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VOLKER RUDOLF from the Department of Animal Ecology and Tropical Biology at the University of Wuerzburg in Germany, studies the ecology, the reproductive mode and the larval biology of the frog species Phrynobatrachus guineensis (Anura, Ranidae). This species was first described by GUIBE & LAMOTTE 1961 from Mont Tonkoui, Ivory Coast, but the reproductive mode and the tadpoles remained unknown, until in 1998 both were discovered in Tai National Park. Phrynobatrachus guineensis is the first species of African ranids known to reproduce in tree-holes. The work with this species is part of the BIOTA project for West Africa, and belongs to an amphibian monitoring program led by Dr. M.-O. Roedel. The main focus of the monitoring programme is to establish amphibians as a bioindicator system to evaluate the state of West African rain forests in general and that of TNP in particular.
Most of the 56 recovered species of frogs in TNP live in swampy parts of the Tai forest because they need open water for their reproduction or larval life. Many different types of amphibian reproductive modes are known for the species in the TNP. But just a small minority of specialists is not dependent on ponds or rivers for their reproduction and larval life. One of them is Phrynobatrachus guineensis. This small frog uses water accumulations in treeholes, roots or even snail-shells. They attach small numbers of single eggs above the water surface to the walls of the holes, where they develop. After four days, the tadpoles drop into the water and continue their development until they leave the holes after less than a month as small froglets. Due to this special and recently unknown reproductive mode, they are not dependent on ponds and rivers. Therefore this species is of special interest for the biomonitoring program.

In his research about the ecology of this species in the Tai National Forrest, VOLKER RUDOLF focus on the choice of the sites in which reproduction takes place, what affects this choice and its effects on the reproduction and larval life itself. Nothing is known about the factors being important for this choice and how they affect the larval development and live. The tadpole-densities in these holes are up to ten times higher than known from other species. What are the reasons for this high densities and what effects do they have on the larval live. To answer this questions the methods used in his studies combine daily monitoring, observation of marked individuals and field- as well as laboratory-experiments.

This exceptional reproductive mode, which takes place in these microhabitats, makes this species not only to an interesting species for the biomonitoring in the TNP. It although offers an excellent model to study an ecological system and allows to examine density effects in natural and experimental conditions.

Dr. Mark - Olivier Rödel ist der Koordinator des Amphibienprojektes im Taï- Nationalpark. Seine Arbeit führte schon zur Beschreibung von drei neuen Amphibienarten, zwei Fröschen und einer Kröte. Er ist Author eines Standardwerkez zu den Amphibien Westafrikas. Seine Arbeit wird auch über BIOTA finanziert.

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