It's two metres (6 ft) long, sway-backed and very nonchalant, thoroughly conversant with the dog-deterring properties of wire-mesh.
No, it's not a Nile crocodile; it's a Nile monitor (Varanus niloticus), Africa's biggest lizard.
Like all monitor lizards (called leguaans in South Africa and goannas in Australia), these guys are unnervingly opportunitistic predators. Although I like them pottering around (because they chomp the cobras), I'm a bit nervous that this one may munch the cats too. I'm also surprised the dogs are showing such zeal, as Magic's enthusiasm for monitor-hunting suffered a serious setback one day last summer.
It was a really hot day and I returned from the field to find Magic (my husky cross) missing. However, I could hear muffled barking: high-pitched yaps, sharpened by a note of panic. Bewildered, I followed the sound through the backyard to the small outside toilet. I never use this toilet, but I usually leave the cubicle door ajar. Today it was closed, and Magic was evidently shut inside.
But who would shut her in? When I tried the door, it wouldn't budge. Something heavy was blocking it on the inside. After a great deal of struggling (actually - I'm embarrassed to admit - I had to lie in the dirt, brace myself against a tree and use my feet to push the door in ... oh, my shameful lack of upper body strength), I finally managed to force a small gap. I squeezed through painfully, intending to then move whatever was lodged behind the door. Only once I was inside the tiny cubicle - in the warm, fetid darkness - did I realise that Magic and I were not alone.
Crouched halfway up one wall was an extremely large (2 m/6 ft) monitor lizard. It was eyeing me warily; it's blue forked tongue flicking in and out rapidly.
|Nile monitors (Varanus niloticus) hang out near permanent water. They're gifted swimmers, taking to the water when threatened (hence my toilet?) and using their long muscular tails for propulsion.|
Photo posted on Flickr by Hyper7pro.
Apparently Magic had pursued the fleeing monitor into the toilet cubicle and, in the resulting tussle, one of them had knocked over an old ceramic toilet bowl that was standing behind the door. I don't know how long the pair had been forced to room together (I'd been away about five hours) but judging by the smell – a vile mixture of dog and monitor excrement - it had been a while.
Moving the toilet fixture proved challenging. It was too heavy to drag, so I had to use my feet again. But sharing a tiny cubicle with a highly stressed and impressively armed lizard, along with a large and anxious dog, was unpleasant enough without having to sit on the floor with them. The monitor, now hissing and puffing ominously, responded to my movements by lurching across the cubicle in a long-clawed scramble. Magic, I noticed, leapt out of its way with great alacrity. The creature came to rest on top of the cistern, puffing threateningly and lashing its hefty tail back and forth, alarmingly close to my face. Despite these impediments I eventually managed to shove the toilet fixture a few inches further from the door, and Magic shot out. The monitor was equally keen to leave, although it was kind enough to let me to go first.
Magic seemed a little traumatised after this encounter (to be honest, so was I) but, in retrospect, she may simply have been feeling ill. It's now known that monitor lizards have special, venom-producing glands in their mouths. An MRI scan of the world's largest monitor, the Komodo dragon, (don't ask how) revealed six venom glands in its lower jaw, each drained by a duct leading to between the teeth. Researchers have detected venom in at least three Aussie species, but I don't think anyone has yet looked at the African monitors.
Monitor venom is a heady cocktail of ten toxins, seven of which are also made by snakes. Mixed with copious saliva and administered by a bite, the poison prevents blood clotting and dilates blood vessels, lowering blood pressure and inducing shock. When researchers injected rats with monitor venom, they went completely still (the rats, not the researchers... although, thinking about it, the researchers probably deserved it more).
But don't panic! Monitor bites aren't life-threatening; they secrete only tiny quantities of toxin.
But perhaps what's more interesting, is that while the researchers were trying to figure out where and when venom-production first began, they did DNA tests that revealed that monitors and iguanas (a couple of whom are also venomous) are more closely related to snakes than to other kinds of lizards (such as skinks, chameleons and geckos). Monitors and snakes shared a common great granddaddy (who was, of course, toxic) about 200 million years ago.
Nile monitors are surprisingly sociable creatures. They sometimes team up to pinch crocodile eggs (one lures mum away while the other excavates the eggs) and they often spend the winter months snugged up together, hibernating communally within a large rock crevice in a riverside cliff or koppie. Photo by Michael Ransburg.