Common Group: Monitors & Tegus Common name: Dumeril's Monitor, Brown Roughneck Monitor, Black Roughneck Monitor Scientific Name: Varanus Dumerilli, Varanus Rudicollis Distribution: Southeast Asia, including Thailand, Malaysia, Borneo, and Sumatra Size: 3.5' - 4.5' for V. Dumerilli, 4'-5' for V. Rudicollis
The Dumeril's Monitor and Black Roughneck Monitor are two closely related monitors that have been little studied in their natural habitat. Even so, both species of monitors are known for their fondness for water as well as their excellent climbing abilities. These monitors spend so much time in water that their nostrils have a specially adapted scale that seals shut while the monitor is underwater, allowing them to remain submerged for extended periods of time with ease.
The two species have similar care requirements, and they are often confused. The Black Roughneck has a slenderer snout and spinier neck scales than the Dumeril's, as well as being black while the Dumeril's is brown. One of the biggest differences between the two would be what the monitors are thought to eat in the wild - the Dumeril's could be considered a specialized crab eater, while the Black Roughneck is thought to eat mainly insects. Both monitors dine readily on a variety of prey items when properly maintained in captivity.
Dumeril's Monitors hatch out of their eggs with brilliant orange heads and deep black bodies, but these intense markings fade quickly, often within just a few weeks. Black Roughneck Monitors also hatch out with interesting patterns, but they fade as well as the monitor matures. Due to the secretive nature of both species, they can be seasonally difficult to come by, especially as babies.
Size and Longevity:
Dumeril's monitors regularly grow to at least 3 feet long, some as great as 4 feet, while the largest Dumeril's on record was 5 feet long - including its 36 inch tail. Black Roughneck Monitors regularly grow over 4 feet long, with some individuals as long as 5 feet or more. It generally takes at least 2 - 3 years for monitors to begin to approach their full adult length, and older adult animals can be expected to be larger than young adult animals. Roughneck Monitors of both species are relatively dainty lizards with slender bodies and long tails. With proper care, either of the roughneck monitors can be expected to live at least 10 years, with 15 or 20 years not an uncommon average. These monitors are not commonly kept, though, and their scarcity combined with misinformation and improper husbandry resulting in early death leads to little information being known about exactly how long these monitors can live for.
Roughneck monitors are not among the largest monitors ever, but they do require suitable space to move around and thermoregulate. A single hatchling can be temporarily kept in a 20 or 30 gallon glass aquarium, but in order to provide optimum temperatures for digestion and growth, an enclosure that is at least 36" by 16" by 16" is ideal to begin with. Once the baby reaches about 16", it's time to upgrade to a larger enclosure.
A single adult Roughneck will do well in an enclosure that is at least 6' by 2' by 2', but if more space can be provided, it will be greatly appreciated by the inhabitant. A deeper enclosure that allows space to put in substrate for burrowing is ideal. It is recommended to house your monitors individually, as in a group the dominant animals often refuse to let the subordinate ones eat. Roughneck monitors of either gender have been known to combat in captivity, and as a result, communal housing is best left to experienced monitor keepers.
Remember that monitors are smart, inquisitive, and powerful animals. Ensure that your cage is escape proof, and if there is ever a question on the size of the cage, bigger is always better!
Heating and Lighting:
Roughneck Monitors are from the tropical forests of Southeast Asia, and should be provided with the heat and humidity commonly found in their native habitat.
Ambient temperatures within the monitor's cage can range from the 80's on the warm side of the enclosure to the low 70's on the cool side. It is vital for the monitor to have a warm basking spot to properly digest its food. If at all possible, in a large cage (6' or greater) the basking site should be around 130 degrees. In smaller cages, a basking site of 100 will usually suffice, but these monitors will do better if given a wide range of temperatures to choose from.
At night, temperatures can safely drop into the mid 70's. If needed, temperatures can be increased using ceramic heat emitters, heat pads, red lights, or black lights. During the day, basking or halogen bulbs should be utilized to create suitable temperatures and plenty of bright light. There are a wide range of opinions on the necessity of UVB or full spectrum lighting when housing monitor lizards. While some very experienced keepers have had success without UVB lighting, for the beginner or even moderately experienced keeper, full spectrum lighting is highly recommended. UVB, calcium supplements, and a varied diet containing lots of whole prey items is the ideal way to ensure that your monitor has strong bones and remains healthy and active for its entire life. In larger enclosures, a self-ballasted mercury vapor bulb can be used both as a source of heat and as a source of UVB. These lights have been shown to be extremely effective and are highly recommended in cages that have enough space for the heat to dissipate. In smaller enclosures, a combination of fluorescent UVB light and basking lights is suitable.
Substrate and Furnishings:
Roughneck monitors are tropical animals and as such should be kept in a humid environment with ready access to a large bowl full of fresh, clean water. These monitors will dig and bury themselves in their substrate, and the use of one of many pulverized coconut husk beddings or similar substrate is highly recommended. Making the substrate layer thick and moist will aid in keeping your monitor hydrated and shedding properly. In addition, a thick cover of sphagnum moss is highly appreciated and utilized as a hiding area.
