Basic information on sex determination of Varanids

[Steeve B]

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[KaHane]

Great post Steeve, I will try these methods out with my monitors:) Oh yeah I got your Email, hope the shipment comes soon!!

[Dom]

great info steeve .. when u say males have longer body then female do u mena in comparason with other monitors or does it also aply for the tail in portion to their body?

I hope I made sense

Dom

[Steeve B]

OK Dom any comparison must be made with members of the same species, body length is calculated from snout to vent, tail is calculated from vent to tip. The rest is quit simple the only problematic I can see is when trying to sex animals of grate size difference. Hope I mad sense lol

[M_surinamensis]

Intending no offense here but, as you said it's the sort of determination which requires a fairly decent body of multiple animals and the observations will be both proportionally different in separate species as well as somewhat subjective based on the individual making the observations and the conditions the individual animals have experienced.

The comment about moving faster for instance, since they're ectothermic organisms, you would have to ensure that the temperature is completely identical when making this determination in multiple animals as well as ensuring that they encounter totally identical stimulus and have identical predisposition to those stimulus.

The other factors can also all be influenced by the environmental conditions that the animal has encountered throughout it's life as well as change as a natural product of general genetic drift.

While it's always great to get guidelines out and it's certainly better than nothing or relying on flipping the animal over and hoping males will evert the hemipenes, I'll stick to finding a competent vet and allowing the animal to be everted via saline injection when I need a positive response.

[Steeve B]

You’re right these observations must take size into consideration, much more useful for exporters and dealers but nevertheless practical with neonates and similar sized monitors.

Speed of motion is an overall observation and has little use in sexing, but if you ask me my males always get there females, in a way I do think they are physically faster then females not only to mate but also escape territoriality.

I don’t quit understand your genetic drift part but who’d like you to elaborate on this pleas.

As for vet sexing well aim not hot for this, I do know J Gauvin and Pilot and with all do respect I much prefer my way,
Saline solution is not accurate nor is it safe for everting hem pens, on many species there’s a slim deference between hem clitoris and male appendage, manual popping when learned properly will give you better results, a side note for those experienced in popping snakes, I never got it right with snakes but aim pretty good with monitors, so there a difference alright.

I also agree that peoples shod talk more about there experience then we can all start to learn something
Kind regards

[Steeve B]

The above sexing observations are complementary to my sexing technique,
On this draft you can see inside view of hem pens, the action zone is where you draw attention to, when applying pressure to the base of hem pens there will be a muscle contraction in the action zone, this muscle contraction is totally absent in females. Theirs no need to ever the hem pens but if you insist on doing so (it will take practice)
You need to apply pressure on the hem pens evertion muscle located on both side of the cloak a, you can not simply roll the hem pen out with your thumb like you do with snake, no you need muscle assistance. There are no set rules in monitor sexing, but these observations by me 20+ years in monitor husbandry combined with my friend life long experience, are quit accurate and not to invasive. Until they get the magic sexing pill out these are the best ways, the other ways are;
Probing, I was only successful with one species Ornatus. Saline injection, I personally treated more then a dozen monitor from prolaps. Endoscopy my friend Hans Georg Horn regardless of my dislike went on to sex one of the 3 lace monitors he sold me, turned out to be inconclusive. Last DNA not reliable in monitors why I don’t know.
Hope you find this tread informative, kind regards



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[M_surinamensis]

With regards to the genetic drift...

I was speaking about the tendency for an individual animal to react in a manner that differs from another individual animal from a distinct and separate part of the range when encountering identical stimulus...

Basically, reptile behavior is based predominantly in instinct, which has a genetic basis, it really only becomes modified after extended periods of time when the instinct "fails" or when presented with a stimulus that there is no instinctual ingrained predisposition towards a certain reaction for. Since the instinct has a genetic basis, in organisms with a slightly larger population or a slightly larger range, there will be a certain amount of genetic drift in numerous traits, behavioral traits included. These variations are generally fairly subtle but it may be the difference between an animal that goes straight for it's prey versus pausing a few seconds or the difference between an animal that moves in a straight line away from a potential threat versus one that might zig zag a bit or always try to work it's way back to a hide...

So there could likely be differences in the speed an animal moves based not just on physical capabilities but also in how quickly they respond to assorted stimulus and in what manner as a minor deviation in behavioral tendencies...

Hope that made sense, it is a bit early here and I just woke up.

Might I ask what sort of success rate you've had with eversion of the hemipenes via the saline injection method? It's obviously not identical to my experience but I'm certain that yours is far more extensive so I was wondering, ball park percentage, what portion of the time you found it successful and what portion you found it unsuccessful or if there were certain species you found it was unacceptable for?

Thanks for the replies.

[V.aw]

Steeve, do you work with blackthroats? I read that you were pairing some up!
if so. Could you possibly post a picture of a male/female as well as their vents? Iam trying to sex mine. I believe ive done it quite accuratly, but iam not sure. iF you can that would be great. Thanks.

