Little water frog

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Little water frog
Little Edible Frog (Pelophylax lessonae) Amplexus; Males with coloring typical of the spawning season

Little Edible Frog ( Pelophylax lessonae )
Amplexus ; Males with coloring typical of the spawning season

Systematics
without rank: Amphibians (Lissamphibia)
Order : Frog (anura)
Subordination : Neobatrachia
Family : Real frogs (Ranidae)
Genre : Water frogs ( pelophylax )
Type : Little water frog
Scientific name
Pelophylax lessonae
( Camerano , 1882)

The little water frog ( Pelophylax lessonae or Rana lessonae ), also known as the little pond frog or pond frog, belongs to the family of real frogs (Ranidae) within the order of the frogs . In addition, it is reckoned according to appearance, way of life and relationships with the water frogs , which many authors have recently placed in their own genus Pelophylax . Within this complex, which is difficult to survey, it forms the parent species of the hybrid pond frog together with the sea frog .

features

Male of the little water frog
The sound bubbles are pure white in the male of the small water frog

The head-torso length of the males is 4.5 to 5.5 centimeters - they are only slightly larger than a tree frog - the females are 5.5 to 6.5 centimeters long. The upper side is mostly grass green in color and speckled with rather regular black or brown spots. In addition, there is the water frog typical middle back line and reddish glandular ridges on the back. Individuals with black-brownish color pattern proportions are also quite common, especially in female specimens. The iris of the male is intensely yellow in color during the mating season, just as otherwise yellow body colors dominate at this time; their vaults are white. The lower legs are noticeably short in relation to the trunk; the heel hump is large and semicircular.

Reproduction

Due to clear changes in the behavior of the pond frogs, the call and reproduction period can be divided into a pre-spawning period, a spawning period and a post-spawning period, as Wahl first discovered in the case of Rana esculenta. The course and duration of the three phases largely determine the water temperature, solar radiation and precipitation. Observations of pond frogs in the Kottenforst near Bonn, North Rhine-Westphalia, show typical behavioral patterns for each phase.

Spawning season

The males appear in the spawning water, swim around and keep a minimum distance of about 2 meters to other frogs. The color on the head and back is dark yellow-green. The males then seek out the bank and occupy certain places. You are making calls to the area, but call activity is still low. The females arriving in the water stay in the central part, where the solar radiation is high.

Spawning season

The number of frogs continues to increase. Calling activity increases with the males; they now make pairing and territory calls. At the same time they form call groups to which 20 to 30 animals belong. A call group takes up an area of ​​approximately 1.5 square meters. The males in a group call at the same time, sometimes for several hours without a break. About 30 minutes before sunset the call groups disband and the males return to their territories on the bank. In the course of the spawning season, the color of the males changes to a light yellow-green.

The females leave the center of the water and swim to the calling males on the bank. There pairs are formed, mainly with large males. The couples stay in sunny places and do not move much. If other males approach within less than about 30 centimeters, the clinging males utter brief mating and territorial calls. If males clasp other males, they defend themselves with calls of liberation. The females lay their eggs in numerous packages that adhere to plants or float on the surface of the water. Small males do not mate until the end of the spawning season. In the meantime, their color changes from light green to dark green. In addition to the pool frogs, there are also small numbers of pond frogs in the population. The male pond frogs are also very active during the spawning season, but none have been observed to mate.

Spawning balls are deposited that are significantly smaller than those of the brown frogs . The eggs are brownish on top, the lower pole is light yellow in color. The spawn can usually be found between mid-May and mid-June. A spawning ball often contains “only” a few hundred eggs. The females deposit several egg balls one after the other. The number of eggs is between 600 and 3000, the diameter of the eggs is 1.5 to two millimeters.

Older tadpoles , with a greenish basic color and a dark pattern of spots, are noticeable for their impetuous escape reactions . The total length is 40 to 80 millimeters. A distinction from other water frog larvae is not possible with certainty.

Spawning time

The coloring of the males becomes darker. They seldom utter mating calls, but still behave aggressively, primarily towards pond frogs. Gradually, the number of frogs decreases by about 70 percent. The remaining frogs show only little movement activity, do not make any mating calls and hardly any more calls for territory.

