The green iguana (Iguana iguana) is one of the most popular reptiles in the pet trade. It is also one of the most difficult to keep successfully. Prior to the purchase of an iguana, the cage, or the cage accessories, one should make every effort to learn about these lizards and their very specific needs. As a reptile owner, you will be responsible for creating a micro-environment that will mimic the animal’s natural environment.
Reptiles are dependent on their environment to provide them with a choice of temperatures within a range specific to each species of reptile. This range is referred to as the preferred optimal temperature zone (POTZ). A reptile will fail to thrive if kept at only one temperature within this range. Similarly, a lighting gradient should be provided; there must be areas of shade or filtered light, as well as an area of bright light in which to bask.
Ultraviolet (UV) light, specifically UVB rays, 280 to 315 nm, are essential to the health of the iguana. When UV rays contact the skin, they cause the conversion of vitamin D into a form that is necessary for the absorption and metabolism of calcium. Disturbances of calcium metabolism result in broken bones, osteoporosis, growth abnormalities, egg binding, tremors, seizures, paralysis and death. These and other signs related to calcium, temperature and lighting problems are among the most common reasons iguanas are presented to reptile veterinarians.
Iguanas require diets high in calcium and fiber. However, without the provision of appropriate temperatures, an iguana will not digest its food properly, its immune system will not function as it should and as a result, the lizard will not grow normally and will be more susceptible to disease. Failure to meet the basic physical and psychological needs of the iguana, including the need for visual security and privacy, will cause stress. Stress leads to a weakened immune system, increased susceptibility to infection, a poor appetite, and failure to thrive.
Iguanas are solitary, territorial creatures. Mature animals do not form recognizable social or group structures. Except during the breeding season, they spend little time together, and females do not provide care for their young. As hatchlings, before hormones have their influence, iguanas group for safety from predators. However, once they reach four to six months of age iguanas should be housed individually as they become territorial.
Aggression among animals often leads to serious, even fatal injuries. Aggressive displays by iguanas are very subtle, and owners may fail to notice signs of impending overt aggression among lizards. Some individuals are dominant, , particularly among the males, and even though they may not physically attack subordinate cage mates, subtle threats, or displays that take place when the owner is not watching are a source of considerable stress for animals that naturally live alone. It is not unusual for a dominant animal to keep cage mates from the food bowl and from the best basking spots. If iguanas must be housed together, plenty of space, visual barriers, multiple basking spots, feeding stations, and water sources are necessary.
Young iguanas should be handled only for a few minutes daily, as anything more than this is stressful. Being out of the cage for any length of time will result in the body temperature dropping and a cool iguana will not thrive. When alarmed or threatened, iguanas, particularly young iguanas, will jump erratically. In a wild situation, they leap from branch to branch and away from danger. In captivity the result may be an unpredictable leap from a shoulder. Be prepared for these sudden leaps and handle the animal securely and close to the ground, as serious injuries can occur.
Resist grabbing the tail of the iguana, as it can easily detach. This is another escape mechanism. More mature animals tend to whip their powerful tails or perform a 360 degree roll in an effort to escape. The sandpaper-like skin of larger animals can make this a painful experience for the handler and gloves and long sleeves may be necessary when handling even a calm animal. Although some individuals do bite, iguanas are not usually an aggressive species towards humans, and such behaviors are usually just an indication of a wish to escape. Some individuals, especially mature males, can become aggressive, even though they have been handled gently all their lives. This may be seasonal and related to hormones, and may be difficult to manage.
Since iguanas are by nature territorial, lizards that have free run of the house can be particularly prone to development of defensive or aggressive behaviors. A sudden change in behavior, whether increased docility or aggression warrants a visit to your reptile veterinarian, as it may signal that the animal is in pain or is ill. There are no simple solutions to dealing with a six foot, aggressive male iguana, but a discussion with your reptile veterinarian is the place to start.
Iguanas in the wild spend a great deal of time basking in the sun, particularly after eating, as the heat of the sun helps them to digest their food. At the same time the animal is absorbing beneficial ultraviolet rays, which are vital to calcium metabolism. This is why in captivity your iguana is attracted to bright light rather than to heat. In the wild finding a nice sunny spot provides him heat as well as ultraviolet light. In captivity, therefore, an iguana’s basking “hot spot” should also be the focus of the ultraviolet light.
