Black monitor

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Black monitor
Gillenibaumann.JPG

Black monitor monitor ( Varanus tristis )

Systematics
without rank: Toxicofera
without rank: Sneaky (Anguimorpha)
Family : Varanidae
Genre : Monitor lizards ( varanus )
Subgenus : Odatria
Type : Black monitor
Scientific name
Varanus tristis
( Schlegel , 1839)

The black monitor monitor ( Varanus tristis ) is a species of monitor monitor ( Varanus ) native to Australia . The species, which is distributed all over Australia, is both tree and ground-dwelling and feeds mainly on lizards as well as insects, bird eggs and young birds.

features

The black monitor reaches a total length of up to 75 cm, the tail length is 1.5-2.3 times the head-trunk length. The scales on the head are small and smooth. The nostrils are a little closer to the tip of the snout than to the eyes. The tail is round in cross section and the scales on it are strongly keeled. The claws are very sharp and strongly curved.

A multitude of color variations exist within the large distribution area. The upper side of the body is mostly gray, brown or black, with numerous pale, but sometimes also pink or blue-gray eye spots. These spots are usually quite dark in adult specimens. The head and neck are black in the southern distribution area, orange in the top end and light brown from the Gulf of Carpentaria to the west to Kimberley. The legs are black and show small white spots.

distribution and habitat

The black monitor lives in all of Australia except for the southernmost regions ( Victoria , large parts of New South Wales and South Australia ). Black monitors inhabit all habitats in which trees with caves can be found, such as dry and semi-humid tropical woodland, but they can also be found in rocky areas.

Way of life

General

Like all monitor lizards, the black monitor is a diurnal loner. As hiding places at night and also during the day, these monitor lizards use tree hollows, occasionally also crevices or building structures. He climbs very well and carries out many of his activities (e.g. sunbathing) in trees, the degree of attachment to trees obviously depends on the distribution. In the Kakadu National Park, the animals begin their activities at around 9:30 a.m. They move on the ground in search of food and rest or sunbathe on trees for 1-2 hours. In other areas (e.g. Great Victoria Desert), however, the black monitor is predominantly tree-dwelling.

The black monitor has pronounced seasonal changes in activity and lays down periods of rest, before which it builds up the largest possible fat reserves. Black monitors hide during this rest period, for example in hollow tree trunks and the like. Ä., And remain largely inactive. There are no prey animals during the dry season. The rest period is very variable in the large distribution area: in Kakadu National Park it lasts from July to October, in Queensland near Ilfracombe from June to September. Only one black monkey was found in the Great Victoria Desert during a study from April through July.

Males move in much larger areas of action than females. In the Kakadu National Park, males use 13 hectares on average, females in 2 hectares on average. In the Great Victoria Desert, these areas amount to an average of 40 ha for males and 4 ha for females. In both sexes, the action spaces overlap strongly with the action spaces of conspecifics. Territorial behavior does not occur. In the Kakadu National Park, black monitors usually cover more than 150 meters a day in search of food. At the time of reproduction, the lizards are much more active.

nutrition

The food of the black lizards consists largely of other lizards; insects, bird eggs, young birds and amphibians (e.g. coral finger tree frog , Litoria caerulea ) are also eaten. When examining the stomach contents of 100 specimens, it was found that lizards make up 70% of the diet. Generally, all lizards that can be overwhelmed are eaten. Pianka (1994) reported about a black monkey that ate a western bearded dragon ( Pogona minor ) of 22.7% of its own body weight.

Sweet (2007) observed the black monkey foraging in Kakadu National Park. The black-headed monitor hunts there is usually at the bottom and look for large areas lambent for food from. The animals cover straight stretches between thick vegetation, tree stumps, root network and piles of leaves, which they examine for lizards hidden there. They push about 1-2 body lengths into piles of leaves and then step out of the pile of leaves with a tense posture in order to possibly prey on startled lizards. Fleeing lizards are usually pursued 2-4, rarely 12 m, then captured and swallowed. The lizards rarely escape. Pianka (1994), on the other hand, reports that traces of black monitors in the Great Victoria Desert always run straight from one tree to another. The black monitor there mainly hunt tree-dwelling lizards (e.g. geckos) and prey on young birds and eggs.

Reproduction

Males and females reach sexual maturity with a KRL of about 20 cm. The mating season is very variable in the large distribution area. In the Great Victoria Desert it falls in the early rainy season in October and November, but in the Kakadu National Park in the early dry season from early May to early June. During the dry season the males become very active and follow the pheromones of the females with a lick of flicks . This motivates the males to make very sudden hikes of up to 723 m. During the mating season, they move far beyond their normal range of action. Mating often takes place in a tree cavity where the male finds the female. In Kakadu National Park, the eggs are then placed in hollow tree stumps in late June and early July. Ä. placed. Clutches comprise 5-17 eggs, on average 10.1 eggs. The young (KRL 7.2-7.3 cm) hatch after about 114-117 days.

