Mertens' water monitor

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Mertens' water monitor
Washington DC Zoo - Varanus mertensi 2.jpg
Smithsonian National Zoological Park
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Varanidae
Genus: Varanus
Subgenus: Varanus
Species:
V. mertensi
Binomial name
Varanus mertensi
Glauert, 1951

Mertens' water monitor (Varanus mertensi), often misspelled Mertin's water monitor, is a species of monitor lizard. The species is endemic to northern Australia, and is a wide-ranging, actively foraging, opportunistic predator of aquatic and riparian habitats. [2] It is named after German herpetologist Robert Mertens. [3]

Contents

Description

Mertens' water monitor grows to a total length (including tail) of about 2.0 m (6.6 ft). 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. [4]

Amongst all monitor species, including the water monitors of Soterosaurus , Mertens' water monitor is morphologically the most well adapted to an aquatic lifestyle, being able to seal its upwards facing nostrils when underwater. [5] It is capable of swallowing prey underwater, which is an ability not reported in any other monitor species other than the Borneo earless monitor (Lanthanotus borneensis). [6] It is also the only monitor species reported capable of using its sense of smell to locate and capture prey underwater. [7]

Distribution 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. [4]

Behaviour

Mertens' water monitor is semiaquatic, a strong swimmer, and seldom far from water. It is often seen basking on midstream rocks and logs, and on branches overhanging swamps, lagoons, and waterways throughout its range. When disturbed, it drops into the water, where it can stay submerged for long periods. [4] It has been observed sleeping underwater. [5]

Feeding

Mertens' water monitor feeds both on land and in the water, mainly on fish, frogs, crabs, crayfish, shrimps, amphipods, and carrion, also taking terrestrial vertebrates, insects, spiders, and human rubbish when available. [4] [8] It's diet consists mainly of freshwater Holthuisana crabs, which are reported to make up 29-83.7% of the biomass found in gut and scat samples. 11.5% of prey biomass was found to be fish. While eggs and frogs are infrequently eaten, large amounts of them are eaten when found. Arthropods including spiders, beetles and water bugs, while frequently eaten, make up a small proportion of ingested prey biomass. [7] It has a good sense of smell and may dig up prey when foraging, including the eggs of freshwater turtles. [9]

Breeding

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. The eggs hatch within 200–300 days after laying, depending on temperature, with the hatchlings able to enter the water and swim immediately. [9] [10]

Conservation and status

Mertens’ water monitor is threatened by the spread of cane toads through its range, through poisoning after eating them. Because of this V. mertensi is listed as Vulnerable under Northern Territory legislation. [9]

Related Research Articles

<span class="mw-page-title-main">Varanidae</span> Family of lizards

The Varanidae are a family of lizards in the superfamily Varanoidea and order Anguimorpha. The family, a group of carnivorous and frugivorous lizards, includes the living genus Varanus and a number of extinct genera more closely related to Varanus than to the earless monitor lizard (Lanthanotus). Varanus includes the Komodo dragon, crocodile monitor, savannah monitor, the goannas of Australia and Southeast Asia, and various other species with a similarly distinctive appearance. Their closest living relatives are the earless monitor lizard and Chinese crocodile lizard. The oldest members of the family are known from the Late Cretaceous of Mongolia.

<span class="mw-page-title-main">Earless monitor lizard</span> Species of lizard

The earless monitor lizard is a semiaquatic, brown lizard native to the Southeast Asian island of Borneo. It is the only living species in the family Lanthanotidae and it is related to the true monitor lizards.

<span class="mw-page-title-main">Monitor lizard</span> Genus of reptiles

Monitor lizards are lizards in the genus Varanus, the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recognized.

<span class="mw-page-title-main">Goanna</span> Several species of reptiles

A goanna is any one of several species of lizard of the genus Varanus found in Australia and Southeast Asia.

<span class="mw-page-title-main">Asian water monitor</span> Species of lizard

The Asian water monitor is a large varanid lizard native to South and Southeast Asia. It is widely considered to be the second-largest lizard species, after the Komodo dragon. It is distributed from eastern and northeastern India and Bangladesh, the Andaman and Nicobar Islands, Sri Lanka, through southern China and Hainan Island in the east to mainland Southeast Asia and the islands of Sumatra, Borneo, Java, Lombok, the Riau Archipelago, Sulawesi. It is one of the most widespread monitor lizards.

<span class="mw-page-title-main">Lace monitor</span> Species of lizard

The lace monitor, also known as the tree goanna, is a member of the monitor lizard family native to eastern Australia. A large lizard, it can reach 2 metres (6.6 ft) in total length and 14 kilograms (31 lb) in weight. The lace monitor is considered to be a least-concern species according to the International Union for Conservation of Nature.

<span class="mw-page-title-main">Sand goanna</span> Species of lizard

The sand goanna, also known commonly as Gould's monitor, the racehorse goanna, and the sand monitor, is a species of large Australian monitor lizard in the family Varanidae.

<span class="mw-page-title-main">Mangrove monitor</span> Species of lizard

The mangrove monitor, mangrove goanna, or Western Pacific monitor lizard is a member of the monitor lizard family with a large distribution from northern Australia and New Guinea to the Moluccas and Solomon Islands. It grows to lengths of 3.5 to 4 ft. It is also known as wbl yb in the Kalam language of Papua New Guinea.

<span class="mw-page-title-main">Emerald tree monitor</span> Species of lizard

The emerald tree monitor or green tree monitor, is a small to medium-sized arboreal monitor lizard. It is known for its unusual coloration, which consists of shades from green to turquoise, topped with dark, transversedorsal banding. This coloration helps camouflage it in its arboreal habitat. Its color also makes the emerald tree monitor highly prized in both the pet trade and zoos alike.

