Microbatrachella capensis, considered one of South Africa’s smallest amphibians, has a snout-vent length in the range of 15 - 18mm and a snout that is generally rounded. A distinguishing feature of this species is that the tongue lacks a median papilla (Branch 1988). Its head is as long as it is wide, with a tympanum that is hidden and not visible to the eye (Minter 2004, Branch 1988). Its pupil is horizontal with an elliptical shape (Minter 2004).
The dorsum of M. capensis is warty, while the ventrum has a smooth skin texture (Rose 1926, Minter 2004). The lower part of the forelimb is less than half the body length (Minter 2004). The finger and toe tips are classified as obtuse in shape, with a faintly shorter first finger than the second finger. The toes are not fully webbed, but rather one-third webbed with a deep notch webbing pattern that continues up until the last phalanx of the toe. At that point, it begins to display a fringe webbing pattern. In contrast to the toes, the fingers show no webbing (Branch 1988).
Males of the M. capensis species have vocal sacs so large that they act to double the body size, as they spread and continue over at least half the ventral surface (Rose 1926).
Microbatrachella capensis closely resembles Cacosternum platys and Cacosternum boettgeri, two species previously considered synonymous, in terms of size and appearance. The species can be differentiated by C. boettgeri exhibiting a flatter sitting position and smoother skin than M. capensis (Rose 1926). The flatter appearances of C. boettgeri and C. platys stem from limbs that extend more laterally than M. capensis. Other differences include no webbing in between the toes for C. boettgeri and C. platys as well as their white-colored ventrums with small dark spots (Minter 2004). Cacosternum boettgeri has a head that has the ability to exhibit lateral movement (Rose 1926). Cacosternum boettgeri overlaps the range and habitat type of M. capensis, but with a more widespread distribution and a more generalized habitat preference. Cacosternum platys also has a unique call from that of M. capensis (Minter 2004).
A live M. capensis frog can be described as having a typically dark background color. The dorsal area of this species displays vast variation in color, ranging from different shades of green, grey, brown, or black. The dorsal area can also either be uniform in those colors or speckled with darker markings. There is usually a thin stripe along the vertebral area, sometimes accompanied by broader lateral stripes (Branch 1988). Live specimens vary in color on the ventral area as well, ranging from an off-white shade to a variable black and white mottling (Minter 2004). The ventral area also varies in terms of patterning, spanning from blotching, marbling, mottling, speckling, or even just a plain brownish white (Rose 1926). For males, the throat area, or gular region, is brown in color with an absence of mottling (Branch 1988).
Tadpoles of M. capensis are considered relatively large in size (Rose 1926).
Individuals vary by ventral coloration and patterning (see above, Minter 2004, Rose 1926). There is also sexual dimorphism with males lacking patterning in the throat area (Branch 1988).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: South Africa
Microbatrachella capensis is endemic to South Africa and can be found in the Western Cape Province. There are four subpopulations within this species and their range occurs 140 km from the Cape Flats and southwest to the Agulhas region. The entire species only inhabits less than 10 km² of area in their range. Their elevation range has a lower limit of 10 m and an upper limit of 80 m (Minter 2004).
Microbatrachella capensis has a unique habitat in the low-lying coastal wetlands. The habitat is dominated by fynbos shrubland growing on neutral to acidic sands. The composition of the wetland includes a dark humus layer and highly acidic waters. The pools that make up the wetland fill during the winter rainy seasons and most dry up during the summer months. However, some pools will keep water year-round. Annual rainfall can be over 50 cm. Microbatrachella capensis relies heavily on these special habitat requirements and therefore is very sensitive to habitat modification (Minter 2004).
Life History, Abundance, Activity, and Special Behaviors
Microbatrachella capensis is a relatively rare species with only 26 breeding sites. However, densities at each breeding site can be high (IUCN 2017). Breeding commences with the rainy season when wetlands begin to fill with water. The peak breeding season is from July to September, but can occur as early as May depending on rainfall (Visser 2010, Minter 2004). Early winter rains signal the frogs to emerge from underground where they have been waiting in a dormant state during the dry season.
Microbatrachella capensis is a highly vocal species during the breeding season. They call during the day and night, but vocalizations increase at night. They will form choruses of hundreds of frogs when environmental conditions are right. Males generally call from vegetation at water level (Minter 2004).
Microbatrachella capensis lays clustered eggs in a clutch of about 20 eggs. The eggs are surrounded by a jelly capsule and when laid, are attached to submerged vegetation. The embryos are black and possess a semilunar shape (Rose 1926). Microbatrachella capensis experience slow development and growth is highly dependent on population size, resource availability, and temperature. Tadpoles spend most of their time on the bottom of the pools, then emerge as metamorphosed frogs in early December. Metamorphosis from egg to frog takes around 3 - 5 months (Minter 2004). Parental care is not common in this family, therefore, it is unlikely that M. capensis expresses parental care (Crump 1996). With that said, it is still unknown whether this is the case for this species.
The research on the diet of M. capensis is limited, however, it is suspected that they eat flying insects, which is a common food source for similar species (Van Dijk 1971).
Trends and Threats
Microbatrachella capensis is one of South Africa’s most threatened amphibians (Baard and Villiers 2000). Currently, M. capensis is listed as “Critically Endangered” according to the IUCN Red List of Threatened Species. In 1994, this species was found to be "Endangered", but due to decline, was re-listed as "Critically Endangered" after an evaluation in 2017 (IUCN 2017).
