Reptiles
Asian Water Monitor
Varanus salvator · also called Asian water monitor, common water monitor, Malayan water monitor
The Asian water monitor is a three-metre lizard that most people in Southeast Asia have simply learned to live alongside. It patrols canals in the middle of Bangkok, basks on temple walls, and swims through mangroves — a giant predator that has adapted to the human world better than almost any other large reptile.
Overview
Asian water monitors range from Sri Lanka and eastern India across Southeast Asia to Indonesia and the Philippines, in wetlands, rivers, mangroves, forest, farmland, and cities. They are semi-aquatic — strong swimmers with a flattened, oar-like tail and high-set nostrils, able to stay submerged for around 30 minutes — and they hunt and scavenge across an enormous range of foods, from fish and rats to carrion and rubbish. They locate most of it by smell, flicking a deeply forked tongue like a snake.
The second-longest lizard
At up to 3 metres and 20+ kilograms, the Asian water monitor is second only to the Komodo dragon in length, and on average may be longer than the bulkier Komodo. It is fast on land, climbs well, and swims better than either.
A city animal
Few large reptiles handle humans as well. In Bangkok the water monitor is a familiar resident of parks, canals, drains, and temple grounds, living on refuse, rodents, and birds, and tolerant of pollution and crowds. It is bold around food but generally flees people, retreating into water or up a tree.
Danger and defence
A cornered water monitor can deliver deep bites and claw wounds and lash with its heavy tail, and like other monitors it has a mild venom (not dangerous to people). Almost all serious incidents involve someone trying to catch or kill one.
Status
The Asian water monitor is Least Concern and remains common, helped by its adaptability. But it is the most heavily traded monitor in the world — millions of skins a year go into leather goods, and it is also eaten and used in traditional medicine — so it is tracked under CITES and some local populations have been reduced.
Asian Water Monitor: common questions
How big does an Asian water monitor get?
Adults are usually 1.5 to 2 metres long including the tail, but large males regularly reach 2.5 metres and the biggest verified individuals are around 3 metres and over 20 kilograms. That makes the Asian water monitor the second-longest lizard in the world after the Komodo dragon, and by some measures longer on average than the (heavier, bulkier) Komodo. Much of the length is a long, laterally flattened tail used for swimming and as a whip in defence.
Are water monitors dangerous to people?
They are large, powerful predators with sharp claws, strong jaws, sharp teeth, and a heavy tail, and a cornered or captured one can inflict deep bites and lacerations, and a bite may become infected. Water monitors also have mild venom (as most monitors do), though it is not medically significant to humans. That said, wild water monitors are generally shy of people and flee into water or up a tree; serious incidents almost always involve someone trying to catch, kill, or handle one. In cities where they are used to people, they can become bold around food.
How do water monitors live in cities?
Extremely well. The Asian water monitor is one of the most successful large reptiles at coexisting with humans. In Bangkok it is a common sight in parks, canals (khlongs), drainage systems, and temple grounds, where it scavenges rubbish, catches rats, fish, and pigeons, and basks openly. It tolerates polluted water, fragmented habitat, and constant human activity, and by consuming carrion and pest rodents it arguably provides a sanitation service, though large numbers can also become a nuisance and a threat to poultry and to other wildlife's nests.
Why are so many water monitors killed?
The Asian water monitor is the most heavily exploited monitor lizard in the world. Millions of skins enter the international leather trade each year — the fine-scaled belly skin is used for watch straps, wallets, handbags, and shoes — and the species is also eaten in parts of its range and used in traditional medicine. Because it is abundant, adaptable, and fast-breeding, the trade has not so far threatened it globally, and it remains Least Concern, but it is monitored under CITES and some regional populations have been depleted.