Wednesday, 20 August 2008

A fortunate find

The Slow-worm is one of those creatures which I rarely stumble across these days, perhaps because it spends the greater part of the year hiding underground or in deep cover. Being ‘cold-blooded’ the Slow-worm tends to thermoregulate by keeping its body in contact with warm surfaces. While our three snakes tend to bask out in the open, the Slow-worm will often warm itself by settling under a piece of tin or other refuse that absorbs the sun’s warmth. Of course, it is with the snakes that the Slow-worm is sometimes confused; despite its cylindrical body and absence of external legs, the Slow-worm is not a snake but a harmless ‘legless’ lizard. Unfortunately, ignorant householders, panicked by the ‘snake-like’ appearance, may soon dispatch any Slow-worm that turns up in their garden. This is not only bad for the Slow-worm but also for the gardener, because Slow-worms eat good numbers of common garden pests, like slugs. Slow-worms differ from snakes in having a visible eyelid and smooth body scales. In addition, the cylindrical body shape is uniform along most of its length, whereas in a snake there is a clear narrowing behind the head to produce a discernable ‘neck’.

Hibernation ends in March and throughout the spring adult Slow-worms indulge in breeding. Mating is a fairly aggressive affair, with the adult males grabbing and holding females by their head. The resulting young are ‘born’ in September or October, hatching from their eggs almost immediately they are laid, giving the appearance of live birth. These young Slow-worms are just eight or nine centimetres in length and have the colour of newly minted metal. As adults they become a shiny metallic grey-brown, like well-aged bronze, often with thin longitudinal stripes of chocolate brown. Some of the older males are adorned by a pattern of pale blue spots, scattered along their head and flanks.

My most recent Slow-worm encounter happened just the other week and was unusual in that the lizard was out in the open, part way across a gravel track. I normally encounter them when turning over sheets of corrugated tin or refuse on areas of rough grassland or heathland. This particular individual had clearly shed its tail at some point in the past, either lost during courtship or shed to distract a would-be predator. The tail is physically shed (as opposed to being pulled off) by the lizard, muscular contractions pulling apart the tail at a point of fracture within the vertebrae. Once shed, the tail will flex and spasm for several seconds, sufficient distraction for the lizard itself to slip away. I managed to take a few photographs and then the Slow-worm was gone, disappearing into thick cover.

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