Growth, Maintenance and Behavior

Physical Appearance

First, I think it's a good idea for you to know what all those things are on your iguana's body and what they are there for.

Nose and Mouth
For example, your iguana has a nose and a mouth just like humans do, but iguanas don't use their noses for smelling the way humans do. The nostrils are used for breathing and for salt excretion. As I will discuss in the Sneezing section, iguanas sneeze out salt through their nostrils. The mouth is used for obvious things like eating and biting, but the tongue is essentially used for smelling. You should notice your iguana stick its tongue out frequently, apparently tasting things as he walks along (like a healthy iguana should) and this is how the iguana "smells", mainly for identification purposes.

The eyes, as you may guess, are used for sight. You may notice that your iguana will sometimes close its eyes if pet on the head or neck. It is not fully understood why this is done, but it is generally recognized that iguanas who do this are not in pain or discomfort.

The ear, or tympanum, is that clear, roundish object on each side of your iguana's head. Green iguanas can indeed hear, unlike many of their reptilian relatives, so please take that into consideration when playing loud music or turning the volume up on the television. Most iguanas are not bothered by loud, constant sound such as music, but you must learn to identify when your iguana is stressed and make the appropriate changes to calm your pet down.

Notable Scales and Flaps of Skin
Generally under the ear is a very large, round scale called the sybtympanic plate. This scale does not have any biological function, but it is considered to be the distinguishing characteristic of the species Iguana iguana. If you ever visit a pet store that has lots of baby green lizards that resemble iguanas but you're not sure of their species, check for the subtympanic plate. If the lizard doesn't have one, then it's probably a baby water dragon or basilisk, lizards that resemble iguanas when young. Under the jawbone is a large piece of hanging skin called the dewlap. The dewlap is usually extended when the iguana is feeling threatened and wants to make itself look big and scary. If your iguana extends its dewlap when you or another iguana goes near it, it may be interpreted as a sign of stress, or at least discomfort. If you walk closer and then gently stroke your iguana on its sides or head and the dewlap relaxes, then your iguana has probably recognized you and is once again at ease. Sometimes your iguana just might want to let you know that you are in its territory, and the dewlap will extend as you approach. In addition to the dewlap, iguanas also have tuberculate scales, which are the small bumps on its neck behind the ears, and the spines that make up its dorsal crest, to help it look big and scary to potential predators or unwanted mates.

The Top and Bottom, and the "Bottom"
The entire back of the iguana (the "top view") is referred to as the dorsal region, and the belly (the "bottom view") is referred to as the ventral region. The cloacal vent is the slit right behind the rear legs on the underside of your iguana. Iguanas use this opening in the skin for discharge of excrement and for access to the mating organs. Males use their hemipenes for mating; basically, they have two penises but only use one at once. The small bumps that line the underside of your iguana's rear thighs are called femoral pores. Especially as your iguana grows, you will notice that there is a hard, waxy substance excreted through the pores. It is speculated that males use this secretion to mark territory. The femoral pores are important to you because their appearance can help distinguish between male and female specimens, as discussed in the Sexing section.

Nail Trimming

You may have noticed by now that iguanas come equipped with twenty sharp claws. It is a good idea to keep them trimmed. When your iguana's nails are too long, they can injure themselves, their cagemates, and especially their owners! Long nails can be trimmed in a number of ways. Some like to use regular human nail clippers, but it has been argued that, by their flat nature, they compress the nail as they clip it, causing discomfort to the iguana. Also available are small bird, dog or cat nail clippers, which look rather like a pair of scissors but with a round notch cut out of the blades. They are geared for round nails rather than flat nails. It is believed that these will not compress the nail as much, thereby causing less discomfort.

Some people prefer to use a powered grinding tool to file down their iguanas' nails. These tools are available in hardware and woodworking stores, or you can also find manicurists' powered filing tools which work the same way. With the flip of a switch, a bit covered with sandpaper spins around and files down sharp nails with ease. The only problem is that, after holding the bit to the nail for a few moments, it can get hot. You should switch from nail to nail frequently to avoid this.

