AMPHIBIAWEB
Phrynomantis microps
family: Microhylidae
subfamily: Phrynomerinae

© 2007 Dr. Peter Janzen (1 of 8)

  hear call (457.7K MP3 file)
  hear call (5035.7K WAV file)

[call details here]

Conservation Status (definitions)
IUCN (Red List) Status Least Concern (LC)
CITES No CITES Listing
Other International Status None
National Status None
Regional Status None

 

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Description
Diagnosed as a medium sized frog with an elongated body; back red; flanks and extremities black, occasionally with red spots. A plump frog with a blunt snout and a prominent sacral region. Body elongated and depressed. A very long neck, which allows it to move the head from side to side. Males measure 37–47.3 mm, females 41–62.4 mm. Distance snout tip–eye shorter than interorbital distance. Tympanum often indistinct, reaching 0.5–0.8 of the eye diameter. Males have a single subgular vocal sac. Comparatively short hind legs without webbing. Enlarged inner metatarsal tubercle with highly variable size, reaching 0.5–1.1 of the shortest toe length. Tips of fingers and toes enlarged to form round or triangular discs. A smooth glandular skin.

A 44 mm female weighed 3.6 g., another with 56 mm SVL 16.7 g. Males, 38–44 mm SVL, weighed 3.5–6.3 g. The size of one year old frogs ranged from 25 to 32 mm (weight: 1.4–3.5 g). Zug (1987) reports on a gravid female measuring 57 mm (SVL). Barbault gives average sizes of 45 (1974a) and 44 mm (1974b). According to Hermann (1989), males reach 45 mm, females 60 mm. The red color of the back extends from the snout tip to the vent. It is often interrupted by a more or less sharply marked black vertebral line. The head in particular may by densely spotted black. Some isolated red spots may be present on the otherwise black arms and legs. A black lateral band stretches from the snout to the vent. In the groin area this band diverges a short way towards the middle of the back. The throat in males is deep black, while in females it is dark brown to dark gray. The breast is usually dark with large white spots; the latter are also found in the groin area, where they are less distinct. The rest of the venter is white to drab gray. The red color is reported to turn silvery gray in dry or warm weather (Hermann 1989). My own observations have shown that this happens in other stress situations, too. For example, the frogs also changed their color when ants were present. Young animals are more slender than adult frogs. The back of metamorphosed froglets is brown, and a black vertebral line is always present. In alcohol the red color turns light gray to dark brown. The black parts turn dark brown.

Voice: The amplitude modulated advertisement call of P. microps lasts 1.1 to 2.5 sec. All pulses last 0.02–0.03 sec. Their frequency ranges from 0.68 to 6.41 kHz. Three to four distinct harmonies are distinguishable. Grafe (1999) gives the dominant frequency with 1.26 kHz. The low melodic trill figured by Schiøtz (1964) is structurally similar. The calls of P. microps and P. bifasciatus, which were formerly considered synonymous, are compared in Van den Elzen & Kreulen (1979).

The white to yellowish eggs are deposited in small to very large floating egg masses. The diameter of the egg incl. jelly ranges from 5.6 to 9.0 mm, depending on the respective position of an egg within the mass. Eggs younger than stage 13 (Gosner 1960) measure 1.6–3.0 mm. A darker pole is exclusively found in recently deposited eggs which have not yet swollen. An egg mass consists of 30–1400 eggs, arranged in tangled strings. Different, distinct clutch sizes may be distinguished. Large ones comprise 800–1400 eggs (N= 20); medium-sized ones comprise 200–500 (N= 16); small ones: 100–160 (N= 18) and tiny ones consist of approx. 60 eggs (N= 8). These egg masses either float free at the water surface, or they are attached to partly submerged vegetation. Smaller egg masses are more likely to be attached to vegetation in shallow water, whereas large ones are usually deposited in deeper water which lack vegetation. Zug (1987) found pigmented eggs in a dissected female. Duellman & Trueb (1986) also report on Phrynomantis species laying pigmented eggs. The P. bifasciatus spawn figured in Wager (1986, p. 63, mistakenly in the Bufo rosei chapter) looks like that of P. microps. The Phrynobatrachus egg mass figured in Passmore & Carruthers (1995, p. 233) is more likely to belong to Phrynomantis, too. In South and East Africa Phrynomantis eggs are deposited in fairly large rounded clumps just under the surface, attached to vegetation. The eggs are light green but turn gray a day or two later (Pickersgill pers. comm.).