Although M. capensis was first discovered in the Cape Flats of South Africa, modern populations may no longer exist in this area due to habitat destruction and fragmentation. Half of the frog’s populations are spaced so far apart that migration between the populations is rare (IUCN 2017). In addition, M. capensis is particularly at risk from habitat loss due to their specialized wetland habitat requirements, such as the endemic Fynbos Biome. Any urbanization or agriculture that modifies their habitat can have devastating effects on their population sizes and their only suitable breeding grounds. Urbanization and agriculture cause a cycle of filling and draining into the low-lying coastal wetlands, and may deposit pollutants that cause eutrophication. Invasive animals or plants can also be too great of competition for these habitat specialists to tolerate (Minter 2004). Microbatrachella capensis rely on undisturbed wetlands, and the continued construction of roads near these wetlands in the Western Cape Province could cause the species to go extinct (Baard and Villiers 2000).
Kogelberg Biosphere Reserve is a protected wetland system in the Western Cape Province of South Africa that aids in providing suitable habitat for M. capensis . This is the only reserve in the area that serves to conserve the remaining viable population and surrounding habitat of M. capensis (Baard and Villiers 2000).
There are a few conservation measures currently at work for M. capensis. Successful breeding in captivity has been recorded, however, providing sufficient food to raise the frogs is difficult. Also, since most of their habitat has been modified, it is hard to find appropriate release sites for reintroduced individuals. Measures to expand protection of their habitat have also been underway. More studies to help understand the life cycle and ecology of this unique species will greatly help in the protection of M. capensis and other endemic species of the South African Cape Province (Branch 1988).
Possible reasons for amphibian decline
General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Subtle changes to necessary specialized habitat
Local pesticides, fertilizers, and pollutants
The species authority is: Boulenger, G.A. (1910). “A revised list of the South African reptiles and batrachians, with synoptic tables, special reference to the specimens in the South African Museum, and descriptions of new species.” Annals of the South African Museum 5(9): 455–538.
Microbatrachella capensis is the only species in its genus (Minter 2004). It is a member of the subfamily Pyxicephalinae (Frost et al. 2006). Many genera including Microbatrachella were originally categorized under the Petropedetinae subfamily, along with the now split subfamily Phrynobatrachinae, based off morphological similarities. Petropedetinae was later split into three separate families and the synapomorphies of the subfamily Pyxicephalinae are recognized as having an exostosis skull, a present occipital canal, a zygomatic ramus longer than the otic ramus, and an overlapping medial ramus of the pterygoid and the parasphenoid ala (Frost et. al 2006).
The genus name "Microbatrachella” is Greek for “little frog”: “micro” meaning "little" and “batrachos” meaning "frog" (Minter 2004). The species was previously known as Phrynobatrachus capensis and Microbatrachus capensis (Frost 2018).
Baard, E. H., de Villiers, A. L. (2000). ''State of Biodiversity: Western Cape Province, South Africa Amphibians and Reptiles.'' Western Cape State of Biodiversity.
Branch, W. R. (1988). South African Red Data Book - Reptiles and Amphibians. NMB Printers, Port Elizabeth.
Crump, M. L. (1996). ''Parental care among the amphibia.'' In Advances in the Study of Behavior, 109-144.
Frost, D. R. 2018. Amphibian Species of the World: an Online Reference. Version 6.0. Accessed 8 Nov 2018. Electronic Database accessible at http://research.amnh.org/herpetology/amphibia/index.html. American Museum of Natural History, New York, USA.
Frost, D. R., Grant, T., Faivovich, J., Bain, R. H., Haas, A., Haddad, C. F., De Sa, R. O., Channing, A., Wilkinson, M., Donnellan, S.C., Raxworthy, C. J., Cambell, J. A., Blotto, B. l., Moler, P., Drewes, R. C., Nussbam, R. A., Lynch, J. D., Green, D. M. (2006). ''The amphibian tree of life.'' Bulletin of the American Museum of Natural History. , 1-291.
IUCN SSC Amphibian Specialist Group, South African Frog Re-assessment Group (SA-FRoG). 2017. Microbatrachella capensis. The IUCN Red List of Threatened Species 2017: e.T13318A77158116. http://dx.doi.org/10.2305/IUCN.UK.2017-2.RLTS.T13318A77158116.en. Downloaded on 18 February 2018.
Minter, L. R. (2004). Atlas and red data book of the frogs of South Africa, Lesotho, and Swaziland. Avian Demography Unit, University of Cape Town, Washington D.C.: SI/MAB Biodiversity Program.
Rose, W. (1926). ''Some field notes on the Batrachia of the Cape Peninsula.'' Annals of the South African Museum, 20, 433-450.
Van Dijk, D.E. (1971). ''Anuran ecology in relation particularly to oviposition and development out of water.'' Zoologica Africana, 6, 119-132.
Visser, J. (1979). ''Calling and spawning dates of the south-western Cape Frogs.'' The Journal of the Herpetological Association of Africa, 21(1), 21-28.
Written by Melissa Crews, Sarah Ahmed, Jivka Grozeva (micrews AT ucdavis.edu, sarahmed AT ucdavis.edu, jvgrozeva AT ucdavis.edu), University of California, Davis
First submitted 2018-11-08
Edited by Rina Lu (2018-11-13)
Species Account Citation: AmphibiaWeb 2018 Microbatrachella capensis: Micro frog <http://amphibiaweb.org/species/3734> University of California, Berkeley, CA, USA. Accessed Nov 13, 2018.
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Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 13 Nov 2018.
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