Calls

Male pool frogs have four types of call: mating call, territory call 1 and 3, and rescue call. According to previous observations, the pool frogs of the population in the Kottenforst near Bonn do not have Revierruf 2, whether it is also for populations from other regions remains to be determined. Mixed calls or interim calls rarely occur, from area call 1 to mating call and from area call 1 to area call 3. Female pool frogs only have the release call.

For the pool frogs in the Kottenforst, the lower call threshold for mating calls is 14 ° Celsius water temperature, the upper one 26 ° Celsius water temperature. Pool frogs near Casanova, Torino, still called when the water temperature was 29 ° Celsius. Several call characteristics are correlated with water temperature and animal size. As the water temperature rises, the duration of the calls and the intervals between them decrease, while the dominant frequency increases. Conversely, the longer the body length, the longer the call duration and the intervals, while the dominant frequency decreases.

Mating call

Sound image of a mating call. The two arrows mark a pulse group with three pulses. The reputation is divided because of the length.

The information relates to a topotypical population near Casanova, Carmagnola, Torino, about 17 km from the type locality Testona. The pond in which the frogs live is located directly at the intersection of SP (Strada Provinciale) 134 and SP 135 and has the coordinates 44.853865 N, 7.797643 E. The population consists of 80–85% Pelophylax lessonae , the rest Part from Pelophylax esculentus .

The males almost always give their mating calls in series, in which the calls are separated from each other by intervals. The pairing calls are made up of very short pulses. Since the amplitude of the pulses changes rhythmically, the pulse train is divided into pulse groups (see illustration). Most of the groups have three impulses, deviations are small, the water temperature has little influence. The majority of the pairing calls are made up of 35 to 41 pulse groups. These also determine the hearing impression. Since the impulse groups follow one another evenly, the calls sound like a regular rattle, which is why they are also known as whirring. The mating calls of the pool frogs are not very loud.

Mating calls were registered by 36 males at water temperatures of 20.5 ° Celsius to 29 ° Celsius. At 20.5 ° C water temperature, the calls last an average of 1450 milliseconds, at 29 ° Celsius only 900 milliseconds. The intervals are shorter than the calls, from an average of 1280 milliseconds at 20.5 ° Celsius to 532 milliseconds at 29 ° Celsius water temperature. These changes are clearly noticeable when you hear the calls.

The first analysis of the mating calls, in which the influence of the water temperature was also determined, was for a single pond frog from the vicinity of Poznań (Poland). The male called between 15.5 and 25.5 ° Celsius water temperature. Further analyzes of the mating calls were carried out in pool frogs that are native to the area around Bonn (North Rhine-Westphalia), at the northern end of Lake Skadar (Montenegro), in the Danube Delta (Romania), in the coastal region of Albania and at Casanova (Piedmont).

The mating calls of the pool frogs of all localities match those of the pool frogs of the above-mentioned topotypical population at Casanova. Small deviations correspond to the variability within the range of a species.

Revierruf 1

The males utter these calls during the entire calling period, either spontaneously or in order to communicate with other males when they enter their own territory or in response to the calls of neighboring males. The calls consist of a series of impulses. They start quietly, the volume gradually increasing to a maximum just before the end. At the end of the call there is also a breakdown into impulse groups. With large males (5.7 to 6.2 centimeters) and a water temperature of 18 to 23 ° Celsius, the calls have an average duration of 300 milliseconds, the dominant frequency is 1200 Hertz.

Revier call 3

The males almost always give area calls 3 individually and after a territory call 1. They are made up of 11 to 14 impulses and, at a water temperature of 18 to 23 ° Celsius, have an average duration of 670 milliseconds, the dominant frequency is 800 Hertz.

Liberation call

Calls for liberation are always associated with a special behavior. With them, males defend themselves against attempts to clasp other males, females express them when they are clasped by males but are not ready to mate. Usually the calls for release are issued in series of three to five calls. They are similar in structure to Revierruf 3, but with an average duration of 270 milliseconds, they are noticeably shorter than this. The calls for release consist of very short impulses. The frequency spectrum reaches up to 4 kilohertz, the sound energy is evenly distributed over all frequencies. As the water temperature rises, the duration of the calls and the intervals decrease, the repetition rate of the impulses increases, but the number of impulses per call does not change.

