Viviparous lizard  (Lacerta vivipara)

The agile viviparous or common lizard 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).