Iguana Breeding Season
Iguana Breeding Season Information
Like all animals, iguanas will breed and typically have a certain time of year that this transpires. We refer to this as "going into season". An iguana that is going into season is going to exhibit some physical and behavioral changes that indicate something is going on. There is no real set time when your iguana will begin to exhibit these changes as each iguana is unique in this regard. Once your iguana has gone into season you will know when to expect it the following year as this will become a recurring pattern.
Identifying the signs of breeding season will prepare you for what is to come and will protect both you and your iguana from what could transpire.
Male Physical Changes
Both male and female iguanas have femoral pores . Males however have larger pores and when breeding season comes around these pores will contain an extruding wax plug as the picture shows below (left - #1).
This waxy protrusion is believed to allow the male to mark his territory and to help female iguanas locate him.
Femoral Gland Secretions
Seasonal variation of lipids in femoral gland secretions of male green iguanas
Femoral gland secretions were collected from 21 captive adult male green iguanas (Iguana iguana) in Orotina, Costa Rica, and San Diego, California, during the breeding (November) and nonbreeding (March) seasons. Lipids were extracted with methylene chloride, weighed, separated by thin-layer chromatography, and analyzed by gas chromatography-mass spectrometry. Free and esterified C14-C26 fatty acids, 5-cholestan-3-ol (epico-prostanol), cholest-5-en-3-ol (cholesterol), cholest-5-en-24-methyl-3-ol (campesterol), cholesta-5,22-dien-24b-ethyl-3-ol (stigmasterol), cholesta-8,24(5)-dien-4,4,14-trimethyl-3-ol (lanosterol), cholest-5-en-24-ethyl-3-ol (-sitosterol), and two uncharacterized sterols were indicated. More lipids were recovered from femoral gland secretions obtained during the breeding than the nonbreeding months, indicating that secretion deposits may be more detectable during the mating season. 
Your male will also produce sperm plugs, which are not the same thing as the wax plugs found in the femoral pores. Sperm plugs, also called seminal plugs, are build-ups of semen that are deposited via the vent around the iguana enclosure or habitat. These deposits can be hard or soft and may be whitish or orangish in color, depending on how recent they were deposited. One of the most notable physical features that your male is going into season will be his coloration. Male iguanas tend to have an increase in orange coloration during their breeding season. There are different levels of orange that can transpire. The iguana above (right) is showing some remarkable orange, as well as his attitude!
Note: On occasion you may see the males hemipenes everted. This is not uncommon and shouldn't alarm you. If the hemipenes do not retract correctly you may encounter what is called a prolapse. A prolapsed hemipene will require vet assistance to prevent it from drying out, dying and becoming infected.
Male Behavioral Changes
The most notable behavioral change that many iguana owners unexpectedly encounter is severe aggression. During the breeding season, males become extremely territorial and feel the need to display and defend their dominance. In the wild this would help him define himself as the alpha male, which would make his breeding prospects higher as he ran off competing males. In captivity this could mean some very unwanted attention toward you, from your once lovable pet.
Males, especially large males, have the ability to cause an adult human some physical distress. Using their tails, claws and teeth, an adult male iguana will charge and attack anyone or thing he perceives as a threat to his dominance. This includes you, your significant other, your kids and other pets in the house. Sometimes the attacks are designed to scare you off and other times they could actually be a sexual advance on you. While this may sound a little off-kilter, your iguana may be interested in mating with you. This could mean your foot, leg or hand. While in theory this may sound humorous, it is anything but funny. When an iguana is keen on breeding with a female iguana, he first grabs her with his mouth on her neck. He does this to position her and to hold her in place. Her skin is designed to withstand these love bites. Your skin is not and these bites could easily turn into serious injuries. Menstruating and ovulating females need to be especially cautious around seasoned males. Seasoned males can sense the slightest change in hormones and during a woman's menstrual cycle some males have been known to attempt to breed with the woman and attack others who go near "their" mate. You can learn more about breeding aggression and how to try and control it on our Breeding Aggression page.
