Kartläggning av långbensgroda Rana dalmatina på Öland - med rekommendationer för biogeografisk uppföljning

Sammanfattning: As a result of e.g. habitat loss and diseases, a global decline of amphibians is a fact. In order to prevent further declines and to improve the conservation status for amphibians in Europe, the member states have to report the status for amphibians every sixth year to EU. In Sweden, the County Administrative Board in Scania is responsible for coordinating the biogeographic monitoring of amphibians. Öland contains the largest population of the agile frog (Rana dalmatina) in Sweden. However, its status in other parts than the well investigated central parts (Mittlandet) of Öland is not well known. Such knowledge is needed in order to optimize a monitoring program at national level. In the inventory I found 3906 egg masses (equivalent to 7812 individuals) at more than 82 occurrence sites for the agile frog outside Mittlandet. Of these, 24 were identified as source ponds (at least 50 egg masses). Before this inventory the population of agile frog in Sweden consisted of approximately 30000 individuals. More egg masses were found in wetlands with high proportion of surrounding deciduous forest (buffer zone of 1000 m), with a short distance to the nearest site with egg masses, a low proportion of open land, and relatively few roads. The probability of finding other amphibians was greater in source ponds than in satellite ponds (i.e. ponds with less than 50 egg masses). Therefore a future monitoring of the agile frog should include documentation of other species in at least source ponds. The data suggest that in order to detect a future population change greater than the natural fluctuation levels (35 %) of the agile frog, at least nine source ponds sites have to be surveyed at two independent occasions. To detect a change in the frequency of occurrence at sites with agile frogs, of 50 %, at least 45 sites have to be visited at two independent occasions. Due to the finding of several unknown populations of the agile frog in Öland the impact of environmental factors need to be further investigated in order to give recommendations for future monitoring programs of the agile frog.