Slow worm
| Slow worm | ||||||||||||
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Slow worm on driveways in northern Germany |
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| Scientific name | ||||||||||||
| Anguis fragilis | ||||||||||||
| Linnaeus , 1758 |
The slow worm ( Anguis fragilis ) is a lizard within the family of Sneak (Anguidae). According to the new system, it is more precisely referred to as the western slow worm. In Central Europe it is one of the most common reptiles . With its legless, elongated body, it resembles a snake and is often mistaken for one. This misunderstanding is even reflected in the scientific genus name given by Carl von Linné ( Latin anguis = "snake"; the species name fragilis means "fragile"). Important distinguishing features to the snakes are the easy breaking of the tail as well as the presence of movable eyelids and external auditory openings typical for all sneaks, even if the latter are covered by scales.
Another common misconception is that the slow worm is blind according to the species name. However, the German name is traced back to the Old High German plintslîcho , which, according to the general opinion, means something like "blinding / blinking sneak" and is likely to refer to the shine of the smooth skin and the typical locomotion. Other names that are not or rarely used today are hazel worms and hard worms .
The slow worm was named Reptile of the Year 2017 by the German Society for Herpetology and Terrarium Science .
features
anatomy
The slow worm has an elongated body with a circular cross-section without extremities and reaches a total length of up to 57.5 cm. The largest specimens can be found in the east and south of the distribution area. On average, most of the adults to be observed are between 35 and 40 cm long. The rather small, high head goes suddenly into the trunk. The tail, which ends in a horny tip, is also not separated from the body and is often somewhat longer than it. Because the animals can easily shed their tails at several predetermined breaking points, quite a few specimens found do not have a fully preserved tail. In contrast to real lizards , the tail section does not grow back after an autotomy ; only a very short, hemispherical stump is formed. In some populations, more than half of adults no longer have a full tail. The head-trunk length - from the tip of the snout to the cloaca - is therefore preferred for field biological body measurements . The cloaca has a transverse gap in the slow worm.
The surface of the skin consists of smooth, round to hexagonal horny scales that overlap like roof tiles and are roughly the same shape above and below the body. There are also several longitudinal rows on the ventral side, and the scales are only slightly smaller there than on the back. In the middle of the fuselage, a transverse row comprises 24 or 26 scales. In total, the trunk has 125 to 150 transverse scale rows and the tail has another 130 to 160 rows. Under the scales there are bone plates (osteoderms), which means that blindworms crawl much more stiffly and clumsily than snakes. The scaling of the head is similar to that of lizards; the pileus shields that bound the head towards the rear are relatively large. The ear openings, however, are mostly completely hidden under the scales. The relatively small eyes have movable, closable eyelids (these are fused in snakes) and round pupils. The rather short tongue is broad, bilobed and does not end in fine tips. To lick, i.e. to absorb odorous substances, blindworms have to open their mouths a little, as they do not have a gap in their upper lip like snakes. The pointed, sometimes quite loosely sitting teeth are curved backwards; There are 7 to 9 of these in the intermediate jaw, 10 to 12 in the upper jaw and 14 to 16 in the lower jaw.
The extremities are completely regressed; only in the embryos are anterior leg rudiments initially detectable, but they later disappear. In the adult animals, only small remnants of a shoulder and pelvic girdle on the spine indicate the phylogenetic descent from leg-bearing ancestors.
Coloring and drawing
In the “youth dress”, blindworms have a very contrasting color scheme and pattern. On the silver-white or golden-yellow top, a black line runs from the back of the head - widened or forked there - to the tip of the tail (" eel line "; sometimes this can be interrupted or completely missing). The flanks, like the belly side, are black and thus sharply set off from the top. With age, the black can lighten into gray, blue or brownish tones. The iris is dark brown in the young.
The bodies of the adult animals have a variable basic color with brown, gray, yellow, bronze or copper tones on top. This basic color is interspersed with more or less distinct dark points and lines or even without drawing. Sometimes they also show the dorsal eel line of the juvenile phase, which has now widened. There are often four to six dark vertical stripes on the sides, which in turn can merge with one another and create a color separation between the back and the flanks. The ventral side is lead gray to black. Due to the variety of point and line drawing patterns, various varieties of the slow worm have been described and named; but these have no taxonomic significance. A special feature is the appearance of blue-spotted individuals; these are almost always older males. Also melanism and other color anomalies occur now and then in the Art. The iris of adult slow worms is reddish yellow.
