# Naive breeding question



## Paschendale52 (Aug 18, 2021)

I'm not breeding any turtles or tortoises at the moment, but I had a thought that a quick internet search didn't turn up an answer to. If we incubate our eggs in a constant temperature and humidity environment, and reptile sex is dependent upon incubation temperature, how do breeders not turn out entire clutches of single sex turtles/tortoises? It seems that since a large number of breeders do this, even though the animals can't be sexed until they reach a few years or so the breeder should know the sex of every animal based on the conditions in which it was incubated.

What am I missing here?


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## wellington (Aug 18, 2021)

It's not 100% accurate.


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## Tom (Aug 18, 2021)

wellington said:


> It's not 100% accurate.


That is not true, sort of... I'll explain.


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## Tom (Aug 18, 2021)

Paschendale52 said:


> I'm not breeding any turtles or tortoises at the moment, but I had a thought that a quick internet search didn't turn up an answer to. If we incubate our eggs in a constant temperature and humidity environment, and reptile sex is dependent upon incubation temperature, how do breeders not turn out entire clutches of single sex turtles/tortoises? It seems that since a large number of breeders do this, even though the animals can't be sexed until they reach a few years or so the breeder should know the sex of every animal based on the conditions in which it was incubated.
> 
> What am I missing here?


Here is what you are missing:
1. No breeder that I know of uses constant temps with lab grade, verified stability and equipment. Many of us are now intentionally introducing a slight night drop in temps to simulate what we think happens in the wild. Some species don't seem to need this, and others seem to benefit from it. Many species require a diapause (cooling period) of weeks or months, before incubation and embryonic development can begin.
2. No breeder I know of is using lab grade calibrated thermometers to monitor and maintain constant temps.
3. This is the big one: Only ONE tortoise species has been studied under lab grade conditions. Sulcatas. Thanks to Richard Fife for making that happen for all of us. @wellington the temps for sulcatas are known and 100% accurate, IF, and only if, the eggs are kept constant at the correct verified temps throughout incubation. If this happens at the correct temps, sulcata clutches can be 100% males or females, or somewhere in-between at middle ground temps. Many breeders of platynota, for one example that I'm familiar with, "incubate for female" and the vast majority of their babies turn out male. In some cases, 100% males at temps that they thought would produce 100% females. I know of another super smart, super experienced breeder that studied bird embryology who has developed a technique for starting tortoise eggs at a cooler temp for a period of weeks, the period when TSD occurs, and then upping temps to "normal" incubation temps for the duration of incubation. Time will tell how accurate his methods are, but I'm betting he knows what he's doing.
4. In the real world seasons change, room temps change, incubators, heating elements and thermostats fail, cold spells hit, heat waves hit... all sorts fo things happen over the course of a 2-18+month incubation period that can affect the TSD of any egg. 2 months for Russians, and 18+ for SA leopards, in case you were wondering...  I've bred and hatched both extremes.
5. Few breeders are willing to incubate at the extremes. The extremes of the acceptable range are what is needed to get 100% males or females, remembering that these temps are only known and studied for one species. 84 will get you all males and 90 will get you all females with sulcata eggs. at 83.5, you'll get failures to develop and hatch. At 90.5 you'll get split scutes and developmental defects. I've seen the result of both. My $12 Home Depot thermometers are nowhere near lab grade accurate. This is why I run at least two in every incubator. I incubate at around 88 which gives me, in theory, a higher percentage of females, but some margin of error to avoid the developmental defects.


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## wellington (Aug 18, 2021)

So, like I said, not 100% accurate!


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## Tom (Aug 18, 2021)

wellington said:


> So, like I said, not 100% accurate!


It IS 100% accurate with sulcatas in the correct consistent temps. Not accurate with any other species or circumstance, and this frustrates me, because many people seem to think it is accurate. Many breeders sell "incubated for female" at a higher price, and they turn out to be all or male or some of them males.


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## wellington (Aug 18, 2021)

Tom said:


> It IS 100% accurate with sulcatas in the correct consistent temps. Not accurate with any other species or circumstance, and this frustrates me, because many people seem to think it is accurate. Many breeders sell "incubated for female" at a higher price, and they turn out to be all or male or some of them males.


Your points are all proving why I said it's not accurate.
Even the fact that it can be accurate in sulcatas, it isn't, because no one does it in the way to be accurate


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## Tom (Aug 18, 2021)

wellington said:


> Your points are all proving why I said it's not accurate.
> Even the fact that it can be accurate in sulcatas, it isn't, because no one does it in the way to be accurate


Okay. I'll give you that.