Systematics

In 1960 Mertens and Wermuth name for Rana esculenta var. Lessonae Camerano, 1882 Piedmont as Terra typica and at the same time classify the variety as a synonym for Rana esculenta , which was considered a good species at the time. In 1986 Balletto et altera selected an animal collected by Camerano in Testona near Moncalieri on the outskirts of Turin as a lectotype and set Testona as the type locality of Pelophylax lessonae ( Rana lessonae ).

Habitat and Distribution

Distribution map according to IUCN data

The little water frog is not as strictly bound to water as its relatives, the pond and sea ​​frog . Typical habitats in northern Germany are z. B. Moor biotopes within forest areas. Adults and young animals are often far removed from the waters. The preferred spawning waters are smaller, vegetation-rich ponds , ponds and ditches as well as swamps and bogs in their vicinity . The species is rarely found on large lakes and rivers. A closer connection seems to exist regionally - especially in the north of the distribution area - to boggy , mesotrophic habitats . Due to these demands, the species is absent in certain, heavily anthropogenically influenced habitats.

With the exception of parts of the north, the species is found all over Germany. Due to the identification problems within the water frog group (compare: pond frog ), the exact distribution of Pelophylax lessonae is still insufficiently researched. The total distribution area extends from France across Central Europe to Russia and Italy.

Hazard and protection

Slowly flowing meadow ditches - a typical habitat in southern Germany

Small water frogs seem - at least at the edges of their range, for example in the north German lowlands - to be more dependent on certain habitat qualities such as boggy waters ( stenoic or stenotopic behavior) and are correspondingly less common and more affected by environmental changes than euryocratic species. In some other regions, their endangerment situation is probably comparable to that of the pond frog, with which they usually also form common populations.

Legal protection status (selection)

National Red List classifications (selection)

  • Red List Federal Republic of Germany: G - Acceptable risk, but status unknown
  • Red list of Austria: VU (corresponds to: endangered)
  • Switzerland's red list: NT (potentially endangered)

literature

  • Rainer Günther: Europe's water frogs. (= Die Neue Brehm-Bücherei. Volume 600). A. Ziemsen Verlag, Wittenberg (Lutherstadt) 1990, ISBN 3-7403-0234-8 .
  • Rainer Günther, Jörg Plötner, Immo Tetzlaff: About some characteristics of the water frogs (Rana synkl. Esculenta) of the Danube Delta. In: Salamandra. Volume 27, 1991, pp. 246-265.
  • Rainer Günther (Ed.): The amphibians and reptiles of Germany. G. Fischer-Verlag, Jena 1996, ISBN 3-437-35016-1 .
  • Jörg Plötner: The western Palearctic water frogs - from martyrs of science to a biological sensation. In: Supplement to the journal for field herpetology. Volume 9, Bielefeld 2005, ISBN 3-933066-26-3 .
  • Nasr Mahmoud Mohamed Radwan, Hans Schneider: Social behavior, call repertory and variation in the calls of the pool frog, Rana lessonae (Anura, Ranidae). In: Amphibia-Reptilia. Volume 9, 1988, pp. 329-351.
  • Hans Schneider, Heinz G. Tunner, Walter Hödl: Contribution to the knowledge of the mating call by Rana lessonae Camerano, 1882 (Anura, Amphibia). In: Zoologischer Anzeiger. Volume 202, Jena 1979, pp. 20-28.
  • Hans Schneider and Institute for Scientific Film: Rana lessonae (Ranidae) - calls. Film E 2633 by the Institute for Scientific Film (IWF) Göttingen 1981. Accompanying publication by Hans Schneider, publications on scientific films. Biology Section, Series 15, No. 4 / E 2633, 1982, 7 pages.
  • Hans Schneider, Gerhard Joermann: Mating calls of water frogs (Ranidae) of Lake Scutari, Yugoslavia, and reöationship to water frogs of other regions. In: Journal for Zoological Systematics and Evolutionary Research. Volume 26, 1988, pp. 262-275.
  • Hans Schneider, Idriz Haxhiu: Mating call analysis and taxonomy of the water frogs (Ranidae, Anura) in Albania. In: Zoological Yearbooks, Systematics. Volume 121, 1994, pp. 248-262.
  • Hans Schneider: Bioacoustics of the Froschlurche - native and related species. With audio CD. Supplement to the Zeitschrift für Feldherpetologie 6. Laurenti Verlag, Bielefeld 2005, ISBN 3-933066-23-9 , audio examples 14.1-14.4.
  • Ulrich Sinsch, Hans Schneider: Bioacoustic assessment of the taxonomic status of pool frog populations (Rana lessonae) with reference to a topotypical population. In: Journal of Zoological Systematics and Evolutionary Research. Volume 34, 1996, pp. 63-73.
  • Christophe Dufresnes, Joaquim Golay, Johan Schuerch, Tony Dejean, Sylvain Dubey: Monitoring of the last stronghold of native pool frogs (Pelophylax lessonae) in Western Europe, with implications for their conservation. In: European Journal of Wildlife Research. 2020. DOI 10.1007 / s10344-020-01380-3

