# Higher incubation temps produce more males?



## Katmb85 (Aug 8, 2011)

I am not a breeder, just a sulcata PET owner but I am curious about something I have heard...

Is it true that if you incubate eggs at a higher temperature that you will end up with more males and that breeders will do this to limit the number of females produced so other people cannot breed?

Is this a myth?


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## GBtortoises (Aug 8, 2011)

Just the opposite-higher temperatures produce more females. _Lower_ incubation temperatures produce more males.

Having been a tortoise and turtle breeder for over 25 years now I can say that I have never, and do not know of any of my breeder aquaintences, that incubate to produce more males with the intention of limiting the number of females produced, _for any reason_.


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## jeffbens0n (Aug 8, 2011)

Actually it is the opposite. Higher temps generally produce more females, but also can result in shell deformities such as split scutes.


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## ALDABRAMAN (Aug 8, 2011)

I know of several that do incubate for males inorder to limit the future females. Not a myth, business tactic.


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## Tom (Aug 8, 2011)

The biggest sulcata breeder on the face of the Earth told me personally that he does this. He said, "It takes a little longer for them to hatch, but I don't have to worry about being put out of business as quickly." Nobody knows this man's secrets. He's very tight-lipped about things, even with his friends. But he's supposedly got several hundred females on around 15 acres. My figures might be a little off there, but its close.

Richard Fife funded an actual study on this and now they even have the exact temps for sulcatas. 84-86 for males and 88-89 for females. Between 86-88, you'll likely get a mixture of both sexes. Above 90 and the risk of incubation anomalies skyrockets. The temps are likely to be slightly different for different species, but still close.


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## Katmb85 (Aug 8, 2011)

Thanks everyone! I was just curious, thanks for clarifying.


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## dmmj (Aug 8, 2011)

It makes sense keeping the number of females down mean more males to sell and less competition.


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## drgnfly2265 (Aug 10, 2011)

The breeder that I got Bowser from said that I should be getting a male, lol. Surprise, I got a female!


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## dmmj (Aug 10, 2011)

well the temp thing is only a higher percentage of a certain sex, but it is no guarantee by far


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## Yvonne G (Aug 10, 2011)

It also depends upon how good your thermometer is in your incubator. I've been hatching tortoise eggs for many years now and so far all of them that I've been able to keep track of have turned out male. Every year I turn it up another notch. This year my thermometer says 90 degrees. If I don't cook the eggs, I hope to get females!!


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## EricIvins (Aug 10, 2011)

Herein lies the problem that lies with TSD incubation - It isn't as accurate as everyone thinks it really is...........

I have Proportional Thermostats on all my Incubators, and even with the best electronics, I still get a +/- 2 or 3 degree temperature swing because of the way the heat elements work..........I haven't had the best results buying TSD animals, so that, along with what I see in my Incubators, I prefer to sell all my hatchlings as un-sexed........


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## GBtortoises (Aug 11, 2011)

I incubate all of my eggs of every species to produce predominately female offspring 88-90 degrees. Based on feedback over the years and tortoises that I have kept to raise myself, I appear to be producing a ratio of 4:1 female to male. That ratio is not completely accurate because not everyone that has ever purchased one of my offspring has contacted me to let me know what they have. I'm only basing it on the information that I do have. My ratio applies to Eastern Hermann's, Marginateds and Ibera Greeks. 

I _never_ make promises about my hatchlings gender. Because as Eric states above it simply isn't accurate.
I've heard of plenty of stories where people were absolutely assured that they are purchasing a female hatchling of a species because of the temperature that it was incubated at. That's an impossible and in my opinion, a mis-leading statement. 

I also think it's pretty sad that some breeders purposely incubate to produce more males simply because of greed. 

I strongly believe that there is a responsibility for those that breed tortoises to produce captive born tortoises in a manner so that we will some day not be taking them from the wild to fuel our wants. By purposely producing a majority of males of any species you reduce the number of possible animals that can produce eggs (females) thus reducing the number of captive born animals of a species overall. I think that is bad resource management and shows that someone doing so has no concern for the species, just the dollar.


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## Tom (Aug 11, 2011)

GBtortoises said:


> I strongly believe that there is a responsibility for those that breed tortoises to produce captive born tortoises in a manner so that we will some day not be taking them from the wild to fuel our wants. By purposely producing a majority of males of any species you reduce the number of possible animals that can produce eggs (females) thus reducing the number of captive born animals of a species overall. I think that is bad resource management and shows that someone doing so has no concern for the species, just the dollar.



I completely agree 99% of the time. BUT, I'm pretty sure we have enough sulcata egg factories around, that we will never have to remove a sulcata from the wild ever again. In fact we could probably put a few back if we wanted too... I would love to see it get that way with every other species. I think your strategy of trying to produce a majority of females is a great one. 

Your a good man GB. I love the stuff you do and the stuff you write!


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## GBtortoises (Aug 11, 2011)

Tom-I do agree that in some cases, Sulcata being one of them, that there is no reason to remove the from the wild anymore. Which is a good thing one hand. On the other, absolutely too many being produced in captivity. But also in that case, simply producing males is not the solution either. Neither is producing females. The realistic solution to not having Sulcata end as pet store staples, unwanted and very likely dying in the large numbers in the hands of the uneducated is to stop breeding them in captivity. Or at least responsibly controlling the number produced each year in order to keep a balance between young and old. Of course I know that isn't going to happen as long as a breeder can get _something_ for them. 

I'd also love to see captive born tortoises re-introduced to the wild. Probably never happen, too many concerns of introducing disease picked up in captivity back to the wild that the populations are not immune to. In my mind, that would be the responsible thing to do if it can be done "cleanly" with little to no harm to the wild populations.


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## zesty_17 (Aug 12, 2011)

Katmb85 said:


> I am not a breeder, just a sulcata PET owner but I am curious about something I have heard...
> 
> Is it true that if you incubate eggs at a higher temperature that you will end up with more males and that breeders will do this to limit the number of females produced so other people cannot breed?
> 
> Is this a myth?



Higher temps = males for crocodilians, its the opposite for chelonians. 


To be technical, males are produced at both extremes for crocs, with females in the middle. I have not found literature to support this in chelonian females...would be an interesting study though. 



Tom said:


> The biggest sulcata breeder on the face of the Earth told me personally that he does this. He said, "It takes a little longer for them to hatch, but I don't have to worry about being put out of business as quickly." Nobody knows this man's secrets. He's very tight-lipped about things, even with his friends. But he's supposedly got several hundred females on around 15 acres. My figures might be a little off there, but its close.
> 
> Richard Fife funded an actual study on this and now they even have the exact temps for sulcatas. 84-86 for males and 88-89 for females. Between 86-88, you'll likely get a mixture of both sexes. Above 90 and the risk of incubation anomalies skyrockets. The temps are likely to be slightly different for different species, but still close.



interesting, box turtle ranges are a little lower. I have heard ~ 75-80 males, and ~ 83-86 females...


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