Ptychadena oxyrhynchus (Smith, 1849)
Sharp-nosed ridged frog, Uvete olunempumulo ecijilea (Zulu)
|Species Description: Smith, A. (1849). Illustrations of the Zoology of South Africa; Consisting Chiefly of Figures and Descriptions of the Objects of Natural History Collected during an Expedition into the Interior of South Africa, in the Years 1834, 1835, and 1836 .... Vol. III. Reptilia, Part 28. London: Smith, Elder, & Co.|
© 2017 Alberto Sanchez-Vialas (1 of 10)
Voucher specimens:SMNS 8954 1–2 + tadpoles; SMF one male without number.
Voice: The low, creaking call lasts 0.83-0.96 sec and comprises two similar pulses that last 0.01–0.02 sec and that are separated by longer pauses of 0.03 sec. It consists of two independent harmonies with frequencies from 1.39–2.29 and 2.5–3.8 kHz. The pauses between the calls last 0.58 sec. I always had the impression of a very soft call. In South African frogs the advertisement call is very loud (Pickersgill, Vences, pers. comm.). It is a low, harsh, pulsatile screech, which resembles rapidly dragging a stick across iron railings (Pickersgill, pers. comm.). At those places where I have heard the respective call, I exclusively saw P. oxyrhynchus males. However, as I always failed to observe the males while calling it might be that the analyzed calls are in fact those of P. tournieri (compare the respective account). Sonagrams of this species have also been published by Schiøtz (1964c), Amiet (1974b), Passmore (1977) and Passmore & Carruthers (1995). Both the calls in Passmore (1977) and those in Passmore & Carruthers (1995) and Amiet (1995) basically show the same structure as the call recorded at Comoé National Park, but comprise less pulses per call, and their frequency is somewhat lower. Amiet (1974b) pertinently describes the call as a low "cra-cra-cra". The frogs whose calls were recorded by Schiøtz (1964c) were calling from an iron tank, a fact which might explain the different sonagrams. Further, Passmore (1977) describes an "initial" call preceding the advertisement call, and an aggressive call.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Angola, Benin, Botswana, Cameroon, Central African Republic, Chad, Congo, Congo, the Democratic Republic of the, Eritrea, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Malawi, Mali, Mozambique, Namibia, Nigeria, Senegal, Sierra Leone, Somalia, South Africa, South Sudan, Tanzania, United Republic of, Togo, Uganda, Zambia, Zimbabwe
Habitats: During the dry season, single animals are found under stones on river banks, whereas in the rainy period the borders of savanna ponds are colonized. This frog is generally characterized as preferring open landscapes (e.g. Schiøtz 1967, Poynton 1970). Hughes (1988) reports that P. oxyrhynchus lives within any type of habitat with the exception of true rainforest. Humid savanna regions form its typical habitat (e.g. Lamotte 1967b, Walker 1968, Broadley 1971, Poynton & Broadley 1985b, Joger 1981, Gruschwitz et al. 1991a, Simbotwe & Mubemba 1993). Some authors also quote more arid and open forest habitats (e.g. Schiøtz 1963, 1964c, 1967, Amiet 1974b, Poynton & Broadley 1985b). Guibé & Lamotte (1958a), Perret (1966) and Amiet (1975) observed this species both in forests and adjacent savannas. As far as older studies are concerned, observations from rainforest areas are possibly based on false identifications, i.e. the frogs might have been confused with P. aequiplicata (e.g. Sanderson 1936). Loveridge (1942, 1957) believed that a lowland subspecies inhabiting savannas (P. o. oxyrhynchus) and a montane form preferring forest habitats (P. o. gribinguiensis) can be distinguished in East Africa. He placed all western records within either R. o. gribinguiensis or R. o. superciliaris.
Life History, Abundance, Activity, and Special Behaviors
Biology: When the rains set in, the frogs move from the rivers into the open savanna where they are among the first anurans to deposit their clutches. I found P. oxyrhynchus particularly often at small ponds lacking any vegetation. This was the first species that accepted the concrete pools we built for some experiments, too. At these sites, single males called at night from banks. We almost invariably found them sitting on the bare ground without any cover. Exposed calling sites in close vicinity to open water are also described by Lambiris (1988). Small waters serving as spawning sites are mentioned by Poynton & Broadley (1985b) for South Africa, and by Amiet (1974b) for Cameroon. Both the Cameroon frogs (Amiet 1974b) and those at Comoé National Park spawned at the first rainfall. If precipitation happens to be sufficient, breeding takes place throughout the rainy season. At Lamto, the frogs only spawned between February and May (local rainy season: March-November, Barbault & Trefaut Rodriguez 1978). Passmore & Carruthers (1995) report that calling activity in South African frogs lasts from 11.00 h p.m. to 04.00 h a.m.
