Viviparous lizard  (Zootoca vivipara)

The viviparous lizard is classified as Least Concern (LC) on the IUCN Red List (1). Protected in Britain under Schedule 5 of the Wildlife and Countryside Act (1981) with respect to killing, injuring and sale. Listed under Annex III of the Bern Convention (3).

The agile viviparous or common lizard (Zootoca vivipara) is smaller than the related sand lizard (Lacerta agilis), and is extremely variable in colour. Typically, the upper-surface is brownish, with lines of darker markings passing along the back, which are often bordered with white or yellow. Individuals may occasionally have green, grey or reddish upperparts, which can cause problems of identification. Males have bright undersides, typically yellow or orange in colour, but more rarely red with black spots; in contrast females tend to have much duller, pale underparts. Totally black forms occasionally arise in both sexes. In addition to the differences in belly colour, males can also be distinguished from females by their much larger heads, slender bodies, and by the possession of a prominent swelling at the base of the tail (2).

This species is widespread throughout Britain, and is the only native lizard found in Ireland. Outside of Britain, the viviparous lizard has one of the widest ranges of any vertebrate; it is found from France through Europe and across Asia, reaching the Pacific coast. It occurs as far south as the Mediterranean, and is the most northerly of all reptiles, inhabiting Scandinavia and Arctic Russia (2).

Found in a variety of habitats, and prefers open sunny areas. The viviparous lizard tends to occur in dry areas, but also frequents wet heaths. Main habitats include commons, moorland, heaths, sea cliffs, dry stone walls and embankments (4).

During early spring and late autumn (either side of hibernation), the viviparous lizard invests much of its time in basking in the sun. Basking also occurs throughout the summer, when the lizard needs to warm itself up sufficiently in order to hunt, particularly on overcast or cool summer days. When they first emerge in the morning, the body temperature of these cold-blooded (poikilothermic) animals is typically around 15 degrees Celcius; their optimum temperature is 30 degrees Celcius, which is attained through basking.

This lizard is extremely agile and alert, rapidly dashing for cover if disturbed. They hunt in vegetation for invertebrates, which are shaken in the jaws before being chewed and swallowed whole (2).

In England, breeding tends to occur in April and May. Males are at their most vibrant at this time, as they shed their old skin prior to the breeding season. Some fighting occurs between males over females, but this is generally less intense than in the sand lizard. Males take females in their jaws prior to mating; if a female is not receptive, she will bite the male fiercely (2). The eggs take around three months to develop inside the female. As the common name 'viviparous lizard' implies, the female gives birth to live young. Between seven and eight young are typically produced; they are black in colour and surrounded by an egg membrane, from which they will free themselves after around one day. Sexual maturity is reached at two years of age in males, and three years in females (2).

Adults begin to hibernate in October; it is not yet clear where hibernation takes place, but underground refugia or log piles seem likely candidates. In southern England and Wales, male viviparous lizards can emerge from hibernation as early as February (2).

The viviparous lizard is not currently threatened.

The viviparous lizard is protected in Britain under the Wildlife and Countryside Act (1981) against killing, injury and sale (4).

View information on this species at the UNEP World Conservation Monitoring Centre.

For more on this species and other reptiles and amphibians of the UK:

• Herpetological Conservation Trust:
  http://www.herpconstrust.org.uk/