Natural enemies

Larger nesting birds, such as cockatoos , hate black monitors that climb up the birds' nesting tree. Black monitors are mainly hunted by birds of prey, other birds such as B. the Haubenliest ( Dacelo leachii ), snakes, other monitor lizards and mammals such as introduced domestic cats. The life expectancy of the black monkey is around twelve years.

Systematics

The first description of Varanus tristis was made in 1839 by the German zoologist Hermann Schlegel (1804-1884) as a monitor tristis . The holotype is believed to be lost and came from the Swan River in Western Australia. The exact type locality is not known. On the basis of its hemipenis morphology , V. tristis can be assigned to the dwarf monitor lizards of the subgenus Odatria . There Böhme (2003) placed him in the V. timorensis group. The assignment to Odatria was confirmed by Fitch et al. (2006) based on their analysis of mitochondrial DNA . They place V. tristis in the V. tristis group they have raised , in which it is the sister group of Varanus glauerti .

Traditionally, V. tristis is divided into the subspecies V. t. tristis and V. t. orientalis differentiated. V. t. orientalis lives in Arnhem Land and is paler in color than other black monitors. The rest of the distribution area is from V. t. tristis inhabited. Fitch et al. (2006) confirmed V. tristis and the subspecies V. t. tristis as monophyletic , but represent the monophyly of V. t. orientalis in question. In addition, specimens from Queensland are brownish in color and morphometrically different from other populations. It is possible that further subspecies await their description or V. tristis will turn out to be a species complex.

swell

supporting documents

  1. ↑ a b c d e f g h i j k l E. R. Pianka (2004): Varanus tristis . In: ER Pianka & DR King (Eds.): Varanoid Lizards of the World , pp. 477-487. Indiana University Press, Bloomington & Indianapolis. ISBN 0253343666
  2. ↑ a b c R. Shannon (2008): Observations on Three Species of Varanus in Ilfracombe, Queensland . Biawak 2 (2), pp. 80-86
  3. ↑ a b c d e E. R. Pianka (1994): Comparative Ecology of Varanus in the Great Victoria Desert . Australian Journal of Ecology 19, pp. 395-408
  4. ↑ a b c d e f g h i j k S. S. Sweet (2007): Comparative Ecology of Two Small Arboreal Monitors in Northern Australia . Mertensiella 16 ( Advances in Monitor Research III ), pp. 378-402
  5. ↑ a b G. G. Thompson, M. de Boer & ER Pianka (1999): Activity areas and daily movements of an arboreal monitor lizard, Varanus tristis (Squamata: Varanidae) during the breeding season . Australian Journal of Ecology 24 (2), pp. 117-122
  6. ^ A b G. G. Thompson & ER Pianka (1999): Reproductive ecology of the black-headed goanna Varanus tristis (Squamata: Varanidae) . Journal of the Royal Society of Western Australia 82, pp. 27-31
  7. ^ ER Pianka (1971): Notes on the biology of Varanus tristis . The Western Australian Naturalist 11 (8), pp. 180-183
  8. ↑ Reptile Manager - Trauerwaran ( Memento of the original from July 25, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.reptilienmanager.de
  9. ^ W. Böhme (2003): Checklist of the living monitor lizards of the world (family Varanidae) . Zoologische Verhandelingen 341, pp. 3-43
  10. ↑ a b A. J. Fitch, AE Goodman & SC Donnellan (2006): A molecular phylogeny of the Australian monitor lizards (Squamata: Varanidae) inferred from mitochondrial DNA sequences . Australian Journal of Zoology 54, pp. 253-269

literature

  • ER Pianka (1994): Comparative Ecology of Varanus in the Great Victoria Desert . Australian Journal of Ecology 19, pp. 395-408
  • ER Pianka (2004): Varanus tristis . In: ER Pianka & DR King (Eds.): Varanoid Lizards of the World , pp. 477-487. Indiana University Press, Bloomington & Indianapolis. ISBN 0253343666
  • SS Sweet (2007): Comparative Ecology of Two Small Arboreal Monitors in Northern Australia . Mertensiella 16 ( Advances in Monitor Research III ), pp. 378-402
  • GG Thompson & ER Pianka (1999): Reproductive ecology of the black-headed goanna Varanus tristis (Squamata: Varanidae) . Journal of the Royal Society of Western Australia 82, pp. 27-31

Web links

Commons : Varanus tristis  - collection of images, videos and audio files