This is a page I've put together in hopes that it might be of some use to those who are having problems with aggressive males due to breeding season. These are the things that I've encountered which may help you understand your male iguana's behavior better. Remember, iguanas are wild animals, don't expect one to behave like a domesticated dog.
Disclaimer- These are my observances (ramblings ;-) ) of the males (and females too) in my care- past and present. For more information on breeding and iguana behavior (and taming/dealing with aggression)I highly suggest getting James W. Hatfield III's book Green Iguana The Ultimate Owner's Manual
From what I've seen and experienced, an iguanas' aggression can be put into three different catagories- Territorial, Fear & Breeding. The first two catagories are not limited to just males.
1) Territorial aggression- where they see you as they would see another male- a threat to their territory (and they are very territorial). The behaviors I've seen associated with aggression are the lateral flattening (basically it makes him look bigger to the other male), head bobbing, and often the end of their tail will wiggle. They also get a funny look in their eyes. Once you've seen"the look" and have been thr brunt of one of their attacks, you'll never forget what "the look" looks like. Sometimes they hiss and I've even seen a male curl his lower "lips" out a bit as to show off his teeth. With my male, Igor, the skin around his eyes turns black and his crest (the spikes down his back) actually get taller.
With the younger males it seems they don't need much of a reason to be aggressive. As mine got older I've found there are certain factors that trigger this kind of aggression...
A) Seeing other male iguanas- such as having their cage placed in the view of another male's cage where they can look at each other all the time. This sometimes triggers aggression outside breeding season. Quite a few years ago I had two males (Hoot and Gator), whenever Gator caught a glimpse of Hoot, even just as I carried him past Hoot's cage, he'd take it out on me for at least a week! ("the look" in his eye and charging me). Sometimes females get aggressive towards other males. Basically, if you're considering getting another iguana because you feel your iguana is lonely- Don't do it!- unless you're prepared to cage the other iguana separately. All my bigger females hate Igor, so male/female cagemates don't always work out. You may have two iguanas that haven't hit sexual maturity yet and it seems things will work out. Sometimes they do. Sometimes even before sexual maturity one iguana will be the dominant (Alpha Iguana) and will pick on the other/others. It may be as obvious as seeing bite marks on the submissive iguana or it could be something you have to pick up on such as one looking thinner (suggesting the other won't let him at the food bowl- two bowls might not fix the problem either), lethargic (from stress, or even illness, sometimes stress induced), and off in a corner of the cage (or away from the good basking sites- equal height/quality basking sites may or may not help the situation). Separation is usually best.
B) Mirrors- Gator used to walk down the stairs in our old house. There was a closet door at the bottom of the stairs with a full length mirror on it. He'd get so far down the steps, see himself in the mirror and go into the head bobbing and posturing. Sometimes he would get nasty with me, other times he let me pick him up and get him away from the "other iguana".
Certain colors or patterns- During Igor's last season I found that his mood patterns often revolved around the color of clothing I wore. I recall walking into the room wearing a bright yellow-green turtle neck sweater and he was immediately posturing his threat. I went out changed clothes and he was fine. St. Patrick's Day I wore kelly green jeans into the room (without thinking, of course) and Igor came running at me and would circle me and attack at my legs. I changed my clothes and he was again fine. At the end of his breeding season this past May I was in the lizard room. It was a rather hot day and I was wearing a pair of rather short shorts.
I stooped down to clean up some poop he left and before I knew it he had bitten me on the back of my leg/butt area. I still have a scar. It was several weeks before I realized that the reason he bit me was the color of the shorts (teal gingham check). Igor will attack me during his breeding season if I wear any green color or teal. I also know where this could fall under the "fear" catagory...
2) FEAR- There are times when colors or patterns spook an ig and all they want to do is get away. Trying to restrain the iguana can cause it to become defensive. This happened with my one of my iguanas with an article of clothing I was wearing. I tried to hold her I ended up with a nasty welt on my leg from her tail.
If you think about all they go through before they make it to the pet store, it's amazing they ever tame down and trust a human- ever! First most come from iguana farms in South America so they're shipped into the states where they most likely go to a wholesaler, then to the pet stores- that is if they survive all that. And who knows what they go through on this journey and what the conditions they've lived through. And you may have received an iguana that has been through several different owners. Who can blame them if they're scared and on the defensive.
A scared iguana generally will tailwhip, hiss, and bite if need be. This is common in very young iguanas. Just about everything in the wild could eat them and they see you as a potential predator. Be patient with them. Taming them takes time, especially if your iguana's been through some tough times (such as my Oobleck and Helmut). Keep working with the iguana and try not to be afraid yourself. They never seem to tame down if you're always on edge and fearful of getting bit. So if you have to use heavy gloves when handling, do so if it makes you more confident. You might just try sitting next to the iguanas cage and reading a book and/or talking softly to it. If your iguana is in an aquarium, a cage with a front or side door would be better in that you wouldn't be reaching down from above to get him out of the tank. They often think of you as a bird of prey from that position. And if you do build a cage you might want to consider making it large enough for the iguana to grow into, or you'll end up building a new one again in the near future. I hope to have a cage design added to the site soon.
Anyway, many times skittish tailwhipping baby iguanas gain confidence as they get larger and older and if you've been working with them they'll most likely have come to trust you. In the wild, when they are young, they are prey to many animals, so they must be very defensive if they want to live. This is why baby iguanas may be very feisty when young. As they get larger, less and less animals are a problem for them in the wild, so they tend to be a bit more relaxed when they get larger.
