For years, it was thought that iguanas were omnivores, consuming both animal and plant matter. This was compounded by research into raising iguanas for food which found that iguanas fed high quantities of protein grew much more quickly to a size suitable for slaughter. The fact that this diet killed iguanas at around seven years of age mattered little as they were killed and consumed long before then. The recommended diets coming out of this era (and still, unfortunately, found in recently published books), included significant amounts of animal-based protein such as meal worms, pink mice, crickets, chicken and beef flesh, meat-based omnivore or carnivore zoo food products, and cat food. Much of the mainstream veterinary literature apparently just picked up on whatever the available popular pet iguana books listed for diets, so you will often find veterinarians who have not kept up with recent reptile veterinary literature recommending animal protein components ranging from fifty percent protein for hatchlings (Jeffrey Jenkins DVM, client information sheet) down to thirty-three percent (Nancy Anderson DVM, The Compendium 13(8)), fifteen percent (Stephen Barten DVM, Veterinary Clinics of North America Small Animal Practice/Exotic Pet Medicine 23(6)) and no animal protein (Fredric Frye, 1993, who recommends plant-based proteins). Others, such as Thomas Boyer DVM, recommend a higher volume (twenty percent) of certain animal-based foods such as trout and cichlid chows, vertebrates and bird chows, but a lower volume (five percent) if fed monkey biscuits or dog chow (Journal of Small Exotic Animal Medicine 1(1)). Some vets, such as Jenkins and Barten, who previously recommended small amounts of animal protein as being safe, in the past couple of years, based on continued research into iguana nutrition and what they and other vets have been seeing in their practices, have come to the conclusion that no animal protein is suitable or safe.
Dr. C. Richard Tracy, formerly of Colorado State University at Ft. Collins, who has been studying iguana nutrition, states "It is very difficult to give a diet that is too low in protein as long as the animalsget a balanced 'salad' of food (including alfalfa for protein) and also get plenty of UV radiation." (Iguana Times 1(6):15). Jenkins, in his earlier handout, stated "Captive young iguanas do poorly eating a diet of grocery store vegetables. Perhaps because of their rapid rate of growth, it is essential that they be supplemented with protein and a balanced source of calcium." Jenkins is correct in that most people's idea of 'vegetables' includes a long list of low calorie foods containing little in the way of nutrition: lettuces, zucchini, tomatoes, cucumbers, mushrooms, vegetable and bean sprouts and watermelon are some of the more commonly fed non-nutritious foods.
The fact of the matter is, iguanas can--and should--be raised on strictly plant-based diets, with protein coming from plant materials. They do not need, and should not have, monkey, trout or carnivore or omnivore chows, chicken, beef or other animal flesh, dairy products, eggs, worms, mice, crickets, cat food, and dog food. Despite this fact, there are still books being published today which recommend some or all of these foods. Some also recommend feeding bird gravel ("for digestion") which is not only completely unnecessary, but dangerous as the gravel will cause internal injuries and serious, if not fatal, impactions.
According to Boyer (JSEAM 1(1)), Gordon H. Rodda (Herpetological Review, 25(2):85), and John Iverson (Adaptations to Herbivory in Iguanine Lizards, in Iguanas of the World: Their Behavior, Ecology and Conservation, GW Burghardt and AS Rand, eds., 1992, Noyes Publishing, Park Ridge NJ), iguanas are folivores (leaf eaters) in the wild, despite previous reports of their insectivorous and carnivorous natures as juveniles. Though they may occasionally ingest bits of carrion or an insect perched on a leaf, animal protein consumption is accidental--not a conscious dietary choice. Their digestive system is structured to process a high-fiber plant diet, and to extract much (but not all) of their water needs from the foods they eat.
This doesn't mean you can just dump a head of iceberg lettuce in the iguana's enclosure, or use even the bags of prepared salad mixes now increasingly available at supermarkets. And most salad bars, in restaurants and school cafeterias, aren't loaded with much in the way of nutritional foods for your iguana. The key is selecting the right type of vegetables, greens and fruit. For those of you who are not well acquainted with the produce department of major supermarkets or green grocers, or live in countries where these plants may be known by very different names, Wegmans Produce and Virtual Garden websites offer searchable sites with pictures and descriptions.
So how do they get their protein? Alfalfa! Alfalfa is an excellent source of plant protein (just think of what it does for a horse!). Alfalfa pellets (also called rabbit food, or rabbit chow) mixed in with their vegetable salad (which will break it down due to the moisture content naturally found in the vegetables and fruits) provides a good source of protein and calcium, with 15% protein by volume and a 6:1 calcium-phosphorous ratio.
