INTRODUCTION

Lizards are the most widely distributed of all the reptiles and are found on every continent, although most species are found in tropical areas. They are the most diverse of all rep­tiles, varying from arboreal, flying, and rock dwellers to semi- aquatic and to the Galapagos marine iguana (Amblyrhynchus cristatus), which feeds on algae.

In comparison to the shelled chelonians and elongate limbless snakes, lizards are the least highly specialized. Some lizard species, like the slow worm (Anguis fragilis), have lost their limbs so the main way to distinguish lizards from snakes is that they have a short trunk with a long tail, whereas snakes have the converse. They also tend to have four limbs, a shorter, flatter tongue, moveable eyelids, and external ear openings (Pough 1998a). The two halves of the lower jaw are firmly united in a mandibular symphysis and they have several rows of scales on their ventral abdomen (Table 4.1).

Longevity

Smaller lizards live for less than 5 years although Leopard geckos (Eublepharis macularius) have been reported to live for 28 years. Larger lizards like iguanas can live for 10 to 20 years. However, the record lies with a European slow worm (Anguis fragilis) which lived 54 years! (Bellairs 1998h).

Size

Lizards range in size from tiny geckos, weighing a few grams, to the Komodo dragon (Varanus komodoensis), which is 3.6 m long and can weigh up to 136 kg (Bellairs 1998h). Eighty percent of lizards, however, weigh under 20 g (Evans 1986; Pough 2002).