From tiny Day Geckos to stout Water Dragons and lumbering Savanna Monitors, many popularly-kept lizards feed primarily upon live foods including insects and other invertebrates. The most important point for insectivorous lizard owners to remember (and one that my regular readers are sick of seeing!), is that crickets and mealworms alone, even if powdered with supplements, are not an adequate diet for any species. Dietary variety is essential. Fortunately, with a bit of planning, we can collect, breed or purchase a huge array of nutritious invertebrates for the lizards in our collections.
From specialists such as Horned and Caiman Lizards to Tokay Geckos and other generalists, the needs of individual species vary greatly. Please post below for specific information on the lizards in your collection.
Wild Caught Insects
I firmly believe that reptile keepers should place much more emphasis on collecting insects and other invertebrates. While caution concerning pesticides and toxic species is warranted (please see articles linked below), the risks can be managed. Some notable successes that I and colleagues have had with a variety of delicate reptiles can be credited in part to the use of wild-caught insects.
Moths, beetles and their grubs, sow bugs, bee flies, grasshoppers, tree crickets, earwigs, caterpillars, katydids, crane flies, termites, harvestmen, leaf hoppers, small mantids and a variety of others will be eagerly accepted by many lizards. Your pets’ “enthusiasm” towards such novel foods will leave you with little doubt that your efforts have been worthwhile!
Earthworms, a highly nutritious and usually calcium-rich food item, are heavily utilized by zoos and serious hobbyists. While many arboreal lizards will not accept earthworms, they are relished by Water Dragons, Basilisks, Crocodile Skinks, Glass Lizards and others. Earthworms, sow bugs and several others can be bred year-round in captivity; please see the linked articles and post any questions below.
Insect Traps and Collecting Techniques
Many reptile enthusiasts are also interested in invertebrates, and quickly come to enjoy collecting food for their lizards. Don’t be surprised if you wind up with a whole new hobby! I’m always adding new native species to my collection…this summer I focused on Fishing Spiders and Giant Water Bugs.
The Zoo Med Bug Napper is a scaled-down version of the traps I used to collect food for the Bronx Zoo’s reptile, amphibian and bird collections. It is very effective at snaring moths, beetles, and other flying insects.
There are a number of very enjoyable insect collecting methods that you can use to provide your lizards with dietary variety. Some of my favorites are bush-beating, pitfall traps, termite traps, leaf litter collection and sweeping through tall grass with a net.
For those individuals that will feed from tongs or accept non-living foods, canned invertebrates, such as grasshoppers, snails and silkworms, provide a convenient means of varying the diet.
When wild-caught insects are unavailable, the main portion of the diet should not be crickets, but rather a mix of as many species as possible. Earthworms, roaches, butter worms, calci-worms, silkworms, tomato hornworms, sow bugs, harvester ants and others are available on the internet.
I use mealworms and super mealworms sparingly, and usually select only newly-molted (white) grubs.
You should allow feeder insects to consume a healthy diet for several days before offering them to your lizards; please see the linked articles and post below for further information.
Calcium: Fish, Crayfish and Mice
Minnows and shiners, readily accepted by semi-aquatic species such as Merten’s Water Monitors and Caiman Lizards, will help ensure adequate calcium intake. Goldfishes may be offered on occasion, but long-term use has been linked to health problems in certain aquatic turtles.
I have found crayfishes (which can be purchased or collected) to be a valuable food item for a wide variety of lizards. I remove the claws, just to be on the safe side.
A diet rich in pink or adult mice may cause eye, kidney and liver problems in certain species. At the Bronx Zoo, we saw this most clearly in Green Basilisks. While these aggressive predators certainly take the occasional rodent in the wild, research has shown that insects form the vast majority of their natural diet. The same may be applicable to Water Dragons and others with similar lifestyles. A pink mouse every month or so will do no harm. Do not offer adult mice to insectivorous lizards, as the fur may cause intestinal impactions.
Hatchlings, Newborns and other Tiny Lizards
Nutritional variety is especially important to growing lizards, but small feeder insects are not always readily available. House Geckos, Dwarf Chameleons and other tiny species are a challenge to feed properly even as adults.
In addition to 10-day-old crickets and fruit flies, one should experiment with gnats and small moths (try the Zoo Med Bug Napper), termites, house flies, sap beetles, newly-hatched mantids, flour beetle larvae, ants (some species are rejected; others bite or sting), aphids (tiny insects that colonize plant stems) and “field plankton” (insects gathered by sweeping through tall grass with a net).
I powder captive-reared insects with ReptiVite and ReptiCalcium. I do not use supplements on wild-caught invertebrates. Supplement use must be tailored to the species and individual animal. Please post below for further information.
Most heliothermic (basking) lizards cannot produce Vitamin B3 without an appropriate source of UVB light. Please see this article for further information, and post any questions below.