Probabilities in breeding
 

I was just wondering…if you incubate spur-thighed eggs at the higher temperature (for females) what proportion normally end up as boys/girls? Is it generally all female or is it just more females than males!?

If you can keep a temperature constant (within 1/2 a degree C), you can get almost all females at 32C. This happens in the first third of incubation (setting the sex) and the temperature after this makes no difference other than how fast the eggs will hatch. Most incubators aren't this accurate unless you add a more expensive thermostat. 30.5C is the half way point (where you basicly get a 50/50 mix of the sexes). Above this you get more females than males and below this you get more males than females.

Danny

So does that mean most clutches end up mixed because cheap incubators are used? There seem to be an awful lot more males around than females given that everyone incubates at the higher temperature!

you also have to remember that you don't know for certain the sex of a tort untill its a few years old and personally I don't think any incubator is cheap but wouldn't know the most accurate one. I used the herp nursery and allowing for the difference in temp which even the manufacturer states was never able to keep it that constant. There'd always be a degree or so variation which as Dan says is enough to have a mixed hatch, when I sold mine I made it plain that the sex was unknown. I think the most accurate thermostat is a pulse but then you're talking about a home made incubater and how do you check if you never open the door/lid which again would allow for a temp variation.

If you mean "for sale" you have to consider that people tend to hold on to females because they can : reproduce & also live together (usually!) peacefully in groups. Where as males tend to fight with one another & if you haven't got enough females they can become stressed by male attention. So people don't keep many males hence there are nearly always more males available for sale.