Current population survey documents urgent need for action
4th of july 2011
Foto: Frank Körner
The Artland in the northern district of Osnabrück used to be one of the strongholds of the European tree frog in Lower Saxony. The complex landscape with its various structures that combines many small water bodies and hedges offers an ideal habitat for this amphibian species. As recently as 1994, calling tree frogs were documented in over 30 water bodies - altogether several hundred animals lived there at the time. The population decline that can be observed in all of Central Europe has, however, not spared the Artland either. At a field mapping conducted by NABU Osnabrück in 2003/2004, a considerable decline was observed. The dramatic extent of the situation is documented in the results of a current population survey. Birgit Hesselkamp, a graduate engineer for landscape development, volunteered to field map amphibians and spent many hours this spring in the Artland in search of calling tree frogs. She was assisted by Michael Weinert of the regional nature conservation work group in the Artland (Regionalen Arbeitsgruppe für Naturschutz im Artland e.V. (RANA)). Apart from calling males, water bodies were also scanned for tadpoles. The latter provide important information on the reproductive success at a particular body of water. The tree frog will be able to survive only when adequate numbers of offspring are regularly produced. Fears for the frog population were only confirmed by the results of the population survey. Calling tree frogs were spotted at only four water bodies and only one of these showed evidence of offspring. Altogether, only 20 to 30 animals were calling. It is to be feared that the European tree frog will have disappeared from the Artland in a few years.
However, salvation is in sight. One of the objectives of NABU Niedersachsen's LIFE AMPHIKULT project is to create new spawning grounds for amphibians in the Artland. Dr. Markus Richter, project manager of AMPHIKULT, is confident that the European tree frog can be saved: ”Numerous bodies of water that are ideally suitable as spawning grounds have been created by the RANA Association, our on-site project partner. However, the European tree frog has not yet been able to benefit from this. As the current survey shows, the distance between the populations to these ponds is too great for the tree frog to overcome. AMPHIKULT is now attempting to decrease the distance between the frogs and the ponds.” Richter is particularly grateful for the tireless efforts of Birgit Hesselkamp. ”Her voluntary field mapping of the population provides an excellent base for a detailed planning of AMPHIKULT measures.”
Dr. Markus Richter und Birgit Hesselkamp