Varanus exanthematicusSavannah Monitor

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Geographic Range

Varanus exanthematicus, or the savannah monitor, is found throughout most of Africa south of the Sahara (Steel 1996). It is found in west and central parts of Africa and southward toward Zaire (Rogner 1997).

Habitat

Varanus exanthematicus occupies a variety of habitats in Africa. Its preferred habitat is the savannah, but they have adapted to other habitats as well. The lizards have adapted to habitats such as rocky dessert type areas, open forests and woodlands. They are not found in the rainforest or deserts (Steele 1996).

Physical Description

V. exanthematicus has five subspecies (Steele 1996). This is why the measurements and descriptions vary in much of the literature. Varanus exanthematicus is a thick, stockily proportioned monitor. It has wide head, short neck and tail. The tail tapers and has a double toothed crest. Savannah monitors can reach lengths of up to 1.5 meters (Steele 1997). Other sources say they can reach sizes of up to 2 meters (Rogner 1997). Small sub-equal scales cover the cranial region of the animal. The abdominal scale rows number between 60 and 110. The caudal scales of V. exanthematicus are keeled.

Varanus exanthematicus is gray to brown in color. There are rows of circular, dark edged yellow spots across the animal's back. The tail has alternating brown and yellowish rings. The under body and inside of the limbs is a yellowish color. The tongue of V. exanthematicus is snake-like and blue in color (Steele 1996). (Rogner, 1997; Steele, 1996)

  • Range mass
    1 to 70 kg
    2.20 to 154.19 lb

Reproduction

The breeding season for V. exanthematicus is the same as the feasting period. They feast and breed during the wet season (Steele 1996). When a male finds a mate he will follow her around relentlessly, occasionally biting her on the neck and scratching her neck and legs with his claws. Eventually the female allows the two to mate.

The female will dig a nest herself and lay 20 to 50 eggs (Rogner 1997). Other sources say that the female digs nests that are 15-30 cm deep and only lays up to 15 eggs (Bennett 1999). Some females will lay their eggs in termite mounds. The eggs of V. exanthematicus have an unusually high hatch rate of 100 % (Bennett). Incubation of the eggs takes five to six months and the eggs hatch out in March (Rogner 1997). In the sandy farmlands of Ghana it has been reported that up to 55 babies can be found in an area of 150,000m2 during August and September. The juveniles grow the quickest during their first two months (Bennett 1999).

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    12.7 years
    AnAge

Behavior

Male V. exanthematicus are very territorial and will defend their territory very aggressively. If two males come across each other they will try to intimidate each other by making threats. If this does not work, they will wrestle and their bodies will become intertwined as they bite each other. They can inflict severe injuries upon one another (Rogner 1997). When cornered, V. exanthematicus can be very aggressive. It will hiss loudly, thrash its tail and get ready to strike. If all this does not scare off a predator, some have been known to play dead (Steele 1996).

Savannah monitors are most active during the day. They often seek shelter in burrows during the hotter parts of the day. Varanus exanthematicus use their tongue to sense their environment when they are out during the day. They flick their tongue an average of 20 to 40 every two minutes. After they have attacked and bitten prey the tongue flicking rises to as many as 160 flicks every two minutes. This helps the animal to find the injured and escaping prey (Steele 1996).

Food Habits

In the wild the diet of adult V. exanthematicus consists of small mammals, birds, snakes, toads, lizards, and eggs (Steele 1996). Other source contradict this finding and say that there is no proof that V. exanthematicus eat any type of vertebrate (Bennett 1999). Many adults also consume large quantities of snails. Full grown V. exanthematicus have teeth that are quite blunt to help them crack and eat snails. The jaw has evolved to put maximum leverage at the back of the jaw to crush snail shells (Steele 1996). Adults will also eat carrion if they come across it. Juvenile V. exanthematicus are mainly insectivores because they lack the teeth to eat snails. Savannah monitors have evolved a way to eat poisonous millipedes. The lizard will rub its chin on the millipede for up to fifteen minutes before eating it. It is believed to do this to some how avoid the distasteful fluid that the millipede excretes in it's defense (Steele 1996).

Varanus exanthematicus feeding habits revolve around the weather. They use a feast and fast system. They feast during the wet season when food is plentiful and easy to find. During the dry season they live off the fat reserves they built up over the wet season. The wet season last for about eight months. During this time V. exanthematicus can consume up to one tenth of its own body weight in a single day (Steele 1996).

Economic Importance for Humans: Positive

Varanus exanthematicus is very common in the United States in pet store. It is also used in many lizard skin leather products.

Conservation Status

Varanus exanthematicus is listed as a threatened species (Quality Design 1998). In Africa it is persecuted for its skin and as a source of food by the natives. The animal is also exported in great numbers for the pet trade.

Contributors

Doug Diemer (author), Michigan State University, James Harding (editor), Michigan State University.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

native range

the area in which the animal is naturally found, the region in which it is endemic.

threatened

The term is used in the 1994 IUCN Red List of Threatened Animals to refer collectively to species categorized as Endangered (E), Vulnerable (V), Rare (R), Indeterminate (I), or Insufficiently Known (K) and in the 1996 IUCN Red List of Threatened Animals to refer collectively to species categorized as Critically Endangered (CR), Endangered (EN), or Vulnerable (VU).

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Bennett, D. "University of Aberdeen" (On-line). Accessed Oct. 26, 99 at http://www.abdn.ac.uk/~nhi770/monitors.html.

Quality Design, .. 1998. Accessed Oct.25,99 at http://www.pclink.com/dkelly/monitors.htm.

Rogner, M. 1997. Lizards vol-2. Malabar Fl: Krieger publishing.

Steele, R. 1996. Living Dragons. London: Ralph Curtis books.