I came around a corner on the paddyfield exercise track and there she was, 30 metres ahead, facing my way. Six feet long, she (as I fancy) stood shaking an equally lengthy rat snake with its head already in her mouth. The snake likewise twisted and shook itself in a desperate and doomed struggle to get free. As it did so, the water monitor seemed to slurp it in like a grey-black strand of writhing vermicelli. It went down the hungry gullet, thrashing all the way. The assailant was probably not actually slurping. Her rearward-curving teeth help her lift her front mouth forward on her prey without losing her grip.
In all my rambles round the suburbs with frequent monitor sightings, I have observed predation only four times, all fairly recently. Around the time of the rat snake incident, I filmed a large monitor splashing through the flooded paddy with a still-struggling cormorant in its jaws. On a wooden bridge over a paddy stream I videoed a juvenile dismembering a dead rat, holding it tight with its fearsomely clawed forelimbs while pulling on it with its mouth. Bon appetit!!
Lanka’s Asian Water Monitor (a.k.a. ‘kabaragoya’) ranges also through northeast India, Bangladesh, Burma, the Malay Peninsula, Indochina, Philippines and Indonesia. It swears by what could be called its omni-carnivorous diet, consuming any animal matter it can get its jaws on, including insects, spiders, beetles, centipedes, millipedes, molluscs, frogs, fish, crabs, turtles, lizards, even croc eggs and babies. It eats even venomous snakes, probably with help from some inbred immunity. It can climb well enough to pilfer bird nests. It will scavenge carrion, including human corpses. With its scavenging, it cleanses the environment of rotting meat, usually not human corpses, fortunately. Rapid swimmer and runner, it excels in chasing prey down, though it cannot breathe while running.
Poor in hearing and night vision, it profits from superb daytime eyesight and awesome sense of smell. Excellent distance vision helps it spot prey and predators hundreds of metres away. It sees ultraviolet colours invisible to us. Under the hide on top of its head sits a poorly-developed ‘third’ (or ‘pineal’) eye), allowing it to detect directional brightness. It may function in telling time of day and in steering through unfamiliar territory by feeding the sun’s position into mental computations. Its flickering forked tongue detects direction of scent sources by tiny gaps in the time at which molecules strike its left and right sides. This allows it to follow a scent trail toward prey or potential mates.
That flickering forked tongue clues us into its family situation. Monitors find their closest living relatives in snakes, whose tongues look and function similarly. Snakes and monitors together form the biological order ‘squamates.’ Snakes diverged from pre-existing monitors maybe 100-150 million years ago, evolving either from earth-burrowing species or ones that spent lots of time in water. Either way, they gradually lost their limbs to a slithery form of locomotion. Intermediate forms with vestigial hind limbs appear in the fossil record. Some contend that water monitors represent snakes’ closest non-snake cousins.
Monitors in general sport the highest metabolisms among all reptiles, though they remain cold-blooded of course. With most reptiles, unified heart ventricles mixing high- with low-oxygen blood excel neither at renewed oxygenation in the lungs nor high metabolism in the working body. Mid-oxygen blood cannot maximally absorb fresh O2 in the lungs like low-oxygen blood can and also cannot metabolize as rapidly in the working body as high-oxygen blood can. As with crocodilians, only more so, monitor mammal-mimic hearts with dual ventricles keep low-oxygen blood pumped to lungs from mixing with high-oxygen blood pumped to working body. Lungs absorb oxygen richly while concentrated high-oxygen blood facilitates rapid metabolism in the working body.
Monitors exist today as some 80 distinct species, all within a single genus. Various species range from southern Japan, through China, across southern Asia and into Africa. Half their species appear in Australia, monitor capital of the world. That surprising continent once harboured the largest monitor ever inventoried, clocking perhaps as much as seven metres in length and proliferating as top predator for more than a million years. Its scrumptious smorgasbord featured giant kangaroos and other mega-marsupials until it fell extinct 50,000 years ago upon arrival of humans, who may have hunted it into oblivion or out-competed it for prey, much of which also fell extinct.
