European Tree Frog Reintroduction

To reintroduce captive-bred European tree frogs into their former range in Switzerland

Although globally not threatened, the European tree frog, Hyla arborea, is losing ground in Central Europe. In Germany it is rated “Endangered”, in three of the 15 German Federal States even “Critically Endangered”, in Switzerland “Endangered”, and in Austria “Vulnerable”. The German Association for Herpetology and Terraristic (DGHT), an affiliate member of WAZA, has therefore proclaimed the tree frog “Frog of the Year 2008”, calling upon their members to help conserve the species.

The numbers of several amphibian species decreased in the 20th century in the area around the Lake of Lauerz in Central Switzerland. The European tree frog, whose range has been shrinking countrywide during the past 40 years, even became locally extinct in the 1970s. In 1995, the Lake of Lauerz Foundation initiated a habitat restoration programme to help the amphibians, as the Lake of Lauerz is considered an amphibian breeding area of national importance. The lake was legally protected under Federal Law in 2001. In 2006, the programme’s first target was reached in that the number of several amphibian species had increased.

Different experts declared that the restored habitat would be suitable for reintroducing the European tree frog, and at the beginning of 2007 government permission was received to start a reintroduction project.

In 2006, new breeding ponds for European tree frogs were built in the wetlands surrounding the Lake of Lauerz. The reintroduction project started in spring 2007 when the first larvae were transported from a doomed population 60km north of the Lake of Lauerz to the quarantine and breeding facilities of Landscape and Animal Park Goldau. Quarantine procedures and population analyses were done and, after metamorphosis, the subadult frogs were reintroduced to the Lake of Lauerz conservation area. In the following years, larvae and subadult froglets taken either from the wild or from the breeding population at Landscape and Animal Park Goldau should be reintroduced in at least two places. Monitoring will be done to evaluate the success of the reintroduction and protection of the area will be improved.

WAZA Conservation Project 07007 is executed by Goldau Landscape and Animal Park, in collaboration with the Lake of Lauerz Foundation.