Robert Valentic / Heath Monitor (Varanus rosenbergi) male enacting a threat display, in mallee/heath habitat near Pinnaroo, South Australia.

Steven David Miller / A Perentie (Varanus giganteus) using its forked tongue to detect smells, Alice Springs Reptile Centre, Northern Territory, Australia, Captive. May.

David Gallan / Lace monitor (Varanus varius) sensing with tongue, New South Wales, Australia, December.

Suzi Eszterhas / Komodo Dragon (Varanus komodoensis) pair flicking tongues, Komodo National Park, Indonesia

David Fleetham / Komodo dragon (Varanus komodoensis), the world's largest lizard. Rinca Island, Komodo National Park, Indonesia.

David Fleetham / Komodo dragon (Varanus komodoensis), with sailing-boat in background. Rinca Island, Komodo National Park, Indonesia.

Sandesh Kadur / Bengal monitor (Varanus bengalensis) smelling a stone with its tongue, Ranthambore National Park, Rajasthan, India. 2016.

Sandesh Kadur / Two Bengal monitors (Varanus bengalensis) fighting, Ranthambore National Park, Rajasthan, India. 2016.

Mark MacEwen / Komodo dragon (Varanus komodoensis) with tongue on out beach, Komodo National Park, the islands of Komodo, Indonesia. Vulnerable species.

Mark MacEwen / Komodo dragon (Varanus komodoensis) walking with tongue extended on beach, found in the islands of Komodo, Indonesia. Vulnerable species.

Mark MacEwen / Komodo dragon (Varanus komodoensis) with tongue extended on beach, Komodo National Park, Indonesia. Vulnerable species.

Bruno D'Amicis / Desert monitor (Varanus griseus) moving across sand dunes, showing characteristic tracks, in the Sahara, Tunisia.

Cyril Ruoso / Komodo dragons (Varanus komodoensis) scavenging Water buffalo carcass. Rinca Island, Komodo National Park, Indonesia.

Cyril Ruoso / View of Komdodo dragon (Varanus komodoensis) from nest, Rinca Island, Komodo National Park, Indonesia. Non-ex

Cyril Ruoso / Komodo dragon (Varanus komodoensis) scavenging on another Komodo dragon, Rinca Island, Komodo National Park, Indonesia. Non-ex

Cyril Ruoso / Komodo dragon (Varanus komodoensis) in habitat with boat, Rinca Island, Komodo National Park, Indonesia. Non-ex

Chris Mattison / Green tree monitor (Varanus prasinus) with tongue out, captive from SE Asia.

Cyril Ruoso / Komodo Dragon (Varanus komodoensis) drooling, the lizard's saliva is high in bacteria and bites quickly become infected, Rinca Island, Komodo National Park, Indonesia

Cyril Ruoso / Komodo Dragon (Varanus komodoensis) approaching, Komodo National Park, Indonesia

Cyril Ruoso / Komodo Dragon (Varanus komodoensis) using tongue to smell, Komodo National Park, Indonesia

Daniel Heuclin / Timor monitor (Varanus timorensis) captive, from Timor

Chien Lee / Komodo Dragon (Varanus komodoensis) in grass, Nusa Tenggara, Indonesia

Tim Laman / Mangrove / Blue-tailed Monitor (Varanus doreanus)female. Paul Oliver weighs the monitor lizard. Foja Mountains, Papua, Indonesia, 2008. (taken during Conservation International Rapid Assessment Progra...

Georgette Douwma / Komodo dragons (Varanus komodoensis) on beach, Rinca, Komodo National Park, Indonesia, October

Rod Williams / Green / Emerald Tree Monitor (Varanus prasinus) head portrait climbing tree trunk. Captive, from Papua New Guinea, Indonesia

Georgette Douwma / Asian water monitor lizard (Varanus salvator) Malaysia. Sipidan.

Georgette Douwma / Asian water monitor lizard (Varanus salvator) climbing tree, Kinabatangan flood plain, Sabah, Malaysia

Tui De Roy / Komodo Dragon (Varanus komodoensis) large male walking towards camera, Komodo National Park, Komodo Island, Indonesia

Mark Jones / Komodo Dragon (Varanus komodoensis) large male testing ground for scent with specialized forked tongue, Komodo National Park, Komodo Island, Indonesia

Michael Pitts / Mertens water monitor swimming {Varanus mertensi} Litchfield NP Australia

Michael Pitts / Komodo dragon hatching from egg (Varanus komodoensis) Komodo Is Indonesia

Michael Pitts / Komodo dragon, 2-day-old (Varanus komodoensis) in Tamarind tree, Komodo Is

Michael Pitts / Komodo dragon about to lay eggs in burrow made in megapode mound (Varanus komodoensis) Komodo Is

Michael Pitts / Komodo dragons, 2-day-old (V. komodoensis) Hatchlings climb trees to avoid being eaten by predators.

