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Notes on the Feeding of Monitor Lizards - By Jonathan Rheins
NOTES ON THE FEEDING OF MONITOR LIZARDS
Monitor lizards of the genus Varanus have long been popular among reptile enthusiasts of all ages and levels of experience. These large, intelligent creatures can provide an extremely rewarding pet experience if they are properly cared for and their needs met.
In general, the herp-keeping community has advanced in leaps and bounds during the past few decades as all aspects of captive care and breeding were further researched and refined. The result is a current understanding of monitor biology and behavior, that while by no means complete, has led us much closer to our ultimate goal, that of making our pets feel truly at home.
Most aspects of monitor care, such as housing, can indeed be troublesome with larger species, but it is still fairly straightforward; provide your animals with as much space as possible without compromising functionality or security. Feeding however, leaves many more questions unanswered. What to feed them. How much? How often? What about supplements? All of these quandaries are often faced by first time monitor owners who may or may not receive accurate answers.
While current publications on monitor husbandry tend to be quite acceptable, the data in older books is likely outdated. Additionally, monitors are a wildly diverse group of animals, with individual species having specific dietary requirements. Despite this, some generalizations can be made, and most of them will seem completely logical when explored in the proper context.
I am by no means making any claims that the information presented here is exhaustive or written in stone. Rather it is a compilation of data accrued by myself, my colleagues, and various experts over the past years. Monitor nutrition is a highly debated subject, and while many will agree that the insight provided below is proper, some will surely disagree with my recommendations. This is to be expected, as no two husbandry situations are alike, and what works for some, may not work for other.
Finally, be sure to carefully research the need of the specific type of monitor you are keeping. Some species have very specific dietary requirements, while others will eat nearly anything placed before them. Knowledge of your animals natural history, that is where they come from, and how they behave in the wild, can be one of the most important tools when developing a husbandry and feeding regimen.
In the wild, the staple diet of many monitor species is insects and other invertebrates. Recent studies have shown that presumed rodent eaters such as savannah monitors, actually consume mostly termites, millepedes, and scorpions. In captivity, these foods may be difficult to procure, but other insect species are readily available, and should be part of every monitor diet.
Crickets, mealworms, waxworms, and roaches should be considered required items in the monitor diet. Many roach species are now available to monitor owners, and keepers are strongly encouraged to maintain a small breeding colony of them as a constant source of feeders.
Depending on the species of monitor you are keeping, other prey items such as fish, shrimp, and baby chicks can be offered, the frequency of which will depend upon your specific situation.
Commercial monitor and carnivorous lizard diets can be categorized here as well. These diets are formulated to be complete and balanced, but should not be relied upon as a sole source of nutrition. While they are a nice way to add variety, they should be offered as filler, in addition to other foods.
The debate over whether or not to feed rodents to captive monitors is a heated one. In all likelihood, there is probably not a right or wrong answer. Instead, the keeper must carefully evaluate other aspects of their husbandry and from that decide to what degree rodents should contribute to their pets diets.
For many monitor keepers, watching their mini-dinosaurs hunt down and devour a live mouse is all part of the thrill. However, most monitors only rarely eat rodents in the wild, and if fed artificially high numbers of them (as often occurs in captivity) they can quickly succumb to a variety of health problems.
Mice and rats are generally considered to be too high in fat for most captive, exercise-deprived monitors. Additionally, the digestion of large amounts of fur can be difficult for captive monitors, especially those kept in cramped quarters or with sub-optimal basking temperatures.
Keepers who choose to raise their monitors on a rodent-only or mostly rodent diet should be encouraged to avoid unweaned mice, as they have little or no calcium, and are fairly deficient in other vital nutrients. Furthermore, animals fed a diet high in mice should be exposed to basking temperatures at the very high end of the recommended range, and given ample space to run around, dig, and thermoregulate.
It should be noted that rodents are not a completely bad food source. In fact, they are an important part of a balanced diet. They should, however, be fed in moderation, and with the above considerations in mind.
It is widely accepted to feed only pre-killed rodents to monitors. Live mice and rats can easily injure the animal they are intended to feed, resulting in lacerations, infections, or abbesses. Also, by offering non-living rodents, your monitor's hunting instinct will be slightly curbed, and accidents and/or bites may be less likely to occur.
A New Alternative
Keepers who have been working with monitors for any length of time may be aware of this dietary option, while it's existence may come as news to less experienced hobbyists. Quite a few years ago, keepers and animal nutritionists at the San Diego Zoo were experimenting with non-rodent diets for their larger monitor species. At the time, they were working intensively with Komodo Dragons, but the diet that they derived is acceptable for all monitor species.
The exact, original recipe is not really known, but it is widely accepted that it contained nothing more than raw, ground turkey, eggs, steamed bone meal (as a source of calcium), and multivitamins. This original formula has been passed around for years, with subtle changes being made along the way.
I recommend mixing one pound of raw, ground turkey with two raw eggs including the shells. The steamed bone meal is easily replaced by one heaping tablespoon of a high quality calcium/vitamin supplement designed specifically for reptile use. Mix this well, and feed your lizard whatever it will consume in a few moments. The remaining mixture can be frozen in ice cube trays or larger containers for future feedings.
We have had tremendous success (as did the San Diego Zoo) with this diet, and provide it to all of our monitor and tegu species regularly. Up to 70% of your lizards diet can consist of this mixture as long as it prepared as indicated, and as long as the remainder of the diet is as varied and as nutritious as possible.
Foods to Avoid
Foods designed for other types of animals (or humans) should be avoided or fed sparingly. These include cat and dog foods, hot dogs, and red meat. While a serving or two of any of these items will certainly pose no threat to a healthy lizard, large amounts may cause problems including vitamin deficiencies/overdoses and obesity.
I am of the opinion that growing monitors benefit greatly from the use of calcium and vitamin supplements in their diets. Some argue that if fed a varied diet of whole animal prey, monitors will not face any related health issues. I have simply encountered too many monitors raised on un-supplemented diets showing severe signs of dietary nutritional deficiencies to accept this as truth.
Baby and juvenile monitors should have their food dusted with a high quality calcium/vitamin D3 supplement at every feeding. In conjunction with a suitable source of full spectrum lighting, these supplements will allow for proper skeletal growth and muscle development. As the animal approaches adult size, and especially after growth has more or less ceased, the frequency may be adjusted to just a few times a week.
In addition to the calcium supplement, a multivitamin is highly recommended. This should be in the form of a powder that is designed specifically for reptiles. By dusting food items with a vitamin 3 to 4 times a month, you can be assured that your lizard is not being deprived of any vital nutrients.
As previously mentioned, the dietary needs of monitor lizards is still under investigation, and there remains much debate regarding the right and wrong ways to feed these animals. My goal has not been to confuse or create debate, but rather to introduce readers to some of the insight that myself and others have gained through years of experience.
Monitors are amzaing animals, and deserve to live amazing lives. It is our responsibilty to do all that we can to provide them with the very best of care, and a happy healthy life.