29.
Du Toit's Torrent Frog
(Petropedetes dutoiti)
CR
Overview

Du Toit's torrent frog is found in and around the rocky montane streams of Mount Elgon, Kenya, associated with fast flowing streams and waterfalls. The eggs are laid on wet rocks close to torrential streams, and the tadpoles develop clinging to these vertical rock surfaces and grazing algae. It was officially described as a new species in 1935, but has not been seen on Mount Elgon since 1962, despite its habitat being of generally good quality. In view of the rapid disappearance of other montane stream-dwelling species elsewhere in the humid tropics, the impact of disease, such as chytridiomycosis, is a plausible cause of this species’ dramatic decline and possible extinction.

Urgent Conservation Actions

Further surveys of potential habitat to determine if this species survives in the wild; disease screening across known range.

Distribution
Mount Elgon, Kenya
Fact
This species seems to have vanished from decent habitat on Mount Elgon since its last sighting over 40 years ago.
Associated Blog Posts
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Evolutionary Distinctiveness
Order: Anura
Family: Petropedetidae
Du Toit's torrent frog is one of between 16 and about 100 species (depending on which amphibian taxonomy you consult) present within the Petropedetidae family, which diverged from all other amphibians about 70 million years ago in the Late Cretaceous. This group started to evolve separately from the rest of the extant amphibians 5 million years before the extinction of the dinosaurs, which makes them as different from their closest relatives as pigs are to whales! There are just 10 species in the genus Petropedetes (commonly known as the African water frogs).

The Petropedetidae family comprises a group of frogs that are restricted to sub-Saharan Africa. Most of its constituent members are small frogs found in African forests and Savannahs that lay their eggs in temporary pools during the rainy season, although systems of reproduction in this family are fairly diverse, e.g. some species lay eggs on wet rocks in forest streams and the tadpoles develop whilst clinging to vertical rock surfaces – which is the case for Du Toit's torrent frog.
Description
Du Toit's torrent frog is a small species, about 31 mm in total length. The head is slightly broader than long, with distinctly visible eardrums. The toes, but not the fingers, are half webbed, and the digits are strongly thickened with very dilated tips. The skin of the back is distinctly warty and pitted. The skin of the throat and belly is smooth. This species is black in colour, although the digit tips are slightly white-edged. The ventral (or lower) surface of this species is light violet brown and slightly flecked with white. Males and females can be distinguished through close inspection of the eardrum, since males have a tiny projection called the columella which protrudes through the center of the eardrum (also called the tympanum). It is not known exactly why this should occur, but it is thought that this must reduce the vibratory capacity of the eardrum, reducing sensitivity to higher frequencies of sound. This is probably not too disadvantageous for the males because it is generally more important for the females to have good hearing so that they can local potential male mates through their calls.
Ecology
This species is associated with water seeps and fast-flowing streams in montaneforest. Du Toit's torrent frog is a little-studied member of the Petropedetes genus, but it presumably has similar breeding behaviour to its close relatives. It is therefore thought that this species lays eggs on wet rocks close to torrential streams and waterfalls, and that the tadpoles develop whilst clinging to vertical rock surfaces out of the water.

Male African water frogs have been found to possess a pair of “femoral glands” located at the top of the inner thigh. It is not known for certain what function these gland have but, because they are in contact with the female during mating, it is believed that secretions from these glands must have some simulating effect on the female in terms of egg production. Attendance of developing eggs by males has been noted in three species of torrent frog within the Petropedetes genus. Torrent frog tadpoles have very large mouths with many rows of tooth-like structures called denticles. Their mouths are specially adapted to enable these tadpoles to develop on wet rocks out of the water. This prevents them from being swept away in the torrents and waterfalls of their fast-flowing stream habitat. The many rows of denticles probably help fix the tadpoles onto these rocks and graze them for algae and other organic material.
Habitat
Du Toit's torrent frog is found in and around the rocky montane streams of Mount Elgon, Kenya. It is associated with fast flowing streams and waterfalls, as well as water seeps.
Distribution
This species is known only from Mount Elgon, Kenya, at an altitude of around 2,100–2,200 metres above sea level. Previous attempts to locate it on the Ugandan side of Mount Elgon have been unsuccessful.
Population Estimate
There is no current information on the population status of this species, and it has been suggested that it might be extinct. It was last recorded in 1962, and four attempts to locate the species (in wet and dry seasons) since 2001 have been unsuccessful.
Population Trend
This species is thought to be in decline by the IUCN Red List of Threatened Species, and it may already be extinct because it has not been seen since 1962 despite numerous surveying attempts.
Status
Du Toit's torrent frog is listed as Critically Endangered in the IUCN Red List of Threatened Species because its area of occupancy is probably less than 10 km sq., all individuals are in a single subpopulation, and the extent of its forest habitat, and possibly the number of mature individuals, on Mount Elgon are declining.
Threats
The habitat of this species appears to be generally in good condition, although it may be adversely impacted by logging and general encroachment of the forest on Mount Elgon. However, the species cannot now be found at its original locality, or in any other streams on Mount Elgon. In view of the rapid disappearance of other montane stream-dwelling species elsewhere in the humid tropics, the impact of disease, such as chytridiomycosis, is a plausible cause of this species’ dramatic decline and possible extinction.
Conservation Underway
The area where this species was formally discovered in 1935, which is not very precisely known, might be inside, or very close to the Mount Elgon National Park. However its presence has not been confirmed in this protected area. A number of surveys conduced in recent years have failed to locate this species in this, or any other, area. For example, three surveys (each several days in duration) within lower Mount Elgon National Park of this species’ habitat in September 2001, June 2002 and May 2003 failed to find even a singe individual of this species. It is also thought, however, that Du Toit's torrent frog may just be extremely difficult to find because of its rarity.
Projects

