Archives of The Cold Blooded News

The Newsletter of the Colorado Herpetological Society

Volume 32, Number 5;   May, 2005

Monitors

by Shari Anderson

Monitors are a diverse and unique group of lizards that range from the well-known giant, the Komodo dragon (Varanus komodoensis) at 10 ft, to the tiny short-tailed monitor, (Varanus brevicauda) of the western Australian desert at 9 inches. While size, coloration and habitat usage vary from species to species, all monitors are active carnivores with the same basic body design of a stocky body, well-muscled limbs and a powerful tail.

Geographically, monitors range across Africa, the Middle East and Indian subcontinent into SE Asia, the Indonesian archipelago and all of Australia. There are around 50 species, over half in Australia and new species are still being discovered. Monitors exploit a wide range of habitats from near deserts, grasslands and other marginal areas to lush tropical forests. They thrive in terrestrial, arboreal and almost aquatic life-styles.

Although some species like the tree monitors and water monitor will exploit specific habitats, all monitors are adept at digging, running, swimming & climbing. Some species, like the Komodo dragon, will be primarily arboreal as juveniles and then spend increasing periods of time on the ground as they grow and are able to hold their own with their conspecifics. Larger Komodos often consume smaller dragons, usually at communal feeding sites. And while most monitor species have been found to find culinary favor with their smaller brethren, Komodos seem to engage in this behavior more frequently.

The diet of varanids in the wild is as varied as their habitats. The African species, including the savannah (V. exanthematicus) and white-throated monitors (V. albigularis), will take venomous snakes, mammals, birds, other lizards, eggs of any kind, young crocodiles, insects and carrion. Species that favor habitats close to the water include crabs, fish, prawns, frogs and turtle eggs in their diets. Most species are opportunistic and will readily consume any form of animal protein when the situation arises. And yes, while the Komodo has gotten the most press for taking the occasional tourist and villager, the water monitor not infrequently includes human corpses on its menu and even perhaps serves its local community as a scaly sanitation worker.

All monitors are egg layers with clutch sizes ranging from 2 to 60. While most excavate holes to lay their eggs in, several species, including Rosenberg's monitor (V. rosenbergi) from Australia and at least 2 of the African species, the savannah and white-throats, have been known to use termite mounds, which provide the perfect temperature & humidity for monitor eggs, plus provide the first meal for hatchlings. And the mounds created by the Megapode birds for their eggs are also employed by female Komodos.

Depending on which authority you read, monitors may or may not have four chambered hearts like mammals and unlike other reptiles, but their higher metabolism isn't in doubt. They are active diurnal predators that can cover many square miles foraging for food, as revealed through radio tracking. And they are the only lizards that can breathe and run at the same time, which means that while either pursuing prey or evading other predators, monitors can run faster than a man over a not-too-short distance.

Fossil evidence shows that monitors appeared about 90 million years ago and occupied what is now North American, Asia and Africa when the continents were still joined. DNA studies suggest monitors first evolved in SE Asia and 4 subsequent groups diverged about 40 million years ago. The Australian branch includes many of the smaller species, like ackies (V. acanthurus) and the Timor monitor (V. timorensis); the Indo-Australian branch groups together the largest species, including the Komodo, lace monitor (V. varius) and crocodile monitor (V. salvadorii); the Indo-Asian branch groups together such diverse species as Gray's monitor (V. olivaceus) and the water monitor (V. salvator); and the African branch includes the smallest number of species, including the savannah and white throat. The last group has been called the most primitive. A long-standing guessing game of whether the snake evolved from monitors or vice-versa (based on tongue morphology) has been put to rest by Penn State researchers. Using DNA to look at genetic relatedness rather than anatomical structures, they have concluded another and as yet unidentified lizard line is responsible for the origin of snakes.

A fossil varanid, Megalania priscus, lived up until 25,000 years ago in Australia and may have interacted with the first human settlers. It dwarfed the Komodo at 26 feet and weighed up to 2 tons. Today, in the Australian outback, infrequent sightings of an extremely large monitor-like creature have given rise to a legend that Megalania survives, just like the Loch Ness monster legend of Scotland.

Monitors have played a role in human culture probably since we came down from the trees. Called goannas in Australia, monitors have always played an integral part in Aboriginal culture and a key role in their creation myth. The earliest depiction of monitors in art appears in the cave paintings of Bhopal, India from about 10,000 years ago. They are surprisingly absent from Egyptian art, probably because monitors ate crocodile eggs and young crocs. Crocodiles were considered sacred to the Egyptians, and their god, Sobek, is depicted with a crocodile head and human body. The Tuareg tribesmen of Morocco believe the desert monitors (V. griseus) harbor the souls of their ancestors and are therefore regarded as sacred. Throughout much of their range, monitors are regarded as venomous, poisonous, or at least, bestowers of bad luck. My favorite story concerns "weremonitors" of Southern Thailand where people develop forked tongues (no, I have never been anywhere near Thailand). India, perhaps as the home of the Jains, who respect all life, has many interesting tales involving monitors, including one that calls monitors good luck charms for bachelors. Naga Panch ami is a serpent festival celebrated in India that includes tying monitors to poles and smearing them with vermilion. The animals are released after the ceremony, but I'm sure are much more wary of humans.

