No More Shy Guy: Iguanas Looking for Love
By Tara A. Spears
For years I have cheerfully shared my garden flowers with all sorts of wildlife, enjoying the antics of birds, butterflies, and reptiles. When readers, friends, and neighbors complained about the iguanas, I responded, “Just leave them alone-they won’t bite you.” I changed my mind about these typically shy critters in the last week as my two resident iguanas suddenly became aggressive- coming at me instead of scurrying away! This is radically different behavior than what I’ve previously seen from iguanas in all the years of topical gardening. I wondered if they were ill- nope, they don’t get rabies; further research explained the change-they are males in rut.
Understanding Iguanas: The population of green iguanas is decreasing in the wild due to the destruction of their habitat, exporting, and over-hunting. In parts of Latin America, the natives have long-eaten green iguanas, calling them Chicken of the tree or Bamboo chicken. All iguanas are primarily herbivorous, eating a variety of flowers, leaves, stems, and fruit, but they will opportunistically eat small animals, eggs, and insects.
These reptiles are common in the lower altitudes of tropical Mexico. Feeding time will usually be late morning, after the iguanas wake up with the sun and find a nice basking spot to warm up. After feeding, iguanas typically will return to basking to obtain the heat necessary to digest their food. Iguanas are excellent swimmers, so don’t be surprised to find them in your pool. Since they are ectotherms, they require the energy from the sunlight for their bodies to function, thus requiring them to sleep through the night and stay awake during the day. Their poop is generous and they leave it on our pool decks, docks, sidewalks, and rooftops. The two types of iguanas that are in the Riviera Nayarit are the Green Iguana and the Mexican Black Spinytail, although there are hundreds of species worldwide.
Green iguanas tend to grow to a size of 5-7 feet (two meters) long, and can weigh up to 20 pounds (9 kilos). Approximately one-third of the length of the body is the tail. Green Iguanas have a dorsal crest and a large rounded scale on each jowl, with the crest being larger on the males. They have a baggy dewlap hanging from the neck which they wag when mating or defending their territory. Despite its name, the Green Iguana may be brown, gray, black or dark green. The males exhibit orange markings when they are mating. Babies and juveniles are bright green, and adults have black bands on their sides and tails.
The male Mexican Spinytail is mostly black with white and yellowish blotches; females can have an additional greenish tint. Their most distinctive feature is the dragon-like spiny fringe that runs down the center of their upper back and tail, hence the name. Coming into rut causes an orange coloration in the males. Mexican Spinytail babies are bright green with black markings. Mexican Spinytails can grow up to four feet (1.3 m) in length,and weigh about 15 pounds (7 kilos). Wary and alert, the Mexican Spinytail is not a common sight in the wild. According to expert Virginia Aronson, black iguanas are secretive, shy, and hide in burrows they dig under sidewalks, cement seawalls, or rock piles. See photos taken in my neighborhood.
Sex iguana style: To learn about iguana rut, herpetoculturist Melissa Kaplan is an excellent source of information. She has studied and published several books about iguanas over the last 30 years. I found her research to be very helpful to understanding my resident iguanas and their behavior.
Iguanas in the wild attain sexual maturity at about 18 months of age. Males will develop orange or rusty red coloration on his head and neck, back, and the tops of the legs, besides their behavior will become aggressive. You will see posturing, including increased head bobbing, restlessness, lateral compression of the torso (“hatchet mode” or “hatcheting”), dewlap flaring, crab-walking, and ritualized tail movements. In the wild, males are in season for about 30 days. During that time, they exhibit the color and other changes. Since females roam throughout the territories of several males, and are themselves receptive to mating for only 7-10 days, males mate with several females during the month they are in breeding mode. A female who isn’t receptive is left alone after a generally simple rebuff (head bobbing, foot swatting, or tail lashing). Since males mate with potentially 15-18 females in the wild (they generally mate on one day, rest the next, mate the third day, rest the fourth, etc.). Keep in mind, too, that females don’t have to be mated, or even within a mile, of a male to become gravid (carrying eggs), so not only would you still have a male on the make, you could conceivably (no pun intended) have 15+ gravid females, who can have potentially 30-60 offspring. So that means each horny male can produce 450 additional iguanas a season! Iguanas in rut go potty more than their usual once or twice a day- males do it as a sort of territorial marker, females because as the eggs start taking up more room in their abdomen, their internal organs get compressed and they are unable to store wastes as long as they used to. This explains why there has been more mess in my yard.
