A medium-sized ranid with a pointed snout and four dorsal ridges which usually run from the level of the posterior eye border to the end of the body. The second ridge counted from the vertebra, may be interrupted in the middle of the body. Very rarely, an additional pair of ridges occurs on the last third of the back, i.e. between the first pair. Adult males measure 34–44 mm (SVL), females 34–55 mm. The supratympanal fold starting immediately behind the eye continues as a dosolateral ridge which is usually discontinuous. Quite often, this ridge is interrupted right after the tympanum. The ridge may continue at a more dorsal position, too. However, it never reaches the end of the body. Some prominent warts, which occasionally form a discontinuous lateral ridge, are present on the flanks. The skin of the flanks shows a reticulated structure, whereas that on the back is granulated or smooth. The tympanum is clearly visible and slightly concave, reaching about 0.6–0.8 of the eye diameter. Males have paired lateral vocal sacs, enlarged thenar tubercles and swollen first fingers. The hind legs are sturdy and of moderate length. The thighs measure 0.5, the shanks 0.5–0.6 and the foot, incl. the longest toe, 0.7–0.8 of the SVL. The size of the inner metatarsal tubercle is highly variable, its length being 0.2–0.5 of the shortest toe. The outer metatarsal tubercle is not always clearly visible. Additional subdigital tubercles occasionally occur at the bases of the third and fourth toes. The webbing formula is 1 (0) or (0.5), 2 i/e (1–0.5), 3 i/e (1.5–0.5) or (1–0.5), 4 i/e (1.5–1) or (1) or (1.5), 5 (0) or (0.5). Finger-tips and toe-tips not enlarged.
According to Andersson (1937), the innermost pair of ridges may consist of two slightly overlapping pairs. Loveridge (1941, 1955a) gives a SVL of 38–52 mm for males, and up to 64 mm for females. Both Guibé & Lamotte (1957) and Lamotte & Xavier (1981) give 48 mm for males and 56 mm for females. According to Guibé & Lamotte (1957, 1958a) the additional subdigital tubercles on the metatarsus of the third and fourth toes are always present.
Voucher specimens: SMNS 8951 1–7 + tadpoles; SMF a pair without number.
Coloration: The gray to pale brown dorsum of P. bibroni shows numerous tiny dark brown to black patches. On the back, these patches are restricted to the longitudinal ridges. On the extremities these markings are particularly conspicuous on the hind legs. The ventral parts of the warts, adorning the flanks, partially have black borders. The color of the central back may be similar to that of the sections between the longitudinal ridges, or a yellow orange to red vertebral band may run from the snout tip to the vent. This vertebral band is rather broad at the beginning and considerably thinner at the end. Very rarely, this band is reduced to a thin line. A thin black line runs from the nostril to the eye; its upper part is somewhat paler than the rest. The tympanum may equally be bordered by dark areas below the lateral ridge. However, the black areas never fuse to form a black temporal triangle. The upper section of the tympanum, whose borders are clear, appears somewhat darker. A circular central section of the tympanum often contrasts with its rest. It is usually paler, rarely darker. The vocal sacs are transparent pale gray to grayish black. A yellow longitudinal line with black borders runs along the posterior border of the thighs. It is occasionally discontinuous, very rarely fragmented into a row of patches. The venter is whitish to gray. The borders of the lower jaw may show some dark spots. The upper lip is purely white. The webs usually show some dark pigmentation; very rarely, they may be transparent. Coloration in alcohol is generally similar to live coloration, but somewhat less distinct. The basic color is olive to brown; red turns gray, and yellow turns white.
Voice: The squeaking advertisement call consists of two harmonies lasting 0.23-0.26 sec. The one whose frequency initially amounts to 2.69–3.43 kHz sets in about 0.05 sec later, and it lasts correspondingly longer. At the end, its frequency ranges from 2.69 to 4.16 kHz. The lower part of the call covers the frequency range 0.65–2.20 kHz, its final part ranging from 0.70–1.39 kHz. The pauses separating the calls last 0.70–1.57 sec. Similar sonagrams have been published by Schiøtz (1964c, "goose-like call") and Amiet (1974b).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Benin, Burkina Faso, Cameroon, Central African Republic, Chad, Congo, the Democratic Republic of the, Gambia, Ghana, Guinea, Liberia, Mali, Mauritania, Nigeria, Senegal, Sierra Leone, South Sudan, Togo
Habitats: The frogs can be encountered in all habitats of the Comoé National Park, but their number varies according to the respective season (see below). Their habitats range from humid (Loveridge 1955a) and dry forests to humid savannas (Guibé & Lamotte 1957, Schiøtz 1963, 1967, Walker 1968, Amiet 1974b, Hughes 1988, Gruschwitz et al. 1991a). Within the savanna region, gallery forests (Guibé & Lamotte 1958a, Lamotte 1967b, Böhme & Schneider 1987) and the region between forest and pure savanna are often colonized, too (Wake & Kluge 1969). Dry savannas seem to be avoided. For example, Hughes (1988) does not mention this species for the Sudan savanna of Ghana. Quite often, P. bibroni has been found on the borders of running waters of variable size (Joger 1981, 1982). In comparison with other species, the intermediate selection of savanna and forest habitats is reflected in the number of dermal glands (Quang Trong 1975b).
