European pond turtle

European pond turtle
European pond turtle, photo from the Danube floodplain near Orth an der Donau .
Systematics
Order : Turtles (Testudinata) Subordination : Halsberger tortoises (Cryptodira) Family : New World pond turtles (Emydidae) Subfamily : Emydinae Genre : Emys Type : European pond turtle
Scientific name
Emys orbicularis
( Linnaeus , 1758)

The European pond turtle ( Emys orbicularis ) is a small to medium-sized, carnivorous and predominantly aquatic turtle . It is the only turtle species that occurs naturally in Central Europe (including Germany) , albeit rarely . Their distribution area goes far beyond that, from North Africa in the southwest to the Aral Sea in the northeast.

Regardless of the distribution area, the European pond turtle belongs to the family of the New World pond turtles (Emydidae), not the unrelated Old World pond turtles (Geoemydidae). Together with the Sicilian pond turtle ( Emys trinacris ) it forms the genus Emys . Their closest relatives are the Pacific pond turtle ( Actinemys marmorata ) and the American pond turtle ( Emydoidea blandingii ). She was Reptile of the Year 2015 in Germany.

description

European pond turtle skeleton

Depending on the subspecies and sex, the European pond turtle reaches a back armor length of less than twelve centimeters or more than 20 centimeters, with northern and eastern subspecies generally becoming larger than southern ones. Adult animals show a pronounced sexual dimorphism , with the females becoming larger than the males, their weight usually between 400 and 700 grams. In exceptional cases, however, a weight of up to 1500 grams can be achieved. The coloring of the animals is also very variable. Certain drawing elements can be typical for individual subspecies. The often dark, brown or black back armor (carapace) can carry a pattern of fine yellow dots or lines, which are often arranged on the individual shields radiating from a center. But there are also shapes with dark drawings on a light background. The belly armor (plastron) can be uniformly yellow, cloudy, speckled, dark or even completely black. Most of the time, however, it is characterized by a black center. The limbs and neck are dark brown to black in color and often also have yellow drawing elements.

The shell of the European pond turtle is oval and rather flat, in the females it is slightly more arched than in the males. Belly armor and back armor are connected to one another in the area of ​​the so-called bridge by a flexible layer of cartilage and elastic, membranous tissue. In older animals, the middle seam of the belly armor develops into a hinge that allows the front plastron flap a certain mobility.

The limbs and tail are covered with coarse scales , the skin of the head and neck is smooth. Behind the head, which is wider than the neck, you can see a fold of skin that forms a pocket-like cover when drawn in. The front end of the head, viewed from above, is acute-angled and the jaws have edentulous sharp horn edges. The eyes, which are located at the front of the head, have a round pupil. The color of the eyes can vary according to gender: adult males have a reddish iris in some subspecies, especially in the nominate form Emys orbicularis orbicularis , but mostly they have a brownish iris color. However, the female iris is mostly yellow.

Between the five toes of the front legs and the four of the hind legs tense webbed . All toes are also provided with a claw , whereby the front claws in the males in particular are significantly more curved. The European pond turtle is one of the long-tailed tortoise species. This is particularly pronounced in hatchlings, but even in adult animals the tail is half the length of the carapace. In male animals, the tail root is thickened, the cloaca lies clearly behind the edge of the back armor.

distribution

Distribution area

The distribution area of the European pond turtle extends from Morocco and Tunisia in North Africa to the Iberian Peninsula , southern France , Corsica , Italy with Sardinia and Sicily , Poland , Hungary , Romania , the countries of the Balkan Peninsula and all of Anatolia to the Aral Sea and northern Iran . In Russia, the northern limit of distribution extends roughly to the level of Moscow . The northernmost occurrence is in Lithuania . In the Benelux countries, the Czech Republic and most of Austria, there are at best extremely sparse autochthonous populations. In Switzerland , pond turtles have been observed in sixteen cantons, mainly in the Central Plateau and Ticino . Reproduction has been observed in the cantons of Geneva , Aargau and Thurgau , with the Geneva population being one of the largest in Europe with a density of 64 animals per hectare . The few populations that still exist in Germany are found predominantly in eastern Germany, for example in the area of ​​the Großer Stechlinsee . A particularly interesting collection can be found in the Greater Poland Voivodeship near Leszno . There, not far from the village of Witosław near Osieczna, the Ostoja żółwia błotnego nature reserve was designated especially for them .

habitat

The European pond turtle lives in still or slowly flowing waters, on the shores of inland lakes, in ponds, ditches and the oxbow lakes of rivers. Streams are also settled in the south of the distribution area. It penetrates the brackish zones of the estuaries along the Mediterranean coast . Heavily weedy, nutrient-rich waters with a muddy bottom are preferred. They can occasionally be found even in muddy cattle troughs . Branches protruding from the water, trees felled by beavers , root stumps and other dead wood are needed for sunbathing, and grass clumps , old nests of water birds and the like are also sought out for this purpose. Shallow still water zones that can be warmed by the sun are also important.

