Incubation temperatures and gender

Ted · 14-01-2008, 05:45 PM

to those of you who have successfully bred tortoises:

do you deliberately attempt to get more female than male hatchlings by incubating your eggs at a relatively high temperature? i'm just curious as i guess that it must be a real problem to stop males from fighting, especially if you keep lots of them. also, if you sell the hatchlings, is it sometimes more difficult to sell males?

sandy · 14-01-2008, 06:02 PM

I aim for females, but if the temps go too high, deformaties happen. So I incubate at 32-32.5.
Sometimes the temps fluctuate, so I get a mixed batch. Well I think they are mixed, if I sell
them I dont know for definite<g>.
Certainly better to have more females to males.

Ajay · 14-01-2008, 06:23 PM

<26C Eggs usually die
26-29.5C All male offspring at 74-140 days
30-31.5C Mixed offspring
32-34C All female offspring at 60-75 days
>34C Deformed hatchlings

**egyptiandan64** · 14-01-2008, 08:42 PM

Actually Ajay it's a precise 31.5C where you get a 50/50 mix in Hermanns and Greeks. Above that and you get more females, below that you get more males.

Danny

gtm · 14-01-2008, 08:44 PM

Hi sandy & dan,

What kind of deformities do you get if you over cook your eggs so to speak. I've heard mention of extra scutes but what else can happen?

**egyptiandan64** · 14-01-2008, 09:01 PM

You can get extra scutes at any temperature George. Usually with the higher temperatures you get head deformities, one or no eyes, smaller heads, jaw deformities or just dead in shell with large yolk sacks. There are lots more that can happen and all these can happen at the lower temperatures to, but thats likely to be due to genetics and not temperature. There are always 2 factors when hatching eggs, temperature and genetics. One you can control and the other you can't.

Danny

Ajay · 14-01-2008, 09:12 PM

Quote:

Originally Posted by egyptiandan64

Actually Ajay it's a precise 31.5C where you get a 50/50 mix in Hermanns and Greeks. Above that and you get more females, below that you get more males.

Danny

Thanks Danny, will make a note

but they're not my numbers lol they're from Highfield (1996) (Got myself a shiny new book - Medicine and surgery of tortoises and turtles, great, if a little scary, read)

**egyptiandan64** · 14-01-2008, 09:15 PM

I've had the same book for a year and still haven't read it all Ajay.

It is a great book though.

Danny

Ajay · 14-01-2008, 09:22 PM

It's expensive (and a bit gorey) but worth it (wanted it now for dissertation but future for torts)

I was flicking through parts I thought would be useful for my work and left it open there while I read new posts.. spooky lol

EJ · 14-01-2008, 10:36 PM

I'm sorry... I can't let this pass... Huh????

31.49c you get more males and 31.60c you get more females????? I'll give you the benefit of the doubt... 31c you get more males and 32c you get more females????

How big a sample size was used to determine this...????? How many different species/subspecies was this data tested on...?????

Ajay stated it best. There is a range although it is a relativly restricted range.

Quote:

Originally Posted by egyptiandan64

Actually Ajay it's a precise 31.5C where you get a 50/50 mix in Hermanns and Greeks. Above that and you get more females, below that you get more males.

Danny

14-01-2008, 05:45 PM	#1
Ted Member Incubating Join Date: Sep 2007 Location: Nottingham Posts: 238	Incubation temperatures and gender to those of you who have successfully bred tortoises: do you deliberately attempt to get more female than male hatchlings by incubating your eggs at a relatively high temperature? i'm just curious as i guess that it must be a real problem to stop males from fighting, especially if you keep lots of them. also, if you sell the hatchlings, is it sometimes more difficult to sell males?

14-01-2008, 06:02 PM	#2
sandy Senior Member Adult Join Date: Jun 2006 Location: Kent UK Posts: 12,146	I aim for females, but if the temps go too high, deformaties happen. So I incubate at 32-32.5. Sometimes the temps fluctuate, so I get a mixed batch. Well I think they are mixed, if I sell them I dont know for definite<g>. Certainly better to have more females to males. __________________ < > 60+, keeping ibera, graeca and box turtles \0/ /_\ http://groups.yahoo.com/groups/tortoisefriends

14-01-2008, 06:23 PM	#3
Ajay Senior Member Sub Adult Join Date: May 2007 Location: Durham Posts: 1,000	<26C Eggs usually die 26-29.5C All male offspring at 74-140 days 30-31.5C Mixed offspring 32-34C All female offspring at 60-75 days >34C Deformed hatchlings __________________ Ajay xxx 0.0.2 Testudo hermanni boettgeri 0.0.2 Geochelone carbonaria 0.0.1 Testudo horsfieldii 1.0.0 Eublepharis macularius 1.0.0 Canis familiaris I am no longer a student; AT LAST!!

14-01-2008, 08:42 PM	#4
egyptiandan64 Super Moderator Adult Join Date: Jun 2006 Location: USA Posts: 14,171	Actually Ajay it's a precise 31.5C where you get a 50/50 mix in Hermanns and Greeks. Above that and you get more females, below that you get more males. Danny __________________

14-01-2008, 09:01 PM	#6
egyptiandan64 Super Moderator Adult Join Date: Jun 2006 Location: USA Posts: 14,171	You can get extra scutes at any temperature George. Usually with the higher temperatures you get head deformities, one or no eyes, smaller heads, jaw deformities or just dead in shell with large yolk sacks. There are lots more that can happen and all these can happen at the lower temperatures to, but thats likely to be due to genetics and not temperature. There are always 2 factors when hatching eggs, temperature and genetics. One you can control and the other you can't. Danny __________________

14-01-2008, 08:44 PM	#5
gtm Member Hatchling Join Date: May 2007 Location: Surrey Posts: 659	Hi sandy & dan, What kind of deformities do you get if you over cook your eggs so to speak. I've heard mention of extra scutes but what else can happen?

14-01-2008, 09:15 PM	#8
egyptiandan64 Super Moderator Adult Join Date: Jun 2006 Location: USA Posts: 14,171	I've had the same book for a year and still haven't read it all Ajay. It is a great book though. Danny __________________

14-01-2008, 09:22 PM	#9
Ajay Senior Member Sub Adult Join Date: May 2007 Location: Durham Posts: 1,000	It's expensive (and a bit gorey) but worth it (wanted it now for dissertation but future for torts) I was flicking through parts I thought would be useful for my work and left it open there while I read new posts.. spooky lol __________________ Ajay xxx 0.0.2 Testudo hermanni boettgeri 0.0.2 Geochelone carbonaria 0.0.1 Testudo horsfieldii 1.0.0 Eublepharis macularius 1.0.0 Canis familiaris I am no longer a student; AT LAST!!

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