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

Further Thoughts on Iguana Spaying and Neutering...

©2002 Melissa Kaplan


Spays: Routine but not necessarily safe long-term
We really have no clue about the long-term effects of spaying on green iguanas. We're still just scratching the surface of identifying and figuring out what to do to combat the long-term health problems in human females who are in natural or forced menopause.

Menopause just means the end of menstruation, which in turn means the end of ovulation. Menopause can be due to

  • the natural process of aging, as the body's hormone levels change; the rate of change can be modified by the taking of various hormones including one or more of the three estrogens, progesterone, testosterone, and other hormones
  • or surgically induced (by removing the ovaries, called "spay" in non-human animals); surgical spays cannot be reversed
  • or chemically (as part of fertility treatments and in the case of breast cancers that induced by endogenous and exogenous estrogens); chemical spays can be reversed.

Ovulation may halt before menopause due to a variety of problems, most related to changes in one or more of the body's many hormones, including those most people (and doctors!) don't associate with the "sex" hormones. For example, hypothyroidism (one of the top under-diagnosed diseases in human females) can cause premature cessation of ovulation. Correct the problematic thyroid hormone, and ovulation begins once again. Stress and liver function can also affect serum levels of the different thyroid hormones, so they too may be a factor in ovulation and, possibly, resorbtion.

Note: Resorbing eggs/embryos is actually quite common in the animal kingdom, as are miscarriages (spontaneous abortions). There are a variety of reasons for miscarriages/resorbtion--social, physiological and environmental--some known, most theorized, even in humans.


Spaying: Anything But Routine!
Spaying should not be done lightly in situations where there is no emergent health crisis in the gravid female. Remember that we have decades of research and clinical observation behind dog and cat spays…done mostly by male vets. The whole tenor of veterinary medicine is undergoing some rapid change as more females have entered the profession. (In fact, there are now more, or soon will be, female vets than there are male vets).

For decades, C-sections were one of the most commonly performed--without medical need--surgery on women, and hysterectomies were too often done for vague "emotional" reasons, along with inappropriate prescribing of muscle relaxers and antidepressants without appropriate mental health evaluation and support. Things have been changing along these lines, too, as more women have entered the medical profession as physicians and researchers, but we have still yet to come to terms with the long-term effects of these all to often unnecessary--and life-altering--surgical procedures done more for convenience than due to any medical necessity.

Medical necessity is also becoming--or should be--an issue in veterinary medicine, especially as it relates to green iguanas. Iguanas have undergone spaying and neutering for maybe 5-6 years. We have no longitudinal data on them. There has been no long-term study of the effects of spaying on long-term female health and survival.


Dystocia: Retention vs. Egg-Bound
Too many people (and vets) confuse retention and bound. Retention is the eggs being retained for some reason other than a blocked oviduct. The most common cause for retention is too little calcium, an essential ingredient in both laying eggs and live births. Other hormones may also be lacking. The various -tocins (such as oxytocin) are given to both animals and humans to start contractions in delayed laying/birth, but must be done under a vet's/doctor's supervision as, depending on the reaction, a calcium injection may also be required within an hour or so of the tocin injection.

All too often I hear people talk about how "normal" it is for their iguanas to take days or weeks to lay their eggs. Three weeks after the first egg was laid, and the owners are online posting, "Guess what! Iggy laid aNOther egg this morning!" That's not normal: that's retention!

Delayed/Prolonged laying is usually due to insufficient serum calcium, requiring one or more injections of calcium or doses of calcium glubionate to get things going. Permitting egg laying to go one for more than 24 hours should never be allowed: this is an emergent situation that requires veterinary intervention. Since the most common cause is insufficient calcium, most vets will recommend 5 oral doses of calcium glubionate or an other calcium injection within the next 24 hour period (hours 25-48 after the first egg is laid). If the iguana is still holding eggs, she should be taken to the vet for an exam and consideration of other non-spay methods to get those eggs moving.


The Human Factor
Can prevent 100 percent of all dystocia? No, because there is some element, a very minor element, of chance. But the vast majority of dystocia in green iguanas is husbandry related, not chance. The vast majority of dystocia in green iguanas is husbandry related, not chance. The vast majority of dystocia in green iguanas is husbandry related, not chance. The vast majority of dystocia in green iguanas is husbandry related, not chance.

The most common causes of dystocia (egg binding and egg retention) in green iguanas due to poor nutritional status, mineral deficiency and inappropriate environment are always preventable. Care for iguanas properly from the time they are hatchlings and dystocia is quite rare.