3) Breeding, more of a "love interest"- where all they're interested in is mating. You may notice differences in your male from what I've seen in mine. I think age plays a big factor in how aggressive they are. Mine have, as well as some others who have male iguanas, have found that they often mellow with age.
If a female isn't present often they feel a human caretaker will do just as well, if not better. Sometimes they can be persuaded to mate with a towel, pillow, or even a stuffed animal. CDR, when he was much younger (back in 1993-1994) would go between mating with one of my sweatshirts and a stuffed animal iguana. You may have to play with colors and textures to find something he likes.
Their behavior seems to differ from aggression in that they don't show the threatening posturing. They still head bob and will chase the object of their desire. They also leave "presents" (semen) around during breeding season. You may actually see the male roll his hemipenes in and out of his vent (masturbation). If you try the decoy tactics above and they don't work for your male iguana, you may find you have to keep him caged more often or all during his breeding season, until he is once again himself. You may find that these substitutes work in a following breeding season as the male gets a little older. And maybe, eventually you won't have to worry about the breeding seasons at all.If you do find that your male, or female that is aggressive, please take precautions. The following are tips for use in mainly breeding and territorial situations...
1) Wear protection- gloves, long sleeves (a sweatshirt may provide a little better protection against severe bites), jeans, and shoes while handling your iguana. I probably could have added a hockey helmet with a full face mask the one time I was cleaning Gator's cage when he was in one of his aggressive states. I stooped down to pick up the water bowl from the bottom of the cage when I felt a "whack"
on the top of my head. When I stood up I saw Gator headbobbing with a good chunk of my hair sticking out of his mouth! This brings me to...
2) Keep the aggressive iguana away from your face! This is probably a good rule to keep with any iguana, especially one with a history of aggression (even though I don't do that). They can so some serious damage (plastic surgery kind of damage), even a smaller one can do considerable damage.
3) Also, do not place an aggressive iguana in a superior position (at face level or above your head). You're pretty much asking for trouble by doing this. Even iguanas that usually aren't aggressive can often become aggressive in this situation.
4) Mirrors and other iguanas (generally males) can increase or provoke male iguana aggression, and the latter can add up to costly vet bills if they come into contact with one another. Sometimes keeping these out of view of the aggressive iguana can rectify the problem.
(8/24/99)- I think CDR is entering his breeding season because he's leaving me little "presents". It's about the only cue I have anymore to know he's in season. He hasn't seemed interested in his stuffed animal iguana since he outgrew it and hasn't appeared to need a substitute. He's shown no aggression (territorial or mating) towards me since around 1995.
Helmut hasn't been mentioned since he hasn't shown any aggression other than his usual crankiness (not breeding season related). As soon as he does something I'll add my observations.
(9/99)- Actually, Helmut displays territorial behavior when other males (especially CDR) are around his cage. Outside his cage he's rather timid and submissive.
(10/99)- I was cleaning CDR's cage, got distracted (had to leave the room), and forgot to close his cage door. I came back a few minutes later to find CDR and Igor circling each other. Both had inflicted wounds on each other. Igor's injuries were worse than CDR's. I got CDR back in his cage and cleaned all their wounds.
It seems that my males are generally going into season at different times. Igor goes into season in late February and is annoying until sometime in May. He has the run of the lizard room. I'm finding that the more room he's given, the more annoying his behavior can be- it's like they have more room to protect against intruders (like I said- they are territorial)
During his season I have to be careful not to let other iguanas out at the same time as he's out. He'll try to attack my males and is too rambunctious with trying to breed with my females. (I mean he really never has a chance with them- they're two to three times his size and he only has one eye, though it doesn't stop him from fervently attempting to mate with them). This past breeding season Mandelbrot walked out of her cage while I was cleaning it. Igor seeing her before I could get to her was all over her. Before I could get him off her she bit his arm. It wasn't a bad bite which was fortunate (and it could have been serious considering Mandelbrot's size), but it still got infected even though I cleaned it right away. He had to have his arm lanced at the vet's and was on oral Baytril for around 20 days. Right after he tried to mate with Mandelbrot he attacked me with the same intent. I had an iguana mouth shaped bite on my forearm.7/21/00- Recently I was cleaning cages (okay, I'm always cleaning cages)- Igor was out walking around and Mandelbrot crawled out of her cage while I was cleaning it. Before I could do anything, Igor was trying to mate with her and she attacked him for trying. He really got some nasty bites. I cleaned him up and put him back in his cage. I finish Mandelbrot's cage while she's out and about in the lizards room. I start cleaning Helmut's cage. He walks out and before I knew it, Mandelbrot attacked him for no reason (probably because she was still upset about Igor trying to mate with her). She jumped on his back like she was a male trying to mate. When I let him walk out of the cage, I never figured that would happen because he's slightly bigger than her, but she put him in his place before he ever had a chance. She ripped out one of his spikes and left a bite mark on his back. I cleaned him up and put him back in his cage and then put Mandelbrot away before she could do anymore damage during CDR's cage cleaning. I'll post pictures of the "right after" the incident (Igor and Helmut) and the "now" pics very soon.
1/6/01- I'm adding some links pertaining to iguana aggression...