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## Paschendale52 (Aug 18, 2021)

Thanks guys! That was fascinating. I've only dealt in lab grade temperature control equipment for the last decade or so (work not hobby) so it didn't occur to me that you couldn't target the temperatures exactly. I'm surprised that the bound between failure and 100% population is so slim. I'd shoot for the middle too.


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## turtlesteve (Aug 18, 2021)

Speaking of which, I am working on a home calibration procedure that should be feasible without going to a NIST traceable lab annually. I believe most people are not measuring a calibrated temperature at the eggs, and this is the biggest problem among the whole list of problems that Tom provided.


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## Paschendale52 (Aug 18, 2021)

I would think a standard thermometer feedback loop on a decently insulated incubator could keep ±1 °C


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## Tom (Aug 18, 2021)

Paschendale52 said:


> I would think a standard thermometer feedback loop on a decently insulated incubator could keep ±1 °C


Once you start incubating more than a single clutch or two, most people make their own incubators. Each female sulcata can lay over 100 eggs in a season. I get around 200 eggs from 3 female SA leopards, and near 100 eggs from my platynota. To manage that kind of volume, you need a large incubator. I use an old stand up freezer. I removed the compressor and all the unnecessary stuff and installed radiant heat panels top and bottom controlled by a digital proportional thermostat. Computer fans top and bottom keep the air moving in the whole thing. Water tubs on the bottom add humidity. Opening the door to check eggs can drop the temperature several degrees temporarily.


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## Paschendale52 (Aug 19, 2021)

That makes a lot of sense. The incubators I've seen are fairly small. Do most of the several hundred hatchlings each season end up with consumer hobbyists? Or is it more with zoos/rehab and release type programs?


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## Tom (Aug 19, 2021)

Paschendale52 said:


> That makes a lot of sense. The incubators I've seen are fairly small. Do most of the several hundred hatchlings each season end up with consumer hobbyists? Or is it more with zoos/rehab and release type programs?


I sell mine to other tortoise keepers and also to tortoise businesses that resell them to their customers.

Zoos don't generally deal with private breeders. The AZA appears to have been gradually taken over by animal rightists and ignorant bureaucrats. The vast majority of breeding success and innovation comes from the private sector, yet the AZA has taken an elitists stance on the matter. Its inconvenient for the people involved, but its the individual species that suffer the most due to these misguided policies.

No one can release CB animals back to the wild. In the rare circumstances where this happens, there are reams of paperwork, vet testing, government approvals, and many obstacles to overcome. The possibility of introducing a non-native pathogen into the wild population is a very serious potential problem, and it is difficult for anyone to declare a bunch of CB babies free from any and all pathogens. I think many of us have dreams of repopulating wild native areas with the species we love if the problems that caused the population reduction/extinction of a given species are ever sorted out, but for now it remains a dream.


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## tortoisenana (Aug 20, 2021)

Is it possible to determine sex by blood test even in New baby torts?


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## turtlesteve (Aug 20, 2021)

tortoisenana said:


> Is it possible to determine sex by blood test even in New baby torts?



Yes it is possible, but I am not aware of any such test available to private breeders.


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## zovick (Aug 20, 2021)

tortoisenana said:


> Is it possible to determine sex by blood test even in New baby torts?


@turtlesteve and @tortoisenana

Unless things have changed, I do not agree that blood tests can accurately determine the sexes of young tortoises. There was a very well-known researcher, a veterinarian who worked in conjunction with San Diego Zoo, who was developing a blood test for sex determination in tortoises back in the mid-1990's. He told me that it was working very well on the tortoises he had tested (primarily hatchling sulcatas and Desert Tortoises) which were blood tested and then euthanized and dissected to confirm the blood test results by examination of the actual gonads. In fact, he said he had been 100% correct in his test studies.

I was working with the Bronx Zoo as a Field Associate in Herpetology at the time, and we were very happy to learn of this possibility as it would eliminate the need to grow many tortoises up for 8-10 years to determine their sexes for several valuable breeding programs we were running.

We sent blood samples from about 25 young Radiated Tortoises to the lab in San Diego to be tested. As a control measure, we included blood samples from 5 adults whose sexes were already known. These samples from the adults were not identified to the lab as being from adults of known sexes.

