A Bugs Nutrition

By Sue Donoghue, DVM, DACVN


Donoghue, S. (2002). A Bugs Nutrition. Chameleons! Online E-Zine, September 2002. (http://www.chameleonnews.com/02SepDonoghue.html)

A Bugs Nutrition

Mmmm, Mmmm Good!

The latest research on those bugs we feed

What prey do you feed your chameleons? Commercial crickets, I imagine, along with other species such as superworms, waxworms, silkworms and perhaps hornworms, cockroaches, and houseflies. Other prey may include commercial or wild-caught stick insects and mantids, lacewings, May beetles and June bugs, grasshoppers, locusts, katydids, sow bugs and even snails.

Do you know what's in these prey that you feed? A basic tenet of feeding is to offer a wide variety of prey. Variety seems to help maintain chameleon interest and cognition. But is it truly helpful in our quest for optimal diets? How critical is variety? Can we attain optimal nutrition by feeding, say, just crickets or just silkworms? More importantly, can we utilize prey as "functional food" - selecting the species to feed in order to meet a specific goal - goals focused on breeding, for example, or perhaps body condition, health, or longevity.

When I first went looking for answers to these questions, I was incredulous at the lack of hard data, sound study design, peer-review, and controlled trials. In the 20+ years since, things have improved, but not by much. Until this year.

The March 2002 issue of Zoo Biology published a paper that, for the first time, examined in detail the nutrient contents of commonly fed invertebrates (Finke MD. 2002. Complete nutritional composition of commercially raised invertebrates used as food for insectivores. Zoo Biology 21:269-285). Not just crickets, but also superworms, giant mealworms, regular mealworm larvae and adults, waxworms, silkworms, and earthworms. Not just calcium, but also amino acids, fatty acids, minerals, and many vitamins including A and D3.

You may remember nutrition charts for prey in our March 2002 issue. That chart was pulled together from over a dozen sources, some decades old with data determined by antiquated methods prone to error, and with few studies undergoing sound laboratory techniques or peer review. In contrast, this new report from a peer-reviewed journal provides details on many species using the identical, advanced laboratory techniques and suitable controls. It helps us to design better feeding strategies, use prey as functional foods, and move the feeding of chameleons along the path of modern nutrition. The study also has some flaws, which we'll cover later. First, let's take a close look at some of the useful information published:

Calories - how to restrict; how to increase

We rely on invertebrates to provide all of the fuels that give energy to a chameleon. Fats and proteins (and a small amount of nitrogen-free extract) inside the prey are digested by the chameleon and converted into energy, measured as calories. This energy permits cell and tissue synthesis, organ function, antibody and enzyme formation, muscle contraction and everything else vital to life. Ounce for ounce, fats provide more than three-times the calories as protein. Which prey has the most calories? The ones with the most fat. Here are examples in a chart calculated (on an 'as fed' or 'wet' basis) from the Zoo Biology paper:

For now, just concentrate on waxworms and silkworms. Waxworms contain relatively less water and protein, but four-times the amount of calories. Why this difference? It's all in the fat. In waxworms, 80% of the calories come from fat, hence the high calorie content (2.7 vs 0.67 calories per gram). In contrast, fat provides only 25% of the calories in silkworms. Because almost all of the calories in these invertebrates come from fat and protein, as fat increases, the proportion of calories coming from protein must decrease (because the total always equals 100%). How can we make use of this information in our chameleon feeding regimes?

Thin chameleons - If you have a chameleon that has had a difficult pregnancy and has lost body condition, she needs calories to replace her lost tissue stores. If you work with wild-caught specimens, a part of conditioning programs involves improvement of body condition. In veterinary clinics and rehabilitation centers, thin chameleons are often presented, and nutrition support is essential adjunctive therapy.

For chameleons that are thin but otherwise relatively healthy, a high calorie food may make up >50% of the diet. Using the above table, wax worms (and superworms) are good bets.

Sick chameleons - If you have a chameleon with an infection of an eye or toe, for example, its protein needs will be higher than that of a healthy chameleon (of the same species, sex, age, husbandry, etc). The same goes for chameleons recovering from surgery. Moreover, anything that causes immune suppression can lead to higher demands for dietary protein - emotional or physical stress, for example, and certain drugs such as steroids.

