Southern Pygmy Toad (Poyntonophrynus vertebralis)

View the above photo record (by Ryan Tippett) in FrogMAP here.

Find the Southern Pygmy Toad in the FBIS database (Freshwater Biodiversity Information System) here.

Family Bufonidae

SOUTHERN PYGMY TOAD – Poyntonophrynus vertebralis

A. Smith, 1848

Identification

Adult:

Size: Females up to 36mm long. Males are distinctly smaller.

A small squat species with an overall light brown or grey colouration. The skin is leathery and consistently granular or warty. The upper sides are fairly plain or may show irregular dark patterning. A thin vertebral line may sometimes be present.

A pale scapular patch is often present between the shoulders and is variable in size.

The tympanum (ear drum) is inconspicuous and partly concealed by glandular warts. The parotoid glands on the neck are indistinct and somewhat flattened.

The undersides are noticeably pale with variable, bold black markings. The skin is leathery and quite granular, especially near the hind legs. The skin on the throat is fairly smooth and may be white or yellowish.

Tadpole:

Size: Up to 20mm

Tadpoles of Poyntonophrynus vertebralis have deep, oval-shaped bodies. Their tails are moderately developed and not as deep as the body. Additionally, the tail is slightly longer than the body and the upper and lower fins are of roughly equal length. The mouth is small and located ventrally near the front of the head. The eyes are situated to the sides on the upper front part of the head.

The overall colouration is dark with many fine golden speckles or spots.

Habitat

Poyntonophrynus vertebralis inhabits primarily the Nama Karoo Biome but is also found in parts of the Savanna and Grassland biomes. The species is largely restricted to summer-rainfall areas, but has been recorded in some parts of the Nama Karoo that are transitional between summer and winter rainfall.

It occurs on a variety of substrates, from brackish soils to gravels, in open sandy and grassy areas and in Karoo scrub. It takes refuge under rocks and logs, in mud cracks, deep leaf litter, and occasionally in the abandoned mounds of Trinervitermes termites, sometimes far from open water (De Waal 1980; H. Braack pers. comm.).

Breeding habitat in the Karoo includes temporary shallow pans, pools or depressions containing rain-water, and occasionally culverts and rocky pools in seasonal water courses (new atlas data). In the Free State, tadpoles have been found in roadside pools, small dams, quarries and rock pools along rivers (new atlas data).

Behaviour

Breeding choruses of P. vertebralis develop from October to March. It is an explosive breeder, congregating in large numbers at temporary pools after heavy spring or summer rains (H. Braack pers. comm.). Visser (1979b) recorded thousands of specimens crossing the national road at Victoria West after rain. The call carries a great distance and a chorus produces a deafening sound (Du Preez 1996).

Males usually call from concealed sites near the water’s edge, but they will call from exposed positions when there is insufficient cover. In large breeding aggregations, males clasp other individuals indiscriminately, regardless of gender. Satellite behaviour, in which silent males intercept and clasp females that are approaching calling males, was observed at both Beaufort West and Middelburg (H. Braack pers. comm.).

Wager (1965, 1986) collected eggs at the beginning of March; this suggests that breeding occurs after mid-summer rains. The eggs measured <1 mm in diameter and were laid in double strands 2.5 mm thick. They were entangled amongst stones and grass 2–4 cm beneath the surface. Although Wager’s aquarium tadpoles completed metamorphosis after about one month, Power (1927a) recorded a developmental period of only 16 days. When feeding, Wager’s tadpoles showed a preference for the stems of aquatic plants rather than algae, whereas Power (1927b) observed tadpoles feeding on algae and mud at the bottom of a natural pool.

Adult frogs prey on termites, ants, aphids, fly and beetle larvae, adult beetles, and mites (Bates and Irish 2002). During large-scale emergences of P. vertebralis in the breeding season, many are killed by road traffic, and Suricates Suricata suricatta and Black Crows Corvus capensis have been observed feeding on the remains. Captive Suricates and Polecats Ictonyx striatus have also been observed feeding on these toads (H. Braack pers. comm.).

Status and Conservation

The Southern Pygmy Toad is not threatened. It is listed as of Least Concern in the IUCN Red List of Threatened Species.

In the Free State, P. vertebralis occurs in Soetdoring, Krugersdift Dam, and Koppies Dam nature reserves (Bates 1997). It has also been collected at Oviston Nature Reserve and Mountain Zebra National Park in Eastern Cape Province. The species enjoys varying degrees of protection under provincial conservation legislation. It may have been negatively impacted by crop agriculture in Grassland-Biome portions of its range, whereas it is probably not threatened in karoid areas where land is used primarily for grazing. However, the Karoo is renowned for periodic outbreaks of the Brown Locust Locustana pardalina, and over-zealous use of insecticides could affect local frog populations. Monitoring of populations of P. vertebralis in protected areas is recommended. Additional information on the breeding biology of this endemic species is needed.

Distribution

Poyntonophrynus vertebralis is endemic to the atlas region, although recent records from North West Province suggest that it may also occur in southern Botswana. Its distribution follows that of the Nama Karoo Biome in the Northern, Eastern and Western Cape provinces and the southern Free State, but it also occurs in grassland and savanna at Kimberley, north of Christiana, and in the Free State. It occurs as far east as Maseru (2927BC) and near Masite (2927CB) in western Lesotho. Recent atlas records have extended the known western limits of the species as far as the Brandvlei district (3020AD) of Northern Cape Province.

Further north, the species has been recorded in two apparently isolated populations, namely, the Koppies area (2727BA) of the northern Free State (Bates 1995), and on the border between Limpopo and North West provinces (recent atlas data) where it appears to occur in sympatry with P. fenoulheti. The confirmed presence of P. vertebralis, based on advertisement calls (atlas data), supports Jacobsen’s (1989) identification of specimens from grid cells 2428AC and 2528CA. The latter identifications were previously considered dubious because these areas were far north of the known range (Jacobsen 1989).

With regard to the apparently disjunct distribution of P. vertebralis in the Free State, Bates (1995) reported the existence of two museum specimens from “Adonasfontein, Winburg”, a locality that cannot be traced. If the latter locality is in the vicinity of Winburg (2827CA), it will bridge the large gap between southern and northern populations in the Free State.

The taxonomy of the “vertebralis group” (Poynton 1964; Poynton and Broadley 1988) requires revision to determine the exact ranges of the various species. An attempt should be made to identify morphological differences between P. vertebralis and P. fenoulheti in areas of sympatry, to assist in the identification of specimens from these areas.

The atlas data is accurate but incomplete.

Further Resources

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

More common names: Suidelike dwergskurwepadda (Afrikaans)

Recommended citation format for this species text:

Bates MF, Tippett RM.  Southern Pygmy Toad Poyntonophrynus vertebralis. BDI, Cape Town.
Available online at http://thebdi.org/2021/09/19/southern-pygmy-toad-poyntonophrynus-vertebralis/

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:

Bates MF 2004 Poyntonophrynus vertebralis Southern Pygmy Toad. 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.