Sex
If you are keeping more than 2 iguanas or if you are planning to keep several iguanas, you will have to consider about their sex. There may be some problems reported which is a female keeper and male iguana pair but in most cases, sex of iguana will not be such a big problem if you are keeping them alone.
Also, if you are planning to breed them, you will need to consider about their sex.
Healthy adult male iguanas will become exclusive to other iguanas when they get mature. Even though they seem to get along when youth, 2 or more males will start to battle after an year or so. The battle will get very aggressive and they may start killing each other if they are kept in a small environment.
So, never buy 2 juvenile at once unless you have 2 rooms which you can give to iguanas. The possibility of the pair which will end up 2 males are 1/4. That is quite high. I recommend you to buy one iguana first. Usually, it is very difficult to determin their sex when they are juvenile.
If the first iguana was a female, then you can add another iguana. But if the first iguana was a male, it will be quite dangerous to add another one. The possibility of second iguana ending up a male will be 1/2 at this point. You have to think of environments to prepare for ending up keeping 2 male iguanas. They have to be kept separately. Or you can get the second iguana which is adult and her sex is certain.
Sex discrimination
Some pet-shops sells iguana by pair. Or they may sell them to you if you ask them that you want them by male-female pair. But don't trust these words. Sex of iguanas are difficult to tell by their appearance when they are younger than 1 year old. Some experienced people may discriminate their sex by using a probe but this also is not 100% and this test may injure the glands of juvenile.
In most cases, "pair" iguana are a pair of an iguana which looks like a male and and an iguana which looks like a female. So buying one iguana at a time is recommended. Think about buying more after one year or more.
After an year or so, there will be some characteristics of sex which you can see from their appearance.
The most reliable point is the "femoral pores" which you can find underneath their thighs. Both male and female has several sequential glands for emitting pheromons. But the femoral pores found in males are more distinctly compare to those of female's. Core wax like object will start to grow from the center and some will stick out few mili-meter and will look like a comb. Femoral pores found in females are indistinct and flat.
You might be able to discriminate this difference in younger iguanas.
Other characteristic found in sex distinction is the size of jaw. There is a special big circular scale underneath their ear which is call the sub-timpanic scale. This part will bulge out in adult male. Sub-timpanic scale seems flat in female. This may be abvious to see but this characteristics appear later than 1 year from birth or more.
Male
Female
Some fortunate keeper can tell that this iguana is absolutely a male by confirming his hemi-penis. Male iguanas sometimes exposes his hemi-penis(by mistake?!). This often occures when excretion. I have seen this even in some very young juvenile. So observe carefully. If his penis was observed, he is a male.
Hemi-penis is hidden tail side of cloaca. 2 dome shaped bulge may be seen at the bottom side of tail right behind the cloaca. This is also a characteristic of a male.
Head bob
Iguanas often shake their heads. This behavior is called the "Head Bob" or "Bobbing". This is their unique communication method as they don't have a vocal organ. As you see, this language is very difficult to human. I live with 15 iguanas for about 10 years but I still can't translate exactly. It sometimes means "I love you, I love you, I love you." but it sometimes means "I hate you, go away! Mad mad mad". The difficult part of this language is, these two opposite meaning phrases seems same to human. I know iguanas can recognize and communicate their thoughts.
Propagation
Healthy iguana will become sexually mature in 1 to 2 years from birth. If proper temperature, diet, lightings, and sufficient space are given, it is quite easy to reproduce in captive environment.
In Northern hemisphere, mating season starts from end of fall or winter and lasts till spring. In my experience(Japan), mating season of our iguana starts around November and lasts till around February or March.
Male iguana starts to chase arround the female and tries to get on her back. Usually, female seems not like to mate and ran away or sometimes they have a big fight. If the male is lot bigger than the female or male is extremely aggressive, female sometimes will have a big injury. You should not place small female and large male in one place at this season.
If they are balanced, male will approach the female and mate.
Adult Iguana Site.
Healthy female iguana usually lay eggs every year whether they had mated or not. Even you are keeping one iguana which is a female, she has a chance to lay her eggs.
Oviposition is usually observed between February to April. But there are exceptions. There are reports who laid in Summer and I have heard of an iguana who lays twice a year, Spring and Autumn.
About one month before oviposition, female iguana will lose her appetite. Some of them lose her appetite completely and only drinks water. This is female iguana's normal behavior so never force feed her. Her digestive tract will be squeezed by her eggs and the intaked food will lose the way out. If she seems to keep her vitality, leave her and this is the best thing to do. If she is healthy female, she will start to dig the floor. This action will get more and more aggressive toword the oviposition. It may be better if you can place some box filled with soil where she can dig. She will probably dig and dig and dig for about 4 to 6 weeks without eating or with little food.
And one day, you will be surprized by seeing bunch of eggs. Iguanas usually lay numbers of eggs. Our 1 year and 10 months old Bingo laid 42 eggs in her first oviposition. Larger females lay about 60 to 70 eggs.
Iguana eggs is an ovary shaped soft shell eggs with a size of approximately 2.5cm x 3.5cm.
If the eggs are found, place them in an incubator carefully. Incubator can be easily built by using an old aquarium tank.
After 70 to 90 days, you will encounter charming babies.
Good luck!