Some people feed tofu as a protein source. The problem with tofu is that it is high in fat and protein, and fat impedes calcium metabolization. Iguanas fed tofu on a regular basis do get calcium deficiencies, especially when any part of the D3-calcium-phosphorus triad is out of balance. If you eat tofu and want to give your iguana a bit of it when you are making some for yourself, then by all means feel free to do so. It should not be fed on a regular basis, and when fed, fed in very small quantities. Some of the other vegetables in the recommended base diet contain protein, as well. Before alfalfa is even added, the diet below contains 11% protein.
Why is animal-based protein such a problem? Excessive amounts of such protein is more than the iguana kidneys can handle; one of the top killers of iguanas is kidney failure. Just why animal protein would have such an effect hasn't been figured out yet. My guess has something to do with the already established efficacy with which the iguana colon breaks down tough plant material. Plants have both a cell membrane and a tough cell wall; animal cells have only cell membranes. Iguanas, under optimum care conditions, can extract 40% of the nutrients from the plant food they eat, making them one of the most efficient herbivores, topping even rabbits. Given this strong, specially adapted gut, they may be breaking down more animal matter into bioavailable components than they can do with plant matter, thus absorbing more animal protein (and fats) than they would eating the same quantity of plant material. (For interesting discussions on colon and digestion, I refer you to the Iguanas of the World book referenced above, both to the Iverson chapter on herbivory and to the McBee and McBee chapter on digestion.)
When people call with problem iguanas, I always ask what they are feeding their iguanas. The answer, invariably, is "vegetables." When I ask what kind of vegetables, the response ranges from "well, you know, just.... vegetables!" or, proudly, "Oh! lettuce, zucchini, broccoli and once a week or so, a little bit of fruit." The fact that iguanas can survive two years or so on a diet comprised of so little nutrients makes it all that much harder to accept all those who die from improper diet and environment.
We have always been told to "eat your vegetables" and in the past couple of years, the news has been full of reports that certain vegetables and fruits may help prevent cancer and a variety of illnesses and diseases. Humans consume a great variety of foods during the course of a day, week and month, and so any one vegetable we may eat consistently, or exclusively, forms only a small part of our total diet, not the primary portion. This is, for many folks, difficult to understand when they are considering their ig's diets. That, combined with trying to keep things as easy or quick as possible for themselves, leads owners to offer a very limited selection of food on a daily basis. Thus we see iguanas who are fed primarily on broccoli and Brussels sprouts, two vegetables which are easily cut into small pieces for iguanas. When combined with the equally convenient soaked monkey biscuit, and kale (all the books list kale as one of the high calcium greens) or packaged, prewashed spinach, you get not a healthy iguana, but one which is stunted and lethargic, lacking in many essential nutrients. Great color, but little energy or interest in the world inside or outside its tank.
When fed in excess, vegetables including broccoli, Brussels sprouts, kale, cabbage, cauliflower, and bok choy cause hypothyroidism, a thyroid deficiency. This slows down the metabolism, causes lethargy, muscle and joint aches. The animal gains weight due to the slowed metabolism, but overall growth is slowed considerably. These vegetables may be fed in small amounts in addition to the regular vegetables, mixed into their salad, but should never comprise the primary part of the salad. Spinach, rhubarb, beets and chards are high in oxalic acid and may cause gout over a period of time.
Additionally, these foods binds calcium, effectively preventing the body from utilizing the dietary calcium. Over a period of time this causes metabolic bone disease, with the body resorbing calcium from the bone to use for various metabolic and cellular processes. The bones begin to look like sponges as the calcium is pulled out of the bone matrix. Swellings along the long bones and tail begin to appear (as fibers are formed around the bone to try to hold the matrix together) and the bones are easily fractured. In advanced cases, the jaws become too soft and swollen for the animal to eat on its own and partial paralysis and tremors may set in. Early on, when the bumps are first felt, the condition may be reversed by changing the diet (and making any necessary changes to the environment). As the disease progresses, however, it requires veterinary intervention: radiographs to assess the degree of bone loss, injections of calcium and prescription calcium supplements administered as well as vitamin D3 injections. If bones are fractured, they may require immobilization. A course of antibiotic therapy may be necessary. All in all, it is much easier (and cheaper!) to feed the proper foods to begin with.
