Monitors

Monitors - Giants among Lizards

About forty species of monitor lizards are found from Africa, through India and south-east Asia to Australia. The genus to which monitors all belong - Varanus - contains the world's largest lizard, the much-feared Komodo Dragon from Indonesia which may reach three metres in length and has been known to prey on humans. All monitors are similar in appearance, with strong limbs, powerful claws, flexible neck and extended, whip-like tail. None are poisonous, although the Gila Monster of Mexico (the world's only poisonous lizard) is distantly related. Monitors are unique among lizards in having a forked tongue, similar to that of snakes. Just two species occur in Southern and East Africa, but both are impressive reptiles and are frequently seen.

Nile Monitor

The Nile Monitor (also known simply as the Water Monitor) occurs in temperate and warm areas with permanent water and is seldom found far from rivers, lakes or dams. It is an outstanding swimmer and quickly takes refuge to water - usually with a loud splash - when threatened. It is most often seen basking on a rock or overhanging tree branch, and sometimes allows humans to approach quite closely.

The Nile Monitor is a rapacious predator with a varied diet. It is particularly fond of crabs and eggs, and readily plunders the nests of ducks, coots and jacanas, and expends much energy in unearthing the buried eggs of terrapins and crocodiles (when the "nest" is unattended!). Juveniles feed mostly on insects and frogs. Adults are preyed upon by crocodiles and pythons, less often by leopards and eagles. Youngsters have a high mortality rate, with predatory fish, herons, snakes and even adults of their own species taking a heavy toll. The maximum length on record is 2.4 metres, but well over half of this length was tail!

Termites incubate the young

In a unique example of insect-aided reproduction, the female Nile Monitor lays her clutch of eggs in the active mound of termites. After the first spring rains, she digs a deep hole in a suitable mound, deposits her eggs - up to 60 - and then scraps some of the soil back to cover them. This rude intervention is quickly attended to by the termites which go about the mound restoration process with vigour. Within a few days the cavity is completely sealed and the eggs then develop - free from any risk of predation - in a living incubator which maintains a constant temperature and humidity. Depending upon environmental conditions, it may take up to a year for the young to emerge - timing their hatching and "escape" with the following season's rains which sufficiently soften the baked exterior of the termite mound.

Tree, rock or savannah?

The "other" monitor lizard in East and Southern Africa is known variously as the Tree Monitor, Rock Monitor, Savanna Monitor or White-throated Monitor. Any of these names is appropriate (except "White-throated", since not all individuals show this feature), but its propensity for climbing trees - even in rocky areas - makes the first name the most sound.

This is a slightly smaller animal than the Nile Monitor, but still an impressive creature well able to look after itself. It has a stockier appearance and proportionately shorter tail than the Nile Monitor, and also differs in having "swollen" slit-shaped nostrils set close to its eyes. Beetles, grasshoppers and land snails are common prey but it will eat anything that it can overpower and readily scavenges from carrion. The Martial Eagle and honey badger are its two most feared predators.

Unlike the Nile Monitor, which always lays its eggs in an active termite mound, the Tree Monitor does so only occasionally, preferring more often to just dig a hole into moist soil.

Fashion victims, chicken-like flesh

The fine skin of monitor lizards have been valued for centuries, being used in the manufacture of shoes, belts and garments. Countless thousands have been slaughtered for this purpose - and the carnage probably continues with those species occurring in south-east Asia. Legislation protects all Varanus species in Africa, but the "tasty, chicken-like" flesh is much sought after by rural folk who must account for large numbers.

What's in a name?

In South Africa, monitors are often referred to as "leguaans" which is probably a corruption of the word "Iguana" - a family of spine-crested, vegetarian lizards to which they are not closely related. Similarly, the Australians sometimes refer to monitors as "goannas". Interestingly, the name "monitor" may also be a case of mistaken identity: common in Egypt, they became known by the general Arabic term for lizards, ouaran. Pronounced waran, this was apparently confused by German naturalists for warnen, which was interpreted as "warning lizards". This was then Latinized to monitor and has given rise to some authors attempting to explain the name by the lizard's alleged habit of keeping a look out, or giving warning of the presence of crocodiles!

Where to see monitors at CCAfrica properties

Both Nile Monitor and Tree Monitor can be seen at just about all of the CCAfrica properties, as they are common and widespread throughout the eastern side of Africa. Some of the largest Nile Monitors are to be found in the Grumeti River of the western Serengeti and a stay at Grumeti River Camp in Tanzania is likely to provide great sightings.

A boat cruise on the Zambezi at Matetsi Water Lodges in Zimbabwe or the Mzinene River at Phinda Private Game Reserve in South Africa will also provide good views of both adult and young Nile Monitors.

The Tree Monitor is frequently encountered at the South African lowveld lodges of Londolozi Private Game Reserve, Bongani Mountain Lodge and Ngala Game Lodge.

Further Reading
Branch, B. 1998. Field Guide to Snakes and Other Reptiles of Southern Africa.
Struik, Cape Town.

Rose, W. 1950. The Reptiles and Amphibians of Southern Africa.
Maskew Miller, Cape Town.

Berra, T. 1998. A Natural History of Australia.
Academic Press, San Diego.

Patterson, R and A. Bannister. 1987. Reptiles of Southern Africa.
Struik, Cape Town.

Posted: Other by CC Africa, Date: 21 November 2006