<span class="mw-page-title-main">Yellow-spotted monitor</span> Species of reptile

The yellow-spotted monitor, also known as the Argus monitor, is a monitor lizard found in northern and western regions of Australia and southern New Guinea.

<span class="mw-page-title-main">Spiny-tailed monitor</span> Species of lizard

The spiny-tailed monitor, also known as the Australian spiny-tailed monitor, the ridge-tailed monitor the Ackie dwarf monitor, and colloquially simply ackie monitor, is an Australian species of lizard belonging to the genus of monitor lizards (Varanus).

<span class="mw-page-title-main">Kimberley rock monitor</span> Species of lizard

The Kimberley rock monitor is a medium-sized species of monitor lizard in the family Varanidae. The species is native to Northern Australia. Also known commonly as Glauert's monitor and the Kakadu sand goanna, it belongs to the subgenus Odatria.

<span class="mw-page-title-main">Rosenberg's monitor</span> Species of lizard

The Rosenberg's monitor is an Australian species of varanid reptile found in southern regions of the continent. They are large and fast predators with rugged bodies and long tails, having a combined length up to 1.5 metres, that will consume any smaller animal that is pursued and captured or found while foraging. They occur in the Australian Capital Territory, New South Wales, South Australia, Victoria, where it may be rare or locally common, and more frequently observed in Western Australia, where it is sometimes abundant.

The black-spotted ridge-tailed monitor, also called commonly the black-spotted spiny-tailed monitor, the lemon-throated monitor, the northern ridge-tailed monitor, Whites monitor, and the yellow-throated monitor, is a subspecies of lizard in the family Varanidae. The subspecies is native to Australia's tropical Northern Territory. It is listed as Least Concern on the IUCN Red List as it is considered common and not threatened. It was first described in 1987. It is also known as White's dwarf goanna.

<span class="mw-page-title-main">Dumeril's monitor</span> Species of lizard

Dumeril's monitor is a species of lizard in the family Varanidae. The species is endemic to Southeast Asia.

Varanus keithhornei, commonly known as the canopy goanna, Keith Horne's monitor, blue-nosed tree monitor, or Nesbit River monitor, is a species of monitor lizards native to northeast Australia. It is a member of the Varanus prasinus species group.

<span class="mw-page-title-main">Kings' monitor</span> Species of lizard

Kings' monitor, also known commonly as Kings' goanna, Kings' rock monitor and pygmy rock monitor, is a small species of monitor lizard in the family Varanidae. The species is native to Australia.

<span class="mw-page-title-main">Mitchell's water monitor</span> Species of lizard

Mitchell's water monitor is a semiaquatic species of monitor lizard in the family Varanidae. The species is native to Australia. The species is native to the Northern regions of Australia, and is on IUCN's Red List as a critically endangered species. They can be distinguished by the orange or yellow stripes along their neck and dark spots along their back. They are mainly carnivorous, and eat small prey such as lizard, birds, and insects.

<i>Varanus storri</i> Species of lizard

Storr's monitor is a species of monitor lizard in the family Varanidae. The species is endemic to Australia.

Cryptoblepharus mertensi, also known commonly as Merten's snake-eyed skink, is a species of lizard in the family Scincidae. The species is endemic to the Northern Territory in Australia.

References

  1. Shea, G.; Woinarski, J.C.Z.; Macdonald, S.M.; Cogger, H. (2018). "Varanus mertensi". IUCN Red List of Threatened Species . 2018: e.T83778246A101752340. doi: 10.2305/IUCN.UK.2018-1.RLTS.T83778246A101752340.en . Retrieved 19 November 2021.
  2. Mayes, Phillip James (2006). The ecology and behaviour of Varanus mertensi (Reptilia: Varanidae) (Dissertation submitted for the Degree of Doctor of Philosophy). Perth, Western Australia: Faculty of Natural Sciences, Edith Cowan University.
  3. Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. ISBN   978-1-4214-0135-5. (Varanus mertensi, p. 176).
  4. 1 2 3 4 Cogger HG (1979). Reptiles and Amphibians of Australia. Sydney: Reed. p. 257. ISBN   0-589-50108-9.
  5. 1 2 Auliya, Marc; Koch, André (2020). Visual Identification Guide for the Monitor Lizard Species of the World (Genus Varanus) (552 ed.). DE: Bundesamt für Naturschutz. doi:10.19217/skr552. ISBN   978-3-89624-290-7.
  6. Mendyk, Robert; Shuter, Avishai; Kathriner, Andrew (2015). "Historical Notes on a Living Specimen of Lanthanotus borneensis (Squamata: Sauria: Lanthanotidae) Maintained at the Bronx Zoo from 1968 to 1976". BIAWAK. 9 (2): 44–49.
  7. 1 2 Mayes, P. J.; Thompson, G. G.; Withers, P. C. (2005). "Diet and foraging behaviour of the semi-aquatic Varanus mertensi (Reptilia:Varanidae)". Wildlife Research. 32 (1): 67. doi:10.1071/WR04040. ISSN   1035-3712.
  8. "Varanus Mertensi".
  9. 1 2 3 "Threatened Species of the Northern Territory: Mertens Water Monitor" (PDF). Simon Ward, John Woinarski, Tony Griffiths and Lindley McKay (compilers). Department of Natural Resources, Environment and the Arts, Northern Territory. November 2006. Archived from the original (PDF) on 9 October 2009. Retrieved 10 January 2010.
  10. OzAnimals.com: Mertens’ Water Monitor.