Other notable behavioral changes include an increase in territory display posturing. Head bobbing and posturing when you advance toward the iguana are signs that he is being defensive. These are warning signs to other iguanas and they expect you to abide by them as well. You may also see your iguana dragging his rear legs over objects in his enclosure, room or your house. This could be to leave some scent marking behind to deter other males or to offer females a trail to locate him.
A decrease in appetite may also be noted. During breeding season the male has one primary focus, which is to breed. This takes precedent over everything else, including food. Some iguanas will eat less and other will go days without eating anything. Most iguanas will have a fat reserve at the base of their tail and in their legs. When they are fasting their body will call upon these calories to help get them through.
Iguanas may be able to cope with the reduced calorie intake but they are far from capable of dealing with the dehydration that is possible from them refusing food. Iguanas receive most of the fluids from the foods they eat. When they stop eating they essentially stop hydrating themselves at the same time. It is crucial that you keep your iguana hydrated by keeping fresh, clean water in the enclosure at all times. Offer your iguana treats like fruit that are high in moisture and spray your iguana several times throughout the day. If your iguana allows you to you can also give your iguana baths daily.
During breeding season your iguana is raging with hormones that throw everything out of balance as both you and he were accustomed to. An iguana that only defecated while bathing may begin defecating all over his enclosure or your house. If this is all that has changed with your iguanas behavior, consider yourself lucky.
Female Physical Changes
The only notable physical change to a female iguana during breeding season will be her size. Female iguanas will develop eggs whether they have been mated or not. The developing eggs will enhance the size of the iguana and will become very noticeable later in her gravidity, prior to laying.
You can view x-rays of a gravid female on our Gravid Iguana X-rays page.
Dystocia, also called egg binding, fetal retention, egg retention or post-ovulatory stasis is when the reptile is not capable of properly passing her eggs through the oviduct or cloaca. This is an issue that every female iguana owner has to worry about. Most iguana owners who experience this resolve to having their iguana spayed to prevent future issues. Dystocia can be fatal. You can learn more about egg binding on our Dystocia page.
Female Behavioral Changes
Female iguanas will also experience a lack of appetite as the eggs begin developing. This is in part to the lack of room as the eggs consume what little space is there. As her body is developing the eggs she may stop eating like the males do. Dehydration, as with the males, is a very serious issue and should be countered by keeping fresh, clean water in the enclosure at all times. Offer your iguana treats like fruit that are high in moisture (sprinkled with added calcium for egg development) and spray your iguana several times throughout the day. If your iguana allows you to, you can also give your iguana baths daily.
Calcium deficiency can also be a big factor for a female that has stopped eating. (Calcium deficiency is more common in females who weren't properly cared for prior to becoming gravid.) The eggs require calcium and the body will draw that calcium from wherever it is present, which includes the bones. This can lead to diseases like Metabolic Bone Disease (MBD). You can learn more about MBD on our Metabolic Bone Disease page. Increase the amount of calcium your iguana is consuming when you realize she is gravid.
As her gravidity progresses your female will begin seeking out a place to lay her eggs. She may appear anxious and be seen digging throughout her enclosure. Providing your iguana with a suitable nesting site may help alleviate the stress and anxiety. You can learn how to build suitable nesting boxes on our Iguana Nesting Boxes page.
Sexing Female Iguanas
Females are easier to sex because they lack all of the items that define a male. Females do not have a hemipenal bulge. They tend to have undefined jowls and lack "brain bumps". They are typically slimmer and have smaller heads than males do. The femoral pores of a female are much less defined than a male. Most of the pores on a female will be barely noticeable, the exception being the first few which may be pronounced.
Author: Richard Brooks
1. Iguana Femoral Pores © Lacey LaDuke
2. Green Iguana - Chleby Zoo © Cheva
3. Hatfield III, James W.. Green Iguana The Ultimate Owners Manual. Dunthorpe Press, 2000.
4. Journal of Chemical Ecology Volume 18, Number 5, 703-712
5. Orange Flared © Sureshdias [CC-BY-SA-3.0]