Male Iguanas in Season and Human Females

archived 10-22-99
Archive file# r102299e
donated by James Vandale

Male Iguanas in Season and Human Females

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 pheromoneal (hormonal) changes in their own species than we humans now are. Some, like the green iguanas, have special chemosensory organs, such as the iguana's vomeronasal (Jacobson's) organ, used to detect these chemicals. 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 so their femoral pores) 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.

Whether they actually care is another thing. Out of all the males I have had through here in the past 3 years (~80-90), 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 these 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 enamoured of me. One of them, Elvys, behaved differently than the other, Freddy, during this time. Elvys never tried to actively mate with me although he became more clingy than usual during my menstrual periods. Outside of the season, he was completely tame and even solicited attention and physical contact. During the 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 charge human females.

Freddy, on the other hand, tried to mate with me every year during "our" season (his season, me menstrual or premenstrual - 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 them... He 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 wore 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 of 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.

Iguana males attacking menstruating human females was first described in the literature several years ago by male veterinarians (Frye, FL, D.R. Mader and B.V. Centofanti. 1991. Interspecific (Lizard:Human) Sexual Aggression in Captive Iguanas (Iguana iguana). Bulletin of the ARAV 1(1):4). I have been the only one that I know of to report (albeit informally) on 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 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 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 both (I rescued Fred after he had been languishing for over a year on consignment in a pet store owned by two males). 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). He, 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). He later that first season mated with my female iguana, and has shown now changes in his behavior towards me during my cycles during his season. Since that first year, hasn't altered his behavior towards me at all during his season.

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 occurance 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.

Kaplan, Melissa. 1997. Male iguanas in season and human females.
© 1997 Melissa Kaplan

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