Michael Pitts / Komodo dragon hatchling emerging from megapode mound (Varanus komodoensis) Komodo Is

Michael Pitts / Komodo dragon female head profile portrait (Varanus komodoensis) Komodo Is Indonesia

Jason Venus / Desert monitor {Varanus griseus} Sahara desert

Michael Pitts / Komodo dragon hatchling, 4 days old. Komodo Island, Indonesia. The young climb trees to escape being eaten by adult dragons.

BARBARA TODD / Komodo dragon, Indonesia.

Michael Pitts / Komodo dragon {Varanus komodoensis} hatching from egg, Komodo Island, Indonesia.

Jurgen Freund / Komodo Dragon on beach with tourists, Komodo Island

Tony Heald / Southern savanna (Rock) monitor {Varanus albigularis} panting Etosha NP, Namibia

Michael Pitts / Komodo dragon on beach, Komodo Is (Varanus komodoensis) Indonesia

Steven David Miller / Perentie {Varanus giganteus} Northern Territory, Australia, Alice Springs Reptile Park - largest Australian monitor lizard

Nigel Cattlin / Asian water monitor (Varanus salvator) basking on rock, on bank of River Kwai, Kanchanaburi, Thailand.

Fabio Pupin / Rock monitor, (Varanus albigularis), popping out of grass, Ruaha NP, Tanzania, January . Non-ex.

Yashpal Rathore / Bengal monitor (Varanus bengalensis) Tadoba National Park, India

Yashpal Rathore / Bengal monitor (Varanus bengalensis) basking on the tree, Jim Corbett National Park, India

Steven David Miller / Rosenberg's goanna (Varanus rosenbergi) on rock. Species in decline on mainland and less so on Kangaroo Island. Flinders Chase National Park, South Australia. February.

Duncan Murrell / Asian water monitor (Varanus salvator) near the LAHG Research Station in the Sabangau (peat-swamp) Forest, Central Kalimantan, Indonesia.

Robert Valentic / Heath monitor lizard (Varanus rosenbergi) in threat display responding to a perceived threat. Baudin Beach, Kangaroo Island, South Australia.

Robert Valentic / Heath monitor lizard (Varanus rosenbergi) male patrolling a coastal bluff, Baudin Beach on Kangaroo Island, South Australia.

Rod Williams / Blue-spotted tree monitor (Varanus macraei), Batanta Island, West Papua, captive

Bernard Castelein / Common indian monitor (Varanus bengalensis), Keoladeo NP, Bharatpur, India

Steven David Miller / Close up of the scutes, or scales of a Perentie (Varanus giganteus), Alice Springs Reptile Centre, Northern Territory, Australia, Captive. May.

Suzi Eszterhas / Komodo dragon (Varanus komodoensis) yawning, Komodo National Park, Indonesia

Suzi Eszterhas / Komodo dragon (Varanus komodoensis) Komodo National Park, Indonesia

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) exiting Burrowing bettong warren. Barrow Island, Western Australia, November 2001.

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) in front of Burrowing bettong warren, Barrow Island, Western Australia, November.

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) territorial fight, Barrow Island, Western Australia,

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) Cape Range NP, Western Australia.

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) Cape Range NP, Western Australia.

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) feeding on Burrowing bettong / (Bettongia lesueur) Barrow Island, Western Australia.

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) feeding on Burrowing bettong (Bettongia lesueur) Barrow Island, Western Australia.

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) feeding on Burrowing bettong (Bettongia lesueur) Barrow Island, Western Australia.

Jiri Lochman / Perentie monitor lizard (Varanus giganteus) feeding on Burrowing bettong (Bettongia lesueur) Barrow Island, Western Australia.

David Gallan / Four juvenile Lace monitors (Varanus varius) preparing to exit termite mound, New South Wales, Australia , October.

