971b), along with domestic stock.

Outside of the atlas region, C. boettgeri occurs in the savanna regions of Namibia, eastern Botswana, southern Zambia and the Zimbabwe plateau. The disjunct populations that occur in the grasslands of northern Tanzania, southern Kenya and Ethiopia, previously referred to C. boettgeri (Poynton 1964; Poynton and Broadley 1985b), differ in advertisement call and skeletal and genetic characteristics, and apparently represent an undescribed taxon (E. Scott in prep.).

Similarly, the populations in the winter-rainfall Western Cape, recently referred to C. platys (Channing 2001) but previously synonymised with C. boettgeri (Poynton 1964), display different advertisement calls, in addition to a marked mtDNA sequence divergence, compared to their savanna counterparts (E. Scott in prep.). However, the limits of distribution of the Western Cape form are currently unknown, since it is almost impossible to separate preserved museum material on external morphology alone. The atlas distribution map presented here does not distinguish between C. boettgeri and C. platys because over most of the atlas period, their seperate taxonomic status was not recognised. Reliable diagnostic field characters have not been described.

Further Resources

The use of photographs by Jean-Paul Brouard is acknowledged. Other images by Ryan Tippett.

Common Caco Cacosternum boettgeri  (Boulenger, 1882)

Other Common Names: Boettger’s Caco, Boettger’s Dainty Frog (Alternative English Names); Gewone Blikslanertjie (Afrikaans)

Recommended citation format: Scott, E; Tippett, RM. (2025). Common Caco Cacosternum boettgeri. Biodiversity and Development Institute, Cape Town. Available online at https://thebdi.org/2022/02/15/common-caco-cacosternum-boettgeri/

This species text has been updated and expanded from the text in the
2004 frog atlas: Scott, E. (2004). Common Caco Cacosternum boettgeri. In Minter LR et al 2004.

References: 

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

Carruthers, V; du Preez, L. (2017). Frogs of southern Africa: A Complete Guide. Struik Nature, Cape Town.

Channing, A. (2001) Amphibians of Central and Southern Africa. Protea Book House, Pretoria

Similar Species

Southern Caco (Cacosternum australis)

Cape Caco (Cacosternum capense)

Klipheuwel Caco (Cacosternum aggestum)

Karoo Caco (Cacosternum karooicum)

Namaqua Caco (Cacosternum namaquense)

KwaZulu Caco (Cacosternum nanogularum)

Bronze Caco (Cacosternum nanum)

Mountain Caco (Cacosternum parvum)

Flat Caco (Cacosternum platys)

Rhythmic Caco (Cacosternum rhythmum)

Striped Caco (Cacosternum striatum)

Hogsback Caco (Cacosternum thorini)

View the above photo record (by Luke Kemp) in FrogMAP here.

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

Family Pyxicephalidae

HOGSBACK FROG – Anhydrophryne rattrayi

Hewitt, 1919

Identification

This is one of southern Africa’s smallest frog species with females attaining a body length of 22 mm. The snouts of males are calloused, slightly flattened, usually whitish and presumed to be adapted for excavating nests. Body colour and pattern are variable: the dorsum varies from light grey to dark brown or copper-coloured. Irregular dark mottling and a thin, light vertebral line are sometimes present. A dark mask extends across the eyes from nostrils to armpits. The white ventrum is marbled with dark blotches that do not extend onto the throat (Wager 1963, 1986; Passmore and Carruthers 1995; Channing 2001). (See genus account for further distinguishing characters.)

The advertisement call has been described as a melodious “ping, ping, ping”, repeated rapidly or slowly in bouts of 7–15 notes, or sometimes emitted as single notes (Wager 1986). The notes are 0.05 s in duration with an emphasized frequency of 3500 Hz (Channing 2001). Passmore and Carruthers (1995) recorded a call rate of 4 notes/s, emitted at an emphasized frequency of 3000 Hz.