[Steeve B]

Interesting there’s not much to add except that I don’t attribute much individualism in monitors I prefer seeing genetic traits as genius or even sub-genus. However I do recognise genetic behavioural traits as sexual dimorphism in all species.
One more point of interest is change in morphology due to environmental stress, with is what I tot you where talking about at first.
As for saline solution I have only treated vet sexed animals, I never did it. All monitors treated where young adults, these monitors seem to have muscle damage preventing reintroduction of one hem pens, you could reintroduce it manually but the organ was re expelled upon defecation, the vet point of view on this was an expensive surgery, and in most cases denied any responsibility. So I don’t know what the success rate is, but to me it’s clear that non intrusive sexing is still the best way to go.
Thanks for your informative post, hopefully we will exchange some more, just keep it simple English is not my primary language.
Regards

[Steeve B]

Hello V.aw

I use to keep them, and I am trying to get some more in fact I was supposed to drive to Port credit on Monday Grant kindly kept 6 for me, but the darn snow keeps me in Montreal. As for photos I have a few not very good but I will try to find one for you. Sexing them is pretty easy just by looking at there tails base males will look thinner when you look from above, on lateral view male have I higher tail. In temperament most female of the Albigularis complex are often tail wipers, they will tail slap you over and over as if it was a national sport.
Cheers

[Steeve B]

Here you go V,aw
Not a good photo, the female is the bottom animal, she laid 18 eggs in a sweater box.


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[M_surinamensis]

Originally posted by Steeve B
Interesting there’s not much to add except that I don’t attribute much individualism in monitors I prefer seeing genetic traits as genius or even sub-genus. However I do recognise genetic behavioural traits as sexual dimorphism in all species.
One more point of interest is change in morphology due to environmental stress, with is what I tot you where talking about at first.

I generally don't attribute much of anything in terms of individual behavioral traits to reptiles either, there is an instinctual basis for everything they do so any deviations are minimal but... You get slightly different colors, slightly different sizes or proportions as a result of genetic drift, you can similarly get slight alterations in behavior based on these principles when looking at organisms with a larger range or a greater amount of genetic drift.

I did also mean the alterations in morphology that can result from varying environmental factors as an example of how it might not be as effective when looking at adults from undetermined or non-identical backgrounds but you qualified that afterwards by emphasizing the fact that you've used these methods on neonates or from a larger group.

Excellent thoughts on the matter and I thank you for providing your observations on the subject, I'm inherently skeptical of any new techniques (not your fault) but I'll deffinately keep it in mind and verify your findings through personal observation.

Thank you again.

[V.aw]

Steeve, thanks for the picture but it isnt loading

[Steeve B]

Thank you for taking my posts with a grain of salt, most peoples take them way too seriously. You are a very interesting poster; hopefully we can discuss other subject of interest may it be morphological change by environmental factor, or food -color relation in monitor, looking forward to it.
Best regards






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[M_surinamensis]

Thank you for not being insulted over my initial skeptiscism and questioning, most people, especially those who have worked to gain the credibility they enjoy, get a bit upset when I say that it would take some personal verification before I fully trust in their methods.

It's quite pleasureable to encounter someone who understands it's just a matter of wanting first hand verification of ALL information that's presented (it's the scientist in me) before fully accepting anything as even situationally factual.

I also look forward to any future discussions whatever the topic may be, your posts on this thread have given me much to think about and caused me to make a few calls to some friends who breed/import varanids asking them if I can observe and measure their neonates.

[Steeve B]

Proper evertion method
It’s important for monitor breeders to master this technique, not just for sexing but also when sexual activity is suspected. For aggressive monitors its often preferable to separate them as soon as possible, a sure sing of sexual activity is when your male present a sperm plug like on photo no2.
As I mentioned before everting monitors is unlike everting snakes, and needs muscle assistance.
Photo no1. Shows the way to start the evertion by applying pressure to the hem pens everting muscle.
Photo no2. Shows sperm plug at the end of hem pen.
Kind regards



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[Steeve B]

Exception to the rule
In salvadori from 3feet to 6 feet body and tails are of no use for sex determination, nevertheless they can be sexed quit accurately by head structure at any size male having narrow longer heads then the females short and wider hear, this goes without saying that big adult males will have much bigger heads then females. Also males of all localities have white yellowish tongs when females have pink tongs.
Photo shows both monitors have the exact same measurements being 22in body and 44in tails.
Kind regards



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[Steeve B]

There’s a slight difference between Merauke and Sorong salvadori, they are just a little more difficult as you can see.
These are exactly the same size animals.


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[KaHane]

Great post Steeve!! Thanks for sharing your knowledge.

[Steeve B]

Thanks Kahane hope you got what you needed from it, as it was intended mostly for you. Also you must realise this tread is insinuating sexual dimorphism in monitor lizards, the fact that no one of the scientific community has tried to punch holes in this theory, shows its holding true. Best regards

[markb]

Hi Steve,

I have read your post re: sexing varanid several times, and thought about for several days, and can shoot no holes through your theory/idea, and have tried to with every species, hatchling to adults....its seems a very valid and sound observations to me...
Many Thanks for sharing Steve.
mark

[Steeve B]

Hello Mark nice to see you here isn’t this forum grate or what, stick around and see how much knowledge this forum has to offer. You can tell the Monitor guys this is a true haven, a place where they can share and enlighten us with there monitor experience. Talk soon regards

[Steeve B]

If you try sexing your monitor with the above, can you pleas post some feed back. many thanks