11 July 2012

Dragon of the Month: Slow-worm

Froglife is featuring a different 'dragon' every month in 2012 to celebrate the Chinese Year of the Dragon.  This month, Living Water Officer Iain Maclean has been investigating an often misunderstood repltile, the Slow-worm. 

"Having a look into the reputation of the Slow-worm in the past, it is surprising to learn that it was once considered a venomous and evil creature to be killed and cut up when encountered. Also called the blind worm, it pops up in Shakespeare’s Macbeth where the ‘blind worm’s sting’ is a potent ingredient of the witches cauldron. Another old name of the Slow-worm is ‘deaf adder’ which may be a biblical reference to a venomous snake so wicked it could not be charmed or tamed. As well as this in some fairytales the Slow-worm is said to be forever searching and seeking vengeance for the nightingale after losing its legendary single eye to the bird, hence the reason the nightingale must stay alert all night in song.

In fact the Slow-worm is a benign and beautiful creature (with two eyes!), and presents no real danger to humans. It is more closely related to lizards than snakes, having lost its legs in an example of convergent evolution. Its smooth body allows it to glide through vegetation and catch small soft bodied insects such as slugs; and it can therefore be a welcome predator of pests in the gardens it frequently inhabits. Although Slow-worms may try and sting with the horny tip of their tail when handled, the sting is not venomous and unable to pierce the skin, and in fact when frightened they are just as likely to shed their tail in order to escape.

The name Slow-worm itself is also misleading, as they can move very fast when prompted. Some sources claim the name actually originates from the Anglo Saxon word slay (or slaw) as in a worm which kills (or perhaps a slayer of worms!) or as a slow ‘wrym’ (snake like creature) in comparison to snake species. However the origins of the name and of alternative names such as blind worm are far from clear.

Whatever may be in a name, the Slow-worm is a fascinating creature, and one frequently found in close proximity to humans. It can be the reptile people are most likely to encounter in their daily lives, and can therefore be seen as perhaps our best chance to appreciate the beauty of reptilian beings."

Dragon Factfile: Slow-worm
(Anguis fragilis)

Juvenile and female Slow-worms have a darker stripe along their backs

• The slow worm gives birth to live young (ovovivipary); eggs are hatched within the female’s body.
• Slow-worms can live for decades; the record is a Slow-worm in Copenhagen zoo who lived for 54 years! Although they are expected to live for much less in the wild.
• Slow-worms are vulnerable to predation by cats. The level of predation can have an important effect on local distribution.

Slow-worms have unique head markings and, unlike snakes, they have eyelids 

• Slow-worms range in colour from grey to brown to bronze
• Males are grey-brown, sometimes with blue flecks
• Females are golden brown with a darker underbelly and sides
• Females and juveniles often have a darker stripe along their back
• They can be 4-45cm in length 

Male Slow-worms are grey-brown and sometimes have blue flecks amongst their markings
Differences between Slow-worms and snakes
• Eyes which blink (snakes cannot blink)
• Broad flat tongue with notched tip (snakes have a flickering forked tongue)
• Blunt tail tip (snake tails taper to a fine point)
• Skin with smooth scales, skin appears shiny and polished (snakes have rougher, clearly defined scales).

Photos: Jules Howard and Sivi Sivanesan

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