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

Male Iguanas In Breeding Season and Human Females

©1997 Melissa Kaplan


Some articles here and in other published literature on iguanas speaks to the behavior of male iguanas towards humans during the iguana breeding season, in particular, the increased aggression of some (not all) male iguanas towards their human female during the female's monthly cycles during the iguana breeding season.

Many humans are amazed to find out that most animals can tell the difference between human males and human females. Not only can they tell us apart, however, but they know when human females are going through their monthly cycles. Most animals are better at detecting pheromenal (hormonal) changes in their own species than we humans now are with other humans. Some animals, such as the green iguanas, have special chemosensory organs, such as the iguana's vomeronasal (Jacobson's) organ, used to detect these hormones.

In iguanas, this results in their not only being able to smell the chemical cues laid down by other male iguanas who have marked their territories by dragging their thighs (and the protruding scent-laden waxy femoral pore plugs) along ground and branches (and, in captivity, the carpet, couch and other surfaces the iguana is allowed upon), but in being able to detect the subtle changes in their female keepers. Iguanas can tell when their female humans are menstruating and ovulating. Human females who have been spay--, er, have had a partial or complete hysterectomy, or who are post-menopausal, are still cycling hormonally every month, and the iguanas are able to detect these hormones even in their greatly reduced amounts.

Whether the male iguanas (or female iguanas, since they can tell, too) actually care is another thing. Out of all the males I have had through here in the past 3 years (numbering 80-90 iguanas), I have seen some minor behavioral changes in just a handful. These minor changes included their hanging around watching me or remaining in close proximity more during my menses and ovulation times than at other times of the month - but only during their breeding season. Only two iguanas, both, interestingly enough, Peruvians (or so I am told - both were highly blue all over with reddish eyes and darkly pigmented eyelids) actually became aggressive towards human males who came near me, flirtatious (so to speak) with other human females, and enamored of me. Of the two of them, Elvys behaved differently than did Freddy during these times.

Elvys never tried to actively mate with me although, during my menstrual periods, he became more clingy than during the rest of the month. Outside of the season, he was completely tame and sociable, regularly soliciting attention and physical contact. During his breeding season and my periods, he got extremely hatchety (extended legs, lateral body compression, ritualized body/tail movements and bobbing) when I wore blue, purple or green. He also would increasingly display at human males, and would charge other human females. He would even stalk around human males, especially men new to him, and very deliberately place one of his forefeet on their foot, making it very clear (to me, if not to the human in question) that he, Elvys, was the dominant male.

Freddy, on the other hand, tried to mate with me every year during "our" season (his season, me premenstrual or in menses - doing nothing, I assure you, to make me any less cranky!). The first year I had him, he launched himself right at my neck - twice. This resulted in fingers on both my hands being severely torn and infected for a couple of months. After that, he restrained himself and just went for my hands. I have the most interesting scars laced around my fingers, wrists and palm.

Freddy, too, was more excited when I was wearing "iguana" colors. He always clearly communicated when he was looking to grab me. He became a better indicator to me of my cycles than my calendar was. When he did nail me, it was because I was tired, or being stupid. Like the early evening when I was still wearing a T-shirt printed all over with green iguanas that I had worn that day to a full-day education event. Instead of changing when I came home and resting before spending time with Fred, I responded to his solicitation for attention by petting him and not paying close enough attention to his very clear signals. Oh, and yes, I got my period the very next day. Eventually, there were a few things he found to use as a surrogate for me. He even used them when I wasn't home (see the Transference section in the Dealing with Breeding Aggression article).

Iguana males attacking menstruating human females was first described in the literature in 1991by male reptile veterinarians (Frye, FL, D.R. Mader and B.V. Centofanti. 1991. Interspecific (Lizard:Human) Sexual Aggression in Captive Iguanas (Iguana iguana). Journal of the ARAV 1(1):4). I have been the only one that I know of to report (albeit informally, and subsequently confirmed by other women in the AOL Green Iguana forum and in the Iguanas Mailing List) of some males iguanas responding to human females during ovulation. In talking with other female iguana owners, I find that some of these women, too, see a change in their iguana's behavior when they are ovulating rather than when they are menstruating; some report male iguana behavioral changes during both times of the month.

Frye, et al., reported that male iguanas who were "closely" raised by human females - with the igs eating with the human female, sleeping with them, showering with them, etc. - being most likely to get aggressive during breeding season/menstruation. I found just the opposite: Elvys and Fred came to me when they were both 7 years old; Elvys was raised by a male; Fred by a male/female couple (I rescued Fred after he had been languishing for over a year on consignment in a pet store). On the other hand is my Wally, who, from the time his body was the length of my thumb, napped with me, showered with me, was frequently out and about with me, slept in my room (though not in bed with me). Wally, however, could basically care less about me during breeding season. During his first season, he did hang around me a lot when I was ovulating (walking up to me, putting a foot on me, staring at me with a rather dazed and confused look in his eye). Later that first season mated with my female iguana. Since that first year, he hasn't altered his behavior towards me at all during his season, treating me the same in season as he does out, regardless of where I am in my monthly cycle.

The important thing to remember is that the tamer your iguana is before the start of his first breeding season, the easier it is going to be to deal with him during the season so long as you are aware of what to look for. If you are a human female, be aware not only of triggers that may set him off, but see if you can correlate any changes in his behavior during his season with your own monthly cycles. If you are a human male, be aware that you may be considered as a competitor for territory and, if you live with a sexually mature human female, as competition for mates, as well. My article on Dealing with Breeding Aggression discusses the triggers and what can be done to mitigate your behavior to reduce the intensity or occurrence of aggression.

Finally, remember that not all males get aggressive during their season, and not all will try to mate with their human female keepers. At the present time, I have five males, all sexually mature, and none of them are aggressive to me during their respective breeding seasons.


A Note On Iguana Females
Female iguanas have the same chemosensory equipment as do males, so they can detect the same hormonal changes in humans as can male iguanas. Some human females report that their female iguanas act differently towards them when they are ovulating or menstruating. The behavioral changes are benign: the female spends more time in the presence of the human, tolerates, solicits, or fails to terminate contact with the human as they would do when outside of breeding season and other times of the human female's monthly cycle.

Related Articles

Introducing and Housing Multiple Iguanas Together

Dealing with Male Iguana Breeding Aggression

LuvSocks for Male Green Iguanas

Lizard Tough Guys

Breeding Season Basics

Testosterone, Aggression and Green Iguanas

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