You should also have styptic powder available when trimming your iguana's nails. It is available at many pet stores. In the case that you cut too far and the nail starts to bleed, the styptic powder should be packed onto the nail to stop the bleeding. The only part of the nail that you should clip off, however, is the pointed tip. If you look at your iguana's nails, you will see that there is a quite defined pointed tip, which is attached to the larger part of the nail, which is attached to the toe itself. (It is easier to see in older iguanas.) You do not want to cut the larger part of the nail, for it contains blood vessels. It would be painful for your iguana, and sometimes it is difficult to stop the bleeding. Just clip off the pointed tip, as that is the only part that does damage anyway. You can use a nail file or a powered grinding tool to file the nail down to avoid sharp edges.


Iguanas are, as a general rule, pretty clean reptiles. Compared to many other lizards, iguanas will stay away from their feces and will remain neutral-smelling. But an occasional stumble will send them into a dirtier state and so bathing becomes an essential part of your iguana's life. In addition to bathing for hygienic reasons, an occasional soak in a tub is excellent for your iguana's skin and facilitates shedding.

One thing you must remember when assessing your iguana's state of cleanliness is that it is confined to a relatively small area. Chances are that it is impossible for it to avoid stepping in feces or food as it wanders around the bottom of its cage. Fecal matter and food become impacted in and around its nails, which can result in a nasty infection if your iguana were to accidentally scratch you, itself, or another iguana. So you might want to create a regular bathing schedule for your iguana. Some recommend a bath once every week. Some iguanas enjoy bathing, and others do not. If you put your bath-fearing iguana onto a regular bathing schedule, it will probably get used to the idea over time.

Bath water should be lukewarm. You do not want to drastically change the internal temperature of your iguana by simply placing it in the tub. The water temperature should feel pretty neutral to the touch. Sometimes when the water feels just a little warm, in actuality it can be 90 or 100 degrees, which is too hot. If your iguana pants while bathing, add some cold water! Soaking for 15-30 minutes is recommended, but with prolonged soaking there is a definite possibility that your iguana will defecate in the water. As a matter of fact, soaking in lukewarm water is one of the procedures used to cure constipated iguanas. If your iguana does defecate in the water, you should drain the tub and start again with fresh water.

In addition, the water should not be too deep. Your iguana should be able to stand up and not feel threatened. Iguanas are excellent swimmers and can even stay submerged for long periods of time, but at the same time, they are not aquatic animals and feel more at home in a tree. It is also speculated that in the wild, juvenile iguanas learn to swim by observing adult iguanas. Juvenile iguanas in captivity are generally unable to learn in this fashion. If your iguana thrashes about wildly in the tub, you may want to try lowering the water level. Some iguanas will thrash about wildly no matter how much water is in the tub, so you will just have to get to know how your iguana responds to bathing.

The Poop

Most iguanas poop (that's the scientific term) about once a day. It is uncommon for them to do so more than once a day, but some iguanas do skip days. There should be three parts to your iguana's poop. There should be a solid bowel movement, not unlike a mammal's. There should be a very liquidy part that is pretty gooey, not unlike the consistency of egg white, which is mostly water. Finally, there should be a white section that turns very chalk-like when it dries, which consists of urates. Your iguana's excrement should contain all three parts, although the makeup of each part may vary from day to day.

Many iguana owners attempt to potty train their iguanas because it makes cleanup much easier. I have never successfully potty trained my iguanas for any length of time, but I do know of a few methods that have worked for others. One approach is to use the bath tub. Iguanas tend to poop when they soak in warm water. If, on a daily basis, you let your iguana soak in the warm tub until it defecates, it may get used to the idea and actually start wandering to the tub on its own to do its deed. Usually it is not that simple; some people try generally decreasing the amount of water in the tub until there is none left, thereby getting the iguana to poop even when there is no water present. If your iguana still does not venture to the tub on its own, you might want to try putting newspapers in the tub, getting the iguana used to pooping on the newspapers, and then moving the newspapers onto the floor next to the tub. Some iguanas learn to associate pooping with newspapers, and then search out newspapers to poop on.

