The edible frog is an unwanted addition to Ruissalo’s range of frog species
Sightings of alien frog species have been recorded on Ruissalo island since 2008. These frogs are most likely fertile hybrids of the marsh frog (Pelophylax ridibundus) and pool frog (Pelophylax lessonae), called edible frogs (Pelophylax kl. esculentus). The edible frog is also called the common water frog or green frog.
The edible frog is an invasive alien species that has spread widely across southwest Finland in the last ten years. Its loud croaking drowns out the quieter vocalisations of European common frogs and moor frogs, thus hindering their reproduction. Luckily, however, the edible frog’s spawning period is later than those of our native frog species. Adult edible frogs may also eat the tadpoles of native frog species.
Ruissalo’s first edible frogs may have arrived on ships from the southern parts of the Baltic Sea. With human assistance, these green frogs have quickly established a firm foothold, spreading so far and wide that they can no longer be eradicated.