Today’s largest monitor, Indonesia’s Komodo Dragon, originated in Australia, which it once shared with the now-extinct giant before migrating through the islands to its current dry and isolated homes. It famously takes down large prey like deer and buffalo, aided by venomous saliva delivered in its bites. Toxic anti-coagulants produce non-stop bleeding and shock from sudden pressure drop. Victims who don’t die quickly often flee their tormenters into faeces-laden ponds and die from resulting infections, to be devoured as carrion by gangs of patient Dragons. Ravenous Komodos consume prey in their entirety. Hides, hooves, even bones go down the hatch. Baby Komodos spend a lot of their time up in trees, avoiding adults who will eat them if they can.
Komodo males rear up on hind legs against one another in epic fights over territory and mating privileges. When males grow scarce, female Komodos can produce offspring without mating, a phenomenon called ‘parthenogenesis.’ Those invariably male offspring grow to maturity in nine years or so, providing partners for renewed rounds of sexual reproduction. Despite this reproductive magic, Komodos now rank as an ’endangered’ species (facing very high risk of imminent extinction). As few as one thousand individuals may be alive today. Their restricted five-island range is one problem and they face burgeoning human populations, shrinking forest and expanding agricultural encroachment on their habitat.
Asians happen to be the second largest monitors inhabiting our planet these days and they probably maintain the most extensive range of any, though our local subspecies lives only in Sri Lanka. Their worldwide conservation status stands as ‘least concern.’ With their highly flexible diets, they thrive even amidst heavy human habitation. Their excellent protection from predation stems from sharp teeth and claws, along with long whippy tails and bone-flecked hides. Youngsters perch on trees to avoid crocs, jackals and leopards.
The largest monitor ever measured, at 3.2 metres, lived in Kandy Lake. They look scary but water monitors rarely attack humans unprovoked. They prefer avoidance. Anyone unlucky enough to get bitten by one through some mishap can expect some irritation at the wound site as their saliva is mildly venomous. Severe harm is unlikely because the venom is weak compared with Komodos.
Like their Komodo cousins, water monitor males fight one another. On land, they will get up on hind legs, grappling with forelimbs, throwing one another to the ground and executing various flips and twists. I’ve seen this on video, but not live. I once witnessed two of our more smallish land monitors (Bengal Monitors, a.k.a. ‘thalagoya’) fighting just like Komodos, up on hind legs, grappling, tossing and tumbling on a brutally hot, sunny paddyfield. It looked like they might be contending for a spot of shade under a small tree but something more consequential was probably at stake. After several minutes, one of them backed into a stream and swam away. Yes, land monitors can swim. Like their larger island cousins, they too are fearsome hunters. At Sigiriya this past April, some of us watched a land monitor snatch and carry a hefty bullfrog, which we could hear squealing, its eyes wide in terror. What to do, no?
As it happens, I have witnessed water monitors fighting, not on land but in water. One day near the lake separating Pelawatte from Thaluwatugoda, I watched one swim out from the island toward another swimming the opposite way. They tossed each other around for several minutes, each trying to hold its adversary under water. One finally swam away quickly. Such behavior can be misinterpreted by the misinformed. An unintentionally amusing video shot by credulous tourists in Thailand purports to capture two monitors mating in some water. But here’s the thing: monitors, even water monitors, don’t mate in water (except possibly in rare situations when they can touch bottom and cool themselves at the same time) and they certainly don’t mate face to face. Those lizards on camera were making war, not love. One was pinned under the other, losing power, possibly on the verge of running out of breath. Female water monitors will actually take to water when they wish to avoid a mate-seeking male.
Water monitors confront human exploitation in some parts of their range. Forest people harvest their meat, fat and eggs. In commercial trade, their skins prove useful for crafting fine shoes, belts and handbags. Sri Lanka bans any such usages under its Fauna and Flora Protection Ordinance. But a roadside attraction between Minneriya Park and Polonnaruwa raises questions. A local guy who loves water monitors accepts contributions from visitors who watch him feed them and sometimes get them to do little tricks. They cruise a bayou near his home and visit his compound regularly. The Ordinance bans taking or controlling reptiles without a license to do so. A sign on the road indicates that the operation is government-approved. The place was closed due to drought the day I tried to visit with family and friends back in April. My intended visit would seem to make me an accomplice. I’m not sure how I feel about such a small operation, one that is apparently duly licensed. Visitors may learn to appreciate monitors. But would it not be troubling to see this replicated elsewhere, perhaps at larger scale?
Writer, lawyer and former law professor, Mark Hager lives with his family in Pelawatte.
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