At Lamto, this species is adult at the age of 8–9 months, usually living just another 12 months. The mortality of younger frogs is considerably higher than that of adults (Barbault & Trefaut Rodriguez 1978, Barbault 1984). The said authors report that only one clutch per female and year is produced. Thanks to their enormous muscular power and their very timid habits, these frogs are very difficult to catch. Leaps of 3 m and more reaching heights of 1 m are likely to be just the lower limit: Wager (1986) reports on leaps covering 10 m, i.e. a distance corresponding to 200 times of the frogs body length! At Lamto the diet mainly consists of spiders and orthopterans (Barbault 1974d). Loveridge (1937) and Simbotwe & Mubemba (1993) equally cite arthropods, or more generally small invertebrates, as prey. In the grasslands of Natal Pickersgill (pers. comm.) observed this species in early morning when grass is wet with dew up to a mile away from standing water.
Wager (1986), Lambiris (1988) and Guibé & Lamotte (1958a) give an identical formula. Guibé & Lamotte (1958a) also mention animals with the formula 1 / 2+2 // 2. Their lateral and caudal papillae are said to be arranged in 1–2 rows. The longest tadpole is reported to measure 37 mm, whereas the SVL of freshly metamorphosed frogs measured 15 mm. Lambiris (1988, 1989) gives a TL of 40 mm (BL: 14 mm) and the keratodont formula 2 // 2. The largest tadpole collected by Wager (1986) was 54 mm long (TL). At Lamto, the frogs metamorphose within 3–4 weeks (Lamotte 1983), those in Zimbabwe within 2 months (Lambiris 1989). Orton & Morrison (1946) give 15.5mm for metamorphosed frogs, and 19–26 mm are quoted by Loveridge (1942).
As the data published by Guibé & Lamotte (1958a) are based upon Lamotte & Zuber-Vogeli (1953), they should be evaluated with caution. The latter report on choruses comprising more than 100 males, a statement which does not correspond at all with my observations (see below). Some days later, the collected tadpoles perished, and the authors collected new larvae at the same pond. The appearance of these tadpoles was reported to be similar, whereas their size was either identical or smaller than that of their predecessors. However, I have never observed the growth of captive tadpoles to proceed as rapidly as in the wild even when climatic conditions were identical. As the larvae described by Lamotte & Zuber-Vogeli (1953) hatched within two days, their general development was supposedly identical. In the savanna, I have never observed Ptychadena-tadpoles that needed more than one day for hatching. However, animals from Zimbabwe seem to hatch within two days, although Lambiris (1989) does not indicate whether this happened in captivity or in the wild. The variable form of the oral discs described by Lamotte & Zuber-Vogeli (1953) (e.g. additionally the keratodont formula 1 / 1+1 // 3) possibly supplies evidence for the fact that these tadpoles actually belong to different Ptychadena-species. Tadpoles collected at a given pond and described, assuming that they belong to the same species as the adults observed at that water, might frequently have given rise to virtually useless descriptions. Specifications concerning tadpole morphology are only acceptable if the respective clutches can be assigned to identifiable parents, or if the larvae have been reared up to an age permitting their identification. Most often this is not possible even in already metamorphosed froglets of species of certain genera. Scortecci (1940) gives an additional keratodont formula for animals from Eritrea (1 / 2+2 // 1+1 / 2).
Phaka, F.M., Netherlands, E.C., Kruger, D.J.D., Du Preez, L.H. (2019). Folk taxonomy and indigenous names for frogs in Zululand, South Africa. J Ethnobiology Ethnomedicine 15, 17. [link]
Rödel, M. O. (2000). Herpetofauna of West Africa, Vol. I. Amphibians of the West African Savanna. Edition Chimaira, Frankfurt, Germany.
Originally submitted by: Marc-Oliver Rödel (first posted 2001-05-07)
Edited by: Arie van der Meijden (2023-05-31)
Species Account Citation: AmphibiaWeb 2023 Ptychadena oxyrhynchus: Sharp-nosed ridged frog <https://amphibiaweb.org/species/4947> University of California, Berkeley, CA, USA. Accessed Sep 28, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 28 Sep 2023.
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