Scientific name:
Varanus mertensi
Status:
ENDANGERED (EPBC 2023)
Merten’s Water Monitor is part of the goanna family and grows to around 1.1–1.5 m in length. Its colouring ranges from dark brown, black, or olive-grey on the back, covered in cream to yellow spots.
The underparts are lighter – white to pale yellow – with grey mottling on the throat and blue-grey bars across the chest.
The long tail is flattened along the sides rather than rounded, creating a raised ridge along the top, and is about 1.2 times the length of the head and body.
Merten’s Water Monitors feed both on land and in the water. Their diet includes fish, frogs, crustaceans, insects and other invertebrates, small mammals, smaller reptiles, and carrion. With a keen sense of smell, they are also skilled at finding and digging up submerged turtle nests to eat the eggs.
They live in rivers, creeks, swamps, and streams, often using surrounding rocks and logs for basking and shelter.
Found across tropical northern Australia, from the Kimberley region in Western Australia through to Far North Queensland.
Australia’s most aquatic monitor, Merten’s Water Monitor is a strong swimmer and rarely strays far from water. Its flattened tail works like both propeller and rudder, giving powerful thrust and precise steering. They are often seen basking on midstream rocks, logs, or overhanging branches.
When disturbed, they drop into the water, where they can remain submerged for long periods. Special upward-facing nostrils with watertight valves allow them to breathe at the surface without lifting the whole head above water.
Like all monitor lizards, they have a deeply forked tongue, which they use – just like snakes – to detect scent particles in the air.
If threatened, they inflate their necks in an aggressive display, but will usually escape by retreating into a burrow or diving into the water.
Unfortunately, populations have declined in many regions due to the spread of the toxic Cane Toad (Rhinella marina). Any attempt to eat a Cane Toad is fatal to the monitor.
Merten’s Water Monitors are egg-laying reptiles. During the wet season, females lay clutches of up to 14 eggs in leafy nests. The eggs take 9–10 months to hatch.
Reptile Encounters would like to acknowledge the Traditional Custodians of the land, the people of the Kulin Nation, who have never ceded sovereignty. This always was and always will be Aboriginal land.