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So - you've visited our Sexing Iguanas page and you've figured out your iguana's gender. Now you are wondering what to expect from your iguana during the breeding season. Most healthy iguanas go "into season" at some point each year once they've reached sexual maturity, regardless of whether an iguana of the opposite sex is with them, or whether you plan to breed them (visit Breeding Iguanas In Captivity for more information). The exact time of year varies among individuals, perhaps due to what region of Central/South America they originally came from. A prepared iguana owner knows the signs of breeding season and is prepared to deal with it on a yearly basis. Males and female iguanas both present their owners with their own set of challenges during this time. Read on to learn what you can expect.

Males During Breeding Season: Physical Changes - Physical signs that a male iguana is in breeding season are an increase in orange coloring in the skin, an enlargement of the waxy protrusions from the femoral pores (see photo below), and the presence of sperm plugs seen either protruding from the vent or found in the enclosure or habitat area. Sperm plugs are dried packets of semen that often appear as long, translucent orange or cream colored objects. Males in season may also leave fresh semen around too, which is sometimes compared in color and consistency to melted mozzarella cheese.

This photo of Jake, a mature male, was taken when he was in breeding season. Notice the large waxy plugs protruding from his femoral pores. Compare this to the photo of Jake's pores when he is not in season, which is located on the Sexing Iguanas page.

Males During Breeding Season: Behavioral Changes - Many owners get quite exasperated with their males during breeding season. Owners of male iguanas should be prepared for possible difficulties when their iguana matures. Since mature iguanas go into breeding season for a period of several weeks, or even months, every year, this is something owners must deal with on a yearly basis. Many male iguanas exhibit behavioral changes during breeding season that can make them very difficult to handle or interact with. Some males can even be dangerous during this time. Behavioral changes may include an increase in head bobbing and display behaviors, an increase in territory patrolling and an increase in territorial defensive behavior. Problems occur when male iguanas defend their territories, which may range from their enclosure, to one room, to an entire house, with violent attacks. These attacks may be initiated by a normally docile male against the owner he usually trusts and has bonded with. These attacks can be unpredictable and severe. Iguanas can deliver serious bites, especially when their owner is caught off-guard. It is imperative that owners of male iguanas be on the lookout for this type of territorial aggression during breeding season. Not all males exhibit this type of behavioral change. Many remain their normal, docile selves. However, the very real possibility exists for this type of behavior, so all owners of mature male iguanas should be prepared for it.

A question that often comes up is whether or not aggressive males can be neutered to lessen the impact of breeding season hormones on their behavior. The answer to this is still unclear. There are some vets who will do this procedure, but it is quite difficult and can be risky if the vet is not knowledgeable. In addition, there is little evidence to support the idea that such a procedure actually lowers aggression in males with this behavioral pattern. At the present time, the better way to go is to be prepared to deal with possible behavioral problems rather than relying on a potentially risky and uncertain surgery to solve the problem.

In addition to territorial behavior, there are other behavioral signs that a male is in season. He may experience a decrease in appetite. In the wild, male iguanas spend the breeding season courting females and defending territories. They spend little time eating during this period. It is important to keep your iguana hydrated during this time, since he may become dehydrated from a lack of moist foods. Frequent baths, an increase in room humidity and daily spritzing can help. Feeding small amounts of high-water treat foods (peeled grapes, watermelon) can also help.

Males may also "forget" their proper toilet habits as they get distracted by the breeding instincts they are experiencing. Owners may find themselves cleaning up more messes than usual. For this reason, it may be necessary to confine your male to his enclosure more than usual during this time. Good toilet habits will often return when the breeding season is over.

Another behavior that males often exhibit during breeding season is, reasonably enough, mating behavior. Many males will stalk their owners not to attack with aggression, but to attempt to mate with an unsuspecting foot or leg. Menstruating human female owners should be particularly aware and on the lookout for such amorous behavior in their male iguanas, because males often seem to be especially interested in their female owners during that time of the month. Although such mating attempts sound humorous, they can be dangerous, because during mating the male grasps the back of the female's neck with his teeth. Her tough skin can withstand these "love bites". Human skin cannot.

Below are photos of iguanas mating. Notice how the males have a grasp on the females' necks. This helps the male maneuver the female into position and hold her still. In the top photo, male Bumpy (right) mates with female Hopper (left). In the bottom photo, Jake (on top) mates with Donnie. Notice how their tails are entwined.



Be on the lookout for such mating behavior in your male. If you see it, try offering him a green towel, sweatshirt or stuffed toy. Males will often "mate" with such substitute objects, and will deflect their attentions from you to the "love toy". Watch your male carefully to be sure he does not accidentally ingest any pieces of the toy while he "mates" with it.

Below are photos of Hal, a mature male, as he "mates" with his "love toy" - a stuffed grasshopper. Notice how he has a grip on the toy with his teeth, as he would a female during mating.

During this mating behavior, you will likely see your male evert his hemipenes from his vent. This is natural behavior, and is nothing to be worried about. It can, however, be quite alarming to see the first time.

This is a photo of male iguana hemipenes. This photo was taken just after mating occurred between Bumpy and Hopper (see above photo).

