By Rick Kleyn
Iguanas are not kept as pets in South Africa to the same degree that they are kept in other parts of the world, but they are becoming increasingly popular. They are true lizards but are strictly vegetarian, or more specifically, folivores. This means that they consume primarily leaves in their natural environment. They are also hindgut fermenter, which means that they require microbes to ferment the high-fiber foods they ingest before the nutrients may be utilized. This is similar to how ruminants (cattle) digest food. This process of digestion requires a high body temperature, and for this reason, wild iguanas will usually bask for about four hours in the morning to elevate their body temperature prior to foraging.
It was originally believed that baby and juvenile green iguanas were omnivores or partial insectivores. It is true that young animals are confined to the ground or the lower branches of trees, and that they only reach the upper branches later in life. This has lead people to draw the wrong conclusions, but it does not change the fact – young iguanas are indeed folivores and they continue to be plant-eaters throughout their lives. However, wild iguanas may occasionally eat carrion, insects and they may even cannibalize hatchling iguanas. For these reasons many people make the mistake of feeding young iguanas a meat only diet. Meat only diets lead to metabolic bone disease, which is charaterised by lack of bone mineralization, swollen legs, loss of appetite and lack of movement. The reason for this is that meat contains high levels of phosphorus, low levels of calcium and hardly any vitamin C. In short, meat has what is known as an inverted Ca:P ratio and what little calcium there is in the diet is used for maintaining normal body function at the expense of skeletal development.
Most people are aware of the shortcoming of a meat only diet, and sadly this has lead to over supplementation of home mixed diets with both vitamins and minerals. It needs to be remembered that Vitamin A, fed in excessive amounts is highly toxic. Surplus minerals are the major cause of death in adult animals and the bones become very brittle and susceptible to breakage.
How then do we feed iguanas correctly? Although they are herbivorous they will develop a taste for inappropriate food items. They will eat popcorn, dog food, insects and any number of other products. The use of dog food and/or monkey food in the diet leads to protein and fat levels are also too high for an iguana and gout and other nutritionally related diseases will occur.
Iguana owners often perceive ingredients to be either “good” or bad” (i.e. lucerne and crickets are good and lettuce is bad) and believe that if they use only “good” ingredients they will feed their animals a perfect diet. The truth is all animals need the correct nutrients and not the correct ingredients. To get a mixture right without specialist knowledge and computer software is unlikely.
It is difficult to know how much to feed iguanas. It suggested you feed according to body condition. If they get too thin, simply feed more and you should prevent them from becoming too fat.
As with the diets of all captive animals, 50 to 60% of the dry matter content of the diet should be made up of a well balanced, specialist product, a number of which are available on the market. I would expect that the pellets that are fed should contain at least 25% protein, 2% calcium and 1% phosphorus.
The remainder of the diet should be made up of dark-green leafy vegetables, to closely simulate the leaves that wild iguanas consume. This would include such items as turnip greens, watercress, lucerne or clover. Lucerne pellets may also be used. Limited amounts of beetroot leaves and spinach contain oxalates which may bind dietary calcium. Brussels sprouts, broccoli, cabbage and cauliflower bind iodine and may result in goiter, although this is unlikely to be a problem if the correct proportion of a balanced diet is offered. Be aware that the darker, outside leaves of most vegetables are more nutritious than the paler, inside leaves. 10 to 15% percent of the diet can be made of fresh or frozen (thawed first) vegetables.
Fruit tends to be the preferred food of iguanas but they are generally high in moisture and are generally mineral-poor. They should therefore only be used as a top-dressing, or to increase the palatability of the mix for the finicky lizard. Other treats such as hibiscus flowers and leaves rose petals, geranium flowers, nasturtiums, carnations and dandelions can be fed from time to time. It is not necessary to feed live food to iguanas.
When putting a diet together you need to bear in mind that most fresh green vegetables contain between 70 and 80% water. I have calculated a typical diet below:
This mixture will lead to a diet that provides enough protein and energy for the animals and will also overcome the dangers of both over or underfeeding vitamins and minerals.
From a practical feeding point of view, hatchlings, and iguanas measuring up to 14 inches in length should be fed finely chopped food twice daily. A grater works well to reduce food items to pieces small enough for a hatchling to swallow. Another advantage to a chopper or grater is that it is possible to make a homogenous mixture of foods to ensure that they can’t eat selectively. Older iguanas, up to three feet in length, can be fed medium chopped food once daily. Adults over 2 1⁄2 years of age (or over three feet in length) can be fed coarsely chopped food every other day. Make sure all foods are washed thoroughly, then chopped and mixed. Ensure that you use clean bowls every day to avoid any nutritional deficiencies.
Follow these simple guidelines and your animals will reach their mature size of some 2 meters and live to a ripe old age.