Ok, I'll start a new topic, input/feedback wanted- "alternative sexing technique"

[treevaranus]

A trick with sexing Indo monitors....

There are several ways of accurately guessing the sex of monitors(for the most part)- I am talking about asian/indo monitors, as they are what I have the most experience with keeping..

There is the traditional methods such as head shape and size, tailbase shape and size, etc... which are at most times very accurate to go by. There are several other things to look for, which could help in your assumptions..

But one thing that I would like to point out, which was originally pointed out to me, which from what I have now seen, almost always holds true as a sexually dimorphic way of deciphering sexes in indo monitors.. And this is the shape of the lower jawbone.

To go by this method, look at your monitor's head in profile from either side. Look at the lower jawbone in respect to the ear. In females, the lower jawbone is virtually linear, and forms a straight line which leads right back to the ear-no curving or bowing of that lower jawbone. On the other hand, males have a curve to their lower jaw, which bows down in the center of the jawbone, creating more of an arched pathway to the ear. I have not seen any adult male indo monitor who has a straight jawbone leading to the ear. In all of the animals which I have looked at(hundreds of photos and individuals), the lower jawbone shows curvature, and is quite apparent, especially when placed next to a female.

Here is an example of what I am talking about using a pair of my Varanus macraei. You can see the difference between the two. Now, if you look at the picture that Neal originally posted, you can see that curvature to the lower jaw, which is cries out male, to me..

I encourage all of you to go through photos of other monitors, and you will see this difference between males and females... Keep in mind that I have only really looked at this phenomena in indo monitors- especially Euprepiosaurid varanids, as well as V. salvator.. But I would imagine that this may hold true for many other/most other varanids...

I'd like to hear your thoughts on this.... Of course, nothing is 100% accurate, but I would have to say that this is a pretty good indicator, especially when used in combination with other sexing techniques...

Take care everyone, have a wonderful day. I've got some other sexing methods and techniques posted on my site. While it is aimed at tree monitors, I do not see why the same methods couldn't be used for other varanids... www.treemonitors.com/sexing

Cheers, have a great day! I look forward to hearing your opinions....Below are some pictures that support my claim... I'd love to hear some feedback...

Bob

here is a female V. boehmei-no curvature

here is a female beccarii-no curvature

here is another closeup shot of a male macraei- curves and does not make a clean straight line back towards the ear

[kap10cavy]

Nice Bob, will that also work with the larger indos?
I have gotten the hang of sexing african species from a few pics and am working on the aussies now.

Scott

[mbayless]

Another way is smell them = in aFrican monitors, which have a noticeable musk, their smell tell you which sex they are - the males smell like roasted almonds, the females like sweet almonds. Sounds silly yes, but it works!

Also x-ray the head, top view and you can see the sex of an animal by how its skull is shaped = like Bob's assessment of the jaws, which I have never heard of before but seems right on, shows that monitors, like mammals, show a secondary sex characteristics, males become 'men' and girls become 'ladies'.... except in Berkeley, where androgeny seems to be the norm rather than the exception

markb

[treevaranus]

Hey Scott,

Yes, it will work on other indo species as well; we have looked at the indicus/doreanus group, salvator group, as well as some of the odatria, and this appears to be a somewhat reliable method. Like i said, I am sure there are exceptions to every rule, but I feel that this is a great way of helping you distinguish sex.

Another characteristic that I have always noticed, but never reallly applied until having it recently pointed out to me by an "MS"l, is the size of the nasal cavity. Males will typically possess a larger cavity, which results in a larger/taller nasal 'ridge'. Being larger in males, a greater surface area in the nasal cavity perhaps allows for a greater sense of smell, as there is a greater surface area for scent detection.

The presence of larger cavities in males could possibly suggest that they are much more active, and use this increased sense of smell to seek out females or patrol their own territory for other males/intruders. I have seen a great difference in activity levels between most of my captives, in that males are far more active than females. Females tend to be rather illusive and spend the majority of their time in hiding. If this is anything like their wild behaviors, a larger nasal cavity in males makes a lot of sense. It's unfortunate that there is so little known about the ecology of most varanids. This would make quite an interesting study.

But here is an example of V. melinus. The photos are small, but you can see the noticeable difference in the curvature of the lower jawbone between the male and female. Note how straight the female's lower jaw is, whereas the male has a pronounced curve. These photos are from DnJ's website, of one of their breeding pairs. Are you guys starting to catch my drift?? Do any of you see the difference?


Cheers everyone, just thought I'd share would some of my colleagues and I have been noticing between sexes... Take care, have wonderful day.

