Diagnosis: Medium sized toad with a very blunt head; unmistakable body shape; very large inner metatarsal tubercle.
Description: A medium-sized toad with a very blunt head and short hind limbs. Males achieve 54–74 mm (SVL), females 58–95 mm. The index ‘distance eye-snout tip / head width’ is only 0.24. They have large eyes with horizontal pupils. A large high-oval tympanum with a diameter equal to that of the eye is edged by a broad bulging border. A bulging infratympanic ridge beginning behind the corner of the mouth constitutes the ventral border of various large warts situated behind the tympanum. The parotid glands are very large, prominent, broadened caudad and almost smooth. The back and the dorsal part of the extremities are scattered with large smooth warts, with numerous tiny warts in-between. Warts without horny tips. Hands with very large palmar tubercles. During the breeding season, males develop black thorny nuptial pads on the first three digits. These toads have massive hind limbs with short lower legs. Tarsal tubercles are present. The inner metatarsal tubercle is large and flanged. The outer metatarsal tubercle is also enlarged, and contain some rather vague subarticular tubercles. Webbing formula: 1 (0.5), 2 i/e (1–0.5), 3 i/e (2–1), 4 i/e (2), 5 (0.5).Toads from Cameroon (Perret 1966) are apparently much larger than those from Senegal (Franchillon et al. 1984).
Voucher specimens: ZFMK 59509–510 + 3 further specimens, Burkina Faso (see Böhme et al. 1996).
Coloration: The basic coloration of the dorsum varies from a pale yellow brown to a dark olive brown morph. Preserved animals are almost invariably uniform gray. The largest warts and a somewhat exposed stripe on the eyelid are usually red, or at least reddish. In alcohol, the dark red warts often appear violet. The small warts on the flanks are white, being distributed within a lateral stripe which starts behind the large warts situated posterior to the tympanum. The basic color of this stripe is almost black. The upper lips and the forelimbs bear dark bars. The posterior border of the eye is clear gray to bluish white. The venter, the lower lips and the tips of fingers and toes are white, the throat of the males is colored dark to black.
Voice: Schiøtz (1964c) published a call which shows close similarities to that of B. maculatus. Lasting 0.5 sec, it comprises approx. 40 pulses with a frequency ranging from 1.25 to 2.80 kHz, the dominant frequency being 2.2 kHz. Amiet (1976a) reported a call duration of 0.6 sec and a dominant frequency of 2 kHz. This pulsed call is very loud, and it is uttered in longer sequences.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Benin, Burkina Faso, Cameroon, Djibouti, Eritrea, Gambia, Ghana, Guinea, Mali, Mauritania, Niger, Nigeria, Senegal, Sudan
Habitats: Dry, partially sandy savannas and cultivated land in the Sudan and Sahel zones (Schiøtz 1967, Hughes 1988). Perret (1966) characterizes specimens from Cameroon as sand-loving toads inhabiting most of all river banks and oases. Sandy soils are also mentioned by Amiet (1976a). Forge & Barbault (1978) explicitly point out that this species is virtually absent from river valleys, where it is said to be replaced by B. regularis. This species even invades semi-deserts (Schiøtz 1967). Joger (1981) found this toad in an irrigated oasis garden in northern Niger. Schiøtz (1964c) characterizes the breeding habitats as large waters whose banks do not bear any vegetation. On such locations, no other amphibian species were recorded.
Range: This species has not yet been observed at Comoé National Park. According to Frost (1985), its range comprises an area stretching from Mauritania eastward to Sudan, Ethiopia and the Arabian Peninsula. Due to new political boundaries Ethiopia forms no longer a part of the range of B. pentoni (Largen 1998). I found published records for the following countries: Senegal, Guinea, Mali, Burkina Faso, Ghana, Nigeria, Niger, Cameroon, Eritrea, Egypt, Yemen (Nieden 1908, 1910b, Scortecci 1929, Schiøtz 1964c, 1967, Perret 1966, Amiet 1973a, 1976a, 1989, Böhme 1975, Forge & Barbault 1977, 1978, Joger 1981, Francillon et al. 1984, Schätti 1986, Hughes 1988, Böhme et al. 1996, Rödel 1996, Salvador 1996, Joger & Lambert 1997, Largen 1997).
