Rock Monitor
Created | Updated Feb 19, 2013
Rock Monitor
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
This time I feature a reptile, a Rock Monitor, Varanus albigularis. This is Africa’s heaviest and second longest lizard species, reaching 2 m/6’7” in length. The Nile Monitor, Varanus niloticus, is longer, up to 2.4m/8’, but lighter and more slender. Rock monitors are widespread over southern, central and east Africa. They inhabit a variety of habitats, only being absent from open deserts and dense forests. They are quite frequently seen and show little fear of humans. In Afrikaans we call this a ‘likkewaan’; this comes from the term ‘l’iguana’ (the iguana) which Portuguese settlers and explorers called them, although they are not closely related to iguanas. A similar name they’re sometimes called in English is ‘leguan’. The name ‘monitor’ comes from Latin ‘monere’ meaning ‘to warn’, perhaps referring to its threat display.
This large lizard usually walks over the ground with a leisurely, stately gait, its body held high on its sturdy limbs. It can break into a run when threatened, but might also stand its ground, puffing up its body and hissing – the threat display mentioned above. The photo I include is of one we came across in our municipal game reserve; see how thick its neck is puffed up. This one was about a metre in length. We did not want to bother it too much so we did not approach any closer; if we did, might have used its defense strategy, which is lashing out with its powerful tail! I haven’t yet heard of anybody actually being hit by it, but it must be quite painful. It can also bite, which is very painful.
Adult monitor lizards don’t have much to fear; being scaly and tough, only larger predators could harm them. They are often caught and consumed by large eagles like the Martial Eagle, but not much else. Small ones are much more vulnerable. The youngsters might be mistaken for an entirely different species. They are small – still decent-sized for lizards – but have beautifully patterned skins, with bold black and yellow markings. You can still see a vestige of that in the photo, but the patterns fade to a fairly uniform greyish-brown at adulthood. Young monitors are not so frequently seen walking out in the open, but rather clambering around trees and rocky places, where they will hide from predators in holes and crevices. Adults can still climb very well, using their sharp, curved claws to scale trees and rocks. They are adept at raiding birds’ nests. They are opportunistic predators and will eat almost anything they can get. While hunting a monitor will flick its long, pink to bluish, forked tongue out periodically. This tongue is laden with scent receptors, allowing the monitor to smell out potential food sources.
This forked tongue demonstrates the relationship between monitors and snakes. It goes back very far, since the earliest snakes evolved while dinosaurs were still around. But monitors go back even further! They represent an ancient lineage which, as with just about everything, was much more diverse in the past. Most noteworthy was a group that became aquatic and moved back to the sea, the Mosasaurs. They became gigantic, some exceeding ten metres in length: real-life sea monsters. These giant oceanic monitors sadly became extinct along with the dinosaurs, but their land-locked relatives survived. These continued to thrive during the so-called ‘age of mammals’ and in some places remained successful or even dominant predators. The Komodo Dragon, Varanus komodoensis, is the best known example, but there are many other very large monitor lizard species in Australia, Asia and Africa. The largest of all, Varanus priscus which might have exceeded five metres in length, lived in Australia until geologically recent times. It is sometimes called Megalania. Today the genus Varanus includes sixty to seventy known species; though many are large there are also small ones down to as little as 20 cm/8” in length at adulthood, looking much like ordinary lizards.
But monitor lizards are not ordinary. They are in fact very ‘advanced’ in spite of having been around for so long. They are powerful, strongly muscled, and quite active throughout the daytime, except for the hottest parts when they might rest up in the shade. Their high-stepping gait, rather than crawling with their bellies on the ground like other lizards, is an efficient way to move over rough territory while keeping a lookout for food. Their heads are carried on long, flexible necks and can poke into all sorts of cavities in which edible items might reside. Their tongues I’ve already mentioned; another link with snakes is that it now seems that some species like the Komodo Dragon might actually be venomous! At the very least we already know that it harbours a cocktail of bacteria in its mouth that infects and ultimately kills anything that it bites; now it seems that actual venom glands might also be present. These might also be found in other species.
Last but not least, monitor lizards are clever. Their opportunism and versatile behavior allows them to exploit many sources of food, and their brains are amongst or even the most advanced of all lizards’. It’s been demonstrated in tests that they can count up to six and can learn to recognize their keepers. Monitor lizards, especially Komodo Dragons, have also been observed engaging in a variety of playful behaviours in captivity. This is something we still have to wrap our heads around – lizards that play. Most people tend to see reptiles as mindless, instinct-driven brutes, but these lizards clearly are sensitive, not only responding to a great many cues, but also deliberately engaging in spontaneous, creative activity. It is difficult not to think that they are actually having fun while goofing around.
Unfortunately this monitor lizard is becoming a victim of quackery … in the sense that their blood is said to cure AIDS (it does not, I wish to emphatically state). So they are being killed and sold on black markets. This is bad not just for them but also for the people using their blood which does NOT cure AIDS in the belief that it does, sometimes even stopping legitimate anti-retroviral therapy.