For the European pond turtle to survive, it has proven to be problematic that there must always be well-exposed, warm sand hills or other dry locations for oviposition close to where they live. Originally, the turtles were also native to more open vegetations with a steppe-like character. The turtle finds ideal conditions, for example, in the clear streams of the quarry forest of the Zarth nature reserve in the Nuthe-Nieplitz nature park in Brandenburg . However, you can find them in Mecklenburg-Western Pomerania and Brandenburg in Söllen and ponds in the middle of agricultural areas. In Hesse there is an independent population at Reinheimer Teich , whose offspring from the Frankfurt Zoo have been released since 2004; there is also a small population in the Miquel facility in Bockenheim . In Austria the last naturally reproducing population can be found in the Danube floodplains east of Vienna, as well as some abandoned specimens on Wienerberg in the municipality of Vienna. In central France and Poland, occurrences are known in pond landscapes that were created for fish farming.

Way of life

Reproduction

pairing

When mating

Depending on the geographic location and gender, the onset of sexual maturity in European pond turtles varies greatly. Males in southern Spain become sexually mature at the age of four, while females in colder regions sometimes only become sexually mature at the age of 18, with an average of 8 to 10 years. Mating activities begin in early spring, often as early as February or March after the freezing winter has ended . The males drive the females into the water, rise and cling to the back armor. With swinging head movements and snapping, they get the females to duck their heads. This causes the cloaca to protrude further out of the shell so that the penis can be inserted.

Egg laying

Females laying eggs

The eggs are laid mostly in June, with the females usually migrating to the same laying places every year. They can cover long distances in search of a suitable egg-laying place, but the nests are usually less than 500 meters from their normal habitat. For oviposition, dry, sandy areas exposed to the heat of the sun are used that have only weak vegetation. Slopes, embankments, forest edges, etc. oriented to the south are preferred. Occasionally, less suitable places with damp or muddy soil are visited, even fields or unpaved roads are not spurned. The eggs are laid in the afternoons and evenings on very warm days. First, a ten centimeter deep nest cavity is excavated with the hind legs, which widens in a pear shape under a narrow opening. Hard soil can be softened with water that the turtle carried in its anal sacs. After the nest is laid, the nest is carefully closed and the ground consolidated so that the place can only be recognized for a short time by the slightly darker color of the earth.

The clutches contain on average 9 to 15 eggs, but clutches with more than 20 eggs have also been found. In the northern parts of the distribution area the average number of eggs per nest is larger, in the southern parts it is smaller, but there is usually a second clutch in summer. The eggs are around 20 to 25 millimeters long and weigh six to ten grams.

Hatching of the young animals

European pond turtle hatchling

The young hatch in late summer after about 80 to 120 days with a shell length (SCL) averaging 2-3 cm and a weight of 4 to 6 grams. With the help of the egg tooth on the tip of the snout, they scratch the shells near an egg pole and first stretch out the nose and one foreleg, then the rest of the shell is pushed away with the forelegs. The entire hatching process takes several hours, and the hatchlings usually remain in the nest cavity for some time afterwards. In the northern parts of the area, they sometimes even spend the winter there. After leaving the nest, they go to the nearest body of water and prefer to stay there in dense, protective underwater vegetation.

Gender education

The European pond turtle has been counted among the reptiles with temperature-dependent sex determination since the pioneering work of Claude Pieau (from 1974). If their eggs are incubated in the incubator at temperatures below 28 ° C, male pups will hatch. At incubation temperatures above 29.5 ° C, the hatchlings are predominantly female. Both sexes can be incubated between 28 and 29.5 ° C.

