Mertens’ Water Monitor

Mertens’ Water Monitor Varanus mertensi

Type of Animal:

Coastal & inland waters/water edges-rivers, creeks, billabongs, ponds, canals, reservoirs, banks, low brushy areas

N Australia & some offshore islands

Fairly slender monitor lizard, dark brown to black above w/ cream/yellow spots, belly area white to yellowish, yellowish/whitish throat area w/ gray mottling, blue-gray bars on chest, long flattened tail w/ high double dorsal keel, yellowish/speckled/gray barred lower lip

Fish, amphibians, carrion, insects, insect larvae, eggs, crabs, crayfish, shrimp, prawns, worms, small mammals, birds, human scraps, baby crocodiles, spiders, snakes, agamid lizards, fruit

Status in Wild:

Breeding in zoos, aquariums, wildlife centers, & herpetoculture


Additional Info:

Young: Hatchling
Group: Solitary
Male: 8 lbs
Female: 2.5 lbs

9-10 months

Life Span:
20 years

Body Length:
Male: 3 ft
Female: 2.5 ft
Young: 1 ft

Tail Length:
Male: 4.5 ft
Female: 3.75 ft
Young: 1.5 ft

Main predators are crocodiles & water pythons.
Endangered due to water pollution, consumption of toxic cane toads (many can handle toxins but many can’t & die, competition w/ cane toads for food, habitat loss, wildlife trade, & skin trade.
They’re excellent swimmers, being able to close nostrils underwater & use long powerful tail.
Camouflage comes in handy for catching prey & protecting self from crocodiles & water pythons.
Besides using camouflage, they can also inflate neck & whip w/ tail. They can also retreat into burrows.
Females lay 6-15 eggs in burrows early in dry season, w/ eggs hatching at start of wet season.
Babies can swim from the moment they hatch.
Like many monitor lizards, they have excellent sense of smell.
Besides being great swimmers, they’re also great climbers.
Sexually mature at 3 years old.
Active during the day (diurnal).
Often dig burrows near water’s edge where they shelter at night.
Like all monitor lizards, they have forked tongue used to smell air.
Sometimes kept as pets.
They’ll often estivate in dry season & are more active in wet season.

Fun Fact(s):
Like many monitors, they’re voracious feeders.
They’ve been seen using body/tail to herd prey into shallower water.
Like many monitor lizards, they’re fairly intelligent.
Named after German herpetologist Robert Mertens.
When disturbed, they’ll drop into water, where they can stay submerged for up to 30 minutes.

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