That Reptile Blog » Monitors

Monitor Lizard Care, Natural History and Behavior – An Overview

Frank Indiviglio — Thu, 24 Jan 2013 17:04:03 +0000

Hello, Frank Indiviglio here. I’ve had the good fortune of caring for 15-20 monitor species during my zoo career. From the diminutive Storr’s to the massive Water, Lace, Crocodile and Komodo Monitors, all have instilled in me the feeling that they were, somehow, “more complicated” than other reptiles. Indeed, recent studies have confirmed that they are, among lizards, highly advanced. While some are too large for the average household, several moderately-sized and even dwarf varieties are being bred by hobbyists, and all make fascinating and responsive captives.

The following information can be applied to the care of Savannah, Black Tree, Nile, Merten’s and most other monitors. However, details vary; please post below for information on individual species, and be sure to add your own thoughts and observations on monitor lizard care.

Natural History

Seventy-three monitor species (Family Varanidae) range across Asia, Africa and Australia. Nile Monitors (Varanus niloticus), introduced to south Florida, are a major environmental concern there. Lace Monitors (V. varius) and other large speciesare usually the dominant predators in their habitats. While most dwell in warm regions, Desert Monitor (V. griseus) populations in Kazakhstan are adapted to Vermont-type winters.

The 8 inch-long Short-Tailed Monitor (V. brevicauda), is the smallest member of the group. The Komodo Dragon (V. komodoensis), the world’s largest lizard, occasionally tops 10 feet in length.

Monitors take prey ranging in size from termites to deer. The recently-discovered Sierra Madre Forest Monitor (V. bitatawa) and the Philippine Monitor (V. olivaceus) are unique in consuming fruit, while the Komodo Dragon has attacked and killed people.

In 2005, it was discovered that several species produce venom that affects their prey’s blood pressure and clotting ability.

Five new species, one topping 6 feet in length, have been described in the past several years (please see articles below).

Behavior

Monitors are ever-alert, and easily startled by noises and sudden movements. They vary greatly in personality – some become quite docile, while others remain wary of people. All are very responsive, and quickly learn to anticipate regular feeding times.

Crocodile and Water Monitors (V. salvadorii and V. salvator), and other large species, can be dangerous and are not suitable for most private collections. Adult Water Monitors are, pound-for-pound, one of the strongest animals I’ve ever restrained (I was the Bronx Zoo’s head mammal keeper for a time, and so thought I could handle most anything!). All monitors can inflict severe bites and scratches. The mouth and tail (which is whipped about in self-defense), should never be allowed near one’s face. Operating policies in most zoos require that 2 experienced keepers be present when large monitor exhibits are entered.

New monitor facts frequently come to light. Recently, a Black Tree Monitor was observed using its front foot to extract an insect from a crevice; this behavior has not been documented in any other lizard.

Housing

The Enclosure

Hatchlings and small species, such as the 14-inch-long Storr’s Monitor (V. storri), may be housed in 30-55 gallon aquariums.

Merten’s Monitors (V. mertensi) and others in the 3-4 foot range are best kept in homemade cages measuring at least 4x4x4 feet. Height is an important consideration for arboreal species such as Black Tree Monitor (V. beccarii). Savannah Monitors (V. exanthematicus) and others that approach 5 feet in length need correspondingly larger quarters; modified cattle troughs are a useful option.

The 6-7 foot-long Nile, Lace, Crocodile and Water Monitors require room-sized enclosures with drainable pools.

Predator-proof outdoor cages are the ultimate in “luxury accommodations” (some folks use modified bird aviaries). If a safe, escape-proof room is available, out-of-cage exercise time can make a real difference in your lizard’s quality of life.

Furnishings

Stout branches, wooden shelves and secure hide boxes should be arranged according to each species’ individual needs (please post questions below). A water bowl large enough for bathing is essential; the aquatic Merten’s Monitor should be provided with a large swimming area.

Substrate

Sand is suitable for Desert Monitors and others native to arid habitats, while cypress mulch works well for forest dwellers such as Green Tree Monitors (V. prasinus). I’ve found Crocodile Monitors prone to foot abrasions when kept on concrete, and have since used rubber mats or rubber-coated floors for all large species.