Recent research shows that the situation in the field is far more complex than under controlled laboratory conditions. There are many indications that temperature-controlled sex determination (TSD) superimposes a strong genetic contribution in free-range broods. In Emys orbicularis , TSD and GSD (genotypic sex determination) probably work together. This interaction is supported by the fact that in the northern edge regions of the distribution area, where during the sensitive phase of egg development only rarely are soil temperatures reached that are necessary for the emergence of female hatchlings, there are still enough females, and females usually clearly dominate.

nutrition

Ball of feces

The European pond turtle feeds primarily on snails , crustaceans , insect larvae and other invertebrates . But tadpoles , dead fish or carrion are also accepted. She grabs larger chunks with her horny jaws and tears them to pieces with the claws of her front legs, which she devours whole. Contrary to most of the information in the literature, it is not only carnivorous , but also consumes aquatic plants at all ages, such as waterweed , algae and duckweed . In feces and seeds of yellow were Teichrose found which is not entirely clear whether these were randomly taken with other feeds.

The European pond turtle can occasionally be found looking for prey on land, but only eats in the water. This has to do with the fact that she can only swallow underwater. When eating, it holds larger food with its front legs and tears off pieces. To swallow, she jerks her head forward, and the incoming stream of water washes the chunk of food down her throat.

wintering

The hibernation takes place in the water, that is, the animal goes to the bottom of a pond and falls into the so-called winter rigor, whereby the food intake is stopped and the metabolism is greatly reduced. Breathing no longer takes place through the lungs, but through the skin.

Taxonomy and systematics

Taxonomy

Already Aristotle mentioned the terrapin, where he spoke of a "Water Mouse" (mus aquaticus). In the 1st century AD, Pliny first used the name “emys”. The European pond turtle ( Emys orbicularis ) was given the Latin name Testudo lutaria by Conrad Gessner in 1617 . This species name can also be found in Carl von Linné (1758). Linnaeus accidentally assigned another name in his " Systema naturae ", Testudo orbicularis , which was later designated as a species name by William Thomas Blanford in 1876 ​​according to the nomenclature rules that are still valid today. The species name orbicularis ("with small circles") originally comes from Linnaeus and describes the yellow dots on the skin and shell. In the 18th and 19th centuries, the name Testudo europaea , which goes back to Johann Gottlob Theaenus Schneider (1783), was mostly used. The zoological genus "Emys" was described in 1806 by André Marie Constant Duméril . George Robert Gray named the European pond turtle in 1831 "Cistudo europaea" ("European tortoise"). This name was replaced by Emys orbicularis in 1835 by Gabriel Bibron . In addition to Testudo , the generic names Lutremys , Terrapene and Cistudo were also used in the previous century . The genus Emys , which has also included the Sicilian pond turtle in addition to the European pond turtle since 2005, was established by Duméril in 1806.

External system

The closest relatives of the European pond turtle are, in addition to the second European species within the genus Emys, the Sicilian pond turtle Emys trinacris , the Pacific pond turtle ( Actinemys marmorata ) , which is widespread in North America, and the American pond turtle ( Emydoidea blandingii ). The sister group of these genera is a taxon from the representatives of the box turtles ( Terrapene ) and the monotypical tropical turtles ( Clemmys ).

New World pond turtles (Emydinae)	NN     NN    ? American pond turtle ( Emydoidea blandingii )      ? Pacific pond turtle ( Actinemys marmorata )      ? European pond turtle ( Emys orbicularis )      ? Sicilian pond turtle ( Emys trinacris )   NN    Box turtles ( terrapene )      Tropical Tortoises ( Clemmys )      American turtles ( Glyptemys )

Internal system

So far, over 14 subspecies of the European pond turtle have been described, which are assigned to several groups. But only about 11 subspecies are recognized. The nominate form represents the Pontic subspecies Emys orbicularis orbicularis (Linnaeus 1758), to which the animals in Germany also belong. After molecular biological investigations with 423 individuals from the entire distribution area of ​​the genus Emys , however, even 20 different development lines with different distribution patterns were found, whereby seven main development lines emerged. These seven main lines are said to correspond to a separation in the late Pliocene . The further division suggests a large number of retreat areas within the Ice Ages . One of these main lines, haplotype III, was assigned the status of a separate species in 2005, Sicilian pond turtle ( Emys trinacris ).

Occidentalis group

Medium-sized, large-headed pond turtle with a very long intergular seam and ornate, vermiform head markings on a black or dark background. Fore leg usually with two yellow stripes. Both sexes are the same size. Males with yellow, white or brown irises.

