Monday 18 March 2019

Magical blue frogs

Among European frogs, certainly the greatest spring spectacle is performed by Moor Frogs Rana arvalis. The males, usually brown-coloured like many other frogs, turn bright blue during the courting season each spring. This spectacle is not very easy to witness as the blue colouring lasts for only a few days a year. Yesterday, with the help of two friends, one of our long-lasting dreams finally came true. We visited one of the known spawning sites at Ljubljansko barje (Ljubljana moor), just at the outskirts of Slovenia's capital and enjoyed in up to 150-200 colourful Moor Frogs. The frogs were gathering in pools of water in a beautiful floodplain forest of alder Alnus glutinosa and English oak Quercus robur. As a backdrop there were Middle Spotted Dendrocopos medius and Black Woodpeckers Drycopus martius calling in the trees overhead. As Moor Frogs are rare and endangered in Slovenia and moreover also very shy, we payed attention not to disturb them and kept a safe distance, viewing them with the telescope. For this reason, the photos are purely for documentation - watch the video in HD instead. The spawning sites at Ljubljansko barje are potentially vulnerable as they are isolated from other sites where the species occurs - that is: locally in eastern and northeastern Slovenia. Like many other "lekking" animals, also Moor Frogs are rather intolerant to any disturbance at their breeding sites, so great care should be taken when watching, but especially photographing these animals.
A special thank to Kaja and Leon for the precious help and for the good company in the field.