Females who have a history of severe MBD are more likely to have problems laying later, especially if their owners fail to boost calcium intake prior to the onset of breeding season and monitor it during the season, making sure the iguana is getting the necessary injections and/or oral calcium supplements (not powders, but along the lines of liquid calcium glubionate).

There are two causes of dystocia that cannot be controlled for by diet and care:

1. When an egg is too misshapen or large to fit through the oviduct. It gets stuck in the opening to the duct, blocking all the other eggs from passing through. There is a surgical procedure less invasive than a spay that can be done to try to remove the obstacle. A needle is inserted into the egg blocking the oviduct, the contents are aspirated out of the egg into the syringe, thus shrinking the size of the problem egg, enabling it to pass through the oviduct.

2. Genetics, which includes immune and endocrine systems function. You can have four clutchmates, raised in the identical conditions--same environment, diet, supplementation, interaction with humans and other animals, etc.--but they may have four very different outcomes. One may develop and lay her eggs with no problem, while the second develops her eggs but then resorbs then. The third iguana, meanwhile, fails to maintain adequate serum calcium levels, or some or all of her eggs develop abnormally, or some other factor results in an emergent situation. And the fourth? She never develops any eggs, or doesn't until she's in her 9th year. The only difference in these genetically related and reared iguanas is the variables in their genetic code that makes them unique individuals--siblings--rather than identical twins. (Not that identical twins can't react to the same exposures and stresses differently, which is why twin studies are so useful in research medicine and psychology.)

Should we, just because an iguana MAY develop or have a congenital abnormality that prevents her from developing and laying normally, automatically spay all females just to be safe? Using that logic, women in Marin County, California should be lining up for bilateral mastectomies because the rate of breast cancer in that population is far higher (40 percent) than in the general population outside the San Francisco Bay area, 30 percent higher than the SFB area).


But My Vet Says Dystocia Is Very Common!
It is common because most of the iguanas most vets see are ones already so weakened by poor diet and environment--and lack of appropriate attention and care prior to and during breeding season--that many of the iguanas are lucky to survive, period, whether an emergency spay is done or not.

It is indeed heartbreaking when, after you've done everything right, random chance strikes. But spaying "just in case she might have a problem down the line" poses even more risk for an otherwise health female, regardless of species. This is especially true in exotics about whom we know too little about possible the long-term effects. Prevention and proactive monitoring is the key. The scalpel should be the measure of last resort.

Batter an iguana repeatedly with forcing her to go through breeding seasons with too little calcium, fail to get the appropriate veterinary care early in the pregnancy and throughout the pregnancy, and let a struggling iguana go for more than 24 hours after the first egg is laid and you can pretty much force your iguana into an emergent situation where, indeed, surgical intervention of some sort, may be the only alternative. Keep procrastinating long enough, and you can pretty much guarantee that a spay will be the only alternative left. If that's what happens, then a spay is because of what the owner did or did not do, not anything inherent in green iguanas.


Neutering: Aggression Is More Than Just Testosterone
When it comes to neutering males, there are far too many variables involved pre- and post-operatively that are not being taken into consideration, so whatever studies there are, which to date have only been done on small study populations, are suspect because of the variables.

The things that aren't being done or taken into consideration prior to neutering "aggressive" iguanas include:

  • accurate and knowledgeable in-person assessment of iguana-human interactions over a period of time, with behavior modification of both iguana and owner,
  • thorough medical examination of the male, including blood tests, radiography, ultrasonography and laparoscopic examination to rule out all possible physiological abnormalities and disease processes except for neuropathology.
  • thorough post-neuter in-person assessment of iguana-human interactions (as human expectations can affect human behavior, which in turn can affect iguana behavior).

Most vets do not themselves have a lot of experience with raising and keeping healthy iguanas as pets. This means they are not always in a position to evaluate how well the human has worked and is working with the iguana, in terms of taming and socialization. Most vets, veterinary researchers and iguana pet owners consider extreme aggression to be a "normal" behavioral trait in male iguanas, and so fail to take into consideration the physiological or neurological causes of aggression.

While most wild animals, including iguanas, hide when they are in pain, or become quiet, reducing their normal activity, and maybe favor a particular body part or appendage, that is not always the case. They may also become agitated, restless, testy, snappy...and aggressive.

Whether or not we will ever be able to say that extreme aggression as a reaction to severe pain or disintegrating organs or systems, the bottom line is that all these things can result in the extreme aggression commonly associated with "healthy male" iguanas, especially during breeding season, exactly the behavior that is resulting in iguanas being neutered without first being thoroughly examined.

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