Since our iguanas (and other captive herbivores and omnivores) do not get to select from a wide variety of foods during the course of their days, we have to ensure that they get at least a good basic foundation of nutritious foods which have as little adverse impact as possible on their system. Other vegetables and fruits can be added to that foundation as whim or the contents of your refrigerator permits. Providing such a foundation can be time-consuming when the foods are prepared on a daily basis, or even when prepared a couple of days in advance. This, I believe, is why people settle on the "fast foods" mentioned above. (See Food Preparation below.)
While thawed frozen vegetables and greens are undoubtedly the easiest to use, it has been determined that some of the green vegetables lose their thiamin as a result of being frozen (Frye, 1991; unfortunately, there is no hard information on just which green vegetables lose thiamin so it is best to error on the side of caution and avoid them all).
Thiamin (vitamin B1) is important for the nervous system and, in conjunction with the other B vitamins, helps reduce the effects of stress, promotes growth and aids digestion (Mindell, 1985). Thiamin is a water soluble vitamin. Excess amounts in the system are flushed out each day and so must be replaced each day. When thiamin is lacking in the diet, the other B vitamins are unable to perform their functions properly and a variety of problems will result. The most insidious are tremors and partial paralysis. These symptoms are often confused with calcium deficiencies by veterinarians who are not aware of the frozen greens/thiaminase link. They begin to treat the iguana for calcium deficiencies, becoming more aggressive as the iguana fails to respond "properly." This becomes a harrowing experience for the owner, an irritating one for the vet, and an increasingly painful and debilitating one for the iguana.
By all means, keep a bag of mixed vegetables on hand to use in case of extreme emergencies for a couple of meals (be sure to replace with fresh packages at regular intervals to guard against vitamin loss). Consider making extra fresh food, and freeze a couple of weeks worth a couple of times a month, using the frozen food during the month in which it was made. This should not be a long enough time to destroy all the thiamin; the addition of a bit of Brewer's Yeast (a multiple vitamin B supplement) will ensure adequate thiamin. Use about 1/2-1 teaspoon of brewer's yeast per batch of salad.
Remember: no amount of vitamin powders, pills or liquids are going to compensate for a poor diet. What goes for computers goes for iguanas--GIGO: garbage in, garbage out.
We have always been taught that fruits are healthy for us. And they are. But when it becomes the major part of any diet, that diet is not balanced. With iguanas, this becomes particularly critical as most fruits (and vegetables) are very low in calcium and often fairly high in phosphorus. Bananas are almost always accepted by iguanas to the exclusion of every thing else and, being easy to feed, often becomes one of the major plant components of the diet along with lettuce and broccoli. Fruits should compose the smallest part of the diet in iguanas.
Besides being nutritious, the dark leafy greens are also "fun" food. They are the closest we can get to giving the iguana food that resembles the leaves they consume in the wild. While some books and caresheets instruct the owner to cut the greens in small pieces, I prefer to leave them larger, about the size of or a little bigger than the iguana's head, and serve them by themselves in a heaping pile.
You can also provide a bit of natural feeding activity and a nice change from the chopped vegetable/fruit salad by hanging up a whole leaf from the top of the enclosure so that it dangles inside, and let the iguana grab and tear at it as he would in the wild. Use two or more of the following greens daily: collard, mustard (including flowers), dandelion (including flowers), escarole and water cress (note that these greens are in addition to the alfalfa added for protein and fiber). Many markets carry (or will, if you ask them too) dandelion greens. You can use wild-collected dandelion greens and flowers if you are positive they have not been subjected to pesticides, herbicides and other toxins; any dandelions growing by the roadside should not be considered as fit for consumption.)
Use romaine, green leaf and red leaf only in emergencies, and then only for a limited amount of time; although they are more nutritious than their paler cousins, it's not by much. Don't even bother with head (iceberg), Boston and butter lettuces--they lack nutrients and iguanas often become hooked on them to the exclusion of other greens.
Bean and vegetable sprouts do not have much in the way of nutrition. In addition, they are bulky and, if used in a salad, may form too big a part of that salad. This means that your iguana will actually be getting less in the way of nutrition than the same salad without the sprouts. If you have some sprouts around for yourself and your iguana likes them, then go ahead and give him some as a treat.
There are several edible flowers that you can grow yourself or buy in the produce (not flower!) section of the grocery store or plant nursery. The ones you grow yourself and that you buy in the produce section. Plants grown for decorative purposes may have been treated with systemic or topical pesticides; ask the nursery or plant manager if they know. If they don't, err on the side of safety and don't buy them. Edible plants include hibiscus (flowers and leaves) nasturtium (flowers and leaves), rose petals, violets (flowers and leaves), and geraniums. Indoor plants include wandering jew, pothos spider plant and ficus. (Because of their destructive tendencies, it is not a good idea to furnish an iguana enclosure with potted plants - they will be shredded or consumed within a very short time!)