Although impactions due to swallowed substrate are rare, food should be provided in large bowls or via tongs, so that ingestion is limited.

Light

Monitors need daily exposure to UVB light. Use a high-output bulb, such as the Zoo Med 10.0, and position the basking site within 6-12 inches of it. Mercury vapor and halogen bulbs broadcast UVB over greater distances and emit beneficial UVA radiation as well.

Heat

Temperature should be maintained at a range of 79-85 F for most species. Incandescent bulbs should be used to create a basking site of 90-95 F. Ceramic heaters or red/black reptile “night bulbs” may be employed to provide heat after dark. Under-tank heaters may be used to create a warm basking surface.

Provide your monitor with the largest home possible, so that a thermal gradient (areas of different temperatures) can be established. Thermal gradients, critical to good health, allow reptiles to regulate their body temperature by moving between hot and cooler areas.

Humidity

Storr’s and Savanna Monitors, and other desert/grassland adapted species, develop health problems in damp enclosures, while rainforest dwellers such as Blue Tree Monitors (V. macraei) need access to humid and dry areas.

Companions

Males will fight savagely and cannot be housed together, and females sometimes battle for dominance. Juveniles may get along, but they must be watched carefully.

Feeding

Strict attention to diet is essential if you are to succeed with monitors. Nutritional deficiencies can develop quickly, and are difficult to treat. High calcium intake and exposure to UVB light is especially important for young animals.

Small, largely insectivorous species (i.e. Blue and Green Tree Monitors) need a highly-varied diet comprised of roaches, crickets, butterworms, hornworms, super mealworms, wild-caught insects and other invertebrates; pink mice can be offered 1-2 times weekly. Canned snails and grasshoppers, and hard-boiled eggs, can be used to provide variety.

Nile Monitors and similar species fare well on mice and rats alone; whole freshwater fishes are an excellent rodent-alternative for Water and Merten’s Monitors.

Food (other than vertebrates) should be powdered with Tetra ReptoCal or Zoo Med ReptiCalcium. Vitamin/mineral supplements such as Reptivite should be used 2-3 times weekly.

Please check out my posts on Twitter and Facebook. Each day, I highlight breaking research, conservation news and interesting stories concerning just about every type of animal imaginable. I look forward to hearing about your interests and experiences as well, and will use them in articles when possible.

Please also post your questions and comments below…I’ll be sure to respond quickly.

Thanks, until next time,

Frank Indiviglio

World’s Smallest Frogs Added to 2011’s List of Newly-Discovered Amphibians

Frank Indiviglio — Mon, 02 Jan 2012 20:55:03 +0000

Hello, Frank Indiviglio here. Two frog species recently discovered in southeastern New Guinea are smaller than any other 4-legged vertebrate. Within their pea-sized bodies, they pack a brain, lungs, heart, digestive system and most of the other organs that people have…simply astounding!

Tiny Frogs and Fish

The frogs, Paedophryne dekot and P. verrucosa, were collected several years ago, but were only described as new species this year (please see ZooKeys article). Among all the world’s vertebrates, only a single fish, a Southeast Asian relative of the carp (see amazing photo here) is smaller – and the new frogs exceed it in size by only 0.1 mm! Another contender for the title, a leaf-litter frog from Cuba (please see photo of striped frog), is only a tiny bit larger.

Minute Predators and Prey

New Guinea’s new frogs, which have yet to be given a common name, measure 8-9 mm., or 0.3 inches, in length. They inhabit the leaf litter of tropical rainforests, where they are likely on the menu of predators ranging from spiders to small birds. Females produce 2 eggs, but the details of their reproductive biology are unknown.

I’m looking forward to reading more about their lifestyles, especially their diet. Some years ago, I cared for a colony of tiny Kihansi Spray Toads (please see article below) at the Bronx Zoo. They gave birth to live froglets, which were the smallest amphibians I’d ever seen. Some could not even handle a pinhead cricket, and had trouble “wrestling-down” springtails! The new Paedophryne frogs must hunt some very tiny leaf-litter invertebrates.