• North African pond turtle Emys orbicularis occidentalis Fritz, 1993 - dark colored subspecies, hatchlings with dark markings on the belly shell, maximum carapace length of 15 cm; Occurrence: Morocco, Algeria, Tunisia
• Iberian pond turtle Emys orbicularis hispanica Fritz, Keller, Budde, 1996 - lighter subspecies, hatchlings with dark markings on the belly shell, maximum 17 cm SCL; Occurrence: Coto de Doñana (Spain)
• Eastern Spanish pond turtle Emys orbicularis fritzjuergenobsti Fritz, 1993 - lighter subspecies with a conspicuously narrow carapace, belly carapace mostly monochrome yellow, maximum 15 cm SCL; Occurrence: Spanish Mediterranean coast

Galloitalica group

Small to medium sized pond turtles with narrow, rectangular nuchals . Fore leg usually only with a yellow stripe. Males smaller than females and with a white or yellowish iris color. Hatchlings with a small to moderately large, dark plastic figure.

• Mittelländische pond turtle Emys orbicularis galloitalica Fritz, 1995 - subspecies with very different color of the back armor, belly armor mostly yellow, maximum 16.5 cm, but mostly less than 15 cm SCL; Occurrence: South, West France and Italy
• Corsican pond turtle Emys orbicularis lanzai Fritz, 1995 - dark belly and back armor, maximum 15 cm SCL; Occurrence: Corsica
• Sardinian pond turtle Emys orbicularis capolongoi Fritz, 1995 - light subspecies, belly shell monochrome yellow, only rarely with dark spots, maximum 14.5 cm SCL; Occurrence: Sardinia
• Ligurian pond turtle Emys orbicularis ingauna Jesu et al., 2004 - back armor uniformly maroon color, yellow line on the front legs in females and many males, max. 15 cm SCL; Occurrence: in the Ingauna mountain range in western Liguria

Orbicularis group

Very dark colored, mainly medium to large pond turtle. Plastron, at least in males, mostly black, nuchals basically trapezoidal. Fore leg usually with only a narrow yellow stripe. Males with red irises and smaller than females. Plastra of males occasionally with characteristic mottling on a dark background. Hatchlings with a large, large, dark plastic figure.

• Pontic pond turtle Emys orbicularis orbicularis (Linnaeus, 1758 sensu lato) - U. Fritz describes two new sub-forms, sub-form 1 as predominantly black with only a few, light throat spots, up to a maximum of 23 cm SCL, sub-form 2 as slightly lighter with often yellow belly armor and lighter throat coloration in females, maximum 20 cm SCL; Occurrence: Sub-type 1, from Poland to the Aral Sea, sub-type 2, central France, Danube catchment area, Germany, western Poland, in the last two habitats possibly mixed forms with sub-type 1

• Eiselt's pond turtle Emys orbicularis eiselti Fritz, Baran, Budak, Amthauer, 1998 - almost monochrome black, up to 13 cm SCL; Occurrence: Southeast Anatolia

The Kolchische pond turtle Emys orbicularis colchica Fritz, 1994 and Central Anatolian pond turtle Emys orbicularis luteofusca Fritz, 1989 were assigned to the nominate form Emys orbicularis orbicularis after genetic testing .

Hellenica group

Only one subspecies has been described so far:

• Eastern Mediterranean pond turtle Emys orbicularis hellenica (Valenciennes in Bibron, Bory de Saint-Vincent, 1832) - animals vary greatly in size from region to region, from 10 cm to over 19 cm SCL. Back armor dark, belly armor mostly yellow, sometimes with faded dark markings. Males and females differ in their coloration, in females the throat is a solid yellow. Males drawn irregularly; Occurrence: Italy, Balkans

Iberica group

Small to medium-sized pond turtles with yellow throats, nuchals generally trapezoidal, males with brown / black reticulated head markings, females with yellow dots on a dark background. Females smaller than males, irises of males reddish. Hatchlings with expansive, large, dark plastic figures. The subspecies Georgian terrapin Emys orbicularis iberica Eichwald, 1831 is synonymous after genetic examination Emys orbicularis persica proposed also as a synonym of Emys orbicularis persica is the Kurdish pond turtle (Emys orbicularis Kurae Fritz, 1994) and the Oriental pond turtle Emys orbicularis orientalis Fritz, 1994 seen.

