Slow Worms at Dunstable Downs

A slow worm curled up

The countryside team has recently been at our Bison Hill site managing the chalk grassland Site of Special Scientific Interest (SSSI) which has a plethora of interesting species. This week we saw numerous Slow-worms (Anguis fragilis), one of six reptile species native to the UK. These beautiful reptiles despite their name and appearance are neither snake nor worm but in fact a legless lizard!

A range of colours

Slow-worms range in colour from grey-brown to gold or copper depending on the age and gender of the individual. Juveniles of both sexes are gold with dark brown bellies and sides with a dark stripe along the spine.

Females are larger and have a subtle coppery sheen. They have a stripe along the spine and black stripes down the side. Males are paler in colour and may display electric blue dorsal (top) spots. These blue spots have been linked to older and larger males however the research is ongoing.

Fighting for a mate

Competition between males is brutal as they fight intensely with each other. It is thought that their blue spots help the males to show off and appeal to females at breeding time. This is a risky strategy for the males who are more easily spotted by predators.   

Distinguishing features

Slow-worms are fascinating creatures and are distinguished from snakes by a number of physical attributes. Slow-worms, like all lizards, have eyelids in the form of semi-transparent scales which allows them to blink. More tricky to spot are the ear openings and the centrally notched tongue which is different to the classic forked snake tongue.

Interestingly, many elongate lizards, such as the Slow-worm have one lung smaller than the other for reasons that are as yet unclear to researchers. In Slow-worms the left lung is much smaller than the right.

Slow-worms give birth to live young, known as ovoviviparous birth. Litters can vary in size.