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| Adult Balkan frog (Pelophylax kurtmuelleri) from its pond habitat, Kerkini (C) Stamatis Kalogiannis |
Introduction
The Balkan frog or Balkan marsh frog is a recently described species of marsh frog, distinguished by the morphologically identical Eurasian marsh frog (Pelophylax ridibundus) by bioacoustics. It is a species endemic to the Balkan peninsula and is undoubtedly one of the most common and adaptive species of amphibian in most of Greece, being widely distributed across the mainland and several islands. Due to a long history of hybridisation with other Pelophylax species, the taxonomic status of the Balkan frog is very complicated and demands more research. It has also been introduced to a handful of European countries, including Italy, Denmark, France and Switzerland.
Description
Size usually up to 10cm. Coloration and pattern both highly variable; Usually green to brown, with dark patches across the dorsal and lateral area and very often a light yellow or green vertebral stripe. Dorsal folds rather prominent. Skin relatively rough. Inner thighs and groin grey or white, sometimes with dark grey ventral spots of varying intensity. Metatarsal tubercle small and flat, identical to that of P. ridibundus. Tympanum rather large and clearly visible, with males having olive, grey or dark grey vocal sacs and dark or grey nuptial pads on the first fingers. Females are generally larger than males. Larvae usually up to 8cm; spiracle slightly pointed upwards; upper tail-fin extending onto body; tail-tip pointed. Eggs 6-8mm with capsule.
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| Large adult, Kerkini (C) Stamatis Kalogiannis |
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| Adult, Nafpaktia (C) Charis Kouelis |
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| Juvenile, Kerkini (C) Stamatis Kalogiannis |
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| Large adult, Kerkini (C) Stamatis Kalogiannis |
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| Adult, Euboea (C) Stamatis Kalogiannis |
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| Juvenile (C) Plato Stefanopoulos |
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| Subadult (C) Plato Stefanopoulos |
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| Adult, Nafpaktia (C) Charis Kouelis |
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| Larval stage, Euboea (C) Stamatis Kalogiannis |
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| Larval stage (C) Plato Stefanopoulos |
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| Juvenile in the process of metamorphosis (C) Plato Stefanopoulos |
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| Juvenile in the process of metamorphosis (C) Plato Stefanopoulos |
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| Adult, Nafpaktia (C) Charis Kouelis |
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| Adult, Nafpaktia (C) Charis Kouelis |
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| Adult, Karla lake (C) Plato Stefanopoulos |
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| Adult, Nafpaktia (C) Charis Kouelis |
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Adult, Euboea (C) Stamatis Kalogiannis
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Call
Very rich repertoire; most often a loud, fast kekekekek series of varied tones, also individual croaks. Can be heard from a large distance both during the day and night.
Can be both diurnal and nocturnal. Mainly aquatic. Reproductive period lasts from March to as late as July, although may breed during the whole year in right conditions. Total clutch size ranging from 2.000 to 10.000 eggs in several clumps. Larvae usually complete metamorphosis over the course of the summer, some may overwinter. Feeds on a variety of invertebrates and their larvae, such as isopods, arachnids and various insects (odonata, diptera, lepidoptera, hymenoptera, coleoptera, plecoptera, hemiptera and others). Larger individuals may also take small vertebrates; fish, reptiles and other amphibians, even of their own species. Typically hibernates under mud during colder months but depends on temperature and climate conditions; Southern populations may be active throughout the whole year. Mass movements of adults seem to peak on warm, humid summer/fall nights, while dispersion of metamorphs often takes place on wet fall days. It can travel long distances (perhaps several miles) to colonize new bodies of water. It can tolerate drought and will bury itself in the mud, potentially for months, and re-emerge when the pond or stream is filled again.
Habitat
Inhabits all types of freshwater waterbodies, often present in brackish water too. Favours open, sunny habitats and can even be found in very degraded and polluted urban enviroments. Up to 1,000m asl.
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| Slow pool of a perennial stream – habitat of Pelophylax kurtmuelleri |
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| Degraded and polluted urban stream – habitat of Pelophylax kurtmuelleri |
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| River mouth of a perennial stream with saltwater influence – habitat of Pelophylax kurtmuelleri |
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| Flooded vineyard next to the lowland reaches of a stream – habitat of Pelophylax kurtmuelleri |
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| Flooded grassland pond at the edge of a river – habitat of Pelophylax kurtmuelleri |
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| Perennial stream surrounded by rocky substrate and sparse riparian vegetation – habitat of Pelophylax kurtmuelleri |
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| Drying stream with underground flow – habitat of Pelophylax kurtmuelleri |
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| Artificial agricultural canal – habitat of Pelophylax kurtmuelleri |
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| Seasonal marsh covered by dense reeds – habitat of Pelophylax kurtmuelleri |
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| Watering trough – habitat of Pelophylax kurtmuelleri |
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| Stream estuary – habitat of Pelophylax kurtmuelleri |
Distribution
The Balkan frog is one of the most widespread amphibians in Greece. It occurs in all of the mainland except some parts of Thrace (coexists with Pelophylax epeiroticus at the westernmost edges of its distribution as well as on Corfu; overlaps with P. ridibundus and possibly P. bedriagae at the north-eastern edges of its range); on many of the Cyclades islands (incl. Paros, Naxos, Andros, Tinos, Milos), some of the Sporades islands (Skiathos, Skopelos, Skyros), most of the Ionian islands (Corfu, Lefkada, Kefallonia, Zakynthos) and on Euboea.
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Approximate distribution of Pelophylax kurtmuelleri in Greece
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