Habitat

The species inhabits Afromontane Forest at altitudes generally >1100 m. It breeds in moist leaf litter on the forest floor, often near streams and waterfalls. It appears to flourish in the grassland/forest ecotone and also occurs in short grass in small open patches of wetland within forests. Adults are found in wet situations (e.g. near waterfalls), but the eggs are laid in areas where waterlogging is unlikely to occur (Wager 1986; Lambiris 1988a; Passmore and Carruthers 1995; Channing 2001).

Behaviour

Although it has a restricted distribution, A. rattrayi occurs in large numbers at some localities. For example, Lambiris (1988a) counted >70 individuals within c.25 m² in a grassland/forest ecotone. Under favourable conditions, that is, mist or rainy weather, hundreds of males may be heard calling throughout the night and sometimes during the day. Calling has been recorded in summer, October–February (Wager 1986; Channing 2001).

The species reproduces by direct development. Eggs are laid in small holes excavated in the clay soil beneath leaf litter on the forest floor. Wager (1986) recorded a spherical egg chamber, 21 mm in diameter, with a smooth shiny wall and a 9-mm entrance hole in the 3-mm thick roof. The chamber is, apparently, excavated by males. Additional information on nest building and other aspects of reproductive biology is needed.

The pearly white eggs are large, nearly 2.6 mm in diameter, and encased in a 6-mm gelatine capsule. Clutches of 11–20 eggs are laid in a single layer on the floor of the nest and adhere to each other. Larval development and metamorphosis are completed in about four weeks. The newly metamorphosed froglets measure only 4 mm from snout to vent (Wager 1986).

The diet of A. rattrayi includes small leaf-litter crustaceans such as amphipods and isopods (Wager 1986). Collembola appear to form a large proportion of the diet (Lambiris 1988a).

Status and Conservation

Status

A. rattrayi is here classified as Endangered owing to its limited and severely fragmented distribution. It was previously listed as Restricted (Lambiris 1988a) and Near Threatened (Harrison et al. 2001; IUCN 2000).

A. rattrayi is known from Stutterheim Nature Reserve and state forests between Keiskammahoek and Hogsback, including Hogsback Indigenous Forest and Katberg Forest.

Threats

The primary threats to A. rattrayi are habitat loss and fragmentation resulting from the farming of alien trees. Loss and deterioration of habitat, although occurring relatively slowly (estimated rate of <20% in 30 years), are cause for concern in view of the species’ limited areas of occurrence and occupancy. The fact that the frogs are restricted to small, severely fragmented and relatively isolated sub-populations (sensu IUCN criteria) increases the likelihood of extinction of these sub-populations, and reduces the probability of recolonization.

Recommended conservation actions

Although several of the known sub-populations occur in state forests and nature reserves, it is recommended that additional localities be set aside for long-term protection.

The species was infrequently recorded during the atlas period and additional surveys are needed to gain a better understanding of the species’ distribution and conservation status. Limiting-factor research would aid conservation management planning for this species. Habitat management and monitoring of known populations are also recommended (Harrison et al. 2001).

Forestry companies operating in this area, with indigenous forest under their control, should be informed of the conservation status of A. rattrayi and be advised on how to ameliorate the negative impacts of their activities.

Distribution

A. rattrayi is endemic to the Eastern Cape Province where it has a restricted distribution centred in the Amatola Mountains. The species was originally discovered at Hogsback Mountain and was subsequently recorded from forests at Katberg, Stutterheim, Keiskammahoek and Peddie mountains (Wager 1963, 1986; Lambiris 1988a; Castley 1997), although the last-mentioned locality may be incorrect. No new locality records were obtained during the atlas project, and only two of five quarter-degree grid cells, in which the species has been recorded, were confirmed during the atlas period. The species was recorded near Patensie (3324DB) by Visser (1979d), based on a specimen he collected in 1961. This record represents a considerable range extension to the southwest, but could not be confirmed during the atlas period or at any time since the initial observation. Nevertheless, the record is believed to be valid (J.D. Visser pers. comm.). The record at 3327AA (Lambiris 1988a) is apparently an error.

The atlas data give a fairly comprehensive representation of the species’ distribution, but there are few recent (post-1996) records.

