Common (viviparous) lizard

Common lizard by Brett LewisCommon lizard by Brett Lewis

Like all reptiles, the common lizard is ‘cold-blooded’, which means that it is dependent on external heat sources to raise its body temperature. It is an adaptable species, with probably the largest range of any land-living reptile and is able to live in relatively cool, northern climes. Common lizards bask in the sun to raise their body temperatures and it is then that they are most noticeable to the naturalist. On a hot day lizards soon achieve temperatures of about 30oC at which point they move off into cover.

One reptilian adaptation to cooler climates is viviparity – giving birth to fully-formed young rather than laying eggs. Reptile eggs need warm environments for successful development. Common lizards effectively retain their eggs until full-term, so that the mother can incubate them by seeking warm spots where she can bask in the sun. Viviparity does not allow the production of as many young lizards as egg-laying (because egg-layers can produce several clutches per season in contrast to the single brood produced of the common lizard), but it does allow these reptiles to breed in cooler climates. In some parts of its global range common lizards do lay eggs and clutch weights may be as much as 80% of the female’s body weight. Common lizards are also well-adapted to surviving the cold of northern winters. They can survive almost half of the water in their bodies freezing.

Common lizards prefer habitats where there is a mixture of vegetation cover and open areas, such as heathland, dune, scrub, woodland edge and brownfield sites (formerly developed areas that have since fallen into disuse). They can also be found in relatively damp habitats such as fen, where they can sometimes be seen on the edges of boardwalks that provide them with basking spots, just clear of the vegetation. They fare well along the coast and the heathland areas of the Sandlings and Brecks. Like all native reptiles, common lizards have declined in numbers as their favoured habitats have been replaced by intensive farmland and urbanisation. However, they can still be found in the semi-natural habitats maintained within many of Suffolk Wildlife Trust’s reserves such as Snape Marshes and Sutton and Hollesley Commons.