As the name suggests, the Mertens’ water monitor loves the water. During the day the monitor can be found basking on rocks and logs near the shoreline of rivers, creeks, billabongs and lagoons. The monitors are great swimmers and have a special valve in their nostrils that closes when they dive. Their nostrils are also on the top of their head, like a crocodile’s, so that they can stay partially submerged in the water when searching for prey. These big reptiles grow to a metre long and weigh up to 380 grams. They are light grey to dark brown, with a scattering of light yellow/cream spots. Their underbelly is light yellow to cream. When threatened, the Mertens’ water monitor will typically slide into the water and hide under a rock or log.
The Mertens’ water monitor lives near coastal and inland water sources in northern Australia, from the Kimberley in Western Australia to the Cape York Peninsula in Queensland.
Any small creatures it can find in the water, such as frogs, fish, crabs and small mammals. Plus, it will also forage on land for small mammals, birds, eggs and even insects. The monitor is threatened by cane toads, because if it eats them it can die.
The monitors breed during the dry season and the females lay about 9 eggs in a specially built nesting chamber, filled with leaf litter. The eggs hatch within 3-6 months, depending on the temperature. The hatchlings usually enter the water and swim straight away.