Diversity Hotspots

New Guinea has provided a treasure-trove of new species in recent years, with over 1,000 new animals and plants – or over 2 each week – described there since 1998. Indonesia is also offering surprises…I’ve had the pleasure of working with some of these, including the gorgeous Blue Tree Monitor (Varanus macraei); please see article below for more info.

India has also made frog headlines, with at least 25 new species described, and several pleasant re-discoveries of frogs believed to have become extinct. They are a wonderfully-bizarre group of amphibians, as is indicated by their fanciful common names – Meowing Night Frog, Elegant Tropical Frog, Feisty Frog and so on. Please see the article below for photos of India’s unique new frogs.

Please also post your questions and comments below…I’ll be sure to respond quickly.

Thanks, until next time,

Frank Indiviglio

New Test for Cryptosporidiosis, an Incurable Disease of Snakes and Lizards

Frank Indiviglio — Tue, 15 Nov 2011 19:38:49 +0000

Hello, Frank Indiviglio here. A decade or so ago, Cryptosporidiosis became recognized as a major concern in captive snake and lizard collections. Caused by a one-celled parasite known as Cryptosporidium varanii, the disease remains incurable to this day. At the Bronx Zoo, where I worked at the time, tests showed that many snakes already in our collection, along with wild and pet reptiles, might be harboring Cryptosporidium. But diagnosis was difficult and errors were common, resulting in the institution of expensive and time-consuming isolation protocols for new and sick animals. So I was happy to learn of a newly devised test that ensures early, accurate diagnosis of Cryptosporidium…it will surely prove useful to pet keepers and zoos alike.

Crypto and the Pet Trade

A number of factors render Cryptosporidiosis as a major concern, including the popularity of reptile pets and the fact that the parasite can be transferred to people. While not often of major concern to healthy adults, Crypto, as it came to be known, is a danger to immune-compromised individuals (please see article below). A recent survey of 672 pets revealed that 1 in 6 of the Corn Snakes and 1 in 12 of the Leopard Geckos tested harbored Crypto in one form or another.

Crypto is the most common cause of a Leopard Gecko ailment popularly known as “Stick Tail Disease”. The parasite dwells in the small intestine, where it prevents proper absorption of food; various bacteria to take hold as well, due perhaps to damage inflicted on the intestinal walls. Loose stools and weakness follow, and the gecko’s thick tail (which stores fat) wastes away to a mere “stick”. Crypto has caused similar problems in Gila monsters, monitors, chameleons and other species.

Crypto is passed in the feces (in a form known as an oocyst) and can remain alive for years until a host is found. Oocysts are difficult to kill other than by steam, undiluted ammonia and certain disinfectants not generally available to hobbyists.

Crypto in Zoo Animals and Wild Populations

Declining populations of many snakes and lizards makes zoo-based breeding programs all-the-more vital. However, Crypto is incurable; the many zoo animals that now harbor it must be isolated, and cannot be bred as the young will likely be infected as well.

The Importance of the New Test

The first Crypto tests, based on fecal samples, were unreliable because the parasite often appeared sporadically, or in minute populations, and so was easy to miss. Also, related parasites infect the foods eaten by snakes and lizards, and distinguishing between the species of Cryptosporidium present was nearly impossible.

Researchers at the University of Veterinary Medicine in Vienna have recently devised a DNA-based test that quickly and accurately reveals the presence of Cryptosporidium parasites (please see article below). The test also allows one to determine whether the parasite is present in the snake or lizard, or entered via the animal’s food.

Caring for Crypto-Positive Reptiles

Early detection is important because there are medications, such as Paromomycin, that can keep Crypto populations low enough to allow the infected reptile to survive. However, treatment is only effective if instituted within a certain time frame.

Crypto-positive reptiles cannot be cured at this time, and will require lifelong treatment and special care. Dr. Kevin Wright of the Arizona Exotic Animal Hospital has written an excellent paper on this subject (please see below); please read it to learn more about caring for such animals and preventing Crypto transmission.

Please check out my posts on Twitter and Facebook . Each day, I highlight breaking research, conservation news and interesting stories concerning just about every type of animal imaginable. I look forward to hearing about your interests and experiences as well, and will use them in articles when possible.

Please also post your questions and comments here…I’ll be sure to respond quickly.