Iguanas are prey animals in the wild, and so should be housed in relatively quiet areas with good visual security. They are susceptible to the effects of noise and vibration and will not enjoy being stared at by “predators” such as dogs and cats. For these reasons it is best to house iguanas in little used, quiet rooms.
Iguanas that rub their noses on cage walls or dig incessantly are showing signs of stress. Stress can come in the form of excessive handling, improper housing or diet as well as inappropriate temperature, humidity and lighting conditions. You should reassess husbandry conditions and diet periodically. Be familiar with the normal appearance and behavior of the species. Pay regular visits to a veterinarian who is familiar with reptiles, and educate yourself as to the natural history and husbandry requirements of the iguana.
Enclosure, Lighting and Heating
Any reptile enclosure should be easy to clean, well ventilated, properly lit and adequately heated. The cage must be escape proof and secure from interference by children and other animals. Glass aquaria and terraria can be suitable enclosures for smaller iguanas. For larger lizards, well-ventilated polyurethane-coated wood, plastic, Formica, or Plexiglas cages are more suitable. Greenhouses may work where the climate is suitable. Sometimes with the appropriate modifications, it is possible to devote a spare room or a large closet to housing an iguana.
Particularly for the bigger lizards, the cage design should be vertical, rather than horizontal, as iguanas like to climb and lounge on branches. Diagonal and horizontal perches are recommended, and these should be at least the diameter of the iguana’s body. For a large iguana, an enclosure of at least 8 by 4 by 8 feet high is recommended. The horizontal dimensions of the enclosure must be sufficient to allow the animal to stretch out and to move freely. Always provide visual barriers: reptiles do not like to live in a fish bowl.
Regardless of size, an iguana’s enclosure needs to meet the following criteria:
Heat sources can include heat lamps (infrared, ceramic), heat tape and undertank heaters. It also helps to keep the animal in a warm room. This is secondary heat. Heat must be present 24 hours a day, but white light should not be left on for more than 12 hours. It is recommended that the entire enclosure be heated to within the POTZ with, for example, a ceramic heater, which emits heat but no light, and adding a basking heat source, such as a spotlight focused on a small area, to provide an area at the upper end of the POTZ. Installing the radiant heat source (spotlight) at one end of the enclosure provides a temperature gradient. As iguanas should have approximately 12 hours of daylight and 12 hours of darkness, having the spotlight on a timer will accomplish the goals of a regular photoperiod and of decreasing the cage temperature slightly at night.
To prevent burns, be sure that the iguana cannot come into contact with any light or heat bulb. Heat lamps must be screened. Hot rocks are not recommended. These heat irregularly, and commonly cause burns. A hot rock does not heat lizards of any size adequately and since the rocks do not radiate heat significantly, they are not appropriate for basking lizards, such as iguanas. Iguanas have evolved to absorb heat from a radiant overhead source, that is, the sun.
No place in the cage should be cold. Sick lizards often hide, and if the hiding spot is not within the POTZ, the animal’s immune system will not function properly. Use a thermometer to check temperatures, not just in the hot spot, but also in shaded or cooler areas. Ideally, place several thermometers about the enclosure. Do not use your hand to estimate the temperature. “Warm” is too unreliable. Use a thermometer. A hygrometer, a device that measures humidity is another important tool. These can be bought at hardware stores.
Ultraviolet light in conjunction with an appropriate environmental temperature and diet is essential to iguanas. Ultraviolet light should be provided daily for 10 to 12 hours. Some lights are marketed as full spectrum, but do not necessarily emit the correct wavelengths of light. A light should meet the following criteria: CRI (color rendering index) of 90 to 100, and CTI (color temperature index) of greater than 5500 K. Lights recommended include Duratest Vitalite® and Vitalite Plus®, Black Light Fluorescent®, Reptisun® and Iguana Light®. Some lights, although they meet the UV requirements, do not emit natural looking light. None of these lights approaches natural sunlight, in terms of the UVB output and the psychological importance of proper lighting. An individual animal may benefit from a combination of lights. As long as the UV requirements are met, additional lights may be added to improve appetite and behavior.