Another method is to simply notice where your iguana usually poops. If it picks one corner of the room or cage consistently, you might want to put newspapers or a litter box (filled with something harmless like shredded newspaper, not kitty litter) in that corner and see if the iguana still uses that spot.

Many iguanas, for whatever reason, choose soft places to poop over hard places. For example, if given the choice, many will consistently choose a carpet over a tile floor, or even over newspapers sitting on the carpet. You will find this habit especially distressing when your iguana finally decides that your nice, soft cashmere scarf was the softest place in the room. If you are willing to do a lot of laundry, you might want to use old towels to entice your iguana. A bundled-up towel may be just what your iguana wants to use. It keeps the furniture and cage clean, but you must also keep the towel clean to avoid bacterial growth. Before you throw it in the washing machine, it's always a good idea to thoroughly rinse the towel first.

Other methods may work better for you. But you must be willing to take the time to convince your iguana that there are better places to poop than its food bowl, your shoes, or its basking shelf, and work with it on a daily basis. That is the only way you will be able to potty train your iguana.


Your iguana will grow very rapidly until it is about two or three years old. Growth rates in iguanas vary, depending on the individual, and also on diet. I currently have four iguanas that all range in age from 6-8, but their lengths vary from 3.5 feet - 5 feet. The 3.5 foot iguana's growth was stunted due to severe malnutrition when young. Iguanas over 4 years in age should generally be 4.5 - 6 feet in length.

After your iguana turns three or so, it will continue to grow but at a much decreased rate. Iguanas can grow to be six feet long (the tail is usually about twice to three times the length of the body) and weigh about 18 pounds. In captivity, iguanas don't tend to grow as large as they do in the wild, and most people don't expect their iguanas to grow any longer than five feet.


Most iguana owners like to know if their iguanas are male or female. When very young, it is virtually impossible to tell the difference through physical appearance. As they get older, however, there are some visual cues that can help you distinguish between the two sexes. One of the biggest physical differences between males and females is the size of their femoral pores, which line the undersides of their rear thighs. Males' pores are much larger than females' pores, especially in older specimens. Male femoral pores produce a thick waxy secretion, while female femoral pores remain tiny.

Other differences include body size. Females tend to be more heavy-bodied than males, but males generally grow larger, have broader jowls, and have more developed dorsal crests. These differences are much more difficult to see, as iguanas grow at different rates and it is usually not possible to make any really educated guesses until the animal is full grown, or at least sexually mature.

Finally, males develop a bulge behind their cloacal vent as they mature. This bulge is, of course, their hemipenes. (Male iguanas have two penises, together called the hemipenes.) Females do not have such a bulge in that area.

If your iguana's gender is very important to you, you may wish to contact a veterinarian who specializes in reptiles and discuss it with him or her. Experienced individuals can "probe" an iguana to determine its sex. This should only be done by those with experience, and should only be done if it is very important that the gender is known. If performed incorrectly, this procedure can result in injury.


If you have only one iguana that tends to get aggressive in the fall or winter, you probably have a male on your hands that is interested in mating. Some males get especially aggressive at this time and turn on their owners! Some iguanas actually attempt to mate with their owners. Many male iguanas simply act a little territorial during mating season, and exhibit head bobbing and act a little more defensive than usual. Others become violent and the best thing one can do is to stay away from the violent male iguana during mating season. This difficult behavior usually passes after a few weeks, however, and most iguanas turn back into their old, lovable selves after they're through thinking about mating. Lone female iguanas do not tend to change their behavior in this way during mating season.