Thanks, until next time,

Frank Indiviglio

2010’s Reptile Discoveries – New Lizard Species and Facts

Frank Indiviglio — Tue, 24 May 2011 13:44:09 +0000

Hello, Frank Indiviglio here. Several newly-discovered lizards and unexpected lizard facts made herp headlines in 2010. From a female-only species to a 6-foot-long, brightly-colored new monitor, each gave us pause to wonder…”what’s next?!

Two Large Monitors

Undiscovered animals tend to be small and non-descript, but not so with Asia’s new contributions to the lizard role call. The Northern Sierra Madre Forest Monitor, Varanus bitatawa, described last year from northern Luzon in the Philippines, is both large – to 6 feet in length – and colorful. Actually, it remained undetected only to herpetologists…local people have been eating it for quite some time. The newly described giant is arboreal and feeds largely upon fruit.

Limited in distribution to the tiny Indonesian island of Sanana, the Sago Monitor, Varanus obor, was described only a month or so after the Forest Monitor. A bright red head lends this beauty its alternate name – Torch Monitor.

Please see the articles below for detailed information on each of these lizards.

Males Not Needed

A biologist dining at a restaurant in southeastern Vietnam thought it odd that all of the many lizards offered for sale (as dinner) in one cage appeared to be of the same sex (the sexes of food market lizards in that region usually differed in appearance). Further investigation revealed not only that the lizard was unknown to science, but that the species was comprised entirely of females that reproduced asexually – in other words, males had been dispensed with.

The new species, Leiolepis ngovantrii, is a hybrid between a lizard that occupies sand dunes and another that inhabits scrub forest. It occupies the transition zone between the habitats of the 2 parent species. Among vertebrates, asexual reproduction is known in fishes, several lizards (including North America’s Whip-tailed Lizards) and the Brahminy Blind Snake (please see photos).

Evolution in Action

Approximately 20% of the world’s lizards and snakes have evolved the ability to bear their young alive (all are believed to have “started out” as egg-layers). The passage of millions of years, however, has hidden the process and left us to surmise what may have happened.

But we may soon know more. It seems that Australia’s Yellow-Bellied Three-Toed Skink, Saiphos equalis, may be in the process of changing from an egg-laying to a live-bearing lizard! Populations in New South Wales’ warm coastal regions produce eggs, while those inhabiting cool mountain slopes give birth to live young.

Cool temperatures are associated with live-bearing in herps ranging from Alpine Newts to European Vipers, but only 2 other lizards (Bougainville’s Skink and the Viviparous Lizard, please see photo), and 2 salamanders (the Olm and the Fire Salamander) are known to use both strategies.

Studies have shown that the Three Toed Skink is in the early stages of developing a placenta-like organ, making it the only reptile known to be in the actual process of evolving a new form of reproduction.

The Natural History and Captive Care of the Mertens’ Water Monitor – Part 2

Frank Indiviglio — Thu, 05 May 2011 13:54:19 +0000

Hello, Frank Indiviglio here. Please see Part 1 of this article for information about the natural history of the Mertens’ Water Monitor, Varanus mertensi, including the threat posed by introduced Marine Toads, Rhinella marinus.

Cage Size and Style

Mertens’ Water Monitors may be the ideal choice for folks interested in keeping larger monitors, but who lack the room for the true giants. Averaging 3.5 feet in length, they are supremely-adapted predators, hunting equally well on land or in the water. I’ve found that their alertness and aggression when hunting rivals that of any monitor I’ve observed, including the famed Komodo Dragon (keep your fingers out of their cage at feeding time!).

Moderate size not-withstanding, however, they are extremely active and demand a large enclosure equipped with a deep pool (please see photo – the cage pictured houses a Burmese Python, but would work well for Mertens’ Monitors) – don’t try keeping these high-energy lizards in an aquarium.

Custom-built cages with and drainable pools are the best option for Mertens’ Monitors… please see attached photo of Burmese Python cage and write in for details and suggestions.

Heat and Light

The cage should be large enough to provide your lizards with a temperature gradient (75- 84 F), and a basking spot of 95-100 F should be available. Despite their aquatic lifestyle, Mertens’ Monitors must dry off completely if they are to remain in good health and avoid fungal infections of the skin.

