Melissa Kaplan's
Herp Care Collection
Last updated January 1, 2014

Green Iguana: Preparing for Egg Development, Laying and Incubation

And why incubating fertile green iguana eggs isn't necessarily a good idea...

©1994 Melissa Kaplan

If You Are Thinking of Breeding Your Iguanas, Please Read This First...
Before and After Mating
Metabolic Bone Disease and the Gravid Iguana
As Gestation Progresses
Preparing the Egg Box
Incubating...Or Not
Raising Hatchlings

If you are thinking of breeding your iguanas, please read this first...
At this time, I an no longer incubating any eggs I get. With the numbers of phone calls and dumped and rescued iguanas that continue to flood in to me and other herp and iguana rescue people, the idea of trying to find homes for another 50-70 iguanas on top of the 20+ a month that come into rescues, it is not only overwhelming, but impossible. As it is, there are not enough good homes to go around. If you are considering breeding your iguanas, please think carefully about what you will do with the offspring, how you will go about finding homes for potentially 20+ baby iguanas, and what you will do if you cannot find homes for all of them.

Some people have raised the argument that if we don't breed locally we will never be able to stop or significantly reduce the imports. The fact of the matter is that the amount of local breeding won't begin to offset the 500,000-1 million iguanas a year imported into the country and being dumped because their owners don't want them or can't keep them. Captive breeders can't compete with the $2.50- $4 wholesale prices paid for the farmed and illegally exported wild-caught iguanas. If private breeders try to sell their iguanas for more, buyers just go to the stores where they can get a $10 iguana, being out for a bargain, not for a healthy animal from a conservation-minded breeder. Private breeders who try to give away their hatchlings will run into the same problem we rescuers are facing - lots of people who want igs "'cuz their cool, man" [sic] but precious few are willing and able to make the investment in time, space, money, and dedication required to raise a green iguana hatchling to healthy, tame, well-adjusted giant green adulthood.

If the imports of iguanas were severely limited or, better yet, or stopped altogether, then there would eventually be a market for domestically captive bred and hatched iguanas. I say "eventually" as I feel strongly that every iguana sitting in a shelter or rescue should be adopted out to a great home before any breeding is done to satisfy any remaining demand for iguanas. By pricing these captive bred hatchlings appropriately to what they are worth (taking into consideration the cost of properly raising and caring for the adults that produced them as well as the time and resources needed to care for the 50+ hatchlings), the impulse buys and purchases by people who really cannot afford to keep iguanas will be sharply curtailed, resulting in far fewer "pre-owned" iguanas needing new homes every year.

All that being said, I will post email addresses or phone numbers of anyone who has ended up with hatchlings and have offspring for which they are trying to find homes. For people who are looking for iguanas, I strongly urge you to adopt one from the many herp society adoption groups or rescue groups, or obtain one from a private captive breeder. The sooner the demand for cheap pet store imports drops, the sooner we can place all the igs who are already here and need homes.

So, why do I provide the following information? Because, whether we like it or not, most female iguanas are going to get gravid at least once. Since females do not need to be mated with a male to produce eggs, most of the eggs produced will not be fertilized, but the proper care of the female, which must start before the onset of her first breeding season, is necessary to ensure she lays her eggs - fertile or infertile - as easily as possible.

Some people think that, if their iguanas mated, they are thus fated to have hatchlings. Not so. Boil them or freeze them, and then dispose of them. Since the egg yolks and shell may be infected with Salmonella, handle them carefully, do not bury them in the garden or compost heap used to fertilize plants you use for food for your self or your pets. Many people bury them in their non-food garden. Some people hard-boil and eat the eggs: after all, that is why so many gravid wild igs are killed, the eggs being considered a delicacy.

A final word
I have been asked to consider leaving all the information on incubation and hatchling care off of this document until such time as it is acceptable, conservationally and humanely speaking, to privately breed green iguanas. I have decided to leave it here, as there will always be those few individuals who think their experience is going to be different, that they can easily keep, house, feed and rear dozens of hatchlings and find good homes for them, only to find that that isn't the case. The bottom line is that, for the sake of the iguanas, I would rather than they have the information needed to do it right than needlessly risk impairing their adult and hatchlings' ability to survive the rigors of laying and hatching.

Before And After Mating
While male iguanas will begin to slack off a bit in the fall, females who come into season in the fall will start to pack away the food in preparation for egg production. (Note: some iguanas cycle in the spring rather than the fall.) The eggs get so big and take up so much room in their bodies that by the second month of gestation, their food intake has decreased to almost nothing beyond a few sips of water and some leafy greens or a mouthful of salad.

Metabolic Bone Disease and the Gravid Iguana
It is important to boost calcium intake during this time. You can do this by adding slightly more calcium supplement to her food, or giving her the supplement more often. During pregnancy, the additional calcium is used in the development of the eggs. If insufficient calcium is present in the diet (or through insufficient or lack of UVB or too much phosphorous) the body will "mobilize" calcium from the bones. This will result in weakening the bones through loss in density - in other words, cause metabolic bone disease. When blood tests are done on an iguana who is actually suffering from MBD due to calcium being taken from the bone, the serum calcium test will come out with normal calcium levels. A reptile vet who is not aware of the problem may then feel that there is no problem. However, a healthy iguana with no MBD will actually have a high serum calcium level - it may almost look as if she is hypercalcemic. Once she lays the eggs, however, the serum levels drop back to the normal range.

