Incubated for...

Kapidolo Farms

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[PDF] mdsoar.org
Effects of incubation conditions on sex determination, hatching success, and growth of hatchling desert tortoises, Gopherus agassizii
JR Spotila, LC Zimmerman, CA Binckley… - Herpetological …, 1994 - JSTOR
… There was little mortality at intermediate temperatures … E is egg mass. eggs. None of the eggs
incubated under cool (26.0 C), wet (4.0% soil moisture) con- ditions in 1991 hatched … Ap- parently
35.3 C is too high a temperature for normal development of desert tortoise eggs

I am constantly amused by posts of chelonians for sale with the sentence "incubated for females, but no guarantee".

It's a sliding scale, not an absolute switch.

To be less abusive with copy-write I am only including the page with a tell-all figure.

Another reason to hold back and grow-out some of your hatchlings.
 

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Tim Carlisle

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Curious (and I have not read the pdf yet)... is it really possible to sex-out the tortoises based on varying incubation methods?
 

wccmog10

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Funny you should post this- One of the authors of this paper was my faculty advisor. He published several papers about incubation temperatures... I’m supposed to be finding some of them for the other thread about nest temperatures.

Curious (and I have not read the pdf yet)... is it really possible to sex-out the tortoises based on varying incubation methods?

Lots of reptiles- but not all- have what is called TSD (temperature dependent sex determination). Deferent groups work in different ways- lizards have males at higher temps, turtles have females at higher temps (that is the simplified version of explaining it). It’s usually the 2nd quarter or middle third of incubation when the sex is determined. And like @Will mentioned- there is not a cutoff where everything above a certain temperature is one sex and below is another sex. It is a continuum. The “pivotal” temperature is where the sex ratio is 50:50. And of course- different populations can have different pivotal temperatures, and even different individuals within a population can have different pivotal temperatures. Which is why it is important to randomly assign eggs to each of your study groups.

When you are buying a “temp sexed animal” what you are doing is hedging your bets. There is an increased chance of having a female tortoise if it was incubated at a higher temperature. But it is by no means a garuntee- unless the breeder has held back numerous babies and either surgically sexed them laparoscopically or raised them to maturity to know how the eggs of that female turn out at certain temperatures.
 

Tim Carlisle

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Funny you should post this- One of the authors of this paper was my faculty advisor. He published several papers about incubation temperatures... I’m supposed to be finding some of them for the other thread about nest temperatures.



Lots of reptiles- but not all- have what is called TSD (temperature dependent sex determination). Deferent groups work in different ways- lizards have males at higher temps, turtles have females at higher temps (that is the simplified version of explaining it). It’s usually the 2nd quarter or middle third of incubation when the sex is determined. And like @Will mentioned- there is not a cutoff where everything above a certain temperature is one sex and below is another sex. It is a continuum. The “pivotal” temperature is where the sex ratio is 50:50. And of course- different populations can have different pivotal temperatures, and even different individuals within a population can have different pivotal temperatures. Which is why it is important to randomly assign eggs to each of your study groups.

When you are buying a “temp sexed animal” what you are doing is hedging your bets. There is an increased chance of having a female tortoise if it was incubated at a higher temperature. But it is by no means a garuntee- unless the breeder has held back numerous babies and either surgically sexed them laparoscopically or raised them to maturity to know how the eggs of that female turn out at certain temperatures.
Interesting. Appreciate the explaination!
 

Kapidolo Farms

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LIKE!

Funny you should post this- One of the authors of this paper was my faculty advisor. He published several papers about incubation temperatures... I’m supposed to be finding some of them for the other thread about nest temperatures.



Lots of reptiles- but not all- have what is called TSD (temperature dependent sex determination). Deferent groups work in different ways- lizards have males at higher temps, turtles have females at higher temps (that is the simplified version of explaining it). It’s usually the 2nd quarter or middle third of incubation when the sex is determined. And like @Will mentioned- there is not a cutoff where everything above a certain temperature is one sex and below is another sex. It is a continuum. The “pivotal” temperature is where the sex ratio is 50:50. And of course- different populations can have different pivotal temperatures, and even different individuals within a population can have different pivotal temperatures. Which is why it is important to randomly assign eggs to each of your study groups.

When you are buying a “temp sexed animal” what you are doing is hedging your bets. There is an increased chance of having a female tortoise if it was incubated at a higher temperature. But it is by no means a garuntee- unless the breeder has held back numerous babies and either surgically sexed them laparoscopically or raised them to maturity to know how the eggs of that female turn out at certain temperatures.
 

surfergirl

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I have proof of it not being dependable. Lots of breeders try to slide the scale towards female but many times it is still nature's course to change the outcome. I did not care really as I do not breed tortoises. There are good reasons to try to get more females if breeding stock and group enclosures is what is more attractive to keepers.
Hopefully one day we can figure it out so that we do not end up with a bunch of homeless males and can breed for the most ideal sex ratio outcome. Only producing males when they are in demand.
 

Tom

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Thank you for this thread Will.

I've not been amused by this practice though. Its either disingenuous or willfully ignorant when sellers engage in this practice, neither of which are amusing to me.
 

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