High levels of UVB radiation are likely essential, and UVA is beneficial in maintaining normal activity cycles. In the wild, Mertens’ Monitors may aestivate/become dormant during hot, dry weather; captives often show evidence of “confusion” as regards the season, and may breed or cease to feed at odd intervals. Establishing a light/heat cycle that mimics the natural one, and providing UVA radiation, should help in preventing this. In large cages, a mercury vapor bulb will be preferable to fluorescent light sources.

Diet

Wild Merten’s Monitors take an incredible range of prey, from tadpoles to birds eggs (please see Part 1), and it is therefore simple to provide captives with a varied, healthful diet. When rearing young Mertens’ Monitors, I’ve not seen any of the calcium-related bone problems that are common in juveniles of other species.

As mammals form only a small potion of their natural diet, I rely primarily upon whole minnows, shiners and other fishes, and crayfishes, to supply calcium. Pink mice are offered once weekly, furred mice on rare occasions only. Other staples include earthworms, roaches, crickets, super mealworms and other invertebrates, with earthworms used most frequently. Those I housed with Parker’s Snake-Necked Turtles (in a zoo exhibit) even stole turtle chow from the water’s surface!

I did not use supplements, as a large portion of the diet was whole, high-calcium animals such as fishes, pink mice and crayfishes. Young monitors kept at proper temperatures are ravenous, and if fed properly can eat nearly every day without fear of obesity setting in.

Breeding

Clutches range in size from 6-15 eggs; when incubated at 85F they hatch in approximately 275 days.

Mertens’ Monitors have evolved in habitats subjected to fluctuating weather extremes, and their eggs are quite resilient – incubation periods of 180-330 days have been reported.

The Natural History and Captive Care of the Mertens’ Water Monitor – Part 1

Frank Indiviglio — Mon, 25 Apr 2011 19:32:31 +0000

Hello, Frank Indiviglio here. Many lizard-keepers find Mertens’ Monitors, Varanus mertensi, to possess an ideal mix of large and small monitor qualities. While large enough to satisfy the desires of aspiring Crocodile Monitor keepers, they can be comfortable in sizable, but less than room-sized, enclosures.

Description

Mertens’ Water Monitor (not to be confused with the larger Water Monitor, V. salvator – please see photo) is the most thoroughly aquatic Varanid and has a number of specialized adaptations for life in the water. The tail is laterally compressed (as in Crocodiles) to assist in swimming and the nostrils, which can be sealed during dives, are located high on the snout.

Adults are olive or dark brown to black in color, with dark-edged cream or yellow spots; hatchlings are much brighter. They average 3 feet in length, with some individuals approaching 4 feet.

Range

The range extends across tropical northern Australia (Northern Territory, Queensland, and coastal Western Australia) from just west of Cairns to the vicinity of Cape Leveque; it also inhabits several off-shore islands.

Habitat

Mertens’ Monitors live in rivers, canals, ponds and reservoirs. They rarely stray far from water’s edge, but will forage on banks and in low brush. Basking occurs on floating plants, logs or the shore.

Status

They are common in suitable habitat, but threatened by the introduced Marine Toad, Bufo marinus, which is expected to colonize up to 80% of their range in time (monitors consume toads and die as a result of their toxins.

Classified as Vulnerable by Australia and listed on Appendix II of CITES.

Reproduction

Males engage in ritual combat – rising up and wrestling – during the breeding season. Females dig a burrow, which terminates in a leaf-lined chamber, for their eggs.

There is evidence that, at least in certain populations, gravid females migrate to small, temporary water bodies before nesting; perhaps this safeguards the young from Salt Water Crocodiles, Crocodylus porosus, and other river-dwelling predators that share its habitat.

Diet

Even by monitor standards, this species has wide tastes, with crabs and crayfish being especially favored (in my experience, this holds true in captivity also). Other prey includes fishes, frogs, tadpoles, turtle eggs, snails, nestling birds, possums (please see photo), and invertebrates.

Mertens’ Monitors regularly consume carrion, and have been observed foraging in dumps – discarded sausages are reportedly savored with enthusiasm! In more natural surroundings, they use their tails to concentrate small fishes when hunting in the shallows.