Females During Breeding Season: Physical Changes - Like males, female iguanas undergo physical changes during breeding season. A healthy, mature female iguana will develop eggs in her ovaries during breeding season, even if she hasn't mated with a male. This condition is referred to as gravidity, and females carrying eggs are said to be gravid. Some females turn a bit orange on the legs and/or belly during this time, but many exhibit no color change. As the eggs develop, females often stop eating and get thin in the legs and tail. Their bellies, however, may bulge with eggs, giving them a round appearance. As the eggs near the end of their development, the shells develop and the eggs can be felt by gently palpating the belly. Be careful while doing this, though, as the eggs can break inside the female, which is deadly. This pattern of egg development and eventual laying will occur every year, regardless of whether the female has mated.

Below are two X-Rays taken of Vega$. The X-ray on the left was taken when Vega$ was gravid, and her abdomen was full of eggs. The X-ray on the right was taken after Vega$ laid her eggs. It is a good idea to have your vet take a pre-laying and post-laying X-ray, to be sure that all eggs have been laid. Eggs that are retained in the body of the female will cause serious problems.

Although most times you can clearly see the signs of gravidity if you know what to look for, some females may not clearly appear to be gravid. However, there are some behavioral changes that can clue the observant owner to the fact that their female is gravid.

Females During Breeding Season: Behavioral Changes - Many females will exhibit a much decreased appetite as their abdomens fill with eggs. As with males, dehydration is always a potential problem during this time. In addition, gravid females need more calcium, which is used to build the shells of the eggs. Metabolic Bone Disease (MBD) may develop in gravid females, and extra calcium is recommended during this time. Owners should offer their female iguanas small amounts of salad with extra calcium and water-rich foods. Another possibility is to offer a slurry of Ensure™ shakes mixed with fruit, veggies, greens and extra calcium in a blender.

Another behavioral clue that a female is gravid is an increased activity level and digging behavior. In the wild, females build nests by digging tunnels and chambers in the soil, in which they lay their eggs. Pet female iguanas will often spend hours searching the house for a "good" nesting spot, and will often dig at walls, carpets, the floor, windows, and in potted plants. Owners may facilitate the female's nesting desire by providing a nesting box of some sort. There are many designs for nesting boxes, ranging from simple to complex, but a sturdy plastic box or laid-down garbage can filled with sandbox sand and/or potting soil will often do the trick. Be prepared to clean up a lot of dirt as the female spends hours digging it out repeatedly onto the floor! Some females will ignore nesting boxes, or dig in them only to lay their eggs elsewhere, much to their owners' frustration. It is probably a good idea to provide one, just in case. The lack of a good nesting spot can cause some females to withhold egg laying, with dangerous consequences.

Females During Breeding Season: Egg-Laying Problems - Eventually, the time will come for the female to lay her eggs. Below is a photo of Hopper laying an egg (left) and a batch of iguana eggs after laying (right). For more neat photos of egg laying, visit Vegas$' web site, listed at the bottom of this page.

If all has gone well, female iguanas will lay their eggs continuously one after the other all at one time until they are done. If you see one or a few eggs scattered around throughout a period of hours or days, your female may be egg-bound, which means that her eggs are not able to properly exit her body. Other signs that a female is egg-bound include lethargy and straining. If you suspect that your female is egg-bound, get her to the vet immediately. This condition is fatal if not treated. The treatment for egg-binding is to spay the female, which involves the removal of both the ovaries and any eggs present. Some owners of female iguanas chose to have their healthy females spayed to avoid later complications. Although this procedure is easier and more common than neutering males, it should only be done by a vet that is skilled and experienced in this procedure. Spaying a female will eliminate the yearly gravid period, although some spayed females exhibit behavioral signs of "false pregnancies" during breeding season.

Below are some spay photos. The photo on the left is of Primrose. After her period of gravidity, she experienced difficulties, and was spayed. Here you see the incision and stitches on her belly. She recovered well from her surgery. The photo on the right shows developing eggs and ovaries removed from another female, Donnie, during her spay. (See photo of mating iguanas, above, to see Donnie pre-spay.) This clutch, about 30 eggs, is rather small. Females have been known to carry many more eggs than this.




The following photo shows eggs removed from Vega$ during her spay. If you look closely, you can see the membranes that hold the eggs together in the ovaries.


Some females will develop eggs, exhibit decreased appetite and digging/searching behavior, but then resorb the eggs into their bodies before the egg shells develop. Owners of mature female iguanas must be aware of the signs of gravidity and must be on the lookout for such signs in their females. Gravid females should be carefully monitored for any signs of MBD or egg-binding.

For even more information on spaying iguanas, please read Spaying Female Iguanas - What Owners Can Expect.

Conclusion - As you can see, in iguanas, neither sex is "easy care" - not only in terms of reproductive behavior, but overall. Since baby and juvenile iguanas are very hard to accurately sex, new iguana owners must educate themselves about the challenges presented by both sexes, so that they are prepared when their iguana finally reaches maturity. If you prefer one sex over the other, you may consider adopting a mature iguana from your local shelter. There are many out there that need good homes, and at least you will know what to expect!




Vega$ - A Beachy Kind of Ig by Desiree Wong, contains great photos of egg laying.
Ig Aggression Types by Henry Lizardlover is an excellent article on iguana aggression, including some very good photos of what kind of damage an aggressive iguana can do to a person.
Breeding and Reproduction section of Melissa Kaplan's web site - great information here.
Egg Retention in Green Iguanas - An excellent article written by Doug Mader, DVM, for Reptiles Magazine.






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