• Carrie Gardner

Iguana Know More?

Updated: Feb 29, 2020

Green iguanas are probably one of the most common reptiles ever kept through decades. Even long before proper care was even known for them, they were a difficult animals to keep, and that continues to the present day. And it doesn’t help that someone can walk into a pet store and get one for $20.00 without knowing the thousands of dollars that need to be spent just to house them. Many iguanas don’t make it through the first year, or, in Florida, are set free. I even saw a game at my county fair that would have given away either goldfish or iguanas. Luckily he didn’t get the iguanas in before the fair.

Iguana new home.


They don’t make good pets, I'll just state this right at the beginning. And definitely not your first reptile. Even with all of our knowledge of their husbandry and all of the technology and housing that exists, they still are very challenging. Those cute little baby lizards grow up to be lizards over six feet from nose to tail tip and can live for more than 20 years. They have strong jaws with sharp teeth, long sharp claws and the ability to tail whip...and an attitude to go along with it. Males can get territorial. I had a 6.5 foot male for a month before I realized that I couldn’t build him the cage I hoped too. My friend needed a home for him after receiving him from her friend’s sister. So Trevor came to stay with me. He was a people lizard, loved to be held and looking out the window. He was also a free-range lizard because his tank was ridiculously small. He was affectionate and intelligent (I potty-trained him) and I would’ve loved to have kept him. He needed an enclosure that gave him light, hot temperatures, and humidity. I was in a studio apartment and as much as I loved him, he did not love my cat, Reilly. Part of responsible pet ownership is knowing that the best thing you can do for them is to find a place that will care for him, no matter how much you love them. I took him to a reptile store in suburban Chicago and he was sold to a breeder. I’m sure Trevor (the iguana) had a huge smile on his face. Reilly would go on to fear the little lizards in Florida that somehow got into the house and my first bearded dragon.

The not so good side and the good side of being an iguana parent (mute the volume - music is bad)

He's winding up for a tailwhip!

While most people have been bitten and scratched by some animal. Unless they have a lizard or a crocodilian, a tail whip is a new experience. Excluding the top of the head, iguanas have keeled scales, which means it feels like very, very rough sandpaper. When they get perturbed, they hit with their sandpaper tails. It is fast, and it is can hurt. It can leave a scrape-like wound and draw blood. If somebody knows iguana behavior well enough, they know when they're being lined up for a hit. It reminds me of a batter lining up to hit the ball in baseball.

And let’s talk living quarters. It is said that a cage should be able to comfortably allow an animal to stretch out. So roughly, it should be at least seven feet long on all sides. But they are also arboreal, so a climbing apparatus with lots of cover that is bolted in is a must. A hide box on the ground, that can accommodate their size and different areas that they can get food and water. That would make it between eight and nine feet tall. Are you shocked yet? Since they are tropical animals, they love high temperatures and high humidity (the upper 90s for temperatures and high 80s to mid 90s humidity) They need a basking area over 100 degrees and full spectrum lighting. Feeding is another thing to think about. These guys get to over ten pounds and have huge appetites. Fresh greens, fruits, and flowers for adults, and younger ones, insects for the extra protein. Therein lies the problem. They get too big and too expensive. Much more than most owners usually realize, and the owner thinks that they are doing the best thing for the iguana and releases them. Or they die from neglect. In the United States, they are invasive in Florida, Texas, Puerto Rico, U.S. Virgin Islands, and, oddly enough, in Hawaii.

Iguana behavior

Despite the fact that they don’t make great pets for most, these lizards are stunning creatures. They’re called Green Iguanas, but it really varies. Normal iguanas have various shades of green, yellow, brown, and turquoise. Even turning bright orange during mating season (females remain pretty much green.) They are prehistoric looking and fascinating. These lizards are from Central and South America, and a few Caribbean islands. They spend most of their time up in the canopy, only descending to mate, lay eggs, get water, or maybe to bask in the sun. These are stout lizards who prefer trees hanging over water so they can dive right in, even

from a significant height, to escape predators. They are also tough enough to land on solid ground from 40 feet above and not injure themselves. If need be, an iguana's tail, which is half the length of its body, can be broken off to serve as a diversionary tactic to cause confusion while they get away. Though hanging out in trees over water in their native habitat is what they prefer, they can adapt to almost anywhere where it is warm, staying on the ground in open areas, as long as they have an aquatic escape route.