The tadpole of P. microps was first described by Lamotte (1964) from Lamto, Ivory Coast. Tadpoles hatch within 1.5–2 days. They measure approx. 5 mm TL and are almost white. They have external gills, a large yolk sac and two ventral adhesive discs. With these organs, the tadpoles stick to the jelly after hatching. They still lack an oral disc at this stage. Two vaguely defined black lines stretch from the eyes to the tail base. Four days later, all tadpoles swim in mid-water, showing the typical habitus of pelagic Microhylid larvae. They are transparent and lack horny beaks and teeth. The density of the black and golden spots on the body varies from pond to pond, most likely depending on how muddy the water is. The tail fin may be transparent or have a black border. The tip of the tail is usually filamentous. The tadpoles found in muddy water are always rather light colored, and the color morphs described by Lamotte (1964) are more likely to result from different habitats than represent geographic variations. Oval, air filled bubbles are visible from dorsal view, beside the base of the tail. It is not known if these bubbles are specific structures or simply air-filled parts of the intestines. The unpaired spiracle opens at a ventromedian position, approximately on a level with the base of the tail. Tadpoles of stages 25–30 had the following size range (TL, mm) and weight (g): 17/0.08 – 23/0.16. Development of hind legs is complete at a TL of approx. 30mm. The forelegs emerge when the tadpoles measure 11 mm BL (TL: 21–30 mm). The froglets leave the water within 40 days, measuring approx. 10 mm.

The tadpoles of P. bifasciatus and P. annectens described by Power (1926b) and Gradwell (1974) cannot be distinguished from those of P. microps. P. annectens is a suspension feeder; but unlike P. microps, it swims with its head pointing downward (Gradwell 1974).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Benin, Burkina Faso, Cameroon, Central African Republic, Congo, the Democratic Republic of the, Gambia, Ghana, Mali, Nigeria, Senegal, Sierra Leone, Togo

 

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Schiøtz (1967) assumes that P. microps is restricted to grassland and open savannas. In Ghana and Nigeria, he never found this species in dense tree savannas (Schiøtz 1964). Lamotte (1966) characterizes this frog as a savanna-dweller which locally penetrates into the rainforest belt. In Togo and Benin, its range touches the coast in the "Dahomey Gap" (Lamotte 1967). I found this species near Ananda, Ivory Coast, in a region still covered with rainforest in the mid-20th-century. Nowadays the rainforest has mainly been replaced by farmland. Apart from Hughes (1988), who also mentions coastal scrub thickets, P. microps is generally quoted as a savanna species occurring both in the Guinea savanna (Lamotte 1967, Walker 1968, Barbault 1972, 1974, Zug 1987) and in the Sudan savanna (Schiøtz 1967, Schätti 1986, Hughes 1988). It is not restricted to arid savannas, as reported by Lamotte & Xavier (1981). P. microps is found in flooded meadows, in ponds and swamps (Schiøtz 1967), under rotten wood (Schätti 1986), buried in savanna soils (Lamotte 1967), but also in arboreal habitats (e.g., in the buds and tree-tops of palms), where it occurs together with several Hyperolius and and Afrixalus species (Lamotte 1967, Barbault 1972, 1974a, b). Poynton (1964a) notes that Phrynomantis species like to climb. However, he did not classify them as arboreal. Lamotte (1967) describe this frog as a more or less xerophilous species. Most often I found P. microps in subterranean cavities near open water, under rotten tree trunks in open savanna, on the edges of gallery forests and in forest islands.

Range: P. microps inhabits large parts of the West African and Central African savannas (Frost 1985). Schiøtz (1967) describes this frog as a West African species whose range extends to Cameroon. Further east, it is replaced by P. bifasciatus. According to Lamotte (1966), the range stretches from Senegal to Nigeria. In particular, P. microps has been recorded from the following countries: Senegal, Sierra Leone, Ivory Coast, Ghana, Burkina Faso, Mali, Benin, Togo, Nigeria, Cameroon, Central African Republic (Peters 1875, Loveridge 1930, Schiøtz 1963, 1964a, c, 1967, Lamotte 1966, 1967, Barbault 1967, 1972, 1974, Vuattoux 1968, Walker 1968, Euzet et al. 1969, Amiet 1973a, Miles et al. 1978, Schätti 1986, Zug 1987, Hughes 1988, Joger 1990, Rödel 1996, 1998b, Joger & Lambert 1997, Rödel & Linsenmair 1997). The Tanzanian P. microps, mentioned in Loveridge (1930) has been confused with P. bifasciatus.

