Introduction: Probably the most controversial aspect of iguana diets is whether or not to include animal protein (i.e. protein derived from animal products such as meat, eggs or dairy products). There are a couple of reasons why disagreement exists. For one thing, including animal protein as a staple part of the diet was recommended in most standard iguana care books for many years (and unfortunately still is, in most). Secondly, iguanas have the propensity to eat anything they are offered. I once heard someone refer to iguanas as “living garbage disposals”. Thirdly, most people seem to have a deep-seated belief that animals must eat animal protein in order to grow and be healthy – at least while they are young. Perhaps this stems from the fact that most of us are omnivorous ourselves, and we tend to be most familiar with carnivorous pets like dogs and cats. Thus, we are tempted to apply these eating habits to our iguanas, too.
What is the difference between “plant protein” and “animal protein”? Plant protein and animal protein are not different in terms of what they are made of (amino acids). The main difference between them is that animal products contain different ratios of amino acids and higher concentrations of proteins than most plant products do (there are a few high-protein plant products too, such as tofu). Most plants contain proteins in lower levels. In a strictly herbivorous diet, it is important to mix and match different plants to get the variety of proteins and amino acids necessary for good health.
Why the concern about animal protein in iguana diets? There are a couple of reasons why including animal products as a staple part of your iguana’s diet is a bad idea. For one thing, animal products often contain large amounts of fats and cholesterol, which are no better for your iguana than they are for you. Secondly, iguanas’ bodies are designed for maximum utilization of plant foods. They aren’t able to adequately process the high concentrations of proteins found in animal products. Their bodies tend to convert the products of excess protein breakdown to substances such as uric acid, which can be deposited in the tissues in crystallized form, leading to gout (for more information on gout, visit our Other Diseases page). Their kidneys have to work harder to remove the waste products of protein breakdown from the blood, which leads to kidney damage and eventual kidney failure in the long run. Given the fact that most captive iguanas are at least mildly dehydrated much of the time, too much protein in the diet just puts further pressure on already taxed kidneys.
But don’t wild iguanas eat bugs? At this time, there is no scientific evidence to support the idea that wild iguanas eat bugs or other animal products as a regular part of their diet. Only a few studies on wild iguana diets have been done, and the results of these studies support the iguana-as-herbivore idea. There have been occasional reports of wild iguanas hunting and eating domestic chickens, small lizards, etc., but these accounts have not been substantiated by actual scientific data. In fact, there are many factors that may encourage opportunistic eaters like iguanas to turn to alternate food sources for a short time, including habitat disturbance (and given the fact that much of the world’s tropical forests – wild iguana habitat - are rapidly disappearing, this is certainly a factor), drought or other weather changes that may make ordinary food sources unavailable, competition for prime feeding territory, etc. While it is not inconceivable that wild iguanas occasionally ingest animal products by chance or on purpose, there is no evidence that they do so in large amounts or on a regular basis. In fact, the evidence suggests that when plenty of vegetation in large variety is available for feeding, iguanas will stick to a strictly herbivorous diet.
But won’t my iguana be stunted if I don’t give it animal protein when it is a juvenile and is rapidly growing? No. Iguanas that are fed a healthy, well-balanced vegetarian diet from the time they hatch grow to be just as large and healthy as those iguanas that are given animal protein. Animal protein may cause an iguana to grow at a slightly faster rate, but since it is likely to shorten the iguana’s lifespan, it hardly seems like a wise trade-off.
Is there a “safe” amount of animal protein I can give my iguana? Probably. The problem is that, at this time, nobody knows what that magical “safe” level is. Giving your iguana the very occasional bite of your cheese sandwich or letting it share your cottage cheese as a treat probably isn’t going to hurt it – just as it’s not a big deal when you and I occasionally eat a Big Mac and a vanilla shake. It only becomes a problem when we eat junk food four times a week. The question, however, is this: Since we don’t know what the safe level of animal protein is for our iguanas, should we risk it? Do we really want to risk our iguanas’ health by trying to walk up to that borderline between “okay” and “too much”, without crossing it? Can we hope to do that, if we don’t even know where that borderline is?
Conclusion: So, given all the questions surrounding animal protein, what do we know? We know that there is no scientific evidence at this time to support the idea that animal products make up a significant part of wild iguanas’ diets. We know that too much animal protein causes health problems and shortens the life spans in pet iguanas that are given large amounts of it. We know that iguanas raised on strictly vegetarian diets grow, thrive, and are more likely to live out their full life spans. So, when you take all these things into consideration, there seems to be no good reason to include animal products in your iguana’s diet, and plenty of reasons to avoid it.
Animal Protein Issues from Wong's Green Iguana Heaven by Adam Britton is
an in-depth article written about animal protein in an iguana's diet. If you still have
any thoughts of feeding an iguana animal protein, please read this terrific article first
and you'll probably change your mind for the better!