Endangered
Mertens' water monitor
Varanus mertensi
Mertens' water monitor is a lizard or snake in the family Varanidae — Varanus mertensi, recorded as Endangered and tied to Australia.
Appearance
It is dark brown to black above, with many cream to yellow spots. The underparts are paler – white to yellowish – with grey mottling on the throat and blue-grey bars on the chest. The tail is strongly compressed laterally, with a high median dorsal keel, and is about 1.5 times the length of head and body.
Mertens' water monitor grows to a total length (tail included) of about 2.0 m (6.6 ft).
Range and habitat
Mertens' water monitor is found in coastal and inland waters across much of northern Australia, from the Kimberley region of Western Australia, across the Top End of the Northern Territory and the Gulf Country, to the western side of the Cape York Peninsula in Far North Queensland. The species is native to northern Australia, and is a wide-ranging, actively foraging, opportunistic predator of aquatic and riparian habitats.
Pins are Wikidata “endemic to” fields. Orange dots, when present, are GBIF occurrence tiles — survey bias included.
Diet and breeding
Mertens' water monitor is semiaquatic, a strong swimmer, and seldom far from water. Its diet consists mainly of freshwater Holthuisana crabs, that are reported to make up 29–83.7%? Of the biomass found in gut and scat samples.
An amount of 11.5% of prey biomass was found to be fish. Arthropods among them spiders, beetles and water bugs, while frequently eaten, make up a small proportion of ingested prey biomass. Mertens' water monitor lays eggs in a burrow, usually with egg-laying taking place early in the dry season and hatching in the following wet season.
In crisis
Mertens' water monitor is threatened by the spread of cane toads through its range, through poisoning after eating them.
Mertens' water monitor is Endangered on this catalog because that is the IUCN category stored on Wikidata. Confirm the official criteria and any later count on iucnredlist.org.
Sources
Written for this catalog from the English Wikipedia article on Mertens' water monitor, Wikidata item Q1819998. Family and order context is original field-guide writing about the group, not a copied assessment of this one species. Wikipedia text is CC BY-SA. Not an IUCN assessment. Counts, when quoted, can change — confirm them on the recovery programme and on iucnredlist.org.