Range: According to Frost (1985), the range of this species stretches from Gambia to R.D. Congo. I have found records for the following countries: Senegal, Gambia, Sierra Leone, Liberia, Guinea, Mali, Burkina Faso, Ivory Coast, Ghana, Togo, Nigeria, Cameroon, R.D. Congo, Chad, Central African Republic (Noble 1924, Andersson 1937, Mertens 1938, Loveridge 1941, 1955a, b, Guibé & Lamotte 1958a, Taylor & Weyer 1958, Schiøtz 1963, 1964a, b, c, 1967, 1968, Barbault 1967, 1974d, 1984, Lamotte 1967b, 1971, 1998, Walker 1968, Euzet et al. 1969, Maeder 1969, Wake & Kluge 1969, Amiet 1973a, 1974b, Barbault & Trefaut Rodriguez 1978, Miles et al. 1978, Perret 1979b, Joger 1981, 1982, 1990, Hughes 1988, Böhme & Schneider 1987, Gruschwitz et al. 1991a, Böhme et al. 1996, Rödel 1996, 1998b, Joger & Lambert 1997).
Life History, Abundance, Activity, and Special Behaviors
Spawn: 800 to 1500 eggs float at the surface, forming a single layer which is rarely attached to aquatic plants. In captivity, a pair produced 1414 eggs. Most egg films soon disintegrate. Larger portions comprise 50–300 eggs, smaller ones one to a few dozen. The eggs have a brown and a white pole. The jelly is transparent. Including the jelly, the egg diameter varies from 2.9 to 4.2 mm (egg diameter: 1.2–1.3 mm).
It is unclear whether single eggs attached to the bottom of rock-pools belong to this species, too. Including jelly they measure 4.5 mm (egg: 2.1–2.2 mm). The tadpoles hatching from these eggs were equal to those which hatched from floating egg films.
At Lamto, females produce 1333 + 643 eggs (diameter: 1.3 mm; N= 12, Barbault & Treffaut Rodriguez 1978, Barbault 1984). The clutch size proved to depend on the female’s body length.
Tadpoles: Viewed from above, the body shape of the tadpole is ovoid. The tail is quite long but not very broad. The tail fin inserts on the level of the spiracle, and its dorsal part is somewhat broader than the ventral one. Its borders converge evenly towards the tip of the tail, which is reddish in some individuals. The basic color of the body is usually beige. Some black spots may be present. The tail fin is almost invariably transparent. Its borders may be blackish. The black part may be somewhat broader towards the tip of the tail, but never to the degree shown by P. schubotzi tadpoles. The tail fin of P. bibroni is robust and withstands manipulation (compare P. schubotzi). The oral disc is fringed by a discontinuous inner and a continuous outer row of papillae. The caudal extension of the outermost lateral row is fringed by some enlarged papillae. The serrated horny beaks are not very massive. The keratodont formula is 1 // 1+1 / 1. The long slender horny teeth have either one or two tips.
The tadpoles, which still have exterior gills at this time, hatch within half a day, measuring 1.5–2 mm (BL; TL: 4.6–6 mm). In the aquarium, they developed very slowly. Their oral disc began to differentiate 54 h later. Tadpoles measuring 7.1 mm (TL) still possessed exterior gills. The hind legs develop three to five weeks later when the tadpoles measure 10–13 mm (BL; TL: 31–45 mm). Another four days later, the forelegs emerge on the first larvae (BL: 11–13 mm; TL: 35–38 mm), and after another three days, the young frogs (10–13 mm) go ashore. In the wild, the first metamorphosed young have been found one month after the beginning of the rainy season, measuring 11.3–14.5 mm (SVL). The following data are meant to demonstrate the development of the tadpoles (length in mm / weight in g): 22/0.10; 27/0.13; 29/0.2; 31/0.26; 36/0.34.
