Greek frog
| Greek frog | ||||||||||||
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Greek frog ( Rana graeca ) |
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| Scientific name | ||||||||||||
| Rana graeca | ||||||||||||
| Boulenger , 1891 |
The Greek frog ( Rana graeca ) belongs to the genus of real frogs ( Rana ). Together with similar looking species such as the agile frog , the moor frog and the common frog , it is also listed under the collective term " brown frogs ". The species inhabits a rather smaller area in southeastern Europe, specializing in mountain streams and having a more aquatic way of life.
features
It is a medium-sized, rather clumsy brown frog with a short, rounded snout. The head-trunk length of adults is a maximum of seven to eight centimeters. In the so-called heel test - a hind leg is tipped forward along the trunk - the heel joint protrudes slightly beyond the tip of the head (in the common frog, on the other hand, the hind legs are shorter; the heel joint does not reach the tip of the snout). For specialists, further distinguishing features from other brown frogs result from different biometric quotients, e.g. from the distance between the nostrils and from the eyes, from the nostril distance to the eye diameter or from the length of the heel hump in relation to the first toe. The basic color of the upper side ranges from brownish, reddish-brown, yellowish, through olive to gray; there is often a dark spot. In addition to monochrome specimens, those with light “mold spots” can also be observed (this characteristic also occurs in other southern European brown frog species, however). The throat is dark gray in color and has a light center line (compare also: Italian agile frog ). The skin on the abdomen is whitish.
The eardrum within the temporal spot is sometimes only indistinctly visible and reaches a diameter that corresponds to 3/5 of the diameter of the eye. The pupils are horizontally elliptical in shape. The glandular ridges that extend over the back are relatively far apart at the level of the shoulders (in contrast to the common frog).
The males can be recognized by their stronger front legs. They also develop a lead to black-gray “wedding color” during the mating season, appear “wobbly” as a result of the accumulation of lymphatic fluid under the skin and the heat calluses on the fingers are then pigmented black-brown. They have internal sound bubbles to generate the mating calls.
In addition to the nominate form , the Italian frog ( Rana italica ) , which occurs on the Apennine peninsula, was temporarily regarded as a subspecies . In the meantime, however, this is managed as a separate species.
Reproduction and Individual Development
After an aquatic hibernation between October / November and mid-February, the spawning season follows with air temperatures above 4 ° C or water temperatures above 7 ° C. In the populated mountain regions of Greece , this is usually the case between the end of February and the end of March. The males stay in the water while they utter their rather quiet mating calls in the evening and at night, although they can also be submerged. The calls are described as a constantly and quickly repeated "geck ... geck ... geck" or "kru ... kru ... kru". In the mountain stream environment, which is characterized by loud noise, they probably do not play such an important role in finding a partner. Females arriving at the spawning site are clasped axillary . Finally, the small, oval spawning balls are deposited, which are mainly deposited under stones in the stream bed. A spawning ball contains between 200 and 2000 (mostly: 600–800) eggs that are brown on the top and gray on the underside; their jelly shells have a diameter of four to seven millimeters. It takes one to two weeks for the tadpoles to hatch .
The metamorphosis of the larvae takes about another three months. By then the tadpoles - including the oar tails - have reached a total length of approximately 45 (55) mm. The converted frogs will probably reach sexual maturity after three hibernation periods.
Habitat, way of life and distribution
Greek frogs inhabit cool, clear, almost vegetation-free running waters in mountain regions; in Greece mainly between 240 and 1400 m above sea level (1960 m above sea level are mentioned as the maximum altitude distribution). The animals stay either in the water on stones as waiting areas or in the immediate vicinity of the bank. The habitats are structured by rocks and rubble, driftwood and fallen leaves from riparian wood. The tadpoles prefer calm water spots in bays.
The frogs prey on various invertebrates (insects, land snails, spiders, woodlice) during the day and night; they themselves are likely to be eaten by snakes such as the dice snake ( Natrix tessellata ) and the Persian grass snake ( Natrix natrix persa ).
The distribution area is limited to the Balkans and extends from the southeast of Bosnia-Herzegovina through central and southern Serbia , Montenegro , Albania , Macedonia and large parts of Greece (without islands) to the Peloponnese peninsula ; in the east, the south-west and south of Bulgaria and probably the western edge of the European part of Turkey ( Eastern Thrace ) are populated.
Area overlaps with other brown frogs take place at least in some areas. There are sympatric occurrences with the common frog (for example in Bulgaria) and the agile frog (among other things in Greece) - but less often two species occur in the same habitat.
Hazard and protection
The entire population is classified as "LC" (not endangered) by the IUCN , as the species still has a large number of individuals and a relatively extensive range. Nevertheless, there are regional and local threats from habitat loss and water pollution.
Legal protection status
- Fauna-Flora-Habitat Directive (FFH-RL): Annex IV (strictly protected)
- Federal Species Protection Ordinance (BArtSchV): particularly protected
literature
- Andreas & Christel Nöllert: The amphibians of Europe. - Franckh-Kosmos, Stuttgart 1992. ISBN 3-440-06340-2
Individual evidence
- ^ Byron Asimakopoulos, Theodora S. Sofianidou, Hans Schneider: Reproductive and calling behavior in the Greek Frog Rana graeca (Amphibia: Anura) in Greece. In: Zoologischer Anzeiger, Volume 225, 1990, pp. 133-143.
- ^ IUCN Redlist of Threatened Species