# "Reliability" of temperature sex determination



## Redari (Apr 29, 2013)

Hello!

I have been thinking about this for awhile, and am curious about people's experiences.

Do most breeders practice temperature sex determination with their eggs, and if so, how reliable is it? How often do they end up being the 'wrong' sex?

Appreciate your thoughts 

Thanks!


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## wellington (Apr 29, 2013)

I have no experience with eggs. Just what I have read is 50%. People that have actually done it might have better odds.


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## tortadise (Apr 29, 2013)

Depends on species. Elegans and platynota have proven TSD results. Most o will say probably incubate right at the thresholds temperature so could go either way. Also depends on night drops. That can lower your average temp and alter TSD goals.


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## GBtortoises (Apr 29, 2013)

TSD does work to some extent with temperate species of tortoises and turtles. But there is no concrete assurance that by incubating the eggs to produce female or male will guarantee 100% of either. However, by specifically incubating for either it should produce a predominate number of that gender. In most cases in captivity accurate data is difficult to obtain. This is due to the fact that breeders don't keep hatchlings long enough to reach an age that their gender can be positively determined. So buyer feedback has to often be relied upon and is never 100% complete or even accurate. For most species not enough accurate data has been collected from the wild either. 
As far as guarantees of receiving a specific gender when purchasing an inmature tortoise (or turtle), there are none. A few vendors and breeders like to advertise a young tortoise as being either male or female, because the eggs were incubated at temperatures to produce that gender. But in reality, they have no way of positively backing up that claim. It's a 50/50 gamble.


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## N2TORTS (Apr 29, 2013)

GB....*Perfectly Said!*


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## james1974 (May 5, 2013)

It give's you a higher chance of one sex or the other,but nothing is 100%..


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## Yvonne G (May 5, 2013)

I had my incubator set for female leopard tortoises, and the only one I kept turned out to be male.

I had my incubator set for female Manouria emys phayrei, and the six that I kept turned out to be male.

I now have five Russian eggs in the cooker. I have the temp set at 83F degrees. I'm not planning on keeping any of the babies, but I'll try to keep in touch with who they go to and see what sex they end up.


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## Tom (May 5, 2013)

I was not aware that temps were known and tested for elegans or platynota. Thanks for that info Kelly.

The only species I was aware of that had known and lab tested and verified TSD are sulcatas. Richard Fife funded and provided sulcata eggs for a study done on this. If you have lab grade incubators, thermometers and equipment, AND nothing goes wrong or changes during incubation, you CAN guarantee the sex of sulcatas. The problem is that in the real world very few people have a stable environment or lab grade, calibrated, consistent equipment. For sulcatas, 84 will produce all males and 90 will produce all females. I incubate mine at 88-89. In theory, IF my thermometers are correct and IF my incubator and room temp are consistent, I should get a high percentage of females. Those are some big IFs.

I don't know what the real world percentages are. Never seen statistics on this, but I think Barb's 50/50 guess is probably more accurate than some of us would like to think.


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## tortadise (May 5, 2013)

Yeah I need to find the article I was reading on it. I was surprised as well. But I suppose their are many other labs elsewhere.

Here is a good article on the topic itself of TSD.
http://faculty.sxu.edu/~cochran/senior_seminar/sex-determination-reptiles.pdf


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## jaizei (May 5, 2013)

Tom, is this the study you referenced? I came across it the other day, and noticed it mentioned Fife and that his company provided the eggs.

Incubation temperature effects on hatchling growth and metabolic rate in the African spurred tortoise, Geochelone sulcata


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## Tom (May 5, 2013)

I don't think so, but I honestly don't know. I've never seen the actual study. My info above is based on personal conversation with Mr. Fife at the TTPG conference in 2010 and 2011.


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