48.
Helena's Stump-toed Frog
(Stumpffia helenae)
CR
Overview
Helena’s stump-toed frog is a very small Madagascan species, characterised by its short digits and slow-motion movements. “Eye spots” on its back are thought to trick predators into attacking away from its head, which helps this species avoid major injury and increases chances of escape. It is ground-dwelling in the leaf litter of dry, high altitude forest fragments, and is thought to build foam nests on the ground for its eggs. It occurs in the poorly protected Ambohitantely Special Reserve and is threatened by habitat destruction as a result of fires, illegal wood cutting and agriculture.
Urgent Conservation Actions
Protection of the remaining habitat; find more sustainable ways for local communities to harvest wood from the area; reconnecting isolated forest fragments.
Distribution
Central Madagascar
Fact
Helena’s stump-toed frog was named after Helena Bigler, wife of Denis Vallan, who is the scientist who originally described this as a new species in 2000.
Evolutionary Distinctiveness
Order: Anura
Family: Microhylidae
The Microhylidae (the “narrow-mouthed frogs”) are one of the most recently evolved families of frogs and, with a total of over 400 species, are also the largest with the greatest number of genera (nearly 50). They are a very large and diverse family of frogs, widely distributed throughout the tropics. They include both burrowing / terrestrial (ground-dwelling) and arboreal (tree-dwelling) species. The narrow-mouthed frogs diverged from all other amphibians about 80 million years ago, which is around same time that beavers and mice shared a common ancestor.

The narrow-mouthed frogs comprise 10 subfamilies, with Helena’s stump-toed frog is a member of the Cophylinae subfamily, which includes 41 species organised into 7 different genera. In Madagascar, the Microhylid family is represented by 10 genera that are found nowhere else on earth (they are “endemic”). The genus Stumpffia contains just 7 small-sized species that possess reduced fingers and toes, a phenomenon often associated with very small frogs. Another odd feature of the Stumpffia frogs is that they exhibit “slow motion” movements, although they can move much faster if disturbed or threatened.
Description
Helena’s stump-toed frog is a very small species, measuring just 13.8 mm in total length. The fingers are rather reduced in length, as is characteristic of this genus, and there is no webbing between the digits. The tips of the fingers are slightly enlarger, differentiating this species from all the other members of its genus. The skin of the back is slightly granular, with the skin of the belly being smoother. The back is a dark grey marbled colour with two black spots towards the base. These probably function as eye spots to deflect potential predator attacks away from its head. This may sometimes give individuals an advantage against their attackers, improve the chances of escape and/or avoiding serious injury. An orange line runs down the center of the back, extending from the middle of the head to the far end of the body. On either side of line, two lines of weakly elevated bumps are visible. A thin creamy and golden line extends from the top of the arm and passes above the eye to the tip of the nose. The sides of the head are dark grey but not marbled. The dark grey sides of the body are covered by lighter spots. The throat, belly and other ventral (or lower) surfaces are light grey or pink with a few indistinct lighter spots.
Ecology
This is a poorly-known species, which was only discovered relatively recently in 2000. Breeding behaviour has not been observed, but is likely to be similar to that of some of its close relatives (e.g. Stumpffia gimmeli), where adults build terrestrial (or ground level) foam nests in the leaf litter, and eggs hatch out into non-feeding larvae maintained by their yolk supply. So far, this method of reproduction is thought to be unique to the narrow-mouthed frogs. An interesting feature of the Stumpffia genus is that these frogs tend to move in slow motion during normal locomotion, although they are capable of performing long jumps when disturbed.