Individual evidence

  1. ↑ Manfred Wahl: Investigations into the bio-acoustics of the water frog Rana esculenta (L.). In: Oecologia (Berlin). Volume 3, 1969, pp. 14-55.
  2. ↑ a b c d e f Nasr MM Radwan, Hans Schneider: Social behavior, call repertory and variation in the calls of the pool frog, Rana lessonae (Anura, Ranidae). In: Amphibia-Reptilia . Volume 9, 1988, pp. 329-351.
  3. ↑ a b c d Ulrich Sinsch, Hans Schneider: Bioacoustic assessment of the taxonomic status of pool frog populations (Rana lessonae) with reference to a topotypical population. In: Journal of Zoological Systematics and Evolutionary Research. Volume 34, 1996, pp. 63-73.
  4. ^ Hans Schneider, Heinz G. Tunner, Walter Hödl: Contribution to the knowledge of the mating call by Rana lessonae Camerano, 1882 (Anura, Amphibia). In: Zoologischer Anzeiger. Volume 202, Jena 1979, pp. 20-28.
  5. ↑ Hans Schneider: Mating calls and calling behavior with pool and pond frogs in the Kottenforst Nature Park. In: Decheniana . Volume 149, Bonn, 1996, pp. 124-138
  6. ↑ Hans Schneider, Gerhard Joermann: Mating calls of water frogs (Ranidae) of Lake Scutari, Yugoslavia, and relationship to water frogs of other regions. In: Journal for Zoological Systematics and Evolutionary Research. Volume 26, 1988, pp. 261-275.
  7. ↑ Rainer Günther, Jörg Plötner, Immo Tetzlaff: On some characteristics of the water frogs (Rana synkl. Esculenta) of the Danube Delta. In: Salamandra. Volume 27, 1991, pp. 246-265.
  8. ↑ Hans Schneider, Idriz Haxhiu: Mating call analysis and taxonomy of the water frogs (Ranidae, Anura) in Albania. In: Zoological Yearbooks, Systematics. Volume 121, 1994, pp. 248-262.
  9. ^ Hans Schneider, Josef Brzoska: The liberation calls of the Central European water frogs. In: Zoologischer Anzeiger. Volume 206, Jena 1981, pp. 189-202.
  10. ↑ Robert Mertens, Heinz Wermuth: The amphibians and reptiles of Europe. Waldemar Kramer Verlag, Frankfurt am Main, 1960. 264 pp.
  11. ^ Emilio Balletto, MA Cherchi, S. Salvidio, A. Lattes, A. Malacrida, A. Gasperi, G. Doria: Area effects in south western European green frogs (Amphibia, Ranidae). In: Bolletino di Zoologia. Volume 53, 1986, pp. 97-109.
  12. ↑ Lorenzo Camerano: Recherches sur les variations de la Rana esculenta et du Bufo viridis dans le Bassin de la Méditerranée. In: Compte Rendus de l'Association Française pour l'Avancement des Sciences, Paris. Volume 10, 1882, pp. 680-690.
  13. ↑ Little water frog at www.wisia.de
  14. ↑ Online overview at www.amphibienschutz.de

Web links

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