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

Sexing Green Iguanas

©1994. 2000 Melissa Kaplan


Non-invasive sexing needs to wait until the iguana is 8" long snout-vent length (svl) (this is approximately at 12 months of age assuming proper environment and diet from date of purchase or shortly thereafter). Pet stores selling baby iguanas younger than a year of age who tell you what sex they are are, quite simply, lying to you. Iguanas whose overall growth has been severely stunted will continue their sexual development, although it may be delayed. Generally speaking, the following signs will be seen in iguanas who are 2+ years old and under 8" svl. Note that the onset of the first breeding season, occurring at 1.5 years of age or so in a healthy iguana, may not occur for 3-6 years in apparently healthy, but actually malnourished, iguanas.


Femoral Pores
Femoral pores will have begun to expand on the males, with the whitish keratin plug clearly visible in all of the pores. In females, the pores remain pinpoints except for the first 3-5 pores immediately adjacent to the vent may be slightly opened. See the Femoral Pores page for drawings and photos.

During breeding season, the plugs on sexually mature males may extrude from the pores, becoming quite visible in silhouette. It is theorized that they drag their thighs (and the plugs) along the ground/branches/rocks thus marking their territories or announcing their presence by leaving waxy scented trails from the scrapings off of the plugs.


At about 14-16 months, males begin to develop soft small bulges where their hemipenes are tucked into their tails. You will be able to feel them as soft swellings before the bulges are particularly visible.


The dewlap (gular crest) on the male has not yet started to lengthen, but I have noticed that, on males, tiny notches are usually visible in the bottom edge of their dewlaps which are not found on the females.


Dorsal Crest
The dorsal crest on males begins to get taller than the crest on females, especially in the nuchal area (on the back of the neck). This is not an absolute indicator of sex, however. Females from some geographical areas have taller nuchal and dorsal crests than male from other areas. The crests on severely malnourished, sick or mite infested iguanas may not grow at all or their growth may be stunted.


Males do not begin to develop the jowls until they are 3+ years of age. Older females may get jowly, and smaller, submissive males may have very small or no jowls.


Breeding Season "Gifts"
Males will begin secreting a whitish rubbery H-shaped "thing" (for lack of a better word - I've never seen it written up, but every male does it!) which is apparently composed of seminal secretions and old, sloughed off cellular debris. This starts happening when they hit sexual maturity during their first breeding season, and is something to look forward to every breeding season. For more information, please see the article on seminal plugs and deposits.

During the breeding season, ejaculate matter may be seen as a milky white substance floating in the urates.


Seminal/Hemipenal Plugs
Semen and cellular debris may build up inside the inverted hemipenes. As this matter fills up the cavities, they form hard waxy plugs and eventually begin to emerge into the cloaca. There, they are in the way of the feces as the iguana defecates every day, and the tops of the growing plugs become capped with feces. The first that is often seen of these plugs is hard balls of feces protruding from the vents. The article on seminal plugs discusses how to remove these plugs.


Both males and females bob, so you cannot use this as a distinction. However, I have found that generally females bob jerkily, erratically...kind of like they are practicing, whereas dominant males develop the smooth shudder-bobs and regular bobs with great fluidity.

However, there is one exception to the males = smooth bobbing rule: Males who have never been exposed to other males, who have been raised with dominant aggressive males or who have never seen themselves in a mirror or other reflective surface frequently bob like females. The more they do it, however, they will eventually develop the fluid male bobs if they move to a household or otherwise become the dominant male. Females, on the other hand, rarely lose the jerkiness.

Males bob in greeting as well as to gently reassert their dominance on a routine basis (I refer to is as the "I'm king of the hill and you're not" bob) - these are administered from a relaxed reclining position. When they are doing a specific territorial bob to perceived competitor, they will raise themselves up, laterally compress themselves a bit, then bob.

Related Articles

Iguana Care and Socialization

Iguana Egging and Incubation

Iguana Ovaries and Testes

Dealing with Iguana Breeding Aggression

Testosterone, Aggression and Green Iguanas

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