• Persian pond turtle Emys orbicularis persica Eichwald, 1831 - dark back armor, often with very fine yellow spots, maximum 18 cm SCL, mostly smaller; Occurrence: Iran, Turkmenistan

Danger

Predators

The hatchlings and young animals have numerous enemies: wild boar , badger , fox and others dig up the clutch. Crows , ravens , magpies , herons and other large birds chase the hatchlings. They kidnap cats and dogs . Even a kite has been seen with a turtle in its claws. As soon as the young animals are in the water, pike and catfish wait for the prey. In contrast, adult animals have had relatively few predators so far. The raccoon in particular , along with some other neozoa , has become a problem for all development stages of the European pond turtle in recent years. This is able to open the tanks even from fully grown specimens.

Further risk factors

The species is threatened above all by the consequences of human interference in its habitat: draining swamps and wetlands, water corrections, urban sprawl and the destruction of the egg-laying areas are very hard on the turtles. While Emys orbicularis used to be caught and consumed in large quantities as a fasting food, road traffic is arguably the greatest danger today. In search of nesting sites or on the way back into the water, the females are often run over when crossing roads. Fishing has also claimed many victims where it was operated with traps , because the turtles inevitably drown in the fish traps. The IUCN classifies the European pond turtle as low endangered . In Germany it is considered critically endangered .

Protective measures

The European pond turtle is protected in the European Community by the Fauna-Flora-Habitat Directive , Annex IV. In Germany it is therefore subject to a possession and marketing ban in accordance with Section 42, Paragraph 2, Nos. 1 and 2 of the Federal Nature Conservation Act (BNatSchG). Animals that can be proven to have been bred legally are exempt from these prohibitions. For them, however, there is an obligation to report to the responsible species protection authorities. In addition, it is forbidden to catch, injure or kill wild pond turtles and to disturb their reproduction. The species is also listed in Appendix II of the Habitats Directive. The member states must designate special protected areas for the conservation of the species.

There are species protection projects for the last still somewhat intact populations in the German-speaking area in the state of Brandenburg through the Rhinluch / Linum nature conservation station and in the Donau-Auen National Park near Vienna. There are also resettlement projects in Hesse, Rhineland-Palatinate, Mecklenburg-Western Pomerania and Lower Saxony.

literature

• Holger Vetter turtles of the world . Volume 1: Africa, Europe and West Asia. Chimaira, Frankfurt am Main 2002, ISBN 3-930612-27-5 .
• Uwe Fritz: The European pond turtle. Laurenti Verlag, Bielefeld 2003, ISBN 3-933066-14-X .
• Walter Hödl, Maria Rössler: The European pond turtle. Stapfia, Linz 1999, ISBN 3-85474-049-2 .
• Maria Rössler: Current situation, endangerment and protection of the European pond turtle Emys orbicularis (L.) in Austria. In: Stapfia. 69, Linz 2000, pp. 169-178 ( PDF on ZOBODAT ).
• Verena Lacoste, Markus Kutzli: Reintroduction of the European pond turtle Emys orbicularis LINNAEUS in 1758 in the Alsatian Upper Rhine Plain - an ongoing project. TESTUDO (SIGS), 15 (2), 2006 ( PDF; 995 kB on sigs.ch).
• Matthias Kuprian, Sibylle Winkel: The European pond turtle in Hesse. (PDF; 403 kB) - Status report of the pond turtle group, 2006.
• Martina Anne-Claire Meeske: The European pond turtle on the northern edge of its distribution in Lithuania. - Laurenti Verlag, Bielefeld 2006, ISBN 3-933066-31-X .
• Jean-Claude Monney, Andreas Meyer: Position of the coordination office for amphibian and reptile protection in Switzerland (karch) with regard to the reintroduction of the European pond turtle Emys orbicularis (LINNAEUS, 1758) in Switzerland. TESTUDO (SIGS), 17 (4), 2008 ( PDF; 781 kB on sigs.ch).
• Maria Schindler: The European pond turtle in Austria: Development and current status of a species protection program. TESTUDO (SIGS), 17 (4), 2008 ( PDF; 1.1 MB on sigs.ch).
• Norbert Schneeweiß: Demography and ecological situation of the edge populations of the European pond turtle in Brandenburg. State Environment Agency Brandenburg, 2003 ( PDF; 9.1 MB at mlur.brandenburg.de).
• Jens R. Poschadel: Studies on the population structure and social behavior of the European pond turtle Emys orbicularis (Linnaeus, 1758). Dissertation, University of Hamburg, 2003, ISBN 978-3-89825-649-0 .

