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Der Mitchells Waran (Varanus mitchelli) ist eine Art der Warane die endemisch in Australien ist. Er gehört der Untergattung Odatria an. Die Erstbeschreibung dieser Art erfolgte 1958 durch den deutschen Biologen Mertens.
Die Gesamtkörperlänge des Mitchells Waran beträgt im ausgewachsenen Stadium um die 60 cm. Der Schwanz alleine ist 1,7- bis 2,2-mal so lang wie die Kopf-Rumpf-Länge. Die Färbung des Mitchells Warans ist auf der Oberseite dunkelbraun bis blauschwarz oder schwärzlich. Der Kopf ist mit cremefarbenen oder gelben Flecken gesprenkelt. Ihr Körper ist mit unzähligen gelblichen Flecken, Punkten und kleinen Ozellen geschmückt, welche allesamt je einen schwarzen Zentralfleck aufweisen. Ihr gelblicher Temporalstreifen ist nur undeutlich wahrnehmbar. Dagegen sind die Seiten des Halses und die Kehle zitronengelb mit schwarzen Punkten oder Flecken. Auf ihrem Unterkiefer ist ein schwarzer Balken erkennbar. Die Haut unterhalb des Auges ist leuchtend gelb. Alle vier Gliedmaßen sind auf der Oberseite schwarz und haben gelbe Flecken. Die Grundfärbung des Schwanzes ist schwarz mit unzähligen kleinen gelben oder cremefarbenen Flecken. Die Bauchseite von V. mitchelli ist cremefarben mit einem grünlichen Stich. Die Kopfschuppen sind überwiegend glatt. Das Nasenloch befindet sich seitlich nach oben gerichtet auf der Schnauze. Es liegt dabei etwas näher an der Schnauzenspitze als zum Auge. Um die Körpermitte sind 90 bis 130 Schuppenreihen angeordnet. Der Schwanz ist an der Spitze sichtbar abgeflacht, obwohl er an der Basis kreisrund ist. Ein sehr auffallender Doppelkiel ist auf der Oberseite der Schwanzbasis vorhanden. Die Schwanzschuppen sind in regelmäßigen Ringen angeordnet, wobei diese gelegentlich an den Seiten unvollständig sind.
Das Verbreitungsgebiet von V. mitchelli liegt im tropischen Nordaustralien von Derby im Westen bis nach Borroloola im Osten.[1] Die Tiere wurden schon am Daly River, in der Umgebung von Kununurra und um Wyndham gesichtet. Der Mitchells Waran wurde immer als kleiner Vertreter der Wasserwarane angesehen, aber durch sein Habitat hat er eher die Stellung eines Baumbewohners. Man trifft ihn jedoch häufig in der Nähe von Wasser an. Er ist aber nicht im selben Maße auf das Wasser angewiesen, wie z. B. der Mertens-Wasserwaran (Varanus mertensi). Man findet den Mitchells Waran in der Nähe von Sümpfen, Lagunen, Mangrovenwäldern, Flüssen und anderen Gewässern. Seine bevorzugten Rückzugsorte sind Baumhöhlen und Plätze unter abgestorbener Rinde.[2][3] In Gefangenschaft wird der Mitchells Waran im Taronga Zoo (Sydney) gehalten.[4]
Bei Mageninhaltsuntersuchungen wurden Spinnentiere, Grillen, Käfer, Fische, Krebstiere, Frösche, Skinke und Mäuse nachgewiesen. Ihr Jagdverhalten wurde noch nicht ausreichend erforscht.
Varanus mitchelli wurde früher in der Untergattung Varanus gelistet, da er einen leicht abgeplatteten Schwanz hat. BÖHME (1988, 1993) ordnete den Mitchells Waran aufgrund genitalmorphologischer Befunde der Untergattung Odatria zu. Auch sein an der Basis im Querschnitt runder Schwanz war ein weiterer Grund zur Eingliederung in die Untergattung Odatria. Das Artepitheton ehrt Francis J. Mitchell vom South Australian Museum.[5]
Der Mitchells Waran (Varanus mitchelli) ist eine Art der Warane die endemisch in Australien ist. Er gehört der Untergattung Odatria an. Die Erstbeschreibung dieser Art erfolgte 1958 durch den deutschen Biologen Mertens.
Mitchell's water monitor (Varanus mitchelli) is a semiaquatic species of monitor lizard in the family Varanidae. The species is native to Australia.[4] 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.
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.[5][6] The classification Varanus is a Latinization of the Arabic word for monitor lizard, waran.[7] 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.
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 and has small yellow and white spots covering the limbs and head, and ocelli with dark centers as well as yellow stripes along its side.[8][2] The skin is rough, with many wrinkles. Its underside is a light cream color.[8]
Varanus lizards, including V. mitchelli have excellent eyesight, but are "night blind" in the dark.[9] The lizards' retinas do not have rods, the receptor cells for night vision.