The wannabe tennis star.

Physical Appearance

Hatchlings are bright green and anywhere between six to ten inches while adults can be between five to seven feet and can weigh anywhere between

eight to eighteen pounds. Even though they are called “green iguanas” their colors are actually variable, mostly in males. During mating season, males usually turn a beautiful orange or golden color. As I mentioned above, their colors can be turquoise,various shades of green and yellow, brown, and dark bands on their tails. Colors also change depending on their moods, temperatures, or social status. At night, when it is cooler, iguanas are dark in color. This helps them thermoregulate. A darker color allows them to absorb the heat from the sun. When they’ve soaked up enough, their color brightens to reflect heat. Other distinctive feature is a big flap of skin under their chins called a dewlap. These are more prominent with males and they can extend it with hyoid bones. Normally extension happens during territorial disputes, self-defense (to make themselves look scarier), and for thermoregulation. Near the dewlap, below the ears (tympanum) are the subtympanic shields (or helmet scales). These large conical scales seen on each side of their head and are only found on the green iguana. And finally, their “dorsal crest” or those spiny things going from the end of their neck to the base of their tails. Oh, and their toes!! They have crazy long toes! One of my favorite things about iguanas.

Parietal Eye

The white spot on top of his head is the parietal eye

Many lizards, amphibians, and even some fish have one. However, the most advanced is found in the tuatara. A reptile from New Zealand. If you were to look at the top of an iguana’s head, you may see a scale in the middle that looks waxy or white. This is the parietal eye. What is it? It is actually a very primitive eye. It has a lens, a cornea, and a retina but it can’t see images. What it does do is control circadian rhythm and the release of melatonin, maturation of sexual organs, thyroid organs, and endocrine glands. It can detect changes in light, say, so they can detect the shadow of a predatory bird or an owner’s hand coming down from above. It also assists with thermoregulation and acts as a calendar that tells the brain when the nights are getting longer or shorter - as a consequence, it also monitors life cycles like reproduction and sleep. Inside there are two symmetrical parts of the brain structure. One half is the parietal eye, which takes in light and the right half is the pineal gland, that releases melatonin. An optic nerve brings down information to the brain.

Why don’t we have parietal eyes? At one time in the far distant past, where wearing fur was cool because it was attached to us, and there was no such thing as a razor, we had one on our forehead. Somewhere along the line we lost it because we didn’t need it. We DO have a parietal skull bone and a parietal lobe in our brains. We also have the pineal gland located deep in the center of our gray matter. It releases melatonin and many other hormones, like serotonin, that focus on neurological regulation. Serotonin is the “happy hormone” so people are happy, focused, getting sleep at night and are awake during the day. Basically, one of those annoying people who are irritatingly cheerful in the morning while your facial expressions clearly state that it is dangerous, daring anyone to come near you while you’re guzzling down a whole pot of coffee.


Male in foreground and females in back

Green iguanas are sexually dimorphic, meaning that the sexes are distinctively different. Males are larger and appear to have a "block-headed" look about them. Their subtympanic shields and their dewlaps are much larger, and their color varies more. On the inside of their thighs they have what are called femoral pores. It is a line of large pores, filled with a waxy substance that they use to mark territories. Females also have these pores, but they are much smaller. At that time of year, dominant males start marking their territory. These pores are filled with a waxy pheromone that they rub on surfaces, even females. Any male that tries to enter a marked territory will get chased away after a stern head bobbing and extending dewlap thing. However, any female is welcome to hang out. There isn’t a lot of small talk. Males mount the females and grip her shoulders with their mouths, sometimes injuring her.

I bet she can't wait to lay those eggs!

Females have the capability to store sperm for years after mating. Sometime later, she can choose to have another clutch on her own, so if she doesn't feel like mating one year, she can walk away with a tail whip to every male out there and still have a clutch. Though after looking at that poor girl below, I don't know why she would want to have another clutch. After 65 days, she’ll come down from her tree and travel to the nesting site, which can be quite a distance. She lays between 10-30 leathery eggs that are covered up and goes on her way. Incubation takes 90-120 days if the temperature stays between 85-91 degrees. Using their egg tooth, they slice through their egg. They have absorbed the yolk for nourishment and that should last a week or two. The little ones hatch during the wet season when there is plenty of food. For the first one to three years, they will primarily eat insects for the protein to grow to adulthood.