Miscellaneous

This species was named after eminent Russian-born herpetologist Robert Mertens (1894-1975) of Germany’s Seckenberg Museum.

One of Mertens’ Monitor’s adaptations to an aquatic existence is the ability to remain active at low (62F) temperatures. It has been described as “crocodilian” in behavior, sunning on river banks and retreating to water when disturbed. Much of its food is caught in water, but it hunts equally well on land.

Monitor Diversity

Seventy three species of monitor lizards (family Varanidae, genus Varanus) range across Asia, Africa and Australia. Although generally associated with warm climates, the Desert Monitor, V. griseus, may be found as far north as Kazakhstan. They reach their greatest diversity in Australia, where over two-thirds of the world’s species are found. Australian monitors fill ecological roles held elsewhere by predatory birds and mammals.

On to captive care next time…until then, please write in with your questions and comments.

Thanks,

Frank Indiviglio

A Monitor First – Male Rosenberg’s Monitors Cover and Guard Nests

Frank Indiviglio — Fri, 07 Jan 2011 16:04:12 +0000

Hello, Frank Indiviglio here. I remain awed by the learning abilities and complex behaviors evidenced by the Water and Lace Monitors I cared for at various zoos…spend time with any species and you’ll quickly see why. Despite being popular study subjects, monitors are constantly surprising us. For example, the current issue of The Journal of Herpetology (V44, N3, Sept 2010) documents an entirely new behavior for any monitor species – cooperative nest building and nest guarding in Rosenberg’s Monitor (Varanus rosenbergi).

Nest Defense by both Sexes

A 16-year-long study of this species on Australia’s Kangaroo Island has revealed that females guard their nest sites for up to 3 weeks after egg deposition, a behavior that has not been documented for any other monitor (3 species, including the Komodo Dragon, may return to the nest site on occasion, but seem not to remain nearby). Amazingly, in 8 instances a male joined the female in protecting the eggs.

Other Rosenberg’s Monitors are the primary threat to eggs. Females guarding nests attacked male intruders twice their own weight, and repelled them in most cases. The vicious fights that ensued frequently left both combatants with deep wounds and broken ribs and limbs. In those cases where males were also on guard duty, they too joined in the frays, but females were clearly the more aggressive of the pairs.

Cooperative Nest Construction

Female Rosenberg’s Monitors exclusively chose termite mounds as nest sites. In occupied mounds, the resident termites usually closed the nest entrance hole within 3-5 hours after egg deposition. If they did not, the female monitor finished the job.

In another unexpected turn of events, male monitors assisted females in covering nests on 5 occasions.

As you can see, we still have much to learn, even about “well-known” monitors (more has been published on this species than nearly any other). Please observe, read, take notes and pass along what you learn – I‘ll be happy to highlight your observations here.

Thanks, until next time,

Frank Indiviglio

Large, Colorful Monitor Lizard Discovered – the Second New Monitor This Month!

Frank Indiviglio — Mon, 10 May 2010 13:48:08 +0000

Hello, Frank Indiviglio here. Herpetologists still reeling from the recent (April, 2010) discovery of the 6-foot-long Northern Sierra Madre Forest Monitor (Varanus bitatawa) in the Philippines have had yet another shock this week – a large, Red-Headed Monitor Lizard, previously unknown to science, has surfaced in Indonesia! A glossy black body and brilliant red head led to its being christened the Torch Monitor. Also known as the Sago Monitor (Varanus obor), it is the only Varanid that sports red coloration.

An Island Holdover

The Torch Monitor’s only known habitat is the tiny Indonesian Island of Sanana, which is located in the Sula Island Chain, northwest of New Guinea. Writing in the journal Zootaxa, researchers theorize that the Torch Monitor may have become isolated from related species when its island home drifted away from New Guinea millions of years ago. Living in isolation, it evolved into a new species.

A Hotbed of Monitor Diversity

Due to the absence of large carnivorous mammals, monitor lizards reach their greatest species diversity in Indonesia, Australia and New Guinea. From small, arboreal species such as the Black Tree Monitor (please see photo) to the massive Komodo Dragon (please see photo), monitors in this region fill ecological roles held elsewhere by mammals and raptors.