Snakes and lizards,including iguanas, (saurians) have a bi-lobed reproductive organ called the hemipene. This organ is tucked away in the tail, emerging from the body through the vent, generally during mating when it is inserted into the female’s vent. Some males, such as green iguanas, may ejaculate during breeding season outside of mating attempts. The gravid female has an increased activity level and exhibits digging behavior-which I do not appreciate in my garden. In the wild, females build nests by digging tunnels and chambers in the soil, in which they lay their eggs.
Iguana body language: Since we have to coexist with these reptiles, it’s good to learn Iguana language. They don’t make a lot of noises so you have to pay close attention to body language. What looks like a “smile” is actually a snarl. It’s a warning for you to back off. I enjoy watching the iguana antics, but recognize that since they are wild animals these movements are indicative of their attitude and should be respected. Both sexes do head bobbing, but males do it more frequently than females. Bobbing can start at any age. As it is typically used in an aggressive way or to assert dominance, and it is generally executed by iguanas that are secure in their surroundings. Females generally bob in a rather jerky, erratic manner – it almost looks as if they are practicing, just learning how to bob. Females bob when irritated (generally at another iguana, less frequently at humans), such as when annoyed by the attentions of a male, or when warning another iguana away from their basking area.
An iguana’s teeth, which are recessed and attached to the inner edge of the jaw bone, may not be clearly visible at first glance, but they’re there. In fact, a full grown iguana has 120 razor sharp serrated edge teeth capable of inflicting serious injuries. Their teeth are instrumental to their survival since they assist them to efficiently slice through leaves and other plant matter essential to their diet.
There are different reasons an iguana might bite, and different types of ‘bites.’ They range from the ‘kiss’ to the ‘death grip.’ All are potentially dangerous, but it is important to know what your iguana may have had in mind when he bit you. Another type of bite is the “slash and tear”. This is an aggressive one. It means to show you who is the boss. It can come without warning but might be preceded by a snarl (a slightly opened mouth) or puffing and walking sideways while glaring at you. Watch the eyes. If they are wide open, look out! If the tail is starting to twitch, back off immediately.
Usually if you leave iguanas alone, they will not approach you or threaten you or your pets; only if cornered will iguanas bite, scratch, or whip you with their tail in self-defense. Both males and females are territorial and will defend the trees they live in and the area around them–including your entire backyard. Since they are prolific in the tropics, if you dispose of an iguana in your yard, another will come to take its place. If you prefer not to share your yard with iguanas, it is best to iguana-proof your home rather than trying to kill off the animals one at a time.
What to do to make your yard less appealing to Iguanas:
Here are the simple steps you can take in order to make your yard less inviting to iguanas and away from your house:
remove colorful flowering plants from your yard (e.g., hibiscus, impatiens, bougainvillea, and orchids)
- remove fruit trees from your yard (except citrus, which they won’t eat)
- do not plant a vegetable garden in your yard
- cut back tree canopy or keep trees branches away from your roof and the sides of your house. Iguanas will climb screens and while hanging on your window defecate….ewe, what a mess to clean up!
- keep your entire yard free of brush and debris or rock piles
- attach sheet metal guards to tree trunks (to keep iguanas from climbing)
- install a childproof fence around your swimming pool
- spray garlic oil or Neem oil (they don’t like the scent)
- let your dog roam the yard to scare off wildlife
- spray them with a garden hose until they leave