A medium-sized, somewhat stunted ranid with long hind legs. Adult males measure 30–39 mm (SVL), females 36–47 mm. Several rows of vaguely defined dorsal ridges, two of which stretch from the eyes to the center of the back where they gradually fade; two further ridges emerge anterior to the center of the back, stretching backward towards the vent, which they hardly ever touch. Besides, two pairs of very short ridges are usually located further outward. The tympanum is clearly visible and reaches 0.5–0.8 (usually 0.7) of the eye diameter. Males have paired lateral vocal sacs, enlarged thenar tubercles and swollen first fingers. Finger-tips and toe-tips not expanded. The inner metatarsal tubercle almost reaches the shortest toe length (0.5–0.8, most often 0.7). The outer metatarsal tubercle is well-defined. The thighs reach 0.5–0.6 of the SVL, the shank length is 0.55–0.69 of the SVL. The feet. incl. longest toe, usually reaches more than 0.75 (0.68–0.85) of the SVL. The webbing formula is 1 (0), 2i (1) or (0.5), 3 i/e (1–0) or (1–0.5), 4 i (1), 5 (0).
Voucher specimens: SMNS 8952 1–7 + tadpoles; SMF 78624.
Coloration: Dorsum almost uniform red brown to red. Very rarely, a vaguely defined dark marking may be present in the center of the back. It appears more distinct on breeding males. The red back is sharply separated from the belly by a dark band. This band sometimes reaches the dimensions of the lateral line in P. longirostris. Several dark patches of different size are often present on the caudad sections of the flanks. The dark bars on the hind legs are often indistinct. Snout and tympanum region are dark to deep black laterally. The temporal triangle stretches to the base of the arm. Some animals have paler upper lips. The upper part of the iris is silver or golden, the rest is dark. The anterior part of the thigh is dark bordered, at least in its proximad section. The posterior part is mottled in yellow and black. On some animals, the yellow patches of the pattern form one or two longitudinal rows. The venter is white to gray. The border of the lower jaw may be black. The anterior parts of the male’s vocal sacs are black, the rest is pale beige. The webs are pigmented dark. In alcohol the red live coloration either turns even more intense, or the animal appears altogether gray.
Voice: The croaking advertisement call consists of two harmonies reaching from 1.55–2.61 and 3.34–4.9 kHz, respectively. A single note lasts 0.05–0.08 sec, being composed of two to four pulses, each lasting 0.01–0.02 sec, and separated by pauses of the same length. The intervals between the notes last about 0.05–0.11 sec. Similar calls have been published by Schiøtz (1964c, as sp.1) and Amiet (1974b, as P. huguettae). The latter describes the call as a quick "kik kik kik".
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Benin, Burkina Faso, Cameroon, Central African Republic, Chad, Congo, the Democratic Republic of the, Eritrea, Ethiopia, Ghana, Mali, Nigeria, Senegal, Sierra Leone, Togo
Range: Before the publication of Perret (1979b, 1981), this frog was presumably often referred to under other names. It is therefore difficult to describe its range on the basis of the data published in older literature. Frost (1985) simply quotes savanna regions from Sierra Leone to Chad, the Central African Republic and northern R.D. Congo. Reliable records have been published for the following countries: Sierra Leone, Mali, Burkina Faso, Ivory Coast, Ghana, Togo, Nigeria, Cameroon, R.D. Congo, Central African Republic, Eritrea, Ethiopia (Schiøtz 1964a, b, c, Inger 1968, Walker 1968, Amiet 1973a, 1974a, Joger 1981, 1990, Barbault 1984, Schätti 1986, Hughes 1988, Böhme et al. 1996, Rödel 1996, 1998b, Joger & Lambert 1997, Largen 1997a, 1998). The records from Senegal quoted by Mertens (1938a) possibly refer to this species, too. However, the synonyms he gives, Rana guerzea and R. leonensis, are actually synonyms of P. longirostris (Perret 1981). The species Ptychadena sp. from northern Cameroon, compared with Phrynobatrachus plicatus by Amiet (1973a), possibly also belongs to P. schubotzi.