In the wild, these monitors are extremely secretive, and if care is given to allow them their privacy in captivity, they will feel much more secure and be out more than if they feel they have inadequate hiding areas. There are a variety of ways to provide hiding spots, which include cork bark stacks, half logs, flat pieces of wood, thick layers of bedding and moss, caves, and lots of cover in the form of fake plants. A monitor's need to hide and stay warm can be duly accomplished in the form of providing a stack of cork bark or wood underneath the basking light, with the highest level being a few inches away and the hottest spot in the cage, and the lower levels being significantly cooler.
Live plants can be attempted in the cooler parts of the cage, but the monitor's curious nature and love of digging will usually result in the plants' demise. Fake plants are easier to keep clean and will withstand the strains that a monitor is likely to put on them.
The key to success in a monitor's cage is to offer the lizard as many choices as possible. The more options the monitor has to utilize for thermoregulating, hiding, or basking, the better it will do.
Water and Humidity:
These monitors absolutely adore water, and will spend large amounts of time soaking in their water bowls, either with their chin resting on the rim or with their heads completely submerged. Because they spend so much time in their water, it is imperative that the bowl be kept clean to prevent disease and skin infections. In large enclosures, multiple water bowls can be utilized to provide water of varying temperatures and to increase the humidity in the cage. This is one area of difference between the two monitors; Dumeril's Monitors spend hours a day reclining in their water, while the Black Roughneck will typically only venture in for a quick dip. These monitors are from an extremely muggy and humid climate, so steps should be taken to mimic natural conditions within the cage. Things that help with humidity include damp moss piled throughout the cage, ultrasonic foggers, and regular misting, either by hand or automatically with timers.
Little is known about the actual feeding habits of wild roughneck monitors. One scientist theorized that Dumeril's were specialized crab eaters based on their head structure and on field studies that found crabs in the stomach of every specimen caught. Roughneck monitors in captivity have been known to take a wide range of prey items, including: rats, mice, hamsters, birds, lizards, frozen/thawed fish, frozen/thawed krill, live fish (both fresh and salt water), crickets, hissing cockroaches, super mealworms, snails, raw meat (cow and horse), eggs (chicken, quail, and leopard gecko), crabs, crayfish, commercially prepared "bird of prey" diet, dog food, cat food, and even cottage cheese. Dumeril's have also been known to eat the raw turkey and egg diet first formulated by the San Diego Zoo. It should be noted that just because a monitor can eat something, that does not mean that it is a suitable food.
While a wide variety of food will be accepted, some foods are more readily eaten than others and some are far more appropriate as food items than others. While these monitors will eat dog and cat food, it is not recommended as a part of the diet. Ideally, a diet consisting almost entirely of whole prey items with a small portion consisting of the raw turkey and egg diet is best. Suitable prey items include hissing cockroaches, dubia roaches, lobster roaches, crickets, superworms, mealworms, mice, small rats (avoid unweaned rodents as they are high in fat and low in calcium and other nutrients), frozen/thawed crayfish, frozen/thawed crabs, frozen/thawed krill, and frozen/thawed fish. With wild caught prey items, it is important to first freeze them for several hours to ensure that any parasites present in the prey are killed and will not infect your monitor.
All food items, with the exception of rodents, should be dusted with a high quality calcium and/or vitamin powder. Young monitors can be kept mainly on crickets, mealworms, and small roaches, while adult monitors can be fed the entire range of possible food items. Rodents should be fed in moderation, erring on the side of fewer rodents than insects. Captive monitors rarely, if ever, get the same kind of exercise wild monitors do, and care should be taken to ensure that an adult monitor does not become obese.
The turkey and egg diet previously mentioned consists of about 1 pound of lean raw turkey, 2 raw eggs, and a generous tablespoon of a high quality calcium and vitamin powder. Mix everything together, and feed off only what the monitor will consume in the first minute or two. The leftover mixture can be frozen in ice cube trays and cubes can be popped out and thawed out as needed.
In addition to being fascinating and hardy captives, Roughneck Monitors are relatively easy to handle. With calm, confident handling on a regular (but not necessarily frequent) basis, these monitors learn to tolerate and even enjoy human interaction. They do grow long, sharp claws, and an occasional trim may help make handling more comfortable for lizard and owner alike.
Care must be given to allow the monitor plenty of time to acclimate before any attempts at developing an owner-monitor bond can really begin. Once the monitor shows a healthy appetite and eats readily, and does so regularly, start handling it for just a few minutes at a time daily. If the monitor continues to eat and does not spend the time immediately after handling buried beneath the substrate, avoiding you at all costs, increase the handling time slowly but surely, until the monitor does not mind being out for extended periods of time. Always be sure to read your monitor's behavior: If it hides and does not move for days on end after being handled, decrease handling time and frequency. With patience, eventually these monitors can and will become tame.