Incubation Questions

[JoeImhof]

I would love to hear a clarification of this......

If you just take the eggs that start chalking (and therefore I assume are fertile for sure), should the hatch rate of those eggs, only those eggs, be near 100%? Or is there still a lower expected hatch rate of those?

thanks

 

[Tom]

I don't know what I'm doing wrong, but I don't see chalking or much of anything on my eggs. When they get near term they get opaque when candled. Meaning they look like they are full of dirt or something and they are no longer translucent. Sometimes I get the orange glow vs. the yellow or clear, but even that is not 100% for me.

I just pull them out of the ground and put them all in the incubator and wait three months to see what I get...

 

[Yvonne G]

I just wish I knew what temperature made females in the Manouria group. The only official paper I read said they should be cooler than most other tortoises. The first batch that hatched for me 15 or so years ago was incubated at 86F degrees. I still have 4 of those tortoises and they're male. Does that mean that if I up the temp to 88F degrees I'll get female? But that's not the "cool" that the experts tell you about. I have a 3 year old and a hatchling from about 88F but they're still too young to sex. And I'm wondering if I would have a better hatch rate if I cooled the incubator down to the 82/83F degrees ash shown in the paper I read. But at that temp would I for sure get males? I wish more were known about the Manouria. Its coming up on monsoon/nesting season for them and I'd like to do it right this time.

 

[Tom]

I just wish I knew what temperature made females in the Manouria group. The only official paper I read said they should be cooler than most other tortoises. The first batch that hatched for me 15 or so years ago was incubated at 86F degrees. I still have 4 of those tortoises and they're male. Does that mean that if I up the temp to 88F degrees I'll get female? But that's not the "cool" that the experts tell you about. I have a 3 year old and a hatchling from about 88F but they're still too young to sex. And I'm wondering if I would have a better hatch rate if I cooled the incubator down to the 82/83F degrees ash shown in the paper I read. But at that temp would I for sure get males? I wish more were known about the Manouria. Its coming up on monsoon/nesting season for them and I'd like to do it right this time.

I've got a friend who breeds the blacks. I'm going to give him a call for you.

Left him a message. I'll let you know when I hear from him.

 

[bfmorris]

I incubate at the same temps, so I think you are good there.

Just curious if you see split scutes at the 88-89 f temps you indicated you're incubating?

One thing to consider is the time of year that the eggs are produced, fertilized and laid. I have lower fertility on clutches that are produced during hot weather. I have higher fertility on clutches that are produced during colder weather, during the winter months. My fertility rate varies a lot throughout the year. As low as 20-30 % for summer eggs, as high as 80-90% for winter eggs. I have only had two clutches with 100% fertility and both of those were laid toward the end of winter. I have heard similar stories form other keepers. My male sulcata breeds (or attempts to breed) nearly every day, btw.

Have you formulated any theory on the cold/hot weather fertility variations?
Would this report be on sulcata eggs? Are you saying your sulcata produce eggs in summer?

I do not see any split scutes at those temps. Fife told me that typically you will not see split scutes until you start getting above 90. Remember that he funded and supplied eggs for a professional level lab study on this...

In the hottest parts of summer with consecutive days of 110+ and nights that don't cool much, my reptile room can creep into the low 90's. Not a problem for the torts or inverts. I just shut off the lights and heating stuff. In the past I would move any eggs out of the reptile room and into my garage, where it never gets above the low 80s, for summertime incubation. This last summer I left them in the reptile room, but moved them to the concrete floor. Out of roughly 6 summer incubated clutches, one clutch had one split scute, and another clutch had three. So I saw a total of four split scutes this summer. These were my first ever. I won't be incubating in the reptile room any more over summer. Interestingly, "The Crying Tortoise" book says that 8-15% split scutes is normal for wild clutches... My Gpp breeder friend who incubates in the ground also sees around 10% split scutes on his in ground incubated leopards.

And yes sir, I am only reporting about my sulcatas, and yes sir, mine breed and produce eggs in summer now too. They pretty much lay all year long now. I get a clutch per female about every 6-8 weeks. Occasionally one will stretch it to 12 weeks in between.

Very interesting, your summer eggs. In contrast, I have never and I mean never had a female lay eggs in the summer. Mine are very seasonal and always completely finished by the end of May.