Since the gravid iguana will be eating less and less as the gestational period progresses, boosting the calcium in the food may be problematical: if she's not eating, she's not getting the extra calcium. A solution is to give her a different form of calcium that can be administered daily by mouth. NeoCalglucon (calcium glubionate) is a human calcium supplement, usually administered at the rate of 1 cc per kg twice a day. Some vets recommend more for gravid iguanas, or more for gravid iguanas showing signs of MBD. You may wish to talk to your vet about giving NeoCalglucon instead. Your vet may supply you with it, or you can order it, in pint bottles, through your pharmacist (it is not a prescription drug, but most pharmacies don't stock it any more).

As Gestation Progresses
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 generally does not begin to "show" until the last couple of weeks of the gestation period. 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 (gently!) 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.

A rough timetable for the approximately 60 days/8 weeks of gestation, from the start of egg development to laying:

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" svl). Larger iguanas will require a larger area...one of those square-ish 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. To hard, and the iguana can't dig; too loose, and it falls back in to the burrow or cavern. I have found the following proportions to work quite well:

• 14 qts sterile potting soil (available from plant nurseries)
• 1 qt sterile sand (from plant 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 it is too damp, gloppy or heavy, add more soil or sand.

This soil mix will 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 inside 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!). The soil should be warm, getting slightly cooler towards the bottom back of the box. (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 near by, 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 metabolic bone disease (calcium deficiency, with symptoms including 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 calcium injections or Neo-Calglucon supplementation. Be prepared: read up on metabolic bone disease and egg-binding before you need to worry about them.

Incubation...Or Not
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.

Not Incubating The Eggs
If you have decided, based on the information above, to not incubate the eggs, you can remove them from where they were laid, or remove the egg box once the female is done laying them. In the wild, female iguanas do not stick around and tend the nest. Once the eggs are laid and the dirt scraped over the pile, they females head off. In some areas, where there is a dearth of suitable egg-laying sites, there is some competition between females. In these areas, females who have laid will often stick around and guard their nest to try to prevent other females from accidentally digging up the guarding female's eggs while excavate a place for their own.

If you female shows signs of stress at your digging in the egg box or otherwise removing the eggs, take her into another room (a nice long soak in a warm bath would probably be welcomed, anyway), and do the deed once she is out of sight. Or, you can leave them where they are (assuming they are in a confined area or in an egging box and not, say, scattered all over your electric blanket, on your computer keyboard or all over the kitchen, just some of the places igs have laid their eggs!) until she loses interest in them, which, depending on the individual iguana, may be in a few minutes or several days from the time the last egg was laid.

Once the eggs are removed from the laying area, if there is any chance that they are fertile, they cannot just be buried outside in case the conditions in your yard are conducive to naturally incubating the eggs. Two methods commonly used are to freeze the eggs for several days, or to boil them. Both will kill any cellular activity. The eggs can then be disposed of or buried.

When It Is Appropriate To Incubate....
Appropriate is defined as: imports of wild and "farmed" iguanas have been stopped, and few iguanas remain in the hands of herp society adoption committees, herp rescues, and mainstream animal shelters. This will have the effect of allowing those who do choose to commit the time, space and finances to breeding green iguanas to price their hatchlings commensurate with the cost of producing them. Since few people will be able to provide the type of space and care healthy adults and dozens of offspring require, there will be far fewer iguanas available to the general public, thus driving the prices up higher, thus further reducing the demand. O happy day!

In other words, if you are thinking about actually incubating your iguana's eggs to produce hatchlings so you can have a baby ig from your darlings, think again. And again. And again. And if you're still thinking about it, with cheap imports still coming in, please: don't do it.

Still think you know better?

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 leather rather than hard and brittle like a bird egg. Pick up gently at the ends of the egg, and avoid squeezing.

Homemade Incubator
One method of constructing a homemade 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 watertight 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 F or whatever temperature is required to keep the air temperature within the enclosure at 86-87 F. Place two bricks or another container upside down to from 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.

Another incubator set up is to fill a Tupperware-type container with 1 part vermiculite to 1.5 parts water, half bury the eggs in that medium, then cover tightly with the lid. Place in the aquarium set up as above. Open the lid for 30 seconds every other day.

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 must 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.

Incubation Problems
The incubation period is about 90-120 days (in the tightly lidded box set up, hatching has been reported at 73 days at 86 F). 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.

Carefully brush some antifungal powder (such as is made for athlete's foot) on the moldy spots with a cotton-tipped swab. You may need to repeat this several times during incubation if the mold growth returns.

Hatchlings
If you are able to attain and maintain the right incubation conditions (which isn't as easy as it may sound), and you end up with hatchlings, you will need to have a tank all prepared and waiting for them when they hatch. Administer a dab of yogurt which has live bacteria to help establish their gut bacteria before placing them in their tank. Repeat the yogurt daily for several days by placing a dab on a feeding dish for them to lap up. Have a plate of finely minced food waiting for them, and a shallow dish of fresh water. Mist them often. See my Iguana Care, Feeding & Socialization article for housing, heating and feeding information. Generally speaking, hatchlings are cared for just like adults except that they need warmer temperatures, so the low end of their thermal gradients for day and for night shouldn't go as low as for adults and juveniles. Hatchlings also need higher humidity which may be attained by spraying several times a day and keeping a humidifier going at least during daytime hours.

Related Articles

Dystocia (Egg-Binding)

Metabolic Bone Disease

To Spay or Not to Spay

Vitamin supplementation

The Grim Reality