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I need a little bit of clarification on monitor lizard sexual organs. Now, as I understand it, males have what are called 'hemipenes' or in other words, two penises. What do females have? Just an opening in the cloaca? I think I've also read that they have some kind of hemipene-like appendage, but am not sure...

Also, I have read that ackies can change sex. For instance, if there is a group of three females, the largest, most dominant female will change her sex. Is this true of all monitors, or only some?

Who's on top during breeding? Males or females? WIll they switch off? The reason I ask is that I just came across a supposedly female black throat on top of, tails entwined, weird things coming out of the cloaca, etc., what I thought was a male (given that a few years ago one of his hemipenes had to be removed). I thought the supposed female was a female because she has recently been digging holes and laying eggs. The thing about this "female" is the biggest of three monitors (I thought was 2.1), and has recently gotten kind of mean. I thought she was just getting mean because she was burrowing and keeping the males away, but could she have changed sex?

Sorry for the length, any input will be appreciated.

Both male and female evert a sexual organ, both have a similar shape, but among different species what is everted is shaped differently.
Males have hemipenes, some species the hemipene is flowered on the tip if you see the entire or full eversion, otherwise you could mistake what everts as either sex.
Females have hemiclitori, its long thin, and tube shaped with no flowered end like some species have on hemipenes.
You would have to see know full eversions of the species in particular to compare full (not partial) eversons among examples of a species.
As far as monitors changing sex, I dont know if it actually happens, but in some collections among a group of fresh hatchlings sometimes an even number of both sex appear, or later they develop into both, couldnt tell you if thats true or not if they can change very very very young.

Will females ever initiate copulation, or are males the only ones that initiate copulation? Have females ever been observed attempting what looks like copulation (with males or other females) in an attempt to show dominance over another animal (most curious about Blackthroat behavior)?

Thanks

All monitors like dogs will mount each other, male on female, female on female, male on male, female on male. Alot of whats seen among them is dominance when it seems like copulation.
For mating the male seeks out the female and starts a process to convince her to be willing to copuate, then the female if she so chooses allows it.

Thank you for the response.

Also, does this mounting involve eversion or hemipenes/hemiclitoris? For instance, if a female mounts a male to show dominance, would she evert her hemiclitoris and try to stick it in/around the male's cloaca?

I never noticed whether female dominance shows that way, probably not. Maybe rubbing it on the male to scent mark him as they do when scent marking objects.

That you very much, things are much clearer now.

Hello,

Yes males have hemipenes and females a pair of hemiclitoris that are tubular like the hemipenes. Hemipenes generally appear thicker in comparison and have a "flowered" end. They are both similar in appearance on live animals as they don't usually evert completely but my monitors usually give me quick glimpses when they poop and this will have you guessing most of the time.
I have also read what you have about the sex changing phenomenon and believe that the person who posted that has great credibility. I wish you the best- Mike

I posted a article a while back about a virgin komodo dragon female laying fertile eggs and they hatched (all this at a zoo). If this could be true then it would not suprise me if gender of monitors is determined later in life with some species.... like say ackies.

I have seen the "tubes" on one of my female ackies, but I was wondering what the male's hemipenis looked like on a ackie.

Sorry folks, monitor lizards have sex chromosomes. The letter assignment is Z and W (instead of X and Y like us). These chromosomes come from the mom and dad and sex is predetermined at fertilization. V. acanthurus, specifically, has been studied and does, in fact, have sex chromosomes. So that theory is bunk/myth/bs that they "change" sex. What is happening is that groups of lizards will look female to your human eye until a male gets dominant and strong and then appears to become a male. It always was a male. They are not always so easy to sex - some of them are Boy George looking animals. lol

Regarding Komodo's laying eggs alone - That is an odd asexual reproductive event called parthenogenesis where the females eggs on the ovaries double up the number of copies of DNA but fail to split into separate cells. Not to overcomplicate the answer, but only male babies come of this type of parthenogenesis due to the fact that the sex chromosomes (again, it's long been known that varanids have these predetermined sex genes) can only yield two baby types. A male is a ZZ and a female is a ZW (kind of like XY in us except that females are the heterozygous ZW and males ZZ). With DNA replicating and not separating it's impossible to get a ZW female. So only ZZ (males) and WW (inviable -dies off) can occur.

-Krusty