Gender differences
A distinction between males and females is possible on the basis of several characteristics, but not unambiguously in all cases. As a primary sexual characteristic, the males have two evertable hemipenes . Their head is also slightly wider and has larger pileus shields. In contrast, the longest and heaviest slow-worms are predominantly female. In pregnant females, the thickened trunk can be seen against the tail. When it comes to coloring, it is noticeable that females tend to retain the characteristics of youth coloring in many cases, i.e. the eel line on the middle of the back, the sharp color border on the flanks and the dark underside. In the males, however, the color contrast between the upper side and the (less dark) underside is often not as pronounced; this makes them appear more evenly colored. A majority of them also no longer have a dorsal eel line.
distribution
The species has a western Palearctic distribution area, which includes most of Europe and areas of the Middle East. Earlier information on occurrence in Northwest Africa is now doubted and is said to be based on confusion with other legless lizard species. The area of the slow worm is very similar to the vegetation zone of deciduous deciduous and mixed forests of the temperate zone. Within Europe there are extensive gaps in distribution only in Ireland, the south of the Iberian Peninsula, on the Mediterranean islands and in Italian Puglia , in northern Scandinavia, in the northeast of the European part of Russia and on the north side of the Black Sea . In the east, the area extends over the Urals to Tobol to southwest Siberia and the northwestern edge of Kazakhstan. A narrow distribution band runs along the southern coast of the Black Sea through Turkey to the entire Caucasus. An apparently disjoint small sub-area is located on the south coast of the Caspian Sea in northern Iran.
The altitude distribution extends from the lowlands to the high mountains above the tree line ; the species occurs in the Swiss canton of Graubünden up to an altitude of 2100 meters, in the Austrian Alps up to a maximum of 2400 meters.
In Germany, the slow worm is the most common reptile found in almost all regions, and occasionally on the island of Fehmarn ; only on most of the North Sea islands (exceptions: Sylt, Föhr, Amrum) it is missing, as well as in coastal marshland . The wooded low mountain ranges are a main focus of the distribution. In Austria and Switzerland, too - with the exception of high alpine extreme locations - all regions are populated by it.
Systematics
The slow worm is traditionally divided into a western and an eastern “race” (subspecies) according to morphological characteristics - this zoogeographical division is due to the last ice age. The western one is the nominate form Anguis fragilis fragilis , the eastern one is called Anguis fragilis colchica . The border between the two runs in a broad, not always clearly definable transition zone from Finland over the Baltic States, the Carpathian Arch and the Hungarian Plain to the Dinaric Mountains. Blindworms from German-speaking countries therefore only belong to the nominate form. A characteristic of the eastern subspecies is that blue-spotted individuals are much more common.
The slow worms of the Greek Peloponnese and the Ionian Islands , which were previously treated as a further subspecies, are now regarded as a separate species, Anguis cephallonica . Overall, the system of the slow worm is still considered to be insufficiently clarified.
A new molecular biological study, however, postulates a division into four independent species: In addition to Anguis fragilis sensu stricto (previous nominate form), Anguis colchica and Anguis cephallonica , Anguis graeca would be added as another species . In addition, a further distinction between two subspecies in the Caucasian and Caspian regions is proposed for the Eastern slow worm ( A. colchica ).
Habitats
In terms of habitat requirements, the slow worm is considered to be eurytopic , so it uses a large number of different biotopes without specialization. It is often to be found in dense deciduous forests and on their edges, on hedges, in partially drained raised bogs and on bog edges and on bush-lined nist grass lawns , also in heather areas, on fallow land , meadows, on railway embankments, logs, roadsides, in parks and near-natural gardens on the edges of settlements; even dense coniferous forests with only small areas of sunshine are sometimes enough. The animals prefer herbaceous vegetation rich in cover and a certain amount of soil moisture; With regard to the ambient temperature, they need a little less warmth than many other reptiles. In accordance with its broad ecological amplitude, the slow worm can coexist with species in more humid areas (such as wood lizards and adder ) as well as with those more dry habitats (such as smooth snakes and sand lizards ).
She likes to use sheltered, dry, sunny spots, for example on dead wood, dark humus soil and peat or on old bulbs of grass that are located in the vicinity of slightly more humid, but also easily heated, not too shady hiding places (holes in the ground, cavities under tree roots, lying wood, stones, Plastic foil or sheet metal, crevices in the rock, moss cushions, also piles of leaves and compost or piles of firewood). Several animals can often be found at the same time at particularly favorable hiding places.
Way of life
wintering
Blindworms spend the winter frozen in the cold or resting in the above-mentioned hiding places that are as frost-proof as possible. Often they also drill underground passages of 15 to 100 cm in length and close the opening with moss or earth. Hibernation takes place regularly in groups of 5 to 30, exceptionally even more than 100 individuals. The older animals are apparently at a greater depth, while the young animals that join a little later are more close to the entrance. Even common winter quarters with predators such as snakes have been observed. In Central Europe, the majority of the blindworms withdraw into the hiding places in the course of October; they usually come out again from March or early April (at least in the lowlands), if the external conditions permit.
