# Temperatures in incubators determine hatchlings male or females...



## willee638 (Mar 12, 2020)

Some RF breeder claims "not with 100%" accuracy they can pretty much determine their hatchlings to be males or females upon adjusting the temperatures higher for females & lower for males in the incubators, but every breeder has pretty much confirmed with absolute certainty not even them are able to tell a baby hatchling or yearling from just looking at it alone. So new first hand owners of RFs or any other tortoises should stop asking people on how to sex their tortoises before age 4-5 & over already..so never truth pet shop salespersons they lie to sell you more.


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## Tom (Mar 12, 2020)

The only species where this has been actually studied and the correct incubation temperatures are known is sulcatas. In other species it is a guess. A guess that is often wrong. Also, temps fluctuate a lot in the real world, and non lab grade thermometers can be off a degree or two.


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## willee638 (Mar 13, 2020)

Tom said:


> The only species where this has been actually studied and the correct incubation temperatures are known is sulcatas. In other species it is a guess. A guess that is often wrong. Also, temps fluctuate a lot in the real world, and non lab grade thermometers can be off a degree or two.


Thanks, what you say is most likely to be the case. Reputable tortoise breeders probably wouldn't claim what you might get is exactly what you wanted, I think the problem is with pet shops because that's where the public deal with. by the time customers finds out it's years later. It's fascinating how these egg hatching animals can be one gender because of their environment changes, we can get too many of one sex at any time.


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## Bébert81 (Mar 13, 2020)

This is proved that temperature, but not only this parameter, have an influence on sex determination but it's not 100% sure.
Into the wild, depending of the area of the nest here is a tendancy due to temperature and humidity.


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## willee638 (Mar 13, 2020)

Bébert81 said:


> This is proved that temperature, but not only this parameter, have an influence on sex determination but it's not 100% sure.
> Into the wild, depending of the area of the nest here is a tendancy due to temperature and humidity.


In the wild probably the majority of tortoises in a nest won't even get to hatch at all, if temperature & humidity plays a big role even in determining gender then it's all up to nature. Humans can manipulate the best they can to what they desire assuring 100% survival & not only the strong, my problem isn't issues with breeders of tortoises as pets but with novice pet owners & the lack of knowledge given by pet shops for at least basic adequate care & many unfortunately ends up dead anyway. I actually don't mind what sex I end up with as long as it's a healthy tort & I knew it would be a big commitment for the rest of it's life & mine.


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## Tom (Mar 13, 2020)

Bébert81 said:


> This is proved that temperature, but not only this parameter, have an influence on sex determination but it's not 100% sure.
> Into the wild, depending of the area of the nest here is a tendancy due to temperature and humidity.


Yes it is 100% sure with Sulcatas, assuming that the correct temperatures are maintained throughout incubation with no spikes or dips at the wrong time. It is not studied, so not 100% sure in any other species.


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## Toddrickfl1 (Mar 13, 2020)

From what I understand temperature sexing is a good bet, but not 100%.


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## Tom (Mar 13, 2020)

Toddrickfl1 said:


> From what I understand temperature sexing is a good bet, but not 100%.


Not a good bet in any species other than Sulcatas. Sulcatas are the ONLY species that have been studied and temps confirmed in a lab under controlled, detailed, well observed conditions. The temperatures for Sulcatas have been 100% determined. For all other species, we are guessing and we are frequently wrong. No other species has been studied under lab conditions. We should all thank Mr. Richard Fife for this knowledge about Sulcatas. He initiated the study and provided the fertilized eggs.


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## Bébert81 (Mar 13, 2020)

For me this is not an exact science even for sulcata. 
If you are too close to minima and maxima values you can have supernumerary scales or worst deformations.
On my side I will just move the temperature a bit than the pivot temperature to obtain a tendancy and perfect animal as much as possible.


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## Markw84 (Mar 13, 2020)

Bébert81 said:


> For me this is not an exact science even for sulcata.
> If you are too close to minima and maxima values you can have supernumerary scales or worst deformations.
> On my side I will just move the temperature a bit than the pivot temperature to obtain a tendancy and perfect animal as much as possible.