Life History, Abundance, Activity, and Special Behaviors
Spawn: According to Forge & Barbault (1977), a female contained 2600 mature eggs of 2 mm diameter each.
Tadpoles: A typical black toad tadpole whose keratodont formula reads 0 // 1 / 1 + 1. The horny beaks are slender and serrated. The stage of development of the row of papilla could not be studied as the respective specimens were already decomposing. Further elements of the oral disc might have been already damaged as well (the respective tadpoles are figured in Böhme et al. 1996). Perret (1966) describes this tadpole as a typical Bufo larva, and gives the formula 1 / 1 + 1 // 3. According to Forge & Barbault (1977), the larvae hatch within 30 hours at a water temperature of 25–30 °C, metamorphosing nine to twelve days later. Freshly hatched animals measure 6.5–7.5mm (TL; BL = 4–4.5 mm). When nine to twelve days old, the young toads measured 8–10 mm and weighed about 12 mg.
Biology:In Burkina Faso, I have observed these toads during the rainy season. They proved to be both diurnal and nocturnal. At night, many toads crossed a sandy road after heavy rainfall had set in. When termites of the genus Macrotermes began to swarm at the peak of the heat, B. pentoni immediately emerged to profit from this situation. Tadpoles were found in very shallow puddles lined up along paths in dry cultivated land (Böhme et al. 1996). According to Forge & Barbault (1977, 1978), these toads begin to spawn within 24 hours after the first rains of a rainy season had set in. In Senegal, approx. 300 mm of rainfall are registered during this period which usually last about three months (June–October). The toads went to spawn repeatedly. Forge & Barbault (1977, 1978) assume that a single female is capable of producing several clutches within one season. On the contrary, Amiet (1973a, 1989) reports that the breeding season is very limited. Forge & Barbault (1977, 1978) observed that breeding took place even without rainfall if the ponds contained a sufficient amount of water.
Amiet (1989) illustrates a calling male sitting in shallow water. The egg strings are deposed near the bank, being usually wound around aquatic plants. However, Schiøtz (1964c) describes breeding ponds without any bank vegetation. He found calling males terrestrial near water. Forges & Barbault (1977) observed larvae developing at an almost identical speed within one pond. Developmental speed was different between ponds, however. They interpreted this extremely rapid development as an adaptation to virtually unpredictable environmental conditions, e.g. risk of desiccation.
Francillon et al. (1984) detected by means of skeletochronology, that works almost like dendrochronology, that toads in northern Senegal mature when they are about two years old. Up to this stage, their growth rate is most rapid. In the first month after metamorphosis they grow with a daily rate of 0.53 mm (Salvador 1996). These toads live to ages of up to six years. The number of mature animals is highly variable, depending mainly on the amount of rainfall which occurred in the previous years (Francillon et al. 1984).
In Senegal, ants and beetles, mainly scarabid beetles, were the dominant food item (Forge & Barbault 1978). Amiet (1973a) supposes the inflatable body of these toads to be helpful in burying themselves.
This account was taken from Rödel, M.-O. (2000), Herpetofauna of West Africa vol. I. Amphibians of the West African Savanna, with kind permission from Edition Chimaira publishers, Frankfurt am Main.
For references in the text, see here
Rödel, M. O. (2000). Herpetofauna of West Africa, Vol. I. Amphibians of the West African Savanna. Edition Chimaira, Frankfurt, Germany.
Written by M.O. Roedel (roedel AT biozentrum.uri-wuerzburg.de), Post-Doc at the University of Wurzburg, Department of Animal Ecology and Tropical Biology, Wurzburg, Germany
First submitted 2001-05-02
Edited by Vance Vredenburg (2002-01-08)
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