The tadpoles hatching from single eggs attached to the bottom (see above) measured 2.1–2.2 mm (BL; TL: 4.5 mm). Two days later, they were swimming in open water. The larvae still possessed exterior gills and had reached a TL of 6.4 mm. However, their BL still was 2.1mm. One month later, the hind legs were completely developed (BL: 11 mm, TL: 38 mm). The forelegs emerged ten days later when the tadpoles measured 11 mm (BL; TL: 42 mm). Guibé & Lamotte (1958) described a larva whose keratodont formula was 1 // 2. The lateral papillae comprised one or several rows, the caudal ones just a single row. Their tadpoles had tail fins with dark spots which were also present on the tail base. These authors give a maximum TL of 39 mm. Lamotte & Perret (1961b) also give the keratodont formula 1 // 2. According to these authors, there are two rows of papillae, but only in the corners of the mouth. The body is more ovoid and the tail is longer than that of the animals I have examined. Furthermore, the tail pigmentation is altogether dark. A tadpole measuring 27 mm (TL) was already developing hind legs.
Biology: During the dry season, P. bibroni seeks refuge under stones on the river banks or in crevices at the bottom of dry ponds. However, comparatively few animals are found at the latter sites. At Lamto, the frogs spent the dry season dug in the mud of dry ponds (Barbault 1972). Beyond the breeding season, according to Gruschwitz et al. (1991a), this species does not depend on open water.
During the rainy season, I found these frogs always near waters, unless the weather was extremely wet. As soon as the rainy season sets in, choruses develop on river banks and at rock-pools. The latter are also used as spawning sites. Calling males either sit in shallow water, or hide beneath flat stones. The observation published by Schiøtz (1967b), stating that these frogs do not form groups at all, does not apply to the frogs of the Comoé National Park. At Lamto, they will not spawn before March, i.e. their reproductive activities are bound to the rainy season, and last till October (Barbault & Trefaut Rodriguez 1978). According to Amiet (1974b), they have two distinct breeding seasons pear year in Cameroon. There males call as soon as the first rainfall sets in, but the eggs are deposed later than those of the very "early" species P. trinodis and P. schubotzi. As far as savanna ponds are concerned, this applies to the Comoé National Park, too (in comparison with P. trinodis).
At rock-pools on the riverbanks, P. schubotzi and P. bibroni spawn far earlier than P. trinodis, which is virtually restricted to savanna ponds. The two known egg types have already been described. It cannot be excluded that the single eggs, attached to the bottom of ponds, belong to a different species. However, adult frogs encountered in the above-mentioned habitats exclusively belong to P. bibroni and P. schubotzi. The larvae of the latter look completely different to those of P. bibroni. As soon as the savanna ponds are filled with water, P. bibroni starts spawning at these sites, too. Rainfall triggers reproduction. Heavier rainfall causes more frogs to reproduce. However, we observed spawning frogs after very little precipitation, as well.
The clutches are usually found near the bank, but some eggs may float across the pond. Whereas large choruses are found exclusively on larger ponds in the early rainy season, they will also be encountered on smaller water bodies as the season advances. Generally, with the exception of running water, almost any type of water is accepted. Even savanna ponds and savanna rock-pools lacking any vegetation, where the water temperature rises to 40 °C or more, regularly contain clutches.
The tadpoles swim mainly near the bottom, not only in shallow sections near the banks, but also in deep water where the larvae of other Ptychadena species are far less common. However, experiments failed to confirm this habitat selection (Rödel 1998b). Adult frogs are also found at forest ponds, but less often than in the savanna. Humid clearings in the forest harboring an abundant undergrowth of herbs seem to offer excellent life conditions for the young which are occasionally encountered in large numbers at such sites. Adult frogs are purely nocturnal during the dry season. In the rainy period, reproduction takes place exclusively at night, but active animals can be observed at daylight, too. However, their activity area is mainly restricted to the vicinity of the ponds. If the weather happens to be sultry or clouded, individuals, in savanna areas bearing a rich vegetation, are also found far away from any pond.
At Lamto, the diet comprised mainly spiders and orthopterans (Barbault 1974b). There the frogs are said to mature within eight to nine months. Unlike adult animals, eggs, tadpoles and young frogs show a high mortality. The average life expectancy of adult frogs usually amounts to 12 months (Barbault & Trefaut Rodriguez 1978, Barbault 1984). The authors never observed more than one clutch per year per female, but they do not exclude that a second clutch might be produced.
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 2001-05-07
Edited by Arie van der Meijden (2002-01-22)
Species Account Citation: AmphibiaWeb 2002 Ptychadena bibroni <http://amphibiaweb.org/species/5535> University of California, Berkeley, CA, USA. Accessed Oct 19, 2019.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 19 Oct 2019.
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