Since reptilian eyes may see parts of the spectrum that we do not, natural light may be necessary for the environment, food and other reptiles to appear as they should to an iguana. Lighting may also affect the behavior of the animals and in addition to improving their psychological well being, correct light will help to display the animal at its best. Always use the longest tube light you can. A four foot light emits more than twice the UVB rays of a two foot light.
Ultraviolet rays do not penetrate glass or plastic, so to be effective the light, whether natural or artificial, must shine directly on the animal. For the iguana to receive the maximum benefit from UV light, it should be fixed 18 to 24 inches from the basking spot. In larger enclosures, this may be managed by fixing the light vertically or by using more than one light. When the animal can be kept with in the POTZ, sunlight is tremendously beneficial.
When the temperature outside is appropriate (80 to 95 F), expose your iguana to sunlight, either through a screened window or in a secure enclosure outside (provide ventilation, shade, shelter and water). Never place an iguana is a glass or plastic container in direct sun, as the enclosure can reach dangerous temperatures in as little as 5 to 10 minutes. Remember that to be effective in vitamin D and calcium metabolism, not only must the UV rays be present, but the animal must be within its POTZ. Be aware that reptiles, when exposed to natural sunlight, will often undergo dramatic changes in behavior, becoming very active, and sometimes changing color or becoming aggressive.
Substrate and Cleaning
The substrate or floor covering used in the enclosure should be safe, non-ingestible and easy to clean. Do not use corn cob, cat litter, bark, sand or gravel as these are easily swallowed and can cause an impaction or intestinal blockage. Organic substances such as corn cob and shavings are excellent growth media for bacteria and fungi. These substrates may appear clean but they can hide fecal material and leftover food. Dusty substrates, such as some cat litters and shavings, should be avoided, as they can contribute to respiratory disease. Artificial turf, indoor/outdoor carpet or newspaper usually make the best substrates. Paper toweling is best for very small, delicate skinned lizards. Be sure to clean and change the carpet or turf regularly, as it will eventually grow mold. Trim or flame the edges of turf to seal them, as small toes can become trapped in loops of material, and frayed edges can look remarkably like plant material and may be consumed.
A functional, easy-to-clean cage that meets the needs of the lizard should be the goal of the iguana keeper. The more decorative the cage, the more difficult it will be to clean and, as a result, it will be cleaned less often. Questionable or poor hygiene contributes significantly to the burden on a reptile’s immune system. A high environmental bacterial load will increase the chances of any animal’s developing disease. Fecal material should be removed daily and food and water dishes should be cleaned daily. Several times weekly, disinfect the dishes after washing them. Depending on the size of the cage, daily spot cleaning, weekly cleaning, and monthly thorough disinfection is a minimal recommendation.
Use hot soapy water or water and vinegar for cleaning. Only a clean surface can be disinfected. Once a surface is clean, it can be disinfected with a non-toxic product. Avoid phenol products. A three percent bleach solution is safe and effective for most purposes. Your veterinarian likely stocks other products. No single product is ideal for every situation, and organisms can develop resistance to cleaners and disinfectants, so a rotating schedule of use is recommended. Always rinse well after cleaning and disinfecting. Be sure there is good ventilation, as even low levels of safe products can produce fumes harmful to delicate reptile lungs.
All animals need privacy and so an enclosure should include a house or hide. Be sure that the house is also adequately heated. A sick animal will hide and a sick reptile not kept within his POTZ will only get sicker. In the wild iguanas spend a great deal of time in the trees, so provide branches of at least the diameter of the iguana’s body. Fixed platforms are also useful, and “hammocks” can be fashioned for some lizards. If the iguana is to be kept in a tank, it is important that the glass not be uncovered on all four sides. As a prey species, iguanas need to feel safe, not exposed, as one would living in a fish bowl. Use plastic vines, safe plants, branches, aquarium backing and cage furniture to provide visual barriers. Do not use mirrors in the cage, as the appearance of “another iguana” will be stressful to your pet.
Diet and Supplementation
Our understanding of the iguana’s nutritional requirements has changed considerably over the last ten to fifteen years. Current studies will likely lead to further modification to current recommendations. The precise nutritional requirements of the green iguana are not known. For this reason, one must adhere to certain principles based on their known biology when feeding iguanas.
