F. Andreone and J. E. Randrianirina
Little is known about the conservation status of amphibians in Madagascar. Ninety-nine per-cent of the (more than 210) anuran species are endemic and are represented by four families (Hyperoliidae, Mantellidae, Micro-hylidae, and Ranidae). Since many of the Malagasy amphibians are connected with forest habitats it is not unreasonable to suggest that the high deforestation rate occurring in this country has been accompanied by the extinction of many (possibly un-described) frog species. It is therefore a race against time to discover these taxa and protect them. Furthermore, due to their biological peculiarities and very colourful appearance, many frogs are annually exported for the pet trade: Mantella (Mantellidae), some Scaphiophryne and Dyscophus (Microhylidae), and, in a few cases, Mantidactylus and Boophis (Mantellidae). |
A recent conservation synthesis (Andreone & Luiselli, 2003) indicated that the harlequin Mantella, Mantella cowani is likely the most threatened Madagascan amphibian because of a combination of sensitivity to habitat alteration and to exploitation for the pet trade. The few remaining plateau forests where this species still lives are highly fragmented and subject to intensive timber harvesting. The species is known from small forests near Ambatolampy and Antoetra. Furthermore, some museum vouchers record its presence (at least in the past) in other localities. At Antoetra, M. cowani was said to be quite common until several years ago and, for this reason, it has been captured in large numbers (Rakotomavo, 2001).
During January-February 2003, we carried out a pilot project on this Mantella, trying to identify sites with viable populations. Around Antoetra we confirmed the species' presence at four sites. In general, the habitat consists of narrow bands of original upland forests along montane streams, humid, stone walls on montane moors. The surrounding habitat is the "typical" deforested upland savannah. At Site 1, despite an intensive search, only a very few individuals were found. There, the collecting pressure is apparently high since the site is close to the village of Antoetra. Children visit it almost every day to collect the Mantellas. We learnt that the current price per individual of Mantella cowani is 4-5000 FMG vs. 250-500 FMG for Mantella baroni. At Site 2, we found >20 individuals in four research days. At Site 3 there are still large forest fragments surrounded by slash-and-burn agriculture (tavy) with maize cultivation. Within the forest we found frog species typical of the eastern rainforests, while within the forest and nearby tavy we found a rich M. baroni population. A few individuals were phenotypically recognised as M. cowani. Furthermore, we found in the tavy several specimens with intermediate chromatic traits between M. baroni and M. cowani; we suspect that most of them are hybrids. The two species are indeed very closely related (Vences et al., 1999). Finally, we surveyed a fifth site at about 150 Km North of Antoetra, near Ambatolampy. This area too consists of small forest parcels within savannas, and a narrow riverine forest. Along the stream we found only a single specimen of M. cowani. It is difficult to understand if the very low occurrence of M. cowani reflects a real scarcity of the species, or if it is due to unsuitable weather conditions.
In terms of habitat requirements, M. cowani appears a typical stream and moor species. Although we cannot draw a realistic figure of the size of the visited populations, our feeling is that they do not exceed more than a few hundred individuals, usually less than one hundred. We are concerned about the fact that the harvesting of wild animals is likely to affect natural populations. During our stay at Site 1, we heard rumours of the activity of local people, who collected about 250 individuals in one week from about five populations. Since the number of persons engaged was not less than 50, the mean capture capacity is about 1 Mantella per person per day. This is indeed a very low number when compared with the very high densities of M. aurantiaca, M. milotympanum and M. baroni (M. Vences, pers. comm.).
Of course more data are needed to reach a comprehensive conservation scenario. Like all the other Mantellas, M. cowani is currently listed on CITES Schedule II, and because of this is theoretically subject to some control and protection. The very critical ecological situation, however, demands drastic political initiatives. Due to the high retail price, local people are induced to collect a large number of specimens, and to stock them whilst waiting for the final decision of the exporter (with an obvious high mortality). This has an evident negative effect on the natural populations, which already live in degraded habitats. The trade and collecting of M. cowani should thus be prohibited for some years. Since the decline for M. cowani is due to a combination of habitat alteration and capture for the pet trade, a limitation of the latter should hopefully result in the species' recovery where habitat is still suitable. During this period of suspension, research must be carried out to ascertain the population size and a realistic distribution pattern.
Acknowledgements. We thank for financial support DAPTF, WCS and NACC. For companionship and exchange of information thanks to G. Aprea and M. Vences. E. J. Edwards helped with logistics and personal information.
Contact: Franco Andreone, Museo Regionale di Scienze Naturali, Via G. Giolitti, 36, I-10123 Torino, Italy.
and Jasmin E. Randrianirina, Parc Botanique et Zoologique de Tsimbazaza, BP 4096, Antananarivo 101, Madagascar.
References:
Andreone F. Luiselli L.M. (2003) Conservation priorities and
potential threats influencing the hyper-diverse amphibians of Madagascar:
Ital. J. Zool. 70: 53-63.
Rakotomavo E. (2001) Etude de la fili–re Mantella de Madagascar.
Report to Office National pour l'Environnement (ONE), Valorisation de la
Biodiversití.
Vences, M., Glaw, F. & Bohme, W. (1999) A review of the genus Mantella
(Anura, Ranidae, Mantellinae): taxonomy, distribution and conservation of
Malagasy poison frogs. Alytes 17: 3-72.