Steppe monitor
| Steppe monitor | ||||||||||||
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Steppe monitor ( Varanus exanthematicus ) |
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| Varanus exanthematicus | ||||||||||||
| ( Bosc , 1792) |
The steppe monitor ( Varanus exanthematicus ) is a native of Africa representative of the monitor lizards ( Varanus ). The diurnal, ground-dwelling species prey on various invertebrates , but small mammals, young or sick birds as well as eggs and carrion are also eaten. In the dry season it has a rest period. The steppe monitor is probably the most common monitor in terraristics . Pregnant females are often caught, their eggs incubated and the young are raised in so-called monitor farms. After some of them were exported for the pet trade at an early stage, they are then sent to the leather industry.
features
The steppe monitor is a stocky, stocky lizard with a large head and short tail. The nostrils are slit-shaped and are closer to the eye than to the tip of the snout. In captivity the steppe monitor reaches a total length of up to 1.5 m; in nature, however, specimens over 1 m in length are rare. The tail length is about 0.9-1.2 times the head-trunk length . According to a study, 31 adult specimens in Ghana had an average head-torso length of 32 cm (spectrum 23.7-47 cm), the weight averaged 709 g (spectrum 300-1698 g).
The body is brown, sometimes gray or cloudy orange, and shows a variable pattern of light, dark-edged spots on the upper side of the body. These are occasionally arranged in bands or as a mesh pattern. The tail is either uniformly colored or has indistinct, dark banding.
The supraocularia are not enlarged, the other scalps are large and irregularly shaped - they become larger towards the neck and the scale shape approximates more of an oval. Around the middle of the body there are 81-103 rows of scales, from the throat to the base of the hind legs there are 58-73.
The steppe monitor looks very similar to the white-throated monitor ( Varanus albigularis ), there is a risk of confusion.
distribution and habitat
The steppe monitor lives in grasslands, forests, the steppes of the Sahel and, more rarely, wooded river banks in sub-Saharan Africa north of the equator. It does not inhabit rainforests, but it can also be found in agricultural areas and urban areas. The species rarely occurs above 800 m above sea level. It is in the states of Benin , Burkina Faso , Cameroon , Central African Republic , Chad , the two Congo states, Gambia , Ghana , Guinea , Guinea-Bissau , Ivory Coast , Liberia , Mali , Mauritania , Niger , Nigeria , Senegal , Sierra Leone , Sudan and Togo detected.
Way of life
behavior
The steppe monitor is a ground dweller and like all monitor monitors is diurnal. To protect against heat, from enemies and at night, steppe monitors hide in hollow tree trunks or in burrows dug by other animals - young animals in Ghana apparently often in the burrows of the large cricket brachy troops , older animals usually take over burrows from termites or mammals. The animals in Senegal, examined by the French herpetologist Cissé in the 1970s, left their burrows at around 9 a.m., hid again between 2 p.m. and 3 p.m. and, after further activity, went to sleep at 5:30 p.m. Seasonal activity is characterized by the alternation between dry and rainy seasons: In the rainy season and especially in the breeding season, the animals are particularly active, while activity is limited in the dry season, and at the end of the dry season the animals can stay in for up to a month linger in hiding.
Although this species can also climb, it is not as skilful as other species of monitor lizards, and comparatively seldom looks for trees as shelter or foraging. Like most monitor lizards, he is a good swimmer, and like all monitor lizards, a loner.
nutrition
The steppe monitor is not a fussy eater. The prey is located with a flick of the tongue and actively pursued on the ground, or the fall leaves are rummaged through with the snout or prey is dug up. Steppe monitors also penetrate mammalian burrows and prey on the inhabitants. The prey is brought to the surface and swallowed. On a good day, a yearling preyed on up to 18% of its body weight in food.
The food spectrum includes numerous invertebrates and vertebrates. In Senegal, 28 specimens were examined by Cissé for their stomach contents: The animals apparently fast between mid-November and February, this is the driest time of the year. In the remaining months, millipedes , beetles , caterpillars, grasshoppers, lizard eggs, snails and scorpions were detected as prey.
Reproduction
Like all African monitor lizards, the steppe monitor produces large clutches; the young hatch quickly. In Ghana, mating and oviposition occur in November and December. For the laying of eggs 20-25 cm deep and 30-50 cm long burrows are created, which are then filled with soil. Four examined nests in Ghana had 6-29 eggs, an average of 18 eggs. The young hatch there in the early rainy season, from March to April; in particularly dry years, however, the young can hatch later. They then dig their way back out through the roof of the nesting chamber. 67 young animals in Ghana were measured, they had an average head-trunk length of 9 cm and a weight of 6.2 g. The young animals in Ghana seem to have a special relationship with the cricket Brachytrupes membranaceus : They mostly inhabit the burrows of the cricket, and as soon as the young monitor lizards are large enough after a few weeks, Brachytrupes becomes the most important prey animal.
Natural enemies
Steppe monitor lizards are hunted by snakes, birds of prey and young animals also by other monitor lizards. The steppe monitor is also attacked by ticks of the genera Amblyomma and Aponomma .
Systematics
It was first described in 1792 by Louis Augustin Guillaume Bosc , who called the species Lacerta exanthematica and thus assigned it to the lizards ( Lacerta ). The steppe monitor entered the genus Varanus in 1820 by Blasius Merrem , who also founded this genus in 1820. Within the genus Varanus , the steppe monitor is assigned to the African subgenus Polydaedalus . The subspecies V. e. ocellatus is no longer recognized today.
Steppe monitors and humans
The steppe monitor is one of the most heavily populated monitor species, which is particularly widespread as a pet. Every year around 100,000 animals are taken from nature and sold alive. These wild catches are sold very cheaply and are often bought by ill-informed buyers. As a result, many animals do not survive to sexual maturity due to improper husbandry, or become obese and lethargic due to lack of exercise and improper diet (too many rodents, raw meat, dog food). Waran breeders stated that they could meet the need for steppe monitor lizards with their offspring, but that this was not worthwhile due to the low prices of wild-caught animals. On the other hand, specialized monitor farms are now developing in Africa, which could reduce the pressure on wild populations in the future. In order to keep steppe monitors in a species-appropriate manner, a very large, structured terrarium that is adapted to the climatic conditions in nature is required. The diet must be largely insect-based, not fatty foods like dog food or raw meat.
The hides of the steppe monitor are also traded; the extent of this persecution likely exceeds the pressure from the pet trade. Overall, the steppe monitor is still common and widespread and is therefore classified in the IUCN's Red List of Endangered Species as not threatened ( least concern ).
Because of its easy availability, the steppe monitor has very often been a research object for physiology , anatomy, etc., and a kind of " model organism " for other species of the genus.
swell
- D. Bennett: Varanus exanthematicus. In: ER Pianka & DR King (Eds.): Varanoid Lizards of the World. Indiana University Press, Bloomington & Indianapolis 2004, ISBN 0-253-34366-6 , pp. 95-103.
- ↑ a b c d e f according to Bennett (2004) and the literature cited there
- ↑ a b c Varanus Exanthematicus in the endangered Red List species the IUCN 2010. Posted by: Bennett, D. & Sweet, SS, 2009. Accessed February 3, 2011th
- ↑ D. Bennett (2000): Observations on Bosc's Monitor Lizard (Varanus exanthematicus) in the Wild. In: Bull. Chicago Herp. Soc. 35 (8), pp. 177-180.
