HomeAsk A Vet

Neutering An Aggressive Iguana Lizard

The only time my iguana becomes aggressive is around breeding season. I've read conflicting opinions about whether neutering will help this problem. What is your opinion?

Pet Reptile Attacked By Another Animal
Coughing Lizard
The Vet Report: Contrary To Popular Belief, Snakes Can Hear

I have a male iguana that was found on the streets of Brooklyn more than five years ago. He is very well socialized with my other companion animals (seven cats, one dog and an Amazon parrot). The only time he becomes aggressive is around breeding season. I've read conflicting opinions about whether neutering will help this problem. What is your opinion?

I really wish that there was a simple answer to your question. Spaying or neutering (surgical removal of the ovaries plus or minus the shell gland or testicles) has many benefits in our pet dogs and cats, but no such luck with male iguanas.


Dr. Doug Mader, a renowned reptile veterinarian, did a follow-up with many iguana owners who had their male iguanas neutered, and found that the procedure had little, if any, effect on the males’ aggression levels.

Some iguanas are much more dangerous during breeding season, which appears to be the case with your lizard. Males fired up with hormones become much more aggressive and territorial than usual. It becomes extremely important to learn how to read your iguana’s behavioral signs: tail whipping, puffing up, turning sideways, extending the dewlap, tongue licking, hissing and head bobbing are all nature’s way of letting you know that you should beware of your iguana.

A mature male iguana can be very dangerous, and his bite can cause significant damage to humans. Due to his unpredictable nature, you must protect your other pets and interested humans from being injured by your pet iguana. It is your responsibility to ensure the safety of those around you by making sure no one gets hurt. Male iguanas can be particularly dangerous to women during certain times during their cycles, too.

Some researchers are experimenting with hormone therapy to attempt to decrease aggression in male iguanas, but the verdict is still out on whether or not hormone administration may make a male less dangerous during breeding season.

I wish that there was a way to predictably render a male iguana passive and friendly, but we must remember that we are dealing with wild animals, and not domesticated animals that have been selected and bred for a gentle disposition. So, until there is a predicable and safe treatment for aggression, you must just learn to be safe when you are around your male iguana, learn to read his signals and never let your guard down when you are in his enclosure. Be safe!


Margaret A. Wissman, DVM, DABVP has been an avian/exotic/herp animal veterinarian since 1981. She is a regular contributor to REPTILES magazine.

Need a Herp Vet?
If you are looking for a herp-knowledgeable veterinarian in your area, a good place to start is by checking the list of members on the Association of Reptilian and Amphibian Veterinarian (ARAV) web site at www.arav.com. Look for DVMs who appear to maintain actual veterinary offices that you could contact.