Bob
treemonitors.com

[kap10cavy]

I can tell most African species by head shape and nostril placement, but I will ask for a tailbase pic to be sure.
Almonds Mark? Smells more like maple syrup to me.

Scott

[mbayless]

so you know that smell eh Scott? How close did you get to them to smell it - it stunk up my house but good - and I liked the smell; it is the same reasons that they secrete this pheromone that also makes the males head jerky when they mount a female or even male to determine dominance/reproduction readiness....but then any 22 yr can tell you that at any University frat party when a female is in heat (= estrus)....a wonderful thing....
markb

[kap10cavy]

I noticed the smell in the car on the way to the hotel we were staying at. If I want to smell it , all I have to do is change the dirt or throw in some dirt from another lizards cage.

Scott

[Senator Gracken]

unfortunately i does not seem to hold true for black and white argentine tegus, maybe i just missed it but to me the mouth lines both looked curved

my male spike


and the female mercedes

[treevaranus]

Well that's not a shock, considering Tegus are not even closely related to monitors, despite what most people think. Believe it or not, out alligator lizards are more closely related to monitors than tegus are, therefore I am not surprised at all that this may not hold true for Tegus and other teids.

Just because they are both carnivores and have split tongues, does not make them similar or in any way related. The split tongues that tegus and monitors both have, evolved separately, and are not shared by a common ancestor of both taxa.

So I am not sure why you are comparing tegus to monitors????

Cheers,

Bob

[Senator Gracken]

oh for some reason i thought tegus were a type of monitor, i knew they were from the teid family but obviously i got my wires crossed somewhere . my appologies

[treevaranus]

No worries mate,

There are a lot of people out there that think that tegus are "the cousins" to monitors... Animals are grouped together according to their evolutionary histories, not the overall appearance of an animal.. If we went by looks only, we would have green iguanas grouped together with asian water dragons, etc...

Monitor lizards belong to a group (infraorder) of lizards called Anguimorpha, which include Anguids(alligator lizards, etc), Xenosaurids(Xenosaurs), and Varanoids(Heloderms, Varanids, and Lanthanotus), whereas tegus/teids belong to the grouping known as scincomorpha, which includes the skinks and lacertids... Both of these groups have led separate evolutionary pathways, and are quite different from one another.

Therefore, although they are both lizards, and appear to have a similar appearance and habits, they are quite different from one another, as they have both undergone separate evolutionary pathways...

I hope this clears up some confusion you might have.. But to sum it all up, Monitors are not related to Tegus..

Take care,

have a good one,

Bob

[Senator Gracken]

cool, good to know. is there a book you would recomend? i would like to learn more.

[treevaranus]

Yes, as far as monitor lizards go, I would highly recommend you pick up Eric Pianka and Dennis King's new book, "Varanoid Lizards of the World". This is by far, the most comprehensive book covering varanoids( monitors, heloderms, and borneo earless monitor). There are great natural history/species accounts, evolutionary histories, paleontology, ecology, etc....

It is well done, it even has some really great photos representing every species. While it does not offere much as far as captive monitors, it is a must have for any varanophile, as it covers every aspect of their biology.

Check it out, I think you can buy it off of amazon.com or barnes and noble's website as well.

Good luck. That book has everything you need to know about monitors. Well worth the 70 or 80 dollars... Take care,

Bob

[crocdoc]

Originally posted by treevaranus
Being larger in males, a greater surface area in the nasal cavity offers allows for a greater sense of smell, as there is a greater surface area for scent detection.treemonitors.com

Bob, that all sounds fine in theory, except that the primary sense of smell in monitors is their jacobson's organ. They can smell things through their nostrils (my monitors can be seen gular pumping, to flush air through their nasal cavities, when I open their enclosure but will flick their tongues if they think something really interesting is happening, such as food), but their really sensitive organ is the jacobson's organ and I would imagine picking up a female's scent would be far more efficient through that. Unless, of course, the pheromone receptors are in the nasal cavities, in which case it has nothing to do with smell.

Here's a photo of my male checking out the receptiveness of the female just before mounting.

[treevaranus]

Hey Dave,

I was under the impression that the varanid olfactory system is comprised of more components than just the jacobson's organs . I recall reading that the jacobson's organs in varanids is used to pick up heavy chemical particles on the substrate, not the air. I am under the impression that the internal nares is used for picking up chemical scents from the air, and the tongue/jacobson's organ is used for detection of smells on the ground.

I of course might have this mixed up....
Also, do you have any photos of alex and nelish at profile, to see if the jawbone thing appears to be true in V. varius as well??

Cheers Dave, talk to you later..

Bob