Monitors have always been exploited for food and hides. Today, the pressure also includes habitat destruction, habit degradation and the demand from the pet industry. The good news is that the monitor has entered into the mainstream of human consciousness through zoos and their increasingly successful breeding programs; increased tourism and the creation of national parks, like Komodo National Park in Indonesia; increasingly successful husbandry of captive animals, both in public & private hands; increased knowledge through expanding research programs and population studies and a general heightened awareness that all species are part of the global community and the loss of even one individual can affect all of us.

In the relatively short span of 17 years since I acquired my first savannah, there has been a veritable explosion of books and magazine articles on varanid husbandry and virtually all aspects of captive care. There was almost nothing published about savannah monitors in 1987. Now you can find the exact temperature, humidity and length of time to incubate most species of monitor eggs. When I first started thinking about writing this article, I knew I couldn't begin to say anything comprehensive about monitor husbandry or even come up with a one page care sheet. They all require such specific care that I wouldn't know where to begin. On one hand, they all require extra heat, lots of water, strong caging, and specialized diets. Yet their diversity makes most other common statements beyond those listed null & void. Different species have been labeled shy, aggressive, hissers -but not biters, tail whippers - but not biters, biters (sooner or later they all bite), psychos with ADD or couch potatoes. And what's true for one individual within a species may not be true for the next individual.

After acquiring my second or third savannah and still feeling like I had a lot to learn in the husbandry department, someone in the society gave me a 16 page document that he said contained everything I needed to know about savannahs. There were pages & pages describing morphological characteristics, like postocular stripes and 'small nuchal scales' - but no information on common sense, daily husbandry. What good is it to know what subspecies you have, based on the number of transverse rows of ventral scales, if you can't get that animal to eat? Raw information can be useless unless tempered with common sense and hands-on experience.

And nothing works as well as hands-on experience. A monitor has a wide variety of facial expressions - yes it does, even without lips and eyebrows. Couple that with body language & hands-on experience and it is possible to read your animal like a book. Of course, it's still a wild animal that can be unpredictable - that merely puts the sparkle in the relationship. But spend a lot of time with an animal and the relationship - on both sides- can become downright domestic. I have learned that when a savannah is content, its closed eyes will bulge out. The more relaxed, the more convex they become. If an animal's eyes (closed or open) are concave, it's not a happy camper and fingers are much more likely to be bit. And body language can vary greatly from species to species. Some of the body language between savannahs and black throats is identical; some is totally different. I assumed (never assume) that all their traits were similar and I got bit. I know now that his warning signs were clearly present, but at the time, I hadn't learned his dialect yet.

The one thing that monitors demand in a captive situation is respect. Look into their eyes and you will instinctively recognize that 'someone is home'. Scientists are now recognizing that monitors possess an intelligence and even 'culture' that is closer to mammals than other groups of lizards. (Something known for decades by zoo keepers & owners.) Respect them, find out everything you can about the species, throw in a bucket of common sense and you can't help but be captivated by them.

I have shared my life with monitors for so long that I really can't remember what life was like before them. I take their intelligence and curiosity as welcomed, even expected facets in my daily life. A passion for all things varanid has led me down a most curious rabbit hole that has become irresistibly captivating as the years have flown by. My interest in monitors also pushes me to help anyway I can, so I end this with a request for financial help: Gray's monitor, known chiefly as the only monitor that includes fruit in its diet in the wild, is in real danger of extinction. Known in the local dialect as a butaan, it inhabits the ever-decreasing forests of Polillo Island in the Philippines. Ninety percent of its habitat has been degraded. It is also an esteemed food item and under constant hunting pressure. Money donated to the study (started in 1999) will continue the study's non-invasive work, including the use of camera traps and radio tracking, train local Filipino biologists and protect butaan habitat. Please check out the web site: www.varanusweb.com, then click on 'Help V. olivaceus' in the links box. Please consider making a donation that can save species and make a real difference in the future.

Recommended Books:
Auffenberg, Walter. The Behavioral Ecology of the Komodo Monitor. 1981.
Bennett, Daniel. Monitor Lizards Natural History. Biology & Husbandry. 1998.
Bennett, Daniel & Ravi Thakoordyal. The Savannah Monitor Lizard. 2003.
Green, Brian & Dennis King. Goanna. The Biology of Varanid Lizards. 1993.
Murphy, James B. et al (ed). Komodo Dragons. Biology and Conservation. 2002.
Steel, Rodney. Living Dragons. 1996