Both the male and female originally described were diurnal (or day active). The fragmented forest area where they were found contains wetter areas (adjoining the streams; characterised by a 20 m canopy height and a relatively sparse undergrowth) and dry areas (on the slopes, plateaus and ridges; characterised by a lower canopy and denser undergrowth vegetation). Helena’s stump-toed frogs has been found in the leaf little of the dryer slope forest, far from streams and brooks. It may be that this species shows a habitat preference for the presence of thick undergrowth, which provides increase shelter and more prey items. This species probably feeds on small invertebrates found in the leaf litter. Males mainly call for females from the leaf litterat dusk – they have a single, large vocal sac, and do not congregate around water bodies.
Habitat
This is a terrestrial (ground dwelling) species inhabiting montane forest. It has been found in the high plateau rain forests of a lichen-rich area, at elevated altitudes of 1,500 metres above sea level. It is found amongst ground leaf little in dryer forest fragments where undergrowth is denser, but has not been found in altered habitats.
Distribution
This species is known only from two habitat fragments in the vicinity of Ambohitantely, in central Madagascar, at an altitude of 1,500 metres above sea level.
Population Estimate
No accurate population estimates exist for this species, although it is very rarely found.
Population Trend
Helena’s stump-toed frog is considered to be in decline by the IUCN Red List of Threatened Species.
Status
Helena’s stump-toed 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 in the Ambohitantely Special Reserve is declining.
Threats
The main threat to this species is the fact that its forest habitat is disappearing very rapidly due to the impacts of fire, illegal woodcutting by local people, and overgrazing by livestock. Helena’s stump-toed frog is only found in a very small area and no other suitable habitat is found anywhere nearby.

The forests of the high plateau of Madagascar, where this species is found, are some of the most threatened forests in Madagascar. The Ambohitantely Special Reserve, where this species can be found, has been heavily fragmented over the course of centuries. Although it is thought that even the smaller forest patches may contain stable amphibian assemblages, this fragmentation is no beneficial to the survival of the species within because it is also though that few are able to travel between fragments. This is because the landscape around these bits of forest is almost completely cleared, with high temperatures and low humidity, meaning that conditions for amphibian dispersal are highly unfavourable. This may be negatively affecting the genetic make-up of these isolated amphibian populations through high levels of inbreeding. Also, populations may be more at risk of disease because they cannot escape from infected areas.
Conservation Underway
It occurs in the Ambohitantely Special Reserve (or “Réserve Spécial”), which is very poorly protected. The Réserve Spécial of Ambohitantely is a nature reserve containing one of the last forests of Madagascar’s high plateau, and consists of hundreds of islands of forest ranging in size from 0.16 to 1,250 hectares. The total area of these forest remnants total 2,737 hectares, which is about half the total reserve area. Helena’s stump-toed frog has so far been found in forest fragments upwards of 30 hectares, indicating the importance of conserving even relatively small patched of forest.
Conservation Proposed
Improved management and protection of the remaining habitat of this species is urgently needed. This should include working with local communities to find more sustainable ways of harvesting wood from the area. It would probably be beneficial to Helena’s stump-toed frog to increase habitat continuity within its range by connecting some of the forest fragments where it is found. This would increase the ability of remaining individuals to disperse and move their genes between formerly isolated populations.

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 Helena’s stump-toed frog is categorised as Critically Endangered, the possibility of a captive breeding programme for this species should be investigated.
Links
References
AmphibiaWeb: Information on amphibian biology and conservation [web application]. 2006. Berkeley, California: AmphibiaWeb. Available: amphibiaweb. Accessed: 08 December 2006.

Andreone, F., Cadle, J.E., Cox, N., Glaw, F., Nussbaum, R.A., Raxworthy, C.J., Stuart, S.N., Vallan, D. and Vences, M. 2005. A species review of amphibian extinction risks in Madagascar: results from the Global Amphibian Assessment. Conservation Biology 19: 1790-1802.

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

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

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

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.

Vallan, D. 2000. A new species of the genus Stumpffia (Amphibia: Anura: Microhylidae) from a small forest remnant of the central high plateau of Madagascar. Rev. Suisse Zool. 107: 835-841.

Vallan, D. 2000. Influence of forest fragmentation on amphibian diversity in the nature reserve of Ambohitantely, highland Madagascar. Biological Conservation 96: 31-43.

Vallan, D. & Raxworthy, C. 2004. Stumpffia helenae. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. IUCN Red List of Threatened Species. Downloaded on 27 July 2007.

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