Incubation temp vs. hatching size

[DragnDrop]

Normally I incubate crested gecko eggs at room temperature, even in the basement, never letting the temperature get above 72 F (22 C). Years ago when I first bred cresties I did the incubator thing and it worked okay. Then I was told that they hatch bigger and hardier if incubated longer at a lower temperature and as an added bonus there seem to be more females hatching in that temperature range. So, I switched, been doing it that way ever since.
This past winter I decided to do one experiment with temperatures and cresty eggs and post the results. Since it wasn't endangering the geckos nor eggs, it was worth doing. Here's the result:





I'm not trying to pass this off as scientific proof of any kind, but you can get the idea of how different they hatch. The top gecko is one of the ones that hatched last week, pictures in the "What's better than finding a crested gecko hatchling?" thread.
I put this one on the same bottle cap as the new (lower gecko) for scale in the picture. The lower one hatched overnight, found him this morning.
They have different parents but they share some genes. Still the difference in genetics could have some influence on hatching size, but not "THAT" much. Also, the older one has eaten 2 meals of fruit, no bugs that I can tell, but it's not enough food to make him grow incredibly fast to make that much difference in just a few days. Even allowing for almost a week difference in age, you have to admit that there is a difference in hatching size. There is rarely, if ever, any yolk left in the cool incubated eggs, and when there is some, it's barely worth mentioning. Yet the warmer incubated eggs had a big blob of yolk left inside, suggesting that the cooler babies had more time to absorb all the goodies and use them to grow a bit more.

(The lower gecko in this picture is the clutchmate to the top pictured one in the other thread. They hatched Apr 29 and May 4.)

[Asian Jon]

Great post! What a difference.

[babysweet]

Absolutely fantastic work Hilde.

It's information like THIS that needs to be discovered!

Keep up the great work!

Kim

[Betty Miskie]

Excellent post!!! Kinda makes you want to do how mother nature intended and let them incubate without incubators. I for one, do not artificially incubate and right now my eggs are hatching around the 90 day+ mark. Makes the wait so long, but oh so worth it as I find our hatchlings are bigger and healthier as well. Hilde, you just proved it in my eyes.
Betty

[alan]

Wow, thanks for the post. I used to incubate my eggs at 72C hoping for more females but have raised it back up to 78C few days ago because of the long wait for the geckos to hatch. I guess I'll lower the tempretures again. Thanks!

[Buddha]

how long do eggs usuallt take tell they hatch?

[DragnDrop]

The generally accepted incubation time is around 60 days, which makes the 64 days for the 'incubated warm' gecko about average. Any ciliatus eggs I incubate cool (as in the top pictured gecko) take 90+ days, this one being 106 days. It's a heck of a long wait, but it's worth it. The 'cool' babies are way bigger as you can see in this example so they're easier to feed for one thing. They already have the equivalent of a few weeks' growth on the 'warm' babies.

[clint545]

Hilde , how have you found your Male/female ratio from the room temp method?
I've also read that Cresteds incubated at a high temp take longer to reach, or show their sex.
I had bought 2 Cresteds from 2 different sources, and found while they both eat about the same, and are the same age that the one matured alot quicker.
They were both male and the smaller one was about 2 months later than the first one as far as confirming their sex.

[timfriesen32]

I realize this is the wrong place to put this question....but you may have the answer as well....

Do you think this would work with snakes as well?

TIm

[DragnDrop]

Hilde , how have you found your Male/female ratio from the room temp method?

My experience with TDSD is about what is mentioned in the Rhac book by de Vosjoli/Fast/Repashy. Using the cooler temperature range, I get about 2-3:1 female:male ratio. It varies from year to year, but it's always close to that ratio though I've had as high as 80% female. Since I keep them cool in the basement not a thermostatically controlled incubator, the eggs get whatever temperature it gets to in the room. During a heatwave it might get to 73F/23C +/- 1 degree or so, but that's the highest I've seen it and that was during a record breaking summer heatwave a few years ago. I did notice the eggs that were developing during that time hatched a week or two earlier than expected, another bit of unscientific proof that heat shortens hatching time.

The first few years I kept back random hatchlings until sexable, and also asked for feedback from the buyers (most of whom were people I knew, so it was easy to get the info). After a few years of getting 60-80% females, I stopped keeping accurate records.

Last year there were a few early hatches, and I noticed that the eggs were getting some direct sunlight on them for a few hours a day through the window - I'd put them on a shelf I'd never used for eggs before. It would seem those eggs were warmed a bit during the day. I kept back two of those hatchlings from different clutches and both are males. I don't know if that's coincidence or not, I just wanted to see what the odds are of one or both being males after the little bit of heating they experienced.

I've also read that Cresteds incubated at a high temp take longer to reach, or show their sex.

I've noticed that as well, and read it in several books and articles about Rhacs in general.

Do you think this would work with snakes as well?

TIm

I wouldn't risk it with any other species. Rhacs can take temperatures in the 60F range, so the eggs can develop at 'cool' temperatures like I keep them at. I've never bred snakes, but from what I know about them, the ones commonly kept need higher temperatures so chances are their eggs won't make it if kept too cool. But then, what do I know about snake breeding?