Further Resources

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

More common names: Hogsback Chirping Frog, Rattray’s Frog, Rattray’s Forest Frog (Alternative English Names); Hogsback Padda (Afrikaans)

Recommended citation format for this species text:

Burger M, Tippett RM. Hogsback Frog Anhydrophryne rattrayi. BDI, Cape Town.
Available online at http://thebdi.org/2022/02/08/hogsback-frog-anhydrophryne-rattrayi/

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:

Burger M 2004 Anhydrophryne rattrayi Hogsback 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.

View the above photo record (by Alan Manson) in FrogMAP here.

Find the Tropical Platanna in the FBIS database (Freshwater Biodiversity Information System) here.

Family Pipidae

TROPICAL PLATANNA – Xenopus muelleri

(Peters, 1844)

Habitat

X. muelleri inhabits all types of water bodies, including lowland rivers, lagoons, dams and pans (Poynton and Broadley 1985a), mainly in the Grassland and Savanna biomes. It is seldom found in pristine forest habitats, but readily moves into deforested areas (Tinsley et al. 1996).

X. muelleri and X. laevis do not appear to differ with regard to water-quality preferences or requirements. The apparent difference in temperature tolerance does not seem to apply in southern Namibia, where X. laevis occurs at temperatures at least as high as those from which it is apparently excluded in the east (Tinsley et al. 1996). A possible explanation is that X. laevis uses cool refugia within high temperature water bodies. This has been observed in extralimital populations of X. laevis (pers. obs.). Absence of such refugia from some sites would explain the observations of Lambiris (1989a) and Poynton and Broadley (1985a) that the two species are rarely found at the same site.

Behaviour

Little is known specifically about the life history of X. muelleri, although much can be inferred from the characteristics of the rest of the genus. Like other Xenopus, they are known to move en masse, even under dry conditions (Tinsley et al. 1996). Loveridge (1953a) found them aestivating in the mud of a dried pond.

Prey items include beetles, beetle larvae and frogs’ eggs (Barbour and Loveridge 1928), while predators include Hammerkop Scopus umbretta (Loveridge 1953a), Green Water-snake Philothamnus irregularis (Sweeney 1961) and Barbel Clarias gariepinus. X. muelleri has been observed leaving the water to escape barbel (L.R. Minter pers. comm.)

Status and Conservation

X. muelleri is not threatened, and does not warrant conservation action.

Distribution

The distribution of X. muelleri in sub-Saharan Africa is divided into two distinct areas containing animals that are morphologically similar but probably represent allopatric sibling species (Kobel et al. 1996). One of these forms, X. muelleri-East, extends from southeastern Kenya to South Africa, and is the only form in the atlas region. This form includes the type material (from Mozambique), and hence is hereafter referred to as X. muelleri.

Within the atlas region, this species is confined to low-lying areas in northern and eastern Limpopo Province, eastern Mpumalanga and Swaziland, and northeastern KwaZulu-Natal, which form the western and southern limits of the Mozambique plain. Although Fischer et al. (2000) recorded mixed populations and hybridization between X. muelleri and laevis in Mpumalanga (2430BD), the two species are largely allopatric.

The ranges of X. muelleri and laevis are separated by the 18°C mean July isotherm, with muelleri part of a tropical faunal assemblage north and east of this climatic boundary, and laevis part of a non-tropical assemblage distributed to the south and west of the isotherm (Poynton 1964; Poynton and Broadley 1991). It is possible that the distribution of the species reflects differences in temperature tolerance: X. laevis appears to be able to tolerate a wider range of environmental temperatures than X. muelleri, which is more tolerant of high temperatures (Tinsley et al. 1996; see discussion under Habitat).

The atlas data can be regarded as reliable as X. muelleri can be easily distinguished, morphologically, from X. laevis.

Further Resources

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

More common names: Müller’s Platanna, Müller’s Clawed Toad (Alternative English Names); Müller se Platanna, Tropiese Platanna (Afrikaans)

Recommended citation format for this species text:

Measey GJ, Tippett RM.  Tropical Platanna Xenopus muelleri. BDI, Cape Town.
Available online at http://thebdi.org/2022/02/08/tropical-platanna-xenopus-muelleri/

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:

Measey GJ 2004 Xenopus muelleri Tropical Platanna. 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.