A stroll along the seawall.

Mainly because of the pet industry, iguanas have become invasive in Florida, Texas, Hawaii, Puerto Rico, U.S. Virgin Islands, and many Caribbean islands. They're beautiful animals but they are also large lizards that can be damaging and dangerous. Because iguanas are cute and not Burmese pythons, Florida was lackadaisical in trying to control them. Now they are everywhere. In open areas, they dig burrows to shelter in that can seriously compromise infrastructure like sea walls, buildings, roads, and sidewalks, and force out burrowing owls, considered an endangered species. For food they mow through native plants, landscaping, and non-native plants alike. People who live along the coast wake often to the sight of iguanas in their yards and even swimming in their pools. It has turned out to be a major problem.

Me? Capt'n Jack, Capt'n Jack Sparrow

Iguanas can spread salmonella, and those having the job of cleaning it up does risk their health. This population surge isn’t just in the hundreds, it’s in the tens of thousands, possibly hundreds of thousands. Alligator trappers have expanded their business to include iguanas, and they’re making a lot of money off of it. On the Keys, iguanas have eaten the maiden plant for Miami blue butterfly. Despite removing as many iguanas as they could, the butterflies haven’t returned yet. There is no way that they will be ever eradicated (they’ve been here since 1963), but they do need to control them.

The Grand Cayman blue rock iguana

Puerto Rico is overrun with them as is the U.S. Virgin Islands. The Grand Cayman Island is a perfect example of how bad they have gotten. In 2014, they reported 127,660 iguanas. Just two years later, in 2016, there were over 400,000. An experimental hunt captured 14,500 animals - 16 tons worth and it was barely a dent. Florida Fish and Wildlife are desperate to not have a repeat of Grand Cayman's population problem. The Grand Cayman is also dealing with a conservation iguana population problem of their own. The Grand Cayman blue rock iguana is critically endangered. They are rarely seen outside of their protected areas. Luckily, the two can't interbreed but the green iguanas are a significant threat to their food supply.

And then there is Hawaii. They have no native lizards but have a few interlopers now, including the green iguana. Hawaii is VERY strict on what animals can come to the islands, and iguanas don’t make the list. If someone is discovered with an iguana, they can be fined $200,000 and three years in jail.

Did you just say it's $200,000 fine for an iguana?

Cold as ice…

You just wait until I can move!

Iguanas have managed to adapt in Florida (and South Texas) quite well. Except for one thing. They are tropical lizards living in subtropical environments. When temperatures get down to 50-40 degrees, their metabolism and blood flow slows and they become lethargic. Unable to move, they become unable to grip trees and will topple out. They’re “frozen.” As soon as the temperature increases and they get warmer, they wake up and it’s back to business as usual. For people who want to help them and move them from dangerous locations, there is the danger of them warming up and becoming defensive and injuring the well-meaning person. (The iguana warmed up and shuffled away.)

In conclusion

They are stunning animals. I'm a sucker for a big male, too. With all that head bobbing. I would get another one if I could. I know what to expect from them and what they need. Which means I'm not getting one anytime soon...which means they are they are not for beginners, should not be sold cheaply or given away in carnival games. They're specialized and high maintenance. Most importantly, they should not be set free. It is not the best solution for them or the environment. So what to do with them? In Central and South America, where they’re from, they are used as a meat source (tastes like chicken). In the Keys, there are cook books for iguana meat specifically. At one time here in the U.S., iguana meat was $14/lb. up in the northeast somewhere. That is why trapping them is so lucrative in Florida. Their hides can be used for various things. I don’t like having to kill animals to control their populations when we’re the ones to blame. But there is a line that is crossed, and the numbers living wild in Florida that we have allowed to explode in population has crossed that. If allowed to continue, the population will become so large that they can’t be sustained. It’s not their fault, it’s ours. They’re never going to be eradicated, but they can be managed where there isn’t as much conflict with people and local wildlife, where there is a sustainable population and it will be safe to walk under a tree when it’s cold and not worry about being beaned by a 17-pound frozen iguana.

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