Weirdly, I've seen a few split scutes at 84-85 f incubation, and I've seen split scutes in ground incubated specimens. Here, I know in-grounds incubate at much higher temps than artificial incubation because I have conducted temperature readings on ground temps at various depths down to eight feet, year around. Interestingly, at egg nest depths of about 24"- 30", the ground temperature here at ground hatching time (late August) is in the low to mid nineties f. All my temp readings taken with a certified thermistor.

After all this, I still tend to agree that higher temps are the cause of split scutes.

I breed rare Staurotypid turtles and I definitively know that higher incubation temps cause split scutes in them. However in sulcata I think there is more to learn yet regarding cause of the split scutes., and from the ground temps that I've been aware of for many years, there is still lots to learn there also.

 

[Tom]

The summer egg thing is a new phenom for me. In prior years they only laid in winter. I think it is in part due to my warmer night house and the addition of Mazuri to their diet.

I would be very interested in hearing more about your in ground temps. My three foot deep underground boxes hover between 79 and 81 all summer long.

The steady, one temp, artificial incubation thing has always been perplexing to me. There must be quite a lot of variation even just from day to nit in an in ground nest... Love to hear more about your observations.

 

[Yvonne G]

Stuart:

I hope you're not upset that we've more or less taken over your thread. If you'd like us to get back to your topic, just say the word.

 

[ALDABRAMAN]

I would love to hear a clarification of this......

If you just take the eggs that start chalking (and therefore I assume are fertile for sure), should the hatch rate of those eggs, only those eggs, be near 100%? Or is there still a lower expected hatch rate of those?

thanks

From my experience, I can visually see the "chalking" of our fertile eggs at about six weeks. This has been a solid indicator that they were fertile. The "orange glow " as Tom was indicating, I have seen this also and seems to be a solid indicator of fertility. I candle our eggs throughout the development process and can see the outline of the tortoise within the egg. I have not been able to photograph these events successfully, just can't seem to get the right light, etc. to work right.

Here is a good example of 100% fertile clutch of eggs, all have the chalking color, showed redish/orange color within, and i visually seen the mass inside. All twelve hatched out.

 

[bfmorris]

The summer egg thing is a new phenom for me. In prior years they only laid in winter. I think it is in part due to my warmer night house and the addition of Mazuri to their diet.

I would be very interested in hearing more about your in ground temps. My three foot deep underground boxes hover between 79 and 81 all summer long.

The steady, one temp, artificial incubation thing has always been perplexing to me. There must be quite a lot of variation even just from day to nit in an in ground nest... Love to hear more about your observations.

Typically, I see summer clutches in those places animals are kept where it is too cold in winter for the animals to do anything at all outdoors which usually prevents summers from being to harsh, heat-wise. I mean frozen places like Oklahoma, where they spend the winter in indoor pens under spotlights, and lay eggs in mid-late summer after an outdoor period of mating and sunshine.

The nest level ground temps here don't vary that much from day time to night time during summer; they do gradually build until by late June it is quite warm then it stays warm, well into the fall although cooler, still in the mid eighties under there, in fall. Temps may drop a degree or three overnight in July-August, depending on if a summer rain occurs. The impossible to duplicate kind of heat from mass like that appears to do wonders for the animals.

 

[bfmorris]

The steady, one temp, artificial incubation thing has always been perplexing to me. There must be quite a lot of variation even just from day to nit in an in ground nest... Love to hear more about your observations.

I meant to reply to this and then promptly overlooked it.

Yes, the earliest ground clutches do experience varying degrees of see-sawing temps, then less so to none as the season progresses and summer approaches. I'd temper this with the fact that unheated burrowed tortoises lay their eggs later in the year than artificially heated tortoises do, because they must wait for enough gain solely from the sun. So, the unheated animals bypass the egg-killing cold unless unusual weather strikes.

Anyway, what happens is, with ground clutches all ( I believe in captivity the very earliest eggs produced by artificially heated animals are killed, if left in the ground in AZ and So Cal) the eggs wait under there and all begin to develop at the same time once a threshold is reached. Then they all hatch & surface within just a few weeks of each other. So eggs put directly into the incubator I consider as eggs laid at that threshold. I do think day-night heat changes help eggs to breathe, though perhaps of less importance in an above ground incubation container.

 

[SulcataPardalis]

Stuart:

I hope you're not upset that we've more or less taken over your thread. If you'd like us to get back to your topic, just say the word.

No, not at all. It's turned into a very informative thread.