We were very disappointed when the results were sent to us. Two or three of the adults of known sex were mistakenly identified as being the opposite sex from what they actually were. We therefore dismissed the idea of the blood testing as being unreliable even though the researcher had said that he had achieved 100% success in his trials. We felt that the since the researcher already knew the blood test results, he had either been biased when dissecting the baby tortoises in his study and checking the gonads or that the gonads were still so undeveloped that determining the sex of the baby was not yet possible.

This latter point seems to be borne out by the fact that today, the best chelonian endoscopist in the country will not do sex determination endoscopies until the tortoises are 10 months old and weigh over 110 grams. He determined this to be the best protocol in order to avoid any possible errors after doing a few hundred tortoises for me over a number of years at the UGA Veterinary Teaching Hospital.

If there has been any new blood test for sex determination in baby tortoises developed since then, I am totally unaware of it and would like to learn more about it if you have any information.


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## turtlesteve (Aug 20, 2021)

Bill, I am not sure if these are the same tests I recall, as I forget what species was involved. I do recall a specific statement in the paper that testing was only useable on hatchlings because the hormonal signal being tested was temporary (having to do with the TSD process?)

I will see if I can find the article again…


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## Jan A (Aug 20, 2021)

zovick said:


> @turtlesteve and @tortoisenana
> 
> Unless things have changed, I do not agree that blood tests can accurately determine the sexes of young tortoises. There was a very well-known researcher, a veterinarian who worked in conjunction with San Diego Zoo, who was developing a blood test for sex determination in tortoises back in the mid-1990's. He told me that it was working very well on the tortoises he had tested (primarily hatchling sulcatas and Desert Tortoises) which were blood tested and then euthanized and dissected to confirm the blood test results by examination of the actual gonads. In fact, he said he had been 100% correct in his test studies.
> 
> ...


If you have to kill the tort to determine its sex & then even examination of the gonads & testing isn't reliable, seems to me that looking at plastrons, tails & the like isn't as bad as I thought it was...if I'm a tort.
Imagine if we had to do that to humand


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## zovick (Aug 21, 2021)

[


Jan A said:


> If you have to kill the tort to determine its sex & then even examination of the gonads & testing isn't reliable, seems to me that looking at plastrons, tails & the like isn't as bad as I thought it was...if I'm a tort.
> Imagine if we had to do that to humand


Euthanizing animals to advance and increase knowledge, etc., is an accepted practice in scientific research, unfortunately.

I am somewhat out of touch with the scientific community these days, but do believe less of it is being done today than in the past, but I am sure it is still probably kept pretty quiet due to its unpopularity, so it's hard to say with any certainty.


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## Jan A (Aug 21, 2021)

zovick said:


> [
> 
> Euthanizing animals to advance and increase knowledge, etc., is an accepted practice in scientific research, unfortunately.
> 
> I am somewhat out of touch with the scientific community these days, but do believe less of it is being done today than in the past, but I am sure it is still probably kept pretty quiet due to its unpopularity, so it's hard to say with any certainty.


Your answer gives me calmness given what we're doing to humans today. Thanks Zovick, you are wise beyond your years.


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## Tom (Aug 21, 2021)

tortoisenana said:


> Is it possible to determine sex by blood test even in New baby torts?


In theory, yes. In current practice, no. I had not heard of the study that @Zovic cited, but I have heard vague rumblings of more current research happening now. We've been able to DNA sex birds for many years at this point. I think its only a matter of time until someone figures out how to do it for torts. I hope so anyway.


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## TeamZissou (Aug 21, 2021)

turtlesteve said:


> Bill, I am not sure if these are the same tests I recall, as I forget what species was involved. I do recall a specific statement in the paper that testing was only useable on hatchlings because the hormonal signal being tested was temporary (having to do with the TSD process?)
> 
> I will see if I can find the article again…



Steve, was this it?









Identifying Sex of Neonate Turtles with Temperature-dependent Sex Determination via Small Blood Samples


Temperature-dependent sex determination, present in most turtle species, is a mechanism that uses temperature to direct the sex of the embryo. The rapid increase of global temperatures highlights the need for a clear assessment of how sex ratios of organisms ...




www.ncbi.nlm.nih.gov





83-177 days for the hormone to be present seems like a big enough window if the tests could be coordinated after hatching. The the length of time that this hormone is present at measurable levels is probably species dependent. Somebody need to connected with Boris Tezak and see if he can test some tortoises.


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## turtlesteve (Aug 21, 2021)

TeamZissou said:


> Steve, was this it?
> 
> 
> 
> ...



Yes that’s the one! Thanks!


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