This situation leads to some quite “un-monitor-like” habits – the newly discovered Northern Sierra Madre Forest Monitor, for example, subsists almost entirely upon fruit. The Torch Monitor, which may be related to the Forest Monitor, appears to consume a more traditional monitor diet of birds and their eggs, small mammals, invertebrates and carrion.

Discovery of a Huge, Arboreal, Fruit-Eating Monitor Shocks Herpetologists

Frank Indiviglio — Wed, 14 Apr 2010 13:07:56 +0000

Hello, Frank Indiviglio here. It’s well-known that the world still hides countless “undiscovered” animals and plants – even Central Park in NYC recently yielded a previously unknown centipede. However, it is still something of a surprise when large, colorful creatures remain unseen into modern times. Such is the case for the Northern Sierra Madre Forest Monitor (Varanus bitatawa), a spectacularly colored, 6-foot-long lizard that has been designated as a new species in the current (April, 2010) issue of the journal Biology Letters.

Large, Colorful and Unique

The new species, found only in the northern Philippines (Aurora and Isabella Provinces, northern Luzon), has generated awe among lizard enthusiasts – not only for its large size and brilliant black-and-yellow coloration, but also because of a lifestyle that is quite rare among monitor lizards – it is an arboreal fruit eater.

The few other known arboreal monitors are carnivorous and, with the exception of the Crocodile Monitor (V. salvadorii, see photo), are quite small and slender (i.e. the Green Tree Monitor, see photo). The massive Forest Monitor reaches at least 22 pounds in weight. Its diet, as far as is known, consists of Pandanus and Pili Nut Fruits, figs and, possibly, snails.

History: Documenting a New Species

The lizard is only “new” to herpetologists – it has long been hunted for food by the Agta and IIogot people, and, in fact, is found near heavily populated areas. The first known photo of one popped up in 2001, but it was not until 2003 that it attracted serious investigation; an actual specimen eluded biologists until 2009.

Biologists from the Natural History Museum of the Philippines and the University of Kansas (an institution long on the forefront of herpetological research) collaborated to uncover and describe the spectacular creature.

Monitor Diversity

The Northern Sierra Madre Forest Monitor is the third frugivorous monitor lizard to be discovered in the Philippines – these are the only members of the family Varanidae that are not predominantly carnivorous. The Gray’s Monitor or Butaan (V. olivaceus), to which the Forest Monitor may be related, was first recorded in 1845 but was not seen by herpetologists until the mid-1970’s. The other fruit-eater, the Mabitang (V. mabitang) was not officially recognized until 2001. All are believed threatened by logging, mining, deforestation and, possibly, hunting.

The discovery of the Forest Monitor brings to 70 the number of monitor lizard species described thus far. Ranging across Asia, Africa and Australia, they are generally associated with warm climates, but the Desert Monitor, (V. griseus) may be found as far north as Kazakhstan. At 8 inches long, the Short-tailed Monitor (V. brevicauda), is the smallest of the group…the Komodo dragon (V. komodoensis), the world’s largest lizard, occasionally tops 10 feet in length.

Keep Looking!

That such a large, active lizard could remain in relative obscurity for so long fuels the imaginations of those (such as I!) who believe that there are a great many wondrous creatures remaining to be found. Rumors persist in New Guinea of a 20-foot-long tree-dwelling lizard dubbed the “Papuan Dragon” – given the inaccessibility of its presumed rainforest habitat, who knows…?

The Crocodile Monitor Lizard – Reality and Legend

Frank Indiviglio — Fri, 16 Oct 2009 15:04:21 +0000

Hello, Frank Indiviglio here. Despite – or perhaps because of – its immense size, impressive armament of teeth and scarcity, the spectacular Crocodile Monitor Lizard (Varanus salvadorii) is often considered the crown jewel of private and public monitor collections.

I became acquainted with these formidable giants when they were first imported into the USA, and have cared for several at the Bronx and Staten Island Zoos. Their husbandry is straightforward, but little is known about their lives in the wild. Today I would like to summarize what we do know; please see the article referenced below for notes on captive care.

Description

Crocodile Monitors approach 9 feet in length – nearly as long as the famed Komodo Dragon, but less stoutly built. There are recurring but unverified reports of much longer individuals.

