Browsing the pages of Herpetologica and other journals over the years, I several times came across field studies indicating that certain populations of savannah monitors consumed diets composed entirely of invertebrates. In certain seasons, the lizards gorged on either locusts or land snails exclusively for months on end. When some captives fed largely upon rodents showed evidence of kidney and liver damage and intestinal impactions, articles in popular magazines began calling for insect-based diets.
Savannah monitors may approach 5 feet in length, and thus an insect-based diet is difficult to arrange…thousands would be needed weekly in some cases. Zoo Med’s Canned Tegu and Monitor Diet provides a handy solution. Formulated with these lizards in mind, it is readily accepted by most individuals.
After reading the aforementioned articles, I took a moderate position as regarded the savannah monitors under my care in public collections, using canned food as 60-75% of the diet. I supplemented the food of adults
once weekly with vitamin/mineral powder and that of juveniles 3-4 times weekly.
Invertebrate and Vertebrate Food Items
The easiest way to supplement canned food without using mice is to establish a breeding colony of Madagascar hissing roaches (even the well-armored adults are readily accepted) and nightcrawlers. Crayfish, if available to you, are a great monitor food. Other useful food items are land snails (available in seafood markets), tomato hornworms, hard boiled eggs (in moderation, i.e. once monthly) and canned grasshoppers , silkworms and snails. Pink and fuzzy mice (these are preferable to adult mice and rats) may be offered every 10-14 days.
My Observations of Wild Black and White Tegus
My observations of black and white tegus in Venezuela leads me to believe that, at least in llanos habitat, these lizards consume far more large insects, turtle eggs and frogs than rodents. Mammals are taken when available, mainly as carrion or unearthed rodent nests.
I have kept tegus for lengthy periods on rodent-based diets but now counsel more variety…I suggest feeding as described above, but with canned food comprising a smaller portion (i.e. 25-50%) of the diet, and rodents, preferably pink and fuzzy mice, being offered once weekly. If your tegu will accept whole fish (i.e. large shiners), use these in place of mice.
An interesting article on savannah monitor natural history and diet in the wild is posted at http://www.mampam.com/index.php?option=com_content&task=view&id=36&Itemid=76