View the above photo record (by Timo Paasikunnas) in FrogMAP here.

Find the Striped Grass Frog in the FBIS database (Freshwater Biodiversity Information System) here.

Family Ptychadenidae

STRIPED GRASS FROG – Ptychadena porosissima

(Steindachner, 1867)

Habitat

P. porosissima has adapted to a wider range of habitats than the other Ptychadena species in the atlas region: from the sub-tropical coastal environment of KwaZulu-Natal, to temperate grassland along the crest of the great escarpment and the highveld and, occasionally, wooded grassland (Passmore 1978; Jacobsen 1989). It is also widely distributed at high elevations in Malawi and other parts of Africa (Stewart 1967).

In the atlas region, this species inhabits a variety of vegetation types in the Grassland Biome (Jacobsen 1989). In these habitats the altitude ranges from sea level to 2300 m.

The breeding habitat includes vleis, inundated grassland and sedge pans.

Behaviour

Adults have been recorded throughout the year in moist depressions and seepage areas, and occasionally along streams, but may move as far as 500 m from water (Stewart 1967; Jacobsen 1989). They probably survive dry conditions in the same way as other Ptychadena species, for example, by retreating into deep mud-cracks, although no specific instances are recorded in the literature.

Males usually call from concealed positions amongst emergent vegetation within the water, supporting themselves on emergent plants, with the hind third of their bodies submerged (Passmore 1978). Calling peaks between 23:00 and 02:30, at which time temperatures are usually substantially lower; this may represent a pre-adaptation that has allowed this species to invade temperate habitats (Passmore 1978).

Less intense calling continues throughout sporadic dry periods in summer, that is, calling is not dependent on rain, perhaps due to an association with relatively permanent bodies of water (Passmore 1978). In wet weather, choruses may develop during the day (Stewart 1967).

Eggs are laid in shallow water with silty or sandy substrates, and float at the surface (Lambiris 1989a; Channing 2001).

Adults feed opportunistically on terrestrial arthropods (Inger and Marx 1961), as well as earthworms, snails and other frogs (Channing 2001).

Status and Conservation

Although P. porosissima is widespread and occurs in a few protected areas, its distribution is patchy and its conservation status is uncertain. Surveys of populations in conservation areas are needed (Jacobsen 1989).

Distribution

P. porosissima is distributed from Ethiopia, southern Zaire and Angola, southward throughout East Africa to Zambia, Zimbabwe and southern Mozambique (Stewart 1967; Poynton and Broadley 1985b; Channing 2001). In the atlas region it is recorded from a few scattered localities in Limpopo and Gauteng provinces, but is more widely distributed in Mpumalanga, western Swaziland, KwaZulu-Natal, and the northeastern part of Eastern Cape Province, almost reaching East London in the south (3227DD).

Poynton (1964) suggested that P. poyntoni Guibé 1960 from Inhluzane, KwaZulu-Natal, was based on a hybrid population of P. uzungwensis and P. porosissima, and placed P. poyntoni in the synonymy of P. porosissima. Jacobsen (1989) was of the opinion that the Inhluzane population probably reflected the range in variation within P. porosissima, rather than a hybrid population involving P. uzungwensis.

The atlas data are reliable as this species is easily identified by its call and by diagnostic morphological characters. The distribution range shown in the map is reasonably accurate although the coverage is incomplete. More intensive surveys are required in order to clearly demarcate the distribution pattern of this species.

Further Resources

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

More common names: Grassland Ridged Frog (Alternative English Name); Gestreepte Graspadda (Afrikaans)

Recommended citation format for this species text:

Minter LR, Passmore NI, Tippett RM.  Striped Grass Frog Ptychadena porosissima. BDI, Cape Town.
Available online at http://thebdi.org/2022/02/07/striped-grass-frog-ptychadena-porosissima/

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:

Minter LR, Passmore NI 2004 Ptychadena porosissima Striped Grass 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.