If you have multiple iguanas and at least one is male, you might have some big problems to deal with during mating season. Your iguanas may exhibit male-male aggression, and male iguanas can certainly injure one another. Your male iguanas will also try to mate with your female iguanas. First, the male will bite down on the back of the female's neck. Then, once he has her under his control, he will wrap his body around hers so that their cloacas are next to one another. He will then evert his hemipenes and attempt to force them inside the female and deposit his sperm. Sometimes, especially if there is a great size difference, the male will not be at all successful. And as in humans, not all mating attempts result in fertilization of eggs. You will know if your female iguana becomes gravid (pregnant): her abdomen will become large and lumpy, and she will also go off feed for a few weeks prior to egg-laying. If your female iguana does become gravid, you must supply her with a little extra calcium in her diet, and you must supply her with a place to lay her eggs. In addition, female iguanas sometimes develop unfertilized eggs even when there are no males present. There is no way to predict which years female iguanas will produce unfertilized eggs, so you should always be on the lookout for a lumpy abdomen on your female iguanas.

The following information has been supplied by Melissa Kaplan:

"Females need as much exercise (primarily climbing) as possible to ensure smooth laying. One of the most common problems with females in captivity is egg binding resulting in C-section and hysterectomy. Many vets actually recommend spaying females routinely to prevent the problem. It is, of course, less costly for you and less stressful for the ig if she can just get the exercise she needs. This is probably the best argument for keeping igs free roaming or housing them in very large (wide AND tall) enclosures with lots of branches and other climbing apparatus.

The iguana does not begin to "show" until the last couple of weeks of the gestation period. (Which lasts a total of two months.) She will be getting fatter with the eggs as she is losing weight, so she won't look much different, albeit her belly and sides will be more taut. You will be able to feel some of the eggs along her sides before they are developed enough for you to be able to see them. Generally, a row of two eggs on each side will be felt.

Preparing the Egging Box

Females dig burrows underground and excavate a small cavern in which they lay their eggs. They then back out and back fill the cavern and burrow. Interestingly enough, many females reuse the same cavern year after year, and there are recorded instances of more than one female using the same cavern, digging separate burrows to get in....

You need to recreate the digging area by making an egging box, a place for her to dig a burrow and lay her eggs in a cavern. Depending upon the size of the iguana, two huge kitty-litter pans, placed rim-to-rim and duct taped together, with an access hole cut in one end of the upper pan, will do the trick for a smaller iguana (say 10-12" snout-to-vent length). Larger iguanas will require a larger area... one of those squarish outdoor garbage cans (made of plastic, with a lid) work well as they can be laid on their side and not roll around. Duct tape the lid to the can, and cut an access hole at the highest point (which will be in the side of the lid). Essentially, any large, water- or moisture-proof container which you can keep warm, provide an access hole for the iguana but keep it closed enough so that all the excavated dirt doesn't come flying out, and can easily get into yourself to later remove the eggs, will do.

Needless to say, you need to fill the egging box with the proper digging medium before taping it shut. What you need to achieve is soil which you can easily push but which will stay in place when you take your hand away. Too hard, and the iguana can't dig; too loose, and it falls back into the burrow or cavern. I have found the following proportions to work quite well:

14 parts sterile potting soil (from peat, available from nurseries)

1 part sterile sand (From nurseries, or playground sand from hardware stores)

9 cups of warm water

Mix thoroughly together, and test. If it falls back, add more water. If too damp/gloppy/heavy, add more soil or sand.

This can be quite heavy when you have almost-filled a garbage can with this mixture, so be prepared with a dolly or a hand-truck, or prepare it where you are going to be leaving it. If the iguana's enclosure is large enough, then place the egg box in side in a warm area. The box needs to be placed in a quiet warm area. A spare bedroom or closet works well. Place a heating pad under the egg-laying container or direct a basking light on it (making sure not to melt the plastic!). (To make as much privacy as possible to reduce stress, hang a cloth over that part of the enclosure so the iguana cannot see out.)

