User:Egk006/Mitchell's water monitor

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BEFORE EDITS: Mitchell's water monitor (Varanus mitchelli) is a semiaquatic species of monitor lizard in the family Varanidae. The species is native to Australia.


AFTER EDITS: Mitchell's water monitor (Varanus mitchelli) is a semiaquatic species of monitor lizard in the family Varanidae. The species is native to the Northern regions of Australia, and is on IUCN's Red List as a critically endangered species.

Etymology[edit]

BEFORE EDITS: The specific name, mitchelli, as well as the common name, Mitchell's water monitor, are in honor of Australian herpetologist Francis John Mitchell (1929–1970) of the South Australian Museum.


AFTER EDITS: The specific name, varanus mitchelli, as well as the common name, Mitchell's water monitor, are in honor of Australian herpetologist Francis John Mitchell (1929–1970) of the South Australian Museum.[1] The classification Varanus is a Latinization of the Arabic word for monitor lizard, waran.[2] The Mitchell's Water Monitor, as well as other species of Monitors in Australia, are colloquially referred to as goannas in Australia. The name likely came from the word iguana, as the lizards looked like the iguanas of South America to the first European settlers of Australia.[3]

Description and Behavior[edit]

BEFORE EDITS: Varanus mitchelli reaches a total length of up to 70 cm (28 in). It is generally dark in colour and has many small yellow spots or dark-centered ocelli.

The Mitchell's Water Monitor has yellow and orange stripes down its sides and neck.


AFTER EDITS: Varanus mitchelli reaches a length of up to 70 cm (28 in). It has a long, slender neck, and a pointed head. It is generally dark brown or black in color and has small yellow and white spots covering the limbs and head, and ocelli with dark centers as well as yellow or orange stripes along its side and neck.[4][1] The skin is rough, with many wrinkles. Its underside is a light cream color.[4]

Varanus lizards, including V. mitchelli have excellent eyesight, but are "night blind" in the dark. [5] The lizards' retinas do not have rods, the receptor cells for night vision.

V. Mitchelli breed during the dry season, with the females laying eggs between April and June.[6]Clutch sizes have been recorded from 3 to 12. Breeding behaviors are found to be similar to other species of Varanus lizards.[6] They live around 10 years.[7]

A map of the geographic range of the Mitchell's Water Monitor.

Geographic range[edit]

BEFORE EDITS: Mitchell's water monitor is found in the north part of Western Australia and the Northern Territory.

AFTER EDITS: Mitchell's water monitor resides along all northern river systems in the Kimberly Region of Western Australia and the Northern Territory.[4][1] There is no data to suggest that they live on any islands surrounding Australia.[4]

Habitat[edit]

BEFORE EDITS: Mitchell's water monitor is found in the north part of Western Australia and the Northern Territory.

AFTER EDITS: V. mitchelli inhabit fresh or brackish swamps, lagoons, inland rivers and are often found on trees close to the water. They inhabit almost all wetlands in Northern Australia.[7]They prefer to climb trees for shelter, and burrow in tree hollows or under bark.[1][8] If disturbed, V. mitchelli will head to water.[1] V. mitchelli frequently bask on rocks near the water.[4]

Diet[edit]

BEFORE EDITS: Mitchell's water monitor preys on smaller animals of both terrestrial and aquatic origin. Its prey includes: smaller lizards, small mammals, nestling birds, reptile eggs and terrestrial invertebrates (orthopterans, arachnids, beetles etc.). Aquatic prey include: fish, crabs and frogs.


AFTER EDITS: Mitchell's water monitor are active foragers and feed on smaller animals of both terrestrial and aquatic origin.[6] Its prey includes: smaller lizards, small mammals, nestling birds, small reptiles and reptile eggs, and terrestrial invertebrates (orthopterans, arachnids, beetles etc.). Aquatic prey include: fish, crabs and frogs. Its diet changes seasonally according to flooding during the wet season.[6]

In captivity[edit]

BEFORE EDITS: In captivity, Mitchell's water monitor is reported to be very nervous and shy. It is extremely uncommon in captivity.

AFTER EDITS: Though they are rarely kept in captivity, Mitchell's water monitor is reported to be nervous and shy.[6]Average clutch sizes for V. Mitchelli are between 3-11 eggs, though they can lay up to 20 in captivity.[6]They are found to be easily bred in captivity.[6]

Conservation[edit]

This wasn't a section in the article before I edited it. MY EDITS:

Threats[edit]

The current greatest threat to the Mitchell's Water Monitor is the spread of Cane Toads across the Northern Territory in Australia.[4]Toads and frogs are a part of V. mitchelli's diet, though the Cane Toads are poisonous to many species of Water Monitors, including V. mitchelli.[4] Cane Toads have become an invasive species in Australia since their introduction to the area in 1935, and Australia is currently facing an overpopulation of Cane Toads, which presents a problem for the species who mistake the poisonous Cane Toads for endemic toads native to Australia that make up the lizards' usual diet.[9] Not all Cane Toads are lethal. The smaller ones have non-lethal doses of poison compared to the larger toads, however, the Mitchell's Water Monitor and other monitors will go after the larger toads that contain lethal doses.

