This sort of egg usually has a much thicker than usual shell, and in our experience is never fertile. Such eggs are often implicated in egg-binding and can prove very difficult to lay.
For most species, the best results are obtained if the incubation temperature is maintained between 30C and Also in this temperature range, a mixed sex brood is most likely to result. In most cases, lower temperatures produce males, higher temperatures result in females.
As mentioned previously, it depends to a great extent upon the temperature at which the eggs are incubated. In the temperature range suggested, between weeks is about average for most species. The lower the temperature the longer it takes. At around 27C for example, incubation can take 18 weeks or more.
At temperatures above 34C however there is a grave risk of mortality or deformity among the hatchlings. It is best to incubate at the medium range temperatures suggested.
The importance varies with species. Those species which produce softer shelled eggs are much more critical in this respect than those which produce hard-shelled eggs. A good example of the former would be American Box turtle eggs which need to be incubated at a very high ambient humidity if they are not to dehydrate. For most hard-shelled eggs, a medium level of humidity is generally adequate. The easiest way to achieve this is usually just to place a damp sponge in a tray of water somewhere with in the incubator itself.
From the time when they initially pierce the egg, it usually takes between hours. The first small fracture is to permit air breathing to begin - prior to this time the embryos oxygen demand has been met via permeation through the egg shell.
This first small hole