Iguanas, while equipped with a set of very sharp teeth, do not chew their food, instead gulping it rather like a dog. I have seen iguana owners and pet stores who put out a lovely selection of foods--entire broccoli florets, whole grapes, lengths of carrots, cubes of raw acorn squash, dry monkey biscuit, even whole apples--and not realize that their animal is barely, if at all, eating. With the aid of a full-sized or mini-food processor, a Salad Shooter® or similar hand-held or counter top automated food slicer/shredder, or even a pair of strong arms and a good old sharp grater, the Basic salad can be made for a week or more. The salad, stored in an air-tight container in the refrigerator, is ready to whip out, spoon into the iguana's food dish, placing the remainder back into the
refrigerator. If the leafy greens have been similarly prepared (leaves separated, washed, blotted dry, torn into pieces and placed in a ziplock bag with all the air squeezed out), then feeding the iguana quickly - and nutritiously - each morning is a snap.
The base salad should be constructed of fresh, raw vegetables including at least one green and one orange vegetable, parsnip, a fruit, and protein and calcium supplements. At least twice a week, a multivitamin is added in addition to the calcium.
For the green vegetable, use green beans, snap peas or snow peas. Wash well, then steel-knife in the processor or grate. Feel free to throw in carefully washed carrot tops. These tops can be steel-knifed in the processor or placed in a bowl and cut with kitchen food shears into small pieces. Occasionally, a small amount of broccoli, bok choy greens or Brussels sprouts may be added to the regular green vegetable.
For the orange vegetable, select of the orange-fleshed squashes (Kaboutcha has been reported to bring out any blue accent skin colors). If you need to, microwave the harder squashes until they are just soft enough for you to cut into lengths which will fit through the shredder. Also shred the parsnip. Sweet potato and yams may be shredded and used occasionally.
Carrots, while an excellent orange vegetable, do contain a certain amount of calcium oxalic acid, the same stuff that makes spinach so bad. Their levels are not as high, however, and so can be used alternatively with the squashes. Their tops have oxalic acid, too, so use only in moderation.
Other vegetables which may be used in small amounts in addition to the above are sprouted vegetable and beans. Your iguana may also enjoy the occasional taste of mushrooms, bell peppers, onions, oregano, basil, cilantro, other root vegetables, cactus pad, star fruit, asparagus, okra, and any of the summer yellow and green squashes.
For the fruit, figs are the highest in calcium, with dried figs highest of all. Unfortunately, fresh figs are rather expensive unless you are lucky enough to have a tree. Dried figs are available in grocery stores during the November-December holidays, but can often be found throughout the year at health food stores. Raspberries, strawberries, papayas, pears, plums, mangos, apricots, cantaloupe, dates, grapes, soaked raisins, prickly pear cactus and kiwi (both skinned) are all good fruits. They should be steel-knifed or finely chopped, then mixed in with the vegetables.
Protein, in the form of alfalfa chow (aka: rabbit food pellets, alfalfa pellets, sheep chow, even horse chow), can be ground in the food processor (use the steel knife) if your ears can stand the noise, but may also be left whole and mixed with the vegetables where the pellets will be broken down by the moisture in the salad.
Mix thoroughly the vegetables, fruit and alfalfa. Add the calcium and vitamin supplements, and mix thoroughly again. Place in an airtight container and keep refrigerated.
While the proportions of food types remains the same, the actual amount of the foods will vary, increasing as the iguana gets bigger and consumes a greater volume of food. I recommend the following:
1/2 cup shredded green beans
1/2 cup shredded squash
1/2 cup alfalfa pellets
1 medium parsnip, shredded
1/4 cup minced fruit
(During the parsnip crop's off season, use 1/2 cup shredded asparagus, or 1/2 cup drained, rinsed, and chopped canned cooked lima beans, plus additional calcium to make up for the lousy alcium:phosphorus ratio in beans.)
Remember to prepare the foods in very small pieces, finely chopped, minced and shredded. The smaller the pieces, the more they can fit into their stomachs, and the more efficiently it can be digested. The salad, however, does not need to be pureed to a mush.
The amount of calcium and vitamin supplement will vary depending upon the quantity of food you are serving. The rule of thumb, however unscientific it is, is to sprinkle a pinch or two of the vitamin powder on and mix it in. (Most books say to sprinkle it on top; to me that's like having to eat every meal with wheat germ on top. As long as you do not put out much more food than your iguana can eat, and you are feeding nutritious foods, there should not be a problem with the iguana ingesting all the vitamins added to a meal.) See the Vitamin Supplements article on frequency of multivitamin and calcium suppementing.