Mitchell's water monitor resides along all northern river systems in the Kimberly Region of Western Australia and the Northern Territory.[8][2][3] There is no data to suggest that they live on any islands surrounding Australia.[8]
V. mitchelli inhabit swamps, lagoons, inland rivers, and other bodies of water and are often found on trees near the water. It prefers to climb trees to shelter in tree hollows or under bark.[4][5] If disturbed, V. mitchelli will head to the water.[4] V. mitchelli frequently basks on rocks near the water.[6]
Varanus mitchelli is oviparous.[10] V. Mitchelli breed during the dry season, with the females laying eggs between April and June.[11] Clutch sizes have been recorded from 3 to 12. Breeding behaviors are found to be similar to other species of Varanus lizards.[11] They live around 10 years.[12]
The Mitchell's water monitor is reported to be nervous and shy. It is rarely kept in captivity.[13] Average clutch sizes for V. mitchelli are between 3-11 eggs, though they can lay up to 20 in captivity.[14] They are found to be easily bred in captivity.
This lizard grows to a over 2ft in length and requires a large bioactive enclosure, recommendations of 8x4x4 ft are not uncommon, especially if attempting to breed. Providing a seasonal environment and food to mimic natural behaviors is the best onset for breeding although these requirements can be difficult to achieve and reduces their appearance in captivity.
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.[15] Its diet changes seasonally according to flooding during the wet season.[16]
The current most significant threat to the Mitchell's Water Monitor is the spread of Cane Toads across the Northern Territory in Australia.[17]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.[17] 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.[18] The geographic range of the cane toads completely overlaps the geographic range of V. mitchelli.[8] Not all cane toads are entirely 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.[7] V. mitchelli have also been reported to be exported live to be sold in global markets.[19]
Mitchell's Water Monitor is currently classified as critically endangered according to IUCN's Red List.[20] Its population is decreasing.[20] 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.[21] 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.[22] Despite this, the species has persisted at many habitat spots, though as sightings are rare there is no current estimate on the number of individuals in each population of V. mitchelli.[8]
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.[23] These small toads, or "teacher toads" only make the lizards sick, but it is enough to dissuade them from eating the toads again. Other reports of successful CTA include the use of non-living bait.[24] In order for this prevention strategy to work, scientists would have to identify areas of concentrated biodiversity in order for the results to balance out the cost of the bait.[24] 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.
Other efforts are aimed at protecting the current populations of Mitchell's Water Monitor at sites already occupied by cane toads, as it will be extremely difficult to stop the spread of cane toads.[8]
The Northern Territory Government has set up the Island Arks program to help the conservation of species affected by the cane toads.[25]
Mitchell's water monitor (Varanus mitchelli) 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.
Varanus mitchelli Varanus generoko animalia da. Narrastien barruko Varanidae familian sailkatuta dago.
Varanus mitchelli Varanus generoko animalia da. Narrastien barruko Varanidae familian sailkatuta dago.
Varanus mitchelli est une espèce de sauriens de la famille des Varanidae[1].
Cette espèce est endémique d'Australie. Elle se rencontre dans le Territoire du Nord et en Australie-Occidentale[1].
Long de 150 cm, il a une couleur vert foncé avec de petites taches jaunes sur le dos et une gorge jaune. Il est bien adapté à l'eau par sa longue queue et ses narines haut situées qui peuvent se fermer de façon étanche si besoin Il peut atteindre une taille maximale de 70 cm, sa queue représentant les deux tiers de sa longueur totale. Il mesure 8 cm à la naissance, et atteint sa maturité sexuelle à une taille de 22 cm. On rencontre ce reptile dans l'eau douce comme dans les milieux marins, et il est notamment fréquent dans les mangroves, les marais, les côtes, les cours d'eau et les lacs du Territoire du Nord, en Australie. Il se nourrit de poissons et de crabes, mais aussi de grenouilles, lézards, œufs de reptiles, petits mammifères, d'oiseaux au nid et d'invertébrés terrestres. La saison de reproduction a lieu durant la saison sèche, et les femelles pondent une douzaine de petits œufs (2,5 cm sur 1,3 cm) entre avril et juin. Varanus mitchelli passe une bonne partie de la journée à se reposer sur des branches d'arbres surplombant l'eau[2].
Cette espèce est nommée en l'honneur de Francis John Mitchell[3].
Varanus mitchelli[1] este o specie de reptile din genul Varanus, familia Varanidae, descrisă de Mertens 1958.[2][3] Conform Catalogue of Life specia Varanus mitchelli nu are subspecii cunoscute.[2]
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Acest articol referitor la o reptilă este un ciot. Puteți ajuta Wikipedia prin completarea sa. Varanus mitchelli este o specie de reptile din genul Varanus, familia Varanidae, descrisă de Mertens 1958. Conform Catalogue of Life specia Varanus mitchelli nu are subspecii cunoscute.
Varanus mitchelli là một loài thằn lằn trong họ Varanidae. Loài này được Mertens mô tả khoa học đầu tiên năm 1958.[3]
Bài viết liên quan đến bộ bò sát có vảy này vẫn còn sơ khai. Bạn có thể giúp Wikipedia bằng cách mở rộng nội dung để bài được hoàn chỉnh hơn. Varanus mitchelli là một loài thằn lằn trong họ Varanidae. Loài này được Mertens mô tả khoa học đầu tiên năm 1958.