Other threats to the Mitchell's Water Monitor include habitat loss due to land clearing, habitat degradation and change due to climate change, and deaths occurring from contact with humans, such as death on roads.[2]

Status[edit]

Mitchell's Water Monitor is currently classified as critically endangered according to IUCN's Red List.[7] Its population is decreasing.[7]The decrease of V. mitchelli following the introduction of the cane toads has been estimated to be as high as 97% after only three years.[10]At Kakadu National park, almost the entire population of Mitchell's Water Monitor was taken out by the arrival of the cane toads, though a 2020 survey of the area found some individuals of the species.[11]

Efforts[edit]

Researches are trying to find ways to make monitor lizards avoid the cane toads. One current strategy is called Conditioned Taste Aversion Therapy, or CTA. This is where the animal associates a certain food with illness. The animal will avoid this food in the future because of the association. Researchers at the University of Sydney offered small cane toads with a non-lethal amount of poison to monitors in an area where the toads haven't reached yet, and found that the monitors who ate the small toads avoided them in the future.[12]These small toads, or "teacher toads" only make the lizards sick, but it is enough to dissuade them from eating the toads again. As cane toads march across Australia, scientists believe that releasing smaller toads ahead of the larger ones will increase CTA in lizards, and prevent them from eating the toads that contain a lethal amount of poison.

References[edit]

  1. ^ a b c d e Goannas (lizard family Varanidae). Komododragon.biz. Retrieved on 2012-08-22.
  2. ^ a b Macdonald, Stewart (2007). "Mitchell's Water Monitor". AROD.guide. Retrieved October 17, 2022.
  3. ^ "Goanna", Wikipedia, 2022-10-06, retrieved 2022-10-16
  4. ^ a b c d e f g https://nt.gov.au/__data/assets/pdf_file/0019/206461/mitchells-water-monitor.pdf [bare URL PDF]
  5. ^ Jackson, Timothy (2020-05-28). "Are monitor lizards venomous? (the Tale of Toxicofera, part 4)". School of Biomedical Sciences. Retrieved 2022-10-16.
  6. ^ a b c d e f g Gaikhorst, Glen; McLaughlin, James; Larkin, Brian; McPharlin, Meagan (18 May 2009). "Successful captive breeding of Mitchell's water monitor, Varanus mitchelli (Mertens 1958), at Perth Zoo". Zoo Biology. 29 (5): 615–625. doi:10.1002/zoo.20244.
  7. ^ a b c d Shea, G., Woinarski, J. & Cogger, H. 2018. Varanus mitchelli. The IUCN Red List of Threatened Species 2018: e.T83778268A101752345. https://dx.doi.org/10.2305/IUCN.UK.2018-1.RLTS.T83778268A101752345.en. Accessed on 26 September 2022.
  8. ^ "Mampam.com". Retrieved 3 July 2010.
  9. ^ Lower, Brian H.; Shaul, Travis R.; Shaul, Kylienne A.; Weaver, and Ella M. "Cane Toad: Purposefully Introduced, but Instantly a Regret". Environmental ScienceBites.
  10. ^ Doody, J.S., Green, B., Rhind, D., Castellano, C.M., Sims, R. and Robinson, T. 2009. Population-level declines in Australian predators caused by an invasive species. Animal Conservation 12: 46-53.
  11. ^ Einoder LD, Gillespie GR and Buckley KA (2020) Terrestrial fauna monitoring in Kakadu National Park. Northern Territory Department of Environment, Parks and Water Security, Darwin.
  12. ^ "Researchers stop threatened lizards eating toxic cane toads". The University of Sydney. Retrieved 2022-10-16.

External links[edit]

Further reading[edit]

  • Ávalos, J. de & Martínez Carrión, P. (1997). "Warane". Reptilia (Münster) 2 (5): 16–21. (in German).
  • Bennet, D.F. (2003). "Australische Warane". Reptilia (Münster) 8 (5): 18–25. (in German).
  • Bennet, D.F. (2003). "Australian Monitors". Reptilia (Great Britain) (30): 12–19.
  • Bonetti (2002). 100 Sauri. Milan: Mondadori. 192 pp. (in Italian).
  • Bustard, H.R. (1970). Australian Lizards. Sydney: Collins. 162 pp.
  • Cogger, H.G. (2000). Reptiles and Amphibians of Australia, Sixth Edition. Sanibel Island, Florida: Ralph Curtis Publishing. 808 pp.
  • De Lisle, H.F. (1996). Natural History of Monitor Lizards. Malabar, Florida: Krieger Publishing.
  • Eidenmüller, B. (2007). "Small monitors in the terrarium". Reptilia (GB) (50): 12–19.
  • Mertens, R. (1958). "Bemerkungen über die Warane Australiens". Senckenberg. Biol. 39: 229–264. (Varanus mitchelli, new species, p. 256). (in German).
  • Storr, G.M. (1980). "The monitor lizards (genus Varanus Merrem, 1820) of Western Australia". Records of the Western Australian Museum 8 (2): 237–293.
  • Swanson, S. (1976). Lizards of Australia. Sydney: Angus & Robertson. 80 pp.
  • Wilson, Steve; Swan, Gerry (2013). A Complete Guide to Reptiles of Australia, Fourth Edition. Sydney: New Holland Publishers. 522 pp. ISBN 978-1921517280.
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