The science part of it can be exact. But that does not mean a breeder can know 100% if a baby will be male or female as the "science" tells us the pivot point, but also tells us that at that exact pivot point we can expect the odds are 50/50 for male or female. as we go up or down from that pivot point, it does not mean 100% are suddenly female or male. It means we increase the % of females the further we get above the pivot point. So incubating at 89.5° for sulcatas, as an example, does not mean we know the babies will be female, but that at that high a temp, the results will be 95% female. At 88.5° it would be more like 80% female.

As we reach higher temps, we risk deformity. (Although there is good evidence now that aberrant scute is more caused by incubation Ph, water potential of media, and chemical balance of whatever the eggs get exposed to.) So there is a balance of how high to incubate if females are desired, and how much we are trying to push the results closer to 100%.

So there is no way, even knowing 100% the pivot point of a species, to know 100% if you have a baby male or female. You can only skew the results to higher and higher percentages of the result you want as you push the temperatures higher from the pivot point. More than a few degrees is flirting with deformity. As @Tom notes, most thermometers breeders use are not that accurate and a degree can make a huge difference.

Another note is that sulcatas, where the exact pivot point was defined, lay the deepest nests of tortoises. Deeper that the giants as they dig a large body pit before turning around and starting the nest chamber with their hind legs. Sea turtles use this technique as well. A nest over 12" deep has much more stable temperatures throughout the day, only varying about 1°-2°F day to night. So perhaps the stable artificial incubation method lends better to temp sexing there. Most all other tortoises dig nests 7" to top of eggs or less. A that depth, nests with sun exposure can swing 8°-10° day to night. There are also tortoises whose eggs require diapause and go through extended dormant times. So I think as we continue to research we will find the pivot point is not so much an exact temperature, but a threshold of degree hours above a certain temperature, that if exceeded by a certain time in the incubation process, will produce female.

So much we just don't know yet!


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## Kapidolo Farms (Mar 13, 2020)

Tom said:


> Not a good bet in any species other than Sulcatas. Sulcatas are the ONLY species that have been studied and temps confirmed in a lab under controlled, detailed, well observed conditions. The temperatures for Sulcatas have been 100% determined. For all other species, we are guessing and we are frequently wrong. No other species has been studied under lab conditions. We should all thank Mr. Richard Fife for this knowledge about Sulcatas. He initiated the study and provided the fertilized eggs.


Pancakes too. https://www.jstor.org/stable/1566229?seq=1

The only thing that refutes science, is better science. 100% for anything - stands until an exception is found, then a new more encompassing explanation is needed.

@Tom please post the peer reviewed scientific reference for your claim.


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## William Lee Kohler (Mar 16, 2020)

Tom said:


> The only species where this has been actually studied and the correct incubation temperatures are known is sulcatas. In other species it is a guess. A guess that is often wrong. Also, temps fluctuate a lot in the real world, and non lab grade thermometers can be off a degree or two.



What about Highfields work?


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## jaizei (Mar 16, 2020)

Kapidolo Farms said:


> Pancakes too. https://www.jstor.org/stable/1566229?seq=1
> 
> The only thing that refutes science, is better science. 100% for anything - stands until an exception is found, then a new more encompassing explanation is needed.
> 
> @Tom please post the peer reviewed scientific reference for your claim.



I believe this may be the reference

Incubation temperature effects on hatchling growth and metabolic rate in the African spurred tortoise, Geochelone sulcata
Day B. Ligon, Joseph R. Bidwell, and Matthew B. Lovern


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## Tom (Mar 16, 2020)

William Lee Kohler said:


> What about Highfields work?


I've never seen any TSD work from Andy. And he's a tool anyway. He's one of the old school types who says every one else is wrong, cause he said so, despite obvious mountains of evidence to the contrary.


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## willee638 (Mar 16, 2020)

Tom said:


> I've never seen any TSD work from Andy. And he's a tool anyway. He's one of the old school types who says every one else is wrong, cause he said so, despite obvious mountains of evidence to the contrary.


Science is changing & improving everyday, old school probably only means outdated.


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