A single commercial or restricted homemade diet can be dangerous. Iguanas are true herbivores; more specifically, they are folivores (leaf eaters). Although their requirements change slightly as they age, the bulk of their diet should always be dark leafy greens, high in calcium and high in fiber. Since we cannot offer the leaves found in the iguana’s natural environment, every effort must be made to select from what is available. Offer as wide a variety as possible of foods of the highest nutritional quality.
What follows are recommendations based on clinical experience, common sense and sound research:
As iguanas age, their protein requirements decrease. The following is a guideline for healthy iguanas, growing normally:
Cat food or dog food is never appropriate for iguanas, as they cannot digest it properly and it can lead to serious nutritional deficiencies and toxicities. Meat products are often high in fat, vitamin D and phosphorus and low in calcium. Cat food, dog food, other meats and monkey chow should never pass green lips.
Use vitamin and mineral supplements cautiously, as there is a very real risk of overdosing vitamins A and D. Remember that supplementation will not compensate for a poor diet. A multivitamin/mineral supplement designed for reptiles can be given weekly to young iguanas, every two weeks to adolescent iguanas and monthly to mature iguanas. In addition, a calcium carbonate or calcium gluconate supplement, containing no vitamin D or phosphorus (purchased from a pharmacy) is recommended every two to three days for young lizards, every three to four days for adolescent lizards and weekly for mature animals. It is a good idea to discuss the topic of supplementation with your veterinarian, in light of the rest of the iguana’s diet and his health status.
The following are suggested food sources for iguanas. Every effort should be made to offer foods high in calcium as the bulk of the diet, and at least two of these should be included in every feeding. A variety of other foods in the proportions discussed above, should also be provided. Foodstuffs should be washed, mixed, and if the lizard is a picky eater, should be chopped as finely as necessary or run through a food processor to ensure that he does not eat just his favorite things. In the case of young lizards, offer a variety of foods from the beginning to develop healthy eating habits.
Commercial diets are a convenient option when feeding iguanas, but it must be emphasized that these diets are a relatively recent creation, and are subject to minimal regulations with respect to content. Food colorings, preservatives and many other ingredients would never cross an iguana’s path in the jungle, and so it is recommended that none of these diets form the majority of the diet until further research has been done.
A further concern with formulated diets is that they are dry. Some pelleted diets may be soaked, but should not be dripping, as important nutrients may leach out. Low grade, long term dehydration is a common problem for captive iguanas, so it is important that food be moist and that clean water be available at all times. Clean the water dish daily, and check it more often, as many lizards will urinate and defecate in their water dishes. Ideally the dish should be large enough to allow the animal to soak, but must be easily entered and exited.
In addition to providing water and maintaining a humid environment, it is a good idea to soak your pet at least twice a week. Iguanas are natural swimmers and should be allowed to express this natural behavior. Soaking will encourage urination and defecation, and so can become a means to keep the cage clean. Iguanas can also be misted – at least once a day is best. This may help to stimulate the appetite as well as to increase humidity.
The Healthy Iguana
Once your pet has grown accustomed to his new home, over several days or weeks, begin gentle, quiet, daily handling. Follow a routine with respect to cleaning, feeding and handling, as iguanas are creatures of habit. Do not allow your iguana free run of the house. If the iguana carries the bacteria Salmonella, it will spread throughout the house and control over the temperature, humidity and lighting of his environment will be lost and his health will suffer. Unsupervised access to a home carries many innate dangers. Many iguanas will happily eat small shiny objects, and they are frequently injured by falls or by other pets.
Iguanas should be bathed daily, whether in a tub or misted. For hygiene reasons, it is not advisable to use sinks or bathtubs used by people.
As wild animals, iguanas are very susceptible to stress. Any change in appetite or behavior likely warrants a visit to your reptile veterinarian. Subtle changes are often the only ones seen before a reptile is seriously ill.
Common Diseases and Disorders
It is recommended that your iguana be seen by a veterinarian familiar with reptiles, shortly after purchase. A six month visit is advised to evaluate the lizard’s progress, to review husbandry and to catch any problems early in their development. Thereafter, annual visits are suggested, both to examine the lizard and to inform you of any new information in the field of iguana care and nutrition.