This project supports in-country EDGE Fellows to help conserve relevant EDGE species

This study seeks to carry out an assessment of one of the world's critically endangered amphibian species, Petropedetes dutoiti which is endemic to Mt Elgon on the border of Kenya and Uganda.This is an amphibian species associated with seeps and fast moving waters. It was last spotted in the wild in 1962 and had thus been conceived as extinct.

This study aims to determine the current distribution range of Petropedetes dutoiti, the population status and to identify the threats to the species.

It is one of the Evolutionarily Distinct and Globally Endangered species, also listed as Critically Endangered under IUCN. Has a very limited global distribution only restricted to Mt Elgon on the border of Kenya and Uganda.

Conservation Proposed
Research is also needed to establish the reasons for this species’ population crash, including disease screening (especially for chytridiomycosis) and a thorough examination of the factors that are thought to threaten Du Toit's torrent frog. This is also important for the management of other amphibian populations that survive on Mount Elgon. Additional surveys are also required to determine exactly where (if at all) populations survive in the wild to investigate the currenlt population status of this species in the wild. All of the resultant information should be used to create a Conservation Action Plan as a vital first step in galvanising efforts to preserve this species, and its habitat, should it still survive in the wild.

In addition to conserving native habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside of its natural habitat, giving rise to individuals from that species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. Since Du Toit's torrent frog is categorised as Critically Endangered, the possibility of a captive breeding programme for this species should be investigated.
Associated EDGE Community members

Working towards saving of the Critically Endangered Du Toit's torrent frog in Kenya

Links
References
AmphibiaWeb: Information on amphibian biology and conservation [web application]. 2006. Berkeley, California: AmphibiaWeb. Available: Global Amphibian Assessment. Accessed: 08 December 2006.

Channing, A., Moyer, D.C. and Howell, K.M. 2002. Description of a new torrent frog in the genus Arthroleptides from Tanzania (Amphibia, Anura, Ranidae). Alytes 20: 13-27.

Duellman, W. E. and Trueb, L. 1986. Biology of Amphibians. McGraw-Hill, New York.

Frost, Darrel R. 2006. Amphibian Species of the World: an Online Reference. Version 4 (17 August 2006). Electronic Database accessible at: . American Museum of Natural History, New York, USA.

Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. De Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green, and W. C. Wheeler. 2006. The Amphibian Tree of Life. Bulletin of the American Museum of Natural History 297: 1-370.

Groombridge, B. (ed.) 1994. 1994 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland.

Halliday, T. and Adler, C. (eds.). 2002. The new encyclopedia of reptiles and amphibians. Oxford University Press, Oxford.

Howell, K.M. 1993. Herpetofauna of the eastern African forests. In: J.C. Lovett and S.K. Wasser (eds), Biogeography and Ecology of the Rain Forests of Eastern Africa, pp. 173-201. Cambridge University Press, Cambridge.

IUCN, Conservation International and NatureServe. 2006. Global Amphibian Assessment. Global Amphibian Assessment. Accessed on 08 December 2006.

Klemens, M.W. 1998. The male nuptial characteristiscs of Arthroleptides martiensseni Neiden, an endemic torrent frog from Tanzania's Eastern Arc Mountains. Herpetological Journal 8: 35-40.

Lötters, S., Loader, S. & Howell, K. 2004. Arthroleptides dutoiti. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. IUCN Red List of Threatened Species. Downloaded on 25 July 2007.

Lötters, S., Rotich, D., Koester, T.E., Kosuch, J., Muchai, V., Scheelke, K., Schick, S., Teege, P., Wasonga, V.D. and Veith, M. In press 2004. What do we know about the amphibians from the Kenyan central and western highlands? Salamandra 40.

Mattison, C. 1987. Frogs and toads of the world. Blandford Press, U.K.

Obst, F.J., Richter, K. and Jacob, U. 1984. The Completely Illustrated Atlas of Reptiles and Amphibians for the Terrarium. T.F.H. Publication Inc., N.J., U.S.A.

Roelants, K., Gower, D. J., Wilkinson, M., Loader, S. P., Biju, S. D., Guillaume, K., Moiau, L. and Bossuyt, F. 2007. Global patterns of diversification in the history of modern amphibians. Proceedings of the National Academy of Sciences 104: 887-892.

if you can provide new information to update this species account or to correct any errors, please email us at info@edgeofexistence.org


Forum comments
  1. Anonymous
    Unregistered

    I found this information very interesting and i enjoyed learning something new- Thanks!

    Posted 7 years ago #

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