How can you get extra protein into your sick chameleon? Looking at the chart, silkworms and young crickets provide more calories from protein than the other prey studied here. In cases where you perceive the possibility of increased need for dietary protein, try using these prey for >50% of the total diet.

Reproduction - What about reproductively active females? In many ways, the greatest demands occur during vitellogenesis, the time of egg protein (vitellin) synthesis in the liver. The female chameleon makes egg protein from the amino acids found in her dietary protein. Synthesis of egg protein and its transport to the ovaries require calories that originate from either food or body stores. Unfortunately, this nutritionally demanding time is usually unrecognizable by visual examination.

Feeding strategies include provision of optimally balanced fuel sources during vitellogenesis and pregnancy in order to maintain good health all the way through to egg laying. A female that has been underfed or fed an imbalanced diet loses conditioning and, as a result, suffers from negative nitrogen balance and loss of immune function, organ function, cell synthesis, and antibody production.

Look for prey with an optimal balance between fat and protein - a good blend is young (especially) and adult crickets, along with silkworms. This strategy keeps dietary protein high enough to meet the requirements during vitellogenesis and pregnancy.

In late pregnancy, eggs take up much of the coelomic space. Because there is little spare room in the coelom for food during this time, every mouthful should be packed with calories and optimally balanced with fat and protein. I look for intakes of about 40/60 (fat/protein) up to 50/50. For gravid females in poor body condition, try working with silkworms and wax worms, varying the proportions of each as you perceive the needs for calories from protein or fat, respectively.

Crunching the Numbers

What else can be done with this information? You can also count calories. As an example, here's a case I consulted on last week:

Calculating Calorie Intakes

Patient: Juvenile veiled chameleon purchased from a pet store.

History: Patient was presented to the veterinary clinic with severe weight loss, dehydration, and extreme weakness. The attending veterinarian placed an intramedullary (within the marrow cavity of bone) catheter and administered fluids and electrolytes overnight in the ICU. Diagnostic tests found parasites, and the next morning the chameleon began a course of treatment with anthelmintics along with supportive therapy.

Present problem: After two weeks, the chameleon had gained some weight, but still had no muscle on limbs and tail base, and continued with weakness.

Examination: I found this 50 gram chameleon to have little skeletal muscle and weak toe grip. This isn't unusual after an illness or period of starvation when much weight is lost. When re-feeding begins, the increases in weight are due to water uptake and fat deposition. So although this chameleon had gained weight, it represented water and fat, and muscle function remained poor. Muscle is replaced at a slower rate, and it is only in the next 2 to 3 months (or more) that we'll see improvement in this chameleon's muscle size and function.

I next checked his calorie intake. Do you remember our calorie charts in the March 2002 issue? A 50 gram chameleon requires about 3.4 calories daily. I want this patient to have maximum dietary protein intake. Looking at the table above, I selected silkworms (75% of calories from protein) and young crickets (67% of calories from protein). The silkworms contain much water (83%) which should help this young chameleon maintain hydration. To begin, I want to feed about 75% silkworms and 25% crickets:

Calorie need per 24 hr: 3.4

25% from young crickets: 0.8 calories

50% from silkworms: 2.6 calories

Young crickets contain about 0.95 calories per gram (see chart). So about 0.8 grams (800 milligrams, mg) of crickets are needed (0.8/0.95). If our young crickets average about 97 mg (0.097 grams) each, then about 8 small crickets would suffice (800/97). Silkworms contain about 0.67 calories per gram (see chart). So about 3.8 grams (3800 mg) of silkworms are needed (2.6/0.67). If our silkworms average about 1.0 grams (1000 mg) each, then about 3 to 4 silkworms would be offered.

Note: the calorie estimates are for a healthy 50 gram chameleon that is mobile, alert and non-stressed, living in a comfortable environment. I started our patient on 50% of the calculated intake (4 small crickets and 1-2 silkworms daily), and food offerings are being increased gradually as he grows stronger.

This is just the tip of the nutritional iceberg that is the Zoo Biology paper. In subsequent issues, I'll introduce further applications of prey as functional foods, building upon the data presented for amino acids, essential fatty acids, vitamins and minerals.

Sue Donoghue, DVM, DACVN

Susan Donoghue, VMD, DACVN specializes in the research of herpetological nutrition. She is the founder of Walkabout Farm. She can be reached at

Walkabout Farm

PO Box 625

Pembroke, VA 24136


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