The Komodo dragon, Varanus komodoensis.

Notwithstanding, the morphological amplitude within this group is remarkable. While the smallest species, V. brevicauda from Australia, measures only 23 cm from snout to tip of tail at a maximal weight of merely 20 g, the Southeast Asian water monitor, V. salvator, reaches a total length of more than three meters. However, the most infamous member of all varanids, and definitively the most bulky one, is V. komodoensis endemic to a restricted area within the Lesser Sunda Island chain of Indonesia. This charismatic species may grow up to three meters in length and weighs as much as 54 kg. Ecologically, the diversity of monitor lizards is even higher. They are found from deserts to tropical rain forests, from coasts up to mountain areas, being semi-aquatic, terrestrial or arboreal. Although mostly carnivorous, two Philippine species (V. olivaceus and V. mabitang) are even vegetarians.

Extant monitor lizards have a vast range comprising three continents. They are found from Africa (including the Sahara, but with exception of Madagascar) through Arabian peninsula and continental South and Southeast Asia, the Indo-Australian Archipelago (including the Philippines), and the Pacific region finally reaching Australia. Currently 67 species of monitor lizards belonging to nine subgenera are recognized (Böhme 2003, Eidenmüller & Philippen 2008).

New born of Emerald tree monitor, Varanus prasinus.

Monitor lizards are of enormous economic importance for the worldwide pet trade in live specimens but particularly for the international reptile leather trade. Except for five species (V. bengalensis, V. flavescens, V. griseus, V. komodoensis and V. nebulosus), which are CITES-appendix I species, all remaining monitor lizards are listed on appendix II. While the skins of few widely distributed species, like the African Nile monitor (V. niloticus) or the Asian water monitor (V. salvator), are exported in hundreds of thousands each year, other species are sold to varanid enthusiasts in Europe, the US or Japan for several hundred euros per specimen.