Slowworm

Description

Slowworms have an elongate body, circular in cross-section, without extremities, and reach a total length of up to 57.5 cm. Most adults observed, however, tend to be between 40 and 45 cm long, with up to 22 cm of this being accounted for by the snout-vent section, and the remainder by the tail. The rather small, high head merges abruptly into the torso. The tail, which ends in a horny tip, is also not separated from the torso and is often somewhat longer than the latter. Due to the fact that the animals can easily drop their tail at several predetermined breaking points, however, quite a few specimens no longer have a completely preserved tail. Unlike true lizards, the tail section does not grow back after an autotomy. Only a very short, hemispherical stump forms. In some populations, more than half of the adults no longer have a complete tail. Therefore, for field biology body measurements, the snout-vent length - from the tip of the snout to the cloaca - is preferred. The cloaca has a transverse cleft in the slowworm.

The skin surface consists of smooth, round to hexagonal horny scales overlapping like roof tiles, which are approximately the same shape on the upperparts and underparts of the body. Several longitudinal rows of these are also present on the ventral side, and the scales there are only slightly smaller than on the dorsal side. In the middle of the torso, one transverse row includes 24 or 26 scales. In total, the torso has 125 to 150 transverse rows of scales and the tail has another 130 to 160 rows. Beneath the scales are bony platelets (osteoderms), which allow slowworms to crawl much more stiffly and clumsily than snakes. The head scaling resembles that of lizards; the pileus shields bordering the head posteriorly are relatively large. However, the ear openings are usually completely hidden under the scales. The relatively small eyes have movable, closable lids (in snakes these are fused) and round pupils. The rather short tongue is broad-two-lobed and does not run out into fine points. To tongue, i.e., to take in odorants, slowworms must open their mouths slightly, as they do not have an upper lip gap like snakes. The pointed little teeth, some of which are quite loose, are curved backward; there are 7 to 9 of them in the premaxilla, 10 to 12 in the maxilla, and 14 to 16 in the mandible. In advanced age, slowworms have often lost part of their teeth.

The extremities are completely degenerated; only in embryos are anterior leg rudiments initially detectable, but these later disappear. In adults, only small remnants of a shoulder and pelvic girdle on the spine indicate phylogenetic descent from leg-bearing ancestors.

colouration and patterns

As juveniles slowworms have a very contrasting coloration and patterning. On the silvery-white or golden-yellow upperpart a black line ("dorsal line"; sometimes this can be interrupted or missing completely) runs from the back of the head - there broadened or forked - to the tip of the tail. The flanks, like the belly, are black and thus sharply set off from the upperpart. With age, the black may lighten to gray, blue or brownish tones. The iris is dark brown in the young.

The bodies of adults have a variable ground coloration of brown, gray, yellow, bronze, or copper tones above. This coloration is interspersed with more or less distinct dark spots and lines or is also featureless. Sometimes they also show the dorsal line of the juvenile phase, although this has now broadened. On the sides, there are often four to six dark longitudinal stripes, which in turn may merge with each other, creating a color separation between the dorsal side and the flanks. The ventral side is lead-gray to black. Due to diverse patterns of dots and lines, various varieties of the slowworm have been described and named; however, these have no taxonomic significance.

Habitat

In terms of habitat requirements, the slowworm is considered eurytopic, i.e. it uses a variety of different biotopes without specialization. It is often found in dense deciduous forests and their edges, hedgerows, partially drained upland moors and moor edges, and on shrub-lined bristly grass lawns, as well as in heath areas, on fallow land, meadows, along railroad embankments, log jams, roadsides, in parks and near-natural gardens on the edges of settlements; even dense coniferous forests with only small areas of sunlight are sometimes sufficient for it. The animals prefer herbaceous vegetation rich in cover and some soil moisture; in terms of ambient temperature, they are slightly less heat-dependent than many other reptiles. In keeping with its broad ecological amplitude, the slowworm can co-occur with species of more humid areas (such as the common lizard and European adder) as well as those of more arid habitats (such as the smooth snake and sand lizard).

It likes to use sheltered dry sunny places, for example on dead wood, dark humus soil and peat or on old grass bulbs, which are in the vicinity of somewhat wetter, but also easily warmable, not too shady hiding places (burrows, cavities under tree roots, lying wood, stones, plastic film or sheet metal, rock crevices, moss cushions, also leaf and compost heaps or firewood piles). In particularly favorable hiding places, several animals often find themselves at the same time.

The text is a translation of an excerpt from Wikipedia (https://de.wikipedia.org/wiki/Blindschleiche). On wikipedia the text is available under a „Creative Commons Attribution/Share Alike“ licence. Status: 26 May 2021