The range of P. bifasciatus stretches from Somalia to Zaire and South Africa. The range of P. affinis extends from Zaire to northern Namibia and Zambia. P. annectens is reported to occur in Angola and north-western Cape Province, South Africa. Largen (1998) records P. somalicus (Scortecci 1941) from Ethiopia.

Life History, Abundance, Activity, and Special Behaviors
According to my personal observations, P. microps calls from cavities, termite hills and tufts of grass (compare to Schiøtz 1964). After heavy rains the frogs begin to call at dusk. Amplectant pairs usually arrive at the breeding sites after midnight. Spawning may therefore last until the early morning. Males have no fixed calling site. They vocalize while migrating towards the ponds. In this respect, P. microps clearly differs from P. annectens, which is territorial. In the latter species the males even wrestle for calling territories (Channing 1974, 1975, 1976).

Reproduction is triggered both by rainfall and by seasonality. They start spawning in late April to early May and continue till June / July. A second spawning period starts in August / September. In the Comoé National Park, tadpoles are found shortly after the first heavy rains, i.e., in March/April, and till September. In drier years, at the beginning of the rainy season, P. microps only spawns when the amount of rainfall exceeds 18 mm. In moist years however, they spawn after nearly every rain (Rödel 1993, unpub. data). The restriction in dry years seems to be an adaptation against the risk that a pond might dry out before metamorphosis is completed. With more than 18mm of rain most ponds are likely to last long enough for metamorphosis to be completed.

A pair observed spawning deposited several egg batches. Egg laying occurred while the female was submerged, the male partly above the water surface. The vent of the female was directed towards vegetation. The eggs were wound around the plant. The female raised her vent above the surface, slightly bent her back and laid several egg batches. The first small egg mass was deposited near the edge of the pond. The couple then swam to a site, approx. 10 meters away where another 100 eggs were laid. During the following 25 sec they swam 2 meters and laid 80 eggs. Another 15 sec and a meter away they laid 110 eggs. Subsequently, i.e., 12 sec later and 2.5 m apart, 180 eggs were deposited. One minute later, the couple went ashore, with the male still sitting on the back of the female. Thus it seems spawn may be deposited in small batches. Batching is most likely a strategy to minimize the risk of predation and/or desiccation. However, I do not know whether the spawn is distributed over a single night or over several consecutive nights, within a single pond or in several ponds. Two dissected females had heavily meandered oviducts. The number of eggs forming the tiny egg batches (compare "spawn") corresponded to the number found in one sling of a single oviduct; small clumps correspond to the contents of several slings; a medium-sized egg mass approximately contained as many eggs as a complete oviduct, and large ones comprise the content of two oviducts.

In Comoé National Park, I found P. microps larvae almost throughout the rainy season. Contrary to my observations, Lamotte (1967) only recorded tadpoles in June and July at Lamto where the rainy season lasts from March to November (Barbault & Trefaut Rodriguez (1978). In Lamto the tadpoles are restricted to large deep savanna ponds harboring little or no vegetation. Amiet (1973a) wrote that populations in northern Cameroon are explosive breeders, reproducing within a rather short period. However, this impression possibly results from a misinterpretation of the evidence. First of all, the author observed the frogs only over a relatively short period; and secondly, P. microps call at most for 1–3 days after heavy rainfalls. A lot of other frog species continue calling, at least sporadically. It is probable he simply missed further spawning activities which took place later in the rainy season (see above).

Savanna ponds of highly variable size, i.e., one to several hundreds of square meters, are acceptable spawning sites. These may be situated in the savanna as well as in gallery forests. The latter, however are only rarely accepted. At the start of the rainy season, spawning occurs only in larger ponds. As the rainy season advances, and desiccation becomes less and less likely, smaller pools are accepted as well.