David Perpinan / Cloacal prolapse in a captive, juvenile Savannah monitor lizard (Varanus exanthematicus). small repro only

Ann & Steve Toon / Water monitor (leguaan) (Varanus niloticus), Zimanga private game reserve, KwaZulu-Natal, South Africa, September

Sandesh Kadur / Nile monitor lizard (Varanus niloticus). Lake Manyara National Park, Tanzania.

Suzi Eszterhas / Komodo Dragon (Varanus komodoensis), Komodo National Park, Indonesia

Suzi Eszterhas / Komodo Dragon (Varanus komodoensis), Komodo National Park, Indonesia

Bernard Castelein / Nile monitor (Varanus niloticus), Gambia.

Bernard Castelein / Nile monitor (Varanus niloticus), Gambia.

Guy Edwardes / Lion (Panthera leo), pair feeding on Monitor lizard (Varanus niloticus), edge of Chobe River, Botswana.

Axel Gomille / Water monitor (Varanus salvator), swimming and flicking tongue, Thailand

David Fleetham / Komodo dragons (Varanus komodoensis) on shore with saliva dripping from mouth, Rinca Island, Komodo National Park, Indonesia.

David Fleetham / Komodo dragon (Varanus komodoensis) on beach. Rinca Island, Komodo National Park, Indonesia.

David Fleetham / Perentie (Varanus giganteus) walking across sand, Australia.

David Fleetham / Perentie (Varanus giganteus)walking across sand, Australia.

David Fleetham / Komodo dragon (Varanus komodoensis), the world's largest lizard. Rinca Island, Komodo National Park, Indonesia.

David Fleetham / Komodo dragons (Varanus komodoensis) at the coast, flicking its tongue. Rinca Island, Komodo National Park, Indonesia.

David Fleetham / Komodo dragon (Varanus komodoensis) flicking its tongue. Rinca Island, Komodo National Park, Indonesia.

David Fleetham / Komodo dragon (Varanus komodoensis) flicking its tongue on the coast of Rinca Island, Komodo National Park, Indonesia. September 2008.

Michael Pitts / Cameraman Michael Pitts with newly hatched Komodo dragon (Varanus komodensis) at megapode mound where the female laid her eggs. Komodo Island, Indonesia. 1995

Michael Pitts / Komodo dragon (Varanus komodensis) entering hole in nest, created in abandoned megapode mound. Photographed through another access hole in nest. Komodo Island, Indonesia.

Michael Pitts / Komodo dragon (Varanus komodensis) entering hole in nest, created in abandoned megapode mound. Cameraman Michael Pitts filming through access hole in nest. Komodo Island, Indonesia. 1995

Michael Pitts / Komodo dragon (Varanus komodoensis) with Asian water buffalo (Bubalus arnee) in mud hole. The dragon was walking past to in case the buffalo was trapped, which it was not. Komodo Island. Indonesia.

Daniel Heuclin / Desert monitor (Varanus griseus griseus) occurs in Sahara Desert. Controlled conditions.

Daniel Heuclin / Desert monitor (Varanus griseus griseus) occurs in Sahara Desert. Controlled conditions.

Daniel Heuclin / Desert monitor (Varanus griseus griseus) occurs in Sahara Desert. Controlled conditions.

Ann & Steve Toon / Juvenile Nile monitor (Varanus niloticus), resting on tree trunk, Chobe River, Chobe National Park, Botswana, Africa, September.

Naskrecki & Guyton / Marabou storks (Leptoptilos crumenifer) hunting Sharpooth catfish (Clarias gariepinus) in the dried up Mussicadzi River. In the background a bushbuck (Tragelaphus sylvaticus) drinks at another small...

Naskrecki & Guyton / Nile monitor lizards (Varanus niloticus) converging on last remaining puddle of water in the Mussicadzi River to hunt Sharpooth catfish (Clarias gariepinus). Baboons (Papio sp.) and a busbuck (Tragela...

Naskrecki & Guyton / Nile monitor lizards (Varanus niloticus) converging on last remaining puddle of water in the Mussicadzi River to hunt Sharpooth catfish (Clarias gariepinus). Baboons (Papio sp.), a warthog (Phacochoer...

Naskrecki & Guyton / Nile monitor lizards (Varanus niloticus) hunting giant Sharpooth catfish (Clarias gariepinus) in dried up puddle of the Mussicadzi River, Gorongosa National Park, Mozambique.