Black tree monitor
| Black tree monitor | ||||||||||||
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Varanus beccarii (Photo by Greg Hume) |
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| Varanus beccarii | ||||||||||||
| ( Doria , 1874) |
The black tree monitor ( Varanus beccarii ) is an endemic scale reptile (Squamata) from the genus of monitor lizards ( Varanus ) on the Aru Islands . Varanus beccarii belongs to the subgenus Euprepiosaurus , where it is a member of the V. prasinus group. The first description of this monitor species was in 1874 by the Italian herpetologist Giacomo Doria . The specific epithet honors the Italian discoverer of this monitor species Odoardo Beccari (1843–1920).
Appearance and dimensions
The adult specimens of the black tree monitor can reach a total length of 95 cm. The length of the tail, which is round in cross-section, is about 1.7-2.3 times as large as the head-trunk length . This long, muscular tail has evolved into a kind of grasping organ (fifth arm). The color of the whole body is black and without any sign of patterning. In some specimens, the coloration varies slightly to gray under the armpits and on the hips. The large scales of the head are polygonal and smooth. In contrast to the scalp, the scales on the neck and abdomen are slightly keeled. The nostril is located in the middle between the tip of the snout and the eye. Around the middle of the body there are 81 to 86 rows of scales. The difference between males and females is difficult to tell. However, there are a few external differences, such as the head. The adult males usually have a larger head in relation to the females. The animals can best be distinguished from sexual maturity, since the males have two small bumps, their protruding testicles, growing below the base of the tail.
distribution
The black tree monitor is endemic to the Aru Islands . This archipelago is located in the middle of the Arafura Sea , about 150 km south of New Guinea . There the species inhabits the main island Tanahbesar and the surrounding islands Wammer , Kobroor and Trangan .
Way of life
The black tree monitor is one of the few monitor species that live exclusively in trees. From its tail, which has been converted into a grasping organ, one can see particularly well that V. beccarii is a tree dweller. This specialization enables the animals to move faster and better through the branches of the treetops. They live in the tropical rainforests and in the mangrove forests on the coasts of the islands. They mainly eat any type of insect they can prey, preferring to hunt grasshoppers . A large part of the diet of the animals that live in the mangrove trees consists of crabs . It has already been described that Varanus beccarii fetches young birds from their nests and eats them on his forays through the treetops. The males sometimes organize territorial fights and an associated test of strength in order to impress the females or even to defend their territory. Their only natural enemies are large snakes, but they rarely hunt the black tree monitor. Nowadays there are repeated reports of cases where the foxes introduced by humans kill the young of Varanus beccarii . The monitor lizards have not developed a defense instinct against the fox. Therefore, they do not know how to defend themselves when they meet. Because of their tasty meat, they are hunted by the local people.
Systematics
Mertens classified the black tree monitor in 1941 as a subspecies of V. prasinus . After the revision of the V. prasinus complex by Sprackland (1991b), the black tree monitor was raised to species status. Sprackland included the two subspecies V. p. prasinus and V. p. kordensis to form the emerald monitor species ( Varanus prasinus ). The differences in the scaling characteristics had not seemed significant to him. Ziegler and Böhme (1997b) found that the differences between V. p. prasinus and V. p. kordensis are quite pronounced. Therefore they picked up the old taxa again and raised both species to species status. But then they classified the black tree monitor again as a subspecies of V. prasinus . In a study conducted by Ziegler in 2007 to clarify the relationships within the V. prasinus group, DNA tests revealed that the black tree monitor is a separate species.
literature
- D. Bennett: Monitor lizards of the world, world of monitor lizards. Edition Chimaira, Frankfurt am Main 1996, ISBN 3-930612-05-4 .
- W. Böhme: Checklist of the living Monitor Lizards of the world (Family Varanidae). Zoologische Verhandelingen, Leiden 2003, ISBN 90-73239-86-9 .
- B. Eidenmüller, HD Philippen: Terralog - Varanoid Lizards - Monitor lizards and lizards. Edition Chimaira, Frankfurt am Main 2008, ISBN 978-3-89973-356-3 .
- A. Kirschner, T. Müller, H. Seufer: fascination monitor lizards. Kirschner & Seufer Verlag, Keltern-Weiler 1996, ISBN 3-9804207-2-8 .
- R. Mertens: The family of monitor lizards (Varanidae). Senckenbergische Naturforschende Gesellschaft for the work of Robert Mertens, Frankfurt am Main 1997, ISBN 3-930612-13-5 .
- R. Mertens: List of recent amphibians and reptiles: Helodermatidae, Varanidae, Lanthanotidae. (= Das Tierreich / The Animal Kingdom. 79). 2011, ISBN 978-3-11-102474-5 . (Original in: Das Tierreich. No. 79, Berlin 1963, pp. 1–26)
- T. Ziegler, W. Böhme: On the hemiclitoris of the squamate reptiles: Effects on some methods of sex differentiation. In: Herpetofauna. 18 (101), 1996, pp. 11-19.
- Thomas Ziegler, Wolfgang Böhme: Genital structures and mating biology in Squamate reptiles, especially the Platynota, with comments on the system. German Ges. Für Herpetologie und Terrariumkunde, Rheinbach 1997, ISBN 3-9801929-7-0 .
- T. Ziegler, A. Schmitz, A. Koch, W. Böhme: A review of the subgenus Euprepiosaurus: Morphological and molecular phylogeny, distribution and zoogeography, with an identification key for the members of the V. indicus and V. prasinus species groups . In: Zootaxa. 1472, 2007, pp. 1-28.
Web links
- Varanus beccarii in The Reptile Database
- Varanus beccarii on monitor-lizards.net
- Varanus beccarii on mampam.com
Individual evidence
- ^ T. Ziegler, W. Böhme: On the hemiclitoris of the squamatic reptiles: Effects on some methods of sex differentiation. In: Herpetofauna. 18 (101) 1996, pp. 11-19.
- ↑ A. Koch, M. Auliya, T. Ziegler: Updated checklist of the living monitor lizards of the world (Squamata: Varanidae). In: Zoological Bulletin. 57 (2), 2010, pp. 127-136.
- ↑ Harold Cogger, Richard Zweifel: Reptiles and Amphibians. Weldon Owen, Sydney 1992, ISBN 0-8317-2786-1 .
- ^ Description of V. beccarii on mampam.com
- ↑ B. Eidenmüller: monitor lizards way of life, care, breeding. Herpeton, Offenbach 2009, ISBN 978-3-936180-03-9 .
- ↑ Kathryn A. Monk, Yance De Fretes: The Ecology of Nusa Tenggara and Maluku. Periplus Editions, 1997, ISBN 962-593-076-0 .
- ↑ T. Ziegler, A. Schmitz, A. Koch, W. Böhme: A review of the subgenus Euprepiosaurus: Morphological and molecular phylogeny, distribution and zoogeography, with an identification key for the members of the V. indicus and V. prasinus species groups. In: Zootaxa. 1472, 2007, pp. 1–28 (full text)