Introduce your iguana to the container. Hold her up to the opening, let her sniff/taste and look, and then put her down. When she is ready, and if you have prepared the soil/sand mixture properly and the area is quiet and warm, she will go to work. (If she is already going crazy trying to dig through the floor and other surfaces, she is ready.)

It can take 10 hours or so to lay all the eggs; number of eggs varies from 12-40+, with older/bigger ones laying more. First year layers can lay 18 or so, so don't be fooled by the size of the iguana.

Once she lays, she will drag herself out and collapse on her basking area (or set one up for her nearby, with a bowl of water, and introduce it to her at the same time as you do the egg box). Keep an eye/ear out to see when she is done, then be ready with some comfort food for her - she is going to look like a skeleton. I steam brussels sprouts for a couple of minutes until they are bright green, and slice them up and put in a shallow jar lid. I will hand feed her some, then leave her with the plate. Feed lots of high calcium foods, and be generous with the calcium supplements for the next couple of weeks. By the end of the month after laying, she should begin to look like her old self.

If your iguana shows signs of twitching, jerky gait or difficulty using her back legs at any time during the gestation or after she has laid, get her to a veterinarian for Calcitonin injections of Neo-Calglucon supplementation.

Incubating the Eggs

If your female has mated with a male, then there is a chance that the eggs are fertile; iguanas can produce eggs without being around males but, just like chicken eggs, they are not fertile.

If there is the possibility of fertile eggs, you can begin putting together an incubator to have it ready before the end of the gestation period.

Handling the Eggs

Our fingers, no matter how recently we washed our hands, are full of oils and bacteria (beneficial to us, but bacteria just the same) which can harm the eggs. Before handling them at any time during the transfer and incubation process, wear surgical gloves.

Iguana eggs, like most reptile eggs, are white, ovoid (elliptical rather than round) and slightly soft or leathery rather than hard and brittle like a bird egg. Pick up gently at the ends of the egg, and avoid squeezing.

Home-Made Incubator

One method of constructing a home-made incubator is to fill a plastic lidded container with a mixture of vermiculite (not perlite) and water, in equal volumes by weight (the vermiculite should be well saturated but there should be no puddles of water). Poke holes in the lid.

In an aquarium or other water-tight container equipped with an adjustable lid or cover, fill the bottom with several inches of warm water. Using a submersible water heater (as for aquariums), keep the temperature at 86-87 degrees fahrenheit or whatever temperature is required to keep the air temperature within the enclosure at 86-87F. Place two bricks or another container upside down to form a base on which to rest the vermiculite-filled box.

The tank and box together form the incubator. The box will hold the eggs, the water heat and humidify the environment, and the lid of the tank can be adjusted to let out excess humidity and to help regulate the internal temperature. Make sure your two thermometers (the one on the heater and the one monitoring air temperature at the same level as the box) are clearly visible to you.

Once your iguana has laid her eggs and is resting comfortably, you can carefully dig up her eggs and place them in small depressions (made with your thumb or the back of a spoon) in the surface of the vermiculite. Keep the eggs oriented in the same direction: the side of the egg that was facing up when you dug it up should still be facing up when placed in the vermiculite. You can gently mark the tops with a pen. Any eggs which are clumped together are best left together.

After your eggs are in place in the vermiculite, top with a layer sphagnum moss which has been dampened in warm water (this is available along with the vermiculite at nurseries and many hardware and large grocery stores). Place the lid loosely on the vermiculite box, and place on the base in the aquarium. Cover the aquarium leaving a slight opening to vent out excess humidity. Open completely every couple of days for a few minutes.

Commercial Incubators

There are several types of incubators made for the bird industry, both for poultry and pet birds. The Hova-Bator (R) is one type. It is a foam box with ventilation and troughs in the inside bottom into which water may be poured. One suggested use for Hova-bators is to fill several deli cups or margarine containers with the vermiculite-water mixture, and place several eggs in each one. The moss-topped containers are then placed on the screen, and the Hova-Bator cover put into place. The unit should be plugged and brought up to temperature several days before the anticipated date of laying.