Web links

Commons : European pond turtle  - Collection of images, videos and audio files

• Emys orbicularis - Reptile of the Year 2015
• Photos of the European pond turtle on www.herp.it
• EU species protection projects, Germany, Poland, Lithuania
• Species protection project of the Rhinluch nature conservation station in Linum / Brandenburg , accessed on March 28, 2012
• Species protection project Switzerland
• European pond turtle bibliography
• Coordination office for amphibian and reptile protection in Switzerland (karch): Leaflet European pond turtle
• Emys orbicularis in The Reptile Database
• Emys orbicularis inthe IUCN 2013 Red List of Threatened Species . Listed by: Tortoise & Freshwater Turtle Specialist Group, 1996. Retrieved September 27, 2013.

Individual evidence

1. ↑ Coordination office for amphibian and reptile protection in Switzerland (karch): Leaflet European pond turtle ( Memento of the original dated June 6, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
2. ^ Baby turtles back in Lower Austria on ORF on September 29, 2011, accessed on September 29, 2011
3. ↑ Claude Pieau: Temperature-dependent sex determination in "Emys orbicularis". Laboratory and field studies. In: Mertensiella. 10, 1996, pp. 199-207
4. ↑ Marc Girondot, Claude Pieau: Does "Emys orbicularis" have sex chromosomes? Third world congress of herpetology, Prague, 2. – 10. August 1997 summary
5. ↑ J. Servan, M. Dorizzi, C. Pieau, P. Zaborski: Female biased sex ratio in adults of the turtle Emys orbicularis at the northern limit of its distribution in France: a probable consequence of interaction of temperature with genotypic sex determination. In: Canadian Journal of Zoology. 67, 1989, pp. 1279-1284
6. ↑ ^{a b} Uwe Fritz, Tiziano Fattizzo, Daniela Guicking, Sandro Tripepi, Maria Grazia Pennisi, Peter Lenk, Ulrich Joger, Michael Wink: A new cryptic species of pond turtle from southern Italy, the hottest spot in the range of the genus Emys ( Reptilia, Testudines, Emydidae). In: Zoologica Scripta. Vol. 34, No. 4, July 2005, page 351.
7. ↑ P. Lenk, U. Fritz, U. Joger, M. Wink: Mitochondrial phylogeography of the european pond turtle Emys orbicularis (Linnaeus 1758). In: Molecular Ecology. 8, 1999, pp. 1911-1922 PMID 10620234 .
8. ↑ ^{a b c d} Uwe Fritz: The European pond turtle. Westarp Science, Magdeburg 1996, ISBN 3-89432-484-8
9. ^ R. Jesu, R. Piombo, S. Salvidio, L. Lamagni, S. Ortale, P. Genta: Un nuovo taxon di testuggine palustre endemico della Liguria Occidentale. In: Annali del Museo Civico di Storia Naturale di Genova. 2004
10. ↑ ^{a b} Fritz, U., Ayaz, D., Hundsdörfer, AK, Kotenko, T., Guicking, D., Wink, M., Tok, CV, Cicek, K., Buschbom, J. (2009): Mitochondrial diversity of European pond turtles (Emys orbicularis) in Anatolia and the Ponto-Caspian Region: Multiple old refuges, hotspot of extant diversification and critically endangered endemics (PDF; 6.0 MB) ODE 9, 100-114
11. ↑ Protection project European pond turtle in Brandenburg | LfU. Retrieved October 14, 2019 . 
12. ↑ Emys orbicularis in the endangered Red List species the IUCN 2006. Posted by: Tortoise & Freshwater Turtle Specialist Group, 1996. Retrieved on 11 May, 2006.
13. ↑ Federal Agency for Nature Conservation (ed.): Red list of endangered animals, plants and fungi in Germany 1: Vertebrates. Landwirtschaftsverlag, Münster 2009, ISBN 978-3-7843-5033-2
14. ↑ Online overview at www.amphibienschutz.de
15. ↑ Wildlife: The European pond turtle. State Office for Environment, Health and Consumer Protection (LUGV) Brandenburg, accessed on September 8, 2012 . 
16. ↑ http://www.donauauen.at/?area=news&story_id=715
17. ↑ Archived copy ( Memento of the original from December 18, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. 
18. ↑ http://rlp.nabu.de/imperia/md/content/rlp/nirlp_2008-4.pdf
19. ↑ http://www.lugv.brandenburg.de/cms/detail.php/bb1.c.313846.de
20. ↑ Archive link ( Memento of the original from November 29, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.