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
http://treemonitors.com/images/jawbonecomparison.JPG
here is a female V. boehmei-no curvature
http://treemonitors.com/images/ze.jpg
here is a female beccarii-no curvature
http://treemonitors.com/images/zd.jpg
here is another closeup shot of a male macraei- curves and does not make a clean straight line back towards the ear
http://treemonitors.com/images/e13.jpg

[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?
http://www.kingsnake.com/dnj/monitors/melinus2.jpg
http://www.kingsnake.com/dnj/monitors/melinus3.jpg
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 (http://www.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
http://members.shaw.ca/ravenscroft/Spike.jpg

and the female mercedes
http://members.shaw.ca/ravenscroft/Mercedes.jpg

[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 :rolleyes: . 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 (http://www.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.

http://www.pbase.com/crocdoc/image/39062638.jpg

[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

[SHvar]

http://shenderson1.photosite.com/~photos/tn/2923_1024.ts1114583016000.jpg
http://shenderson1.photosite.com/~photos/tn/2930_1024.ts1114583557000.jpg
http://shenderson1.photosite.com/~photos/tn/2934_1024.ts1114588178000.jpg
http://shenderson1.photosite.com/~photos/tn/2935_1024.ts1114588487817.jpg
http://shenderson1.photosite.com/~photos/tn/2936_1024.ts1114588655679.jpg

[mbayless]

The monitor tongue is roughly 3x the length of the head in terms of its spring=loaded structure. It is a remarkable instrument. Monitors have taste buds, which are based on the tongue = the tongue color can change, depending on what a monitor is doing - the monitor can taste the air and the soil, and smell it too; how the jacobson organs plays part in this is perplexing to me - how much do we know of what part it plays in their chemoreceptive world? We know it does play a vital role. All of their sense organs seems to aid it in directional radar like finding abilities from food, girls, and combatants too...
markb

[crocdoc]

Here you go, Bob:

Male top, female bottom (not that it really needs explaining, as it's fairly self evident!)

http://www.pbase.com/crocdoc/image/40335426.jpg

This is a juxtaposition of two photographs, each taken when the male and female were in the exact same part of the enclosure (you can see the repeating patterns on the rock in the background) so you can compare them at relative size. Not too difficult, as the male's head is so much bulkier than the female's. Yes, his lower jaw is a lot bulkier (and therefore curved), as is his snout/nasal cavities.

He's 20% longer than her in total length, yet is around 400% her body weight. Some of that is simple physics (mass being a function of cubic dimension), but even if she were his length she'd be much lighter. With a large male (this male isn't particularly large for the species), the difference in adult size between males and females can be huge.

Here's a conundrum for the science bashers out there: Pair bonding species of most animals have similar sized genders*, whereas sexual dimorphism in size is usually an indication of competition for mates. If lace monitors pair bonded, why are males so much larger?

*Don't even think of including humans as a pair bonding species, for we aren't really a natural pair bonding species and go against most primates in that regard (there are exceptions, and in those species males and females are of similar size). If you don't believe me, watch the Jerry Springer show a few times for examples of how well we cope with pair bonding.

[jungleshadows]

here are some nile profile pics for you, what ya think?? I could do many other varanids if you like so you can test your theory out.

http://img.photobucket.com/albums/v334/jungleshadows/varanus/PICT1995.jpg

http://img.photobucket.com/albums/v334/jungleshadows/varanus/bluenile004.jpg

http://img.photobucket.com/albums/v334/jungleshadows/varanus/Image004.jpg

[mbayless]

Nice pics Jody - DK: that is a good question about pair bonding in animals are same sized genders vrs sexual dimorphic animals is indicative of male competition....have to think about that! Except for V. griseus which mate with the same females seasons after season, being solitary the rest of the year, I cant think of any exceptions to that....not even among fish...thats good DK...and yes you're quite right about Humans too - only the Biblephilic christians (not bibliophiles!) say it is blaphemous for polygamy - but the Utah Mormans and Muslims say it is ok - so who is right? Hell if I know....
mbayless

[treevaranus]

female
female
male

[master pt]

mbayless, hmm according to Dennis King and Brian Green`s monitor book the biology of varanids lizards, " varanids are the only family of lizards which lack taste buds on the tongue and are similar to snakes in this respect. ;)

[mbayless]

Hi masterpi,
Yes, I realized I made a mistake on that.... I misread it when I was double-checking it before I posted it....Thanks for reminding me to correct my error....Im getting old :(

markb

[master pt]

no harm, just wanted to know whats right or wrong.

btw when can we read your new book.

[mbayless]

I am finishing it up now - so I hope soon - Im going over it to find errors, syntax, etc...and follow up a few little points of info I forgot to do 20 years ago.... writing a book is one way to get the files straightend up!

markb

[jungleshadows]

the picture of niles I believe actually goes female ,male ,male.

The female on top is confirmed along with the male at the bottom.

The blue nile appears to be male and has never laid eggs.

here are some others for you

http://img.photobucket.com/albums/v334/jungleshadows/varanus/mgriseus003.jpg
http://img.photobucket.com/albums/v334/jungleshadows/varanus/fgriseus004.jpg
http://img.photobucket.com/albums/v334/jungleshadows/varanus/PICT2175_26686829.jpg
http://img.photobucket.com/albums/v334/jungleshadows/varanus/malerudi006.jpg
http://img.photobucket.com/albums/v334/jungleshadows/varanus/marmomale6.jpg
http://img.photobucket.com/albums/v334/jungleshadows/varanus/Image0142.jpg
http://img.photobucket.com/albums/v334/jungleshadows/varanus/PICT2650.jpg
http://img.photobucket.com/albums/v334/jungleshadows/varanus/Picture014.jpg
http://img.photobucket.com/albums/v334/jungleshadows/varanus/PICT3220.jpg

[treevaranus]

Looking at the picture of that blue nile, I would guess it's a female... But I guess that hasn't been proven yet...lol..

As for the rest of the photos, let me see...
I'd say that it goes:
-male griseus
-female griseus
-male salvadorii
-male rudicollis
-female? sumatran x marmoratus salv.
-male mertensi
-male salvator
-male rudicollis
-female mertensi

How'd I do?? I am pretty sure on all of them but the reptile guru salvator...

[mbayless]

Yeah what Bob said....Bob - you're language/vocabulary is changing! You're beginning to talk 'biologist'!! OMG! hahaha
markb

[jungleshadows]

Won't know on that blue nile until she either lays eggs or he shows what he has. The other reason i believe him to be male is of his tail size and appearance. Also when placed together with my male they wrestled non stop until i sepereated them.

Now I realize that means nothing since female and female will do the same as well as female male etc. So like I said it is not confirmed it is just what I think it is.

Now for the other pictures.

Male griseus
Female griseus
Female salvadori
male rudi
male marmo cross
male merten
female salvator
male rudi
female merten

The 3 you got wrong are confirmed, the only one on the list unconfirmed is the female mertens.