The larvae filter directly below the water surface with their heads pointing upward. They usually prefer to swim in deeper parts of the pond where there is less vegetation. They often form large swarms. The larger the swarm, the more likely they are to swim in open water. Swarm formation however, only occurs when predators are present. The latter are detected both by visual and olfactory cues (Rödel & Linsenmair 1997). The tadpoles react by swarming on detecting the release of body liquids, resulting from injuries caused by predators on conspecific larvae, as well as on other species, e.g., Kassina (Rödel & Linsenmair 1997). 60% of the swarms comprise less than 50 specimens, but the largest consisted of more than 4000 tadpoles. The tadpoles swimming direction lacks coordination except when the wind is blowing, when they turn towards the wind. Vibrations of the pond bottom or ripples in the water never cause the tadpoles to flee, but they immediately react to shadows by seeking refuge in deeper water zones.

Unlike P. annectens, which is encountered exclusively on the ground or in subterranean cavities (Channing 1976, Loveridge 1976), P. microps was frequently found on palms, together with different hyperoliid species. Vuattoux (1968) reports this species in the buds of savanna palms (in 4.9 %), rarely they live in dead palms. However, this frog is capable of burying itself in loose soil. As it needs at least humid soil, it usually selects sites with grass or the buds of palms. Whereas I observed climbing P. bifasciatus in Kenya (Rödel 1990), P. microps from Comoé National Park were found exclusively on the ground, in cavities or under rotten wood. Mahsberg (pers. comm.) observed a frog calling from a hollow tree, about 1.5 m above the ground. It is uncertain whether P. microps at Lamto and at the Comoé National Park really select different refuges during the dry season. The Rônier palms, the main refuge in Lamto, are very rare in the Comoé National Park. Some refuges are possibly used over a longer period. For example, I found two P. microps under the same tree trunk in 1992 and 1993. However, it was not clear whether it were the same P. microps.

According to Vuattoux (1968), Barbault (1974a, b) and Lamotte (1983), P. microps exclusively feeds on ants. The first author found dozens to hundreds of ants (of several genera) in the stomachs of 12 dissected animals. Vuattoux (1968) determined mainly Crematogaster. In contrast, the stomach of a frog which I dissected contained 126 termites of the genus Trinervitermes. Ants were absent, although the frog had been found in the midst of an ant colony. Captive P. microps are known to accept other arthropods, e.g., crickets and millipedes (Hermann 1989, Mahsberg, pers. comm.).

P. microps is not only protected by its coloration, which Schiøtz (1964) and Lamotte (1983) interpret as a camouflage pattern, but this frog also shows a specific defensive behavior (Hermann 1989, Rödel & Braun 1999). The hind legs are bent forward, and the raised vent is presented to the predator. The head is directed towards the ground and bordered by the forelegs. The black groin bands may simulate eyes. P. bifasciatus, several Pleuroderma species and Physalaemus natteri are known to display a similar behavior (Duellman & Trueb 1986). P. microps is frequently found in association with different scorpions, particularly with Pandinus imperator (Mahsberg, pers. comm., pers. obs.) but also with Hottentotta hottentotta and other Buthidae. This might possibly be a defensive strategy. However, our observations on P. microps’ association with highly aggressive ants point in another direction. P. microps seems to spend the dry season in subterranean refuges, but cannot bury into the hard soil. As places that offer enough humidity are normally already occupied by ants or other arthropods, the frogs must reach an "agreement" with these dangerous neighbors. We showed that the tolerant behavior of the ants towards the frogs is due to chemical components of the frogs’ skin (Rödel and Braun 1999). The protective function is not necessarily a result of the toxicity of these components. Ants, like any other social insects, will kill an intruder even if some of the insects have to pay with their lives. P. microps has obviously developed some kind of "defensive coat" which includes a stinging inhibitor, that enables these frogs to survive in the midst of the ants. Kassina fusca, and possibly K. senegalensis, have also developed comparable strategies. Other frogs which normally do not associate with these ants are killed within a few seconds (Rödel and Braun 1999). P. microps is known to have a very toxic skin (Jaeger 1971, Hedges 1983).

Comments
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.

References

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 2001-05-10
Edited by Kellie Whittaker (2011-12-21)

Species Account Citation: AmphibiaWeb 2011 Phrynomantis microps <http://amphibiaweb.org/species/2085> University of California, Berkeley, CA, USA. Accessed Oct 18, 2017.



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Citation: AmphibiaWeb. 2017. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Oct 2017.

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