The incubation period is about 90 days. Check the eggs regularly (say, every several days). Generally speaking, eggs which collapse or turn moldy are not viable. But surprises can happen. If an egg is getting moldy and you want to take a chance on it, separate it from the other eggs by putting it into its own container; remember to wear gloves when doing this, and to avoid knocking the moldy egg against anything as you move it to its new container, and to take off and throw away the gloves, washing your hands and don fresh gloves if you are going to be handling any of the other eggs."

So you may want to make a decision once your iguanas begin to act sexually mature about whether you should separate them or not. If you have multiple males, they can wound each other, sometimes very seriously. Males can also seriously wound females during their mating attempts. You may also wish to decide whether or not you want your male mating with your female, because you might not be ready to deal with egg laying and incubation. If you ever decide to own multiple iguanas, you must be prepared to separate them so they don't injure one another.


Handling iguanas is relatively simple. You should not just use one hand and pick it up from above, around its middle. You should instead use two hands, each one supporting the underside of the iguana in different places. From behind, I place my right hand under the iguana's chest area, and my left hand around the vent area. I also use my left hand/arm to support the tail. This becomes much more important in large iguanas. You basically want to become a big, soft, warm branch for the iguana to climb on. It does not want to be held on to; rather, it wants to hold on to you.

You must be careful with the iguana's claws, however, when you are trying to pick it up. If it is holding on to a branch or especially fabric of some sort, it is probably digging in with its claws. You should not simply grab the iguana and pull straight up. You should instead use your fingers to gently unhook each claw from the material it is hooked into. This way, there is less chance of claws ripping out, legs becoming injured, or your upholstery tearing.


Your iguana will shed its skin throughout its entire lifetime. Juvenile iguanas shed their skin quite often because they grow so quickly. Adults do it as well. Unlike snakes and some other lizards, iguanas do not shed their skin in one large piece. Rather, it comes off in many small pieces. Also, they do not generally shed their skin within a short time. Some iguanas seem to shed constantly. You should not "help" your iguana with its shedding because you might accidentally pull off some skin that was not yet ready to shed. You may want to give your iguana a bath when it is apparent that it is about to shed, however, as it may ease the process.

Head Bobbing

Your iguana may exhibit a head bobbing display. This generally begins happening after the iguana is 1 or 1.5 years old. It can be a territorial display or it could be a mating ritual. If there are no other iguanas around, your iguana may bob its head at you to give you a signal. It may want you to leave it alone or to get away. Iguanas sometimes bob their heads when they see their reflection in mirrors. It is generally recommended that you keep your iguana away from mirrors. If there are other iguanas around, a head bobbing display could be territorial, meaning "get off my branch" or "get out of my way" or "get away from my mate". If you have a male and a female iguana, the male might bob its head at the female if it is interested in mating. All of these are normal displays and should not be worried about, unless your iguanas seem to be acting very territorial toward one another. If this is the case, they may have to be separated.


Your iguana may sneeze quite often. In most iguanas this is a normal behavior. Iguanas do not sweat as humans do, so they do not excrete salt through their skin. Instead, they do it by sneezing. There is no need to alter the salt content of your iguana's diet if it seems to be sneezing a lot or hardly at all. If you house your iguana in a glass enclosure, you will find white spots on the glass. This is simply what your iguana sneezes out. It cleans up relatively easily.

However, iguanas can also contract respiratory infections. This can happen when your iguana is not breathing clean air, such as air surrounding a dusty substrate, and when it is kept in cool conditions. If your iguana breathes loudly, possibly with its mouth open, it might have a respiratory ailment and you should consult a veterinarian. Bubbles or liquid outside the nose and mouth can also be indicative of a respiratory infection. If you ever suspect your iguana to be ill, always keep it a little warmer than usual. (Still provide a temperature gradient, however. See Heating and Lighting section.)