The Crocodile Monitor’s prehensile tail often exceeds 5 feet in length. The body is dark gray to black in color and marked with yellow spots, making for quite a spectacular appearance. The snout area, especially in mature males, is large and bulbous.

Crocodile Monitors are unusually large for canopy dwelling lizards…the 3 foot long black tree monitor is far more typical. However, aided by slender bodies, long claws and prehensile tails, they are very agile climbers.

Their teeth are unique among monitors, being serrated and over-lapping – possibly an adaptation for carrying large prey high above the forest floor.

Range and Habitat

Crocodile Monitors are found only in southern New Guinea. Highly arboreal, they seem restricted to the canopies of mangrove swamps and lowland forests along rivers.

Status

Little studied due to the inaccessibility of their habitat, the Crocodile Monitor’s limited range renders it a conservation concern. Listed on CITES Appendix II.

Reproduction

Females lay 6-12 eggs at a time, and up to 3 clutches per year in captivity (multiple clutches may be a function of food availability), with arboreal nest sites being favored. In common with other tree-dwelling monitors, they likely deposit eggs in tree hollows and similar sites above ground in the wild.

Diet

Their natural diet has been little studied, but probably includes nearly any animal that can be overpowered. Likely candidates would be cuscus, tree kangaroos, naked-tailed rats, bandicoots, possums, bats, birds, frogs, snakes, lizards, invertebrates and carrion.

An Undiscovered Giant in New Guinea?

Long a creature of legend, the Crocodile Monitor is the source of rumors alleging “Papuan Dragons” of 20 feet in length. This specie’s habitat is inaccessible and barely explored….I like to believe that it or an as yet un-described monitor may indeed reach such lengths.

A Calculating Reptile

Like all Varanids, Crocodile Monitors are highly intelligent. One huge adult that escaped its enclosure at the Bronx Zoo wedged himself behind a cage while attempting to hide from myself and a co-worker. As we moved into position to flush him, he very deliberately peered around first one and then the other side of his hideout, trying to keep us both in sight. When we backed off, he followed our progress, again changing position periodically to ascertain where we were.

The lizard remained stationary while we were near, and only ran when we gave him some space. When he did move, the old fellow made unerringly for a more secure retreat that he had obviously “decided upon” while in hiding.

That Reptile Blog » Monitors

Monitor Lizard Care, Natural History and Behavior – An Overview

Natural History

Behavior

Housing

Feeding

Further Reading

World’s Smallest Frogs Added to 2011’s List of Newly-Discovered Amphibians

Tiny Frogs and Fish

Minute Predators and Prey

Diversity Hotspots

Further Reading

New Test for Cryptosporidiosis, an Incurable Disease of Snakes and Lizards

Crypto and the Pet Trade

Crypto in Zoo Animals and Wild Populations

The Importance of the New Test

Caring for Crypto-Positive Reptiles

Further Reading

2010’s Reptile Discoveries – New Lizard Species and Facts

Two Large Monitors

Males Not Needed

Evolution in Action

Further Reading

The Natural History and Captive Care of the Mertens’ Water Monitor – Part 2

Cage Size and Style

Heat and Light

Diet

Breeding

Further Reading

The Natural History and Captive Care of the Mertens’ Water Monitor – Part 1

Description

Range

Habitat

Status

Reproduction

Diet

Miscellaneous

Monitor Diversity

Further Reading

A Monitor First – Male Rosenberg’s Monitors Cover and Guard Nests

Nest Defense by both Sexes

Cooperative Nest Construction

Further Reading

Large, Colorful Monitor Lizard Discovered – the Second New Monitor This Month!

An Island Holdover

A Hotbed of Monitor Diversity

Further Reading

Discovery of a Huge, Arboreal, Fruit-Eating Monitor Shocks Herpetologists

Large, Colorful and Unique

History: Documenting a New Species

Monitor Diversity

Keep Looking!

Further Reading

The Crocodile Monitor Lizard – Reality and Legend

Description

Range and Habitat

Status

Reproduction

Diet

An Undiscovered Giant in New Guinea?

A Calculating Reptile

Further Reading