Serve on a plate, jar lid or, for larger iguanas, in wide-mouthed bowls or crocks, with the leafy greens piled nearby. (Make sure the bowl is one the iguana can easily access; I see owners and pet stores feeding their igs in crocks so tall that not only can the iguana not see in, it would have to actually get into the bowl to be able to get anything to eat!) Again, experience will tell you how much of the greens to offer. If you find the iguana is eating the greens and ignoring the salad (which is common as they do not initially recognize the salad as being "food"), put down the salad in the morning and offer the greens in the afternoon after the salad has been eaten.
For those who are deprived of good selections of iguana fruits and vegetables, here are some suggestions. Asian markets are a good place to find greens like mustard and peavines. Carrots and some form of orange squash can always be found or supplied by first year baby foods such as sweet potato, carrot, and squash when necessary; use the peas or green beans too, if you have to. Baby food fruits such as apple-blueberry, mango, etc. can also be used on occasion. While baby foods are very helpful to have in a pinch, they should not be used as a regular part of the diet. Don't be shy about asking your produce manager to carry some of the foods you need on a regular basis. Also, venture out and check out other grocery stores - often one or two stores carry more produce than do all the others in the same area. Also, don't be shy about asking for help identifying foods that are there.
Try including some leftovers: rice, plain chopped cooked noodles, whole wheat or grain breads mixed in with the salad; boost the calcium supplement a bit to counteract the high phosphorus content of these foods.. Watch out for cheese or fatty sauces and, spicy or sugary foods--iguanas can develop bad eating habits just as easily as people...and they are just as difficult to correct! Be careful when hand-feeding iguanas. While that is often a good way to get a reluctant iguana to eat or to try a new food, they easily become used to hand feeding and will refuse to feed from a dish.
While this may be endearing to the owner, it is not so endearing if the owner must be absent for any length of time (and no one can be found who will or can take to time to sit there and hand feed the iguana) or the owner becomes so busy for a period of time during which hand-feeding becomes difficult or impossible. This will cause the iguana undue stress, and it may stop eating for the duration. This can weaken the iguana immunologically, and it will be more susceptible to illness and injury.
Iguanas often do not accept new foods when they are first offered. It may take several days before they realize it is food. This is one reason why vegetables and fruits should be finely chopped, grated or shredded and mixed thoroughly together--it makes it difficult to pick out the "good" bits. Iguanas' food tastes change over time, just as it does with people. A food that used to make the iguana leap across the room may fall out of favor only to be replaced by a previously detested food. I once cared for an iguana who alternately loved, then disdained, cantaloupe. The same is true when offering hibiscus, nasturtium and geranium leaves and flowers, rose petals and dandelion flowers. The rule is, don't give up. Essential foods can be mixed in with the salad. Fun foods, such as flowers and leaves, can be offered now and again to see if there is any change in taste.
Feeding iguanas is kind of like keeping iguanas. There's a lot to do and learn initially and it may take awhile to develop a pattern, but when done consistently it will become automatic and will leave you more time to enjoy your iguana rather than merely maintaining it.
I have found that many people wait until they get home from work at night to feed their iguanas. Iguanas are diurnal animals who forage, eat and begin digesting the day's food during the mid-day hours, not during the cooler night-time temperatures. A hungry iguana may well eat heartily at night, but much of the digestive processes are delayed, hampering the body's ability to process the maximum amount of nutrients available for uptake.
Many books state that iguanas don't drink; they do. Others say you should put a bowl of water in for some limited period of time, like a half hour a day; since iguanas have not yet been known to vocalize their needs, it is best to always provide a bowl of fresh drinking water. As with the food bowl, make sure that the iguana can see into and reach the water in the water bowl. Make sure, however, that it is not so deep that if he falls in he will drown. A boiled rock can be placed in a large bowl to give him something to stand on, and outside the bowl to act like a ramp or ladder to reach the rim of the bowl.
Note that many iguanas will defecate in their water bowl. While this makes it very easy to keep his enclosure clean, it does present a problem in that the bowl needs to be removed as quickly as possible and replaced with a fresh bowl of water. The dirty bowl should be washed thoroughly and disinfected before being reused.
As stated earlier, igs are great swimmers, and a daily swim is a great time for the iguana to both drink and poop. So consider making a morning bath part of your--and your ig's--daily routine. Be sure to disinfect the tub afterwards.