Daily activity, food and predators
The species is primarily diurnal, on the one hand in the morning from 4 a.m. to around 10 a.m., on the other hand in the evening from 6 p.m. to 9 p.m. In humid and mild weather, for example before thunderstorms or in warm drizzle, it can also be found outside of the hiding places during the rest of the day. Very mild summer nights may also be used for foraging. Blindworms hunt primarily slugs , earthworms and hairless crawler; their backward curved teeth help them hold on to these slippery prey. Among the snails, field snails are particularly important as food, but smaller specimens of large species of slugs are also eaten. The extended range of prey includes woodlice and sapweed , grasshoppers , beetles and their larvae, as well as aphids , cicadas and ants , as well as smaller spiders . Slowworms are not blind, but they have limited visual performance (among other things, they are color blind). The sense of smell and touch play an important role in orientation, including when hunting. The prey animals are grabbed with the jaws and gradually swallowed whole. For a larger earthworm, this can take up to half an hour.
The slow worm, for its part, has many predators, including snakes (especially the smooth snake ), mammals such as fox , badger , polecat , ermine , hedgehog , wild boar and rats as well as numerous birds ( storks , herons , birds of prey , owls , corvids , stranglers ). Thrushes , starlings , shrews , large ground beetles , common toads , lizards and young snakes also chase the young. Domestic cats, dogs and chickens are particularly dangerous for blindworms near human settlements.
In distress and when they are caught, the animals squirm back and forth and often excrete urine and feces from the cesspool. Attempts to bite the attacker are rare. Finally, a piece of tail can be thrown off, which then wriggles and twitches violently for several minutes. This is an effective distraction, especially for birds and mammals.
The morning and evening hours are also used for thermoregulation , in that the slow-worm sunbathes or lies on a surface that radiates the daytime warmth at dusk - these are often asphalt roads and other paths on which the animals are then run over in large numbers. Because of the hidden way of life, the knowledge about the exact daily routine of a blindworm is still very sketchy. This also applies to space requirements, population sizes and densities and other population-ecological issues.
Reproduction and Individual Development
In Central Europe, the mating season of the species is usually between the end of April and June. The males then often wrestle vigorously over the females in so-called comment fights , even though they are in the majority in most populations. The opponents try to push each other to the ground, bite each other and wrap themselves tightly around each other. During mating, the female is bitten in the head or neck region while the male introduces his hemipenes into the female's cloaca. Copulation can take several hours. Sometimes females mate with other males later. The gestation period of the females lasts 11 to 14 weeks; subsequently - between mid-July and the end of August, sometimes even later - they usually give birth to between eight and twelve young (extreme values: 2 to 28). At birth, the 7 to 10 cm long young animals are in a very thin, transparent egg shell which they pierce immediately afterwards ( ovoviviparia ). They initially weigh less than a gram and still have a yolk residue.
Before their first hibernation, the young hardly grow any more; only in the following year do they increase significantly in length and weight. With a total length of 12.5 to 25 cm and an age of three to five years, young blindworms become sexually mature. In the course of growth, three to four moults take place annually during the entire period of activity. The old skin layer is pushed together from front to back to form bulges and then stripped off. A moulting process can take one to more than two weeks.
In captivity, the animals can get very old; an age of 46 years is documented, 54 years are also mentioned. In the open countryside, however, because of the many predators and anthropogenic hazards, it is very unlikely that blindworms will get that old.
Hazard and protection
The slow worm is considered to be a cultural follower and has long benefited from landscape changes made by humans, as many structurally rich, semi-open biotopes emerged. In the modern landscape of civilization, however, the species suffers high losses from intensive agriculture and forestry, land consolidation, surface drainage, road traffic, settlement and road construction, recultivation measures in excavation pits, the mowing of grass and shrub edge strips and meadows (especially with rotary mowers ), and removal of hiding places, the “cleaning up” of “untidy” embankments and ruderal corridors and much more. In the vicinity of settlements, the use of pesticides such as slug pellets poses a risk of poisoning for slow worms .
Out of ignorance and aversion to the alleged snake, the completely harmless blindworm is still slain or trodden down in large numbers when you meet it. Locally, this can certainly take on continuity-threatening proportions. Blindworms and other small reptiles are hunted by domestic cats and at least injured in the process. Many slow-worms fall victim to vehicle traffic due to their behavior of lying down on paths to stock up on warmth. Even cyclists often don't recognize them in time and run over them.
Despite these losses, the species is still common in Central Europe and is considered safe in German-speaking countries (Germany, Austria, Switzerland). However, it is still under nature and species protection and may not be caught or injured. In particular, you should avoid clinging to the back of your body. Otherwise, this can trigger the shedding of the tail, which means that the animal does not die, but remains mutilated for life.
Legal protection status (selection)
- Habitats Directive : (not listed)
- Federal Nature Conservation Act : specially protected
- Federal Species Protection Ordinance : Appendix 1 (specially protected)
National red list classifications (selection)
- Red List Federal Republic of Germany: n (not endangered, not kept)
- Red list of Austria: NT (endangerment threat; warning list)
- Red List Switzerland: LC (not endangered; however, the population in the Central Plateau and the low-lying areas of the valleys is declining)
swell
This article, as amended on October 18, 2008, is based on the following sources:
- Rainer Günther, Wolfgang Völkl: Blindworm - Anguis fragilis Linnaeus, 1758. In: Rainer Günther (Ed.): The amphibians and reptiles of Germany. Gustav Fischer, Jena et al. 1996, ISBN 3-437-35016-1 , pp. 617-631.
- Heribert Wolfbeck, Klemens Fritz: Blindworm, Anguis fragilis Linnaeus, 1758. In: Hubert Laufer, Klemens Fritz, Peter Sowig: The amphibians and reptiles of Baden-Württemberg. Ulmer, Stuttgart 2007, ISBN 978-3-8001-4385-6 , pp. 619-632.
literature
- Wolfgang Völkl, Dirk Alfermann: The blindworm. The forgotten lizard (= magazine for field herpetology. Supplement 11). Laurenti-Verlag, Bielefeld 2007, ISBN 978-3-933066-33-6 .
- Hans-Günter Petzold : Blindworm and Scheltopusik. The Anguidae family (= The New Brehm Library. Vol. 448). 2nd, unchanged edition, reprint of the 1st edition from 1971. Westarp Wissenschaften et al., Magdeburg et al. 1995, ISBN 3-89432-473-2 .
Web links
- Anguis fragilis in The Reptile Database
- Photos of the slow worm at www.herp.it
- Information and photos at www.reptilien-brauchen-freunde.de
- (Western) slow worm in Austria - information and photos at www.herpetofauna.at
- The Slow Worm - Reptile of the Year 2017 - Information and photos in the Sachsen-Anhalt-Journal (2017)
Individual evidence
- ↑ Hamburger Abendblatt- Hamburg: Are blindworms really blind? August 18, 2011, accessed on July 4, 2019 (German).
- ↑ Wolfgang Böhme : A record-sized specimen of the western slow worm (Anguis fragilis). In: Journal of Field Herpetology. Vol. 19, No. 1, 2012, ISSN 0946-7998 , pp. 117-118.
- ^ Andreas Klinge, Christian Winkler: Atlas of the amphibians and reptiles of Schleswig-Holstein. (PDF; 13.6 MB) State Office for Nature and Environment of the State of Schleswig-Holstein, Kiel 2005, ISBN 3-937937-01-3 , p. 150.
- ↑ Andreas Klinge: The amphibians and reptiles Schleswig-Holstein - Red List. 3rd version, December 2003, State Office for Nature and the Environment of Schleswig-Holstein ( PDF; 573 kB) .
- ↑ Václav Gvoždík, David Jandzik, Petros Lymberakis, Daniel Jablonski, Jiří Moraveca: Slow worm, Anguis fragilis (Reptilia: Anguidae) as a species complex: Genetic structure reveals deep divergences. In: Molecular Phylogenetics and Evolution. Vol. 55, No. 2, 2010, pp. 460-472, doi: 10.1016 / j.ympev.2010.01.007 .
- ↑ Massimo Capula, Luca Luiselli: Ecology of an alpine population of the slow worm, Anguis fragilis Linnaeus, 1758. Thermal biology of reproduction. In: Herpetozoa , Vol. 6, No. 1-2, 1993, pp. 57-63.
- ↑ Blindworm at www.wisia.de
- ↑ Online overview at www.amphibienschutz.de
- ↑ Red List of Reptiles in Switzerland, 2005 (PDF; 688 kB) ( Memento from December 29, 2016 in the Internet Archive )
Forest Lizard (2006) | Common Garlic Toad (2007) | European tree frog (2008) | Dice Snake (2009) | Pond newt (2010) | Wall Lizard (2011) | Common Toad (2012) | Smooth Snake (2013) | Yellow-bellied toad (2014) | European pond turtle (2015) | Fire Salamander (2016) | Slow Worm (2017) | Common Frog (2018) | Mountain Newt (2019)