Habitats: Both river banks and savanna habitats are colonized. In Ghana, P. schubotzi inhabits any part of the country, except the rainforest belt (Hughes 1988). In literature, savannas are quoted as habitats (Schiøtz 1964c, Perret 1981, Böhme et al. 1996), including both humid Guinea (Walker 1968, Barbault 1984) and dry Sudan savannas (Amiet 1974b). Lamotte & Xavier (1981) exclusively quote humid savannas when gallery forests are present. Joger (1981) reports on a "misted" slope and on overgrown brook banks in a hilly landscape.
Life History, Abundance, Activity, and Special Behaviors
Spawn: The single egg layer floats at the surface of the water. The brown embryo is surrounded by a viscous cloudy to sand yellow jelly. Including the latter, the egg diameter varies from 2.7 to 3.2 mm, the egg itself measures 1 mm in diameter. A single female produces 500 to 1000 eggs, forming batches of 50–100 eggs (compare the remarks in the P. pumilio and P. bibroni accounts). The larvae hatch within one day. According to Barbault (1984), females from Lamto produce 2011 ± 851 eggs that measure 1.3 mm in diameter (N = 4).
Tadpoles: The tadpoles are somewhat plumper than those of P. maccarthyensis and have the typical oval shape of all Ptychadena tadpoles. They are almost invariably beige, showing only a few dark spots. Green tadpoles are very rare. The green color may disappear within a few minutes. Unlike that of most other Ptychadena tadpoles, their high tail fins are usually black. The color is either restricted to some patches near the tip, or it covers the entire tail. However, there are also tadpoles with transparent fins.
While the form of the body seems to be almost invariable, two variants with completely different tail lengths are known to exist. Whereas the tail of the plumper morph is just a bit longer than the body, the tail of the second one nearly reaches two times the SVL. In both cases, the dorsal part of the tail fin, which is considerably broader than the ventral one, inserts at the level of the spiracle. The delicacy of the tail fin is also similar on both morphs. It is extremely fragile and will break off at the slightest touch.
Several keratodont formulae are known to exist in both morphs: 1 // 1+1 / 1; 1 // 2 and 1 // 2+2. The horny beaks are serrated and moderately massive. The oral disc is usually surrounded by single lateral and caudal rows of papillae. The caudal papillae may be arranged in two rows. The ends of the short horny teeth form a "shovel" with numerous tips. The surfaces of the caudad papillae often bear horny structures, too.
The tadpoles hatch within a day, bearing exterior gills and measuring about 4.2–6.0 mm (BL: 1.4–2.0 mm). In the aquarium, the gills were still present when the horny beaks began to develop 54 hours later (TL: 7 mm). Another 19 hours later, rudimentary gills and the first horny teeth were present, but complete oral discs were observed not before six days later. The longest larvae without hind legs measured up to 40 mm (TL). Hind legs are developed at a BL of 12–16 mm (TL: 25–47 mm). The forelegs also emerge at this length. Because of the fragile tail fin, the true TL is often difficult to estimate. Tadpoles reared in captivity metamorphosed after six weeks, and the young frogs measured 12–15 mm. In the wild, their development was considerable faster (see below).
Biology: In the dry season, P. schubotzi is found both under stones near rivers and in dry savanna pools where it seeks refuge in crevices and under rotten wood. Gallery forests are never used as breeding sites. They are just crossed when the frogs move to the savanna, with the onset of the rains. As soon as the savanna ponds are filled with water, considerable choruses start to establish on the pond’s edges. Calling males either hide under vegetation, or they call from exposed sites on bare soil.
The spawn is usually deposited in shallow water near the banks, but it floats occasionally to other sections of the pond. Like P. bibroni, P. schubotzi apparently prefers larger ponds. As the rainy season advances, however, both choruses and clutches are as often found in smaller and even tiny waters. As the number of egg batches found in small pools rarely corresponds with the number which may be produced by a single female, it is possible that they are deposited at several adjacent waters for risk spreading (see also P. bibroni). Amiet (1973b) observed calling males at dry, vegetationless sites. In northern Cameroon, they begin to call with the first rainfall. There, their breeding period lasts longer than those of other species inhabiting the arid savannas.
The tadpoles most often inhabit shallow water zones near the banks, swimming usually close to the bottom, both in heavily vegetated and in vegetationless parts of the pond. Freshly metamorphosed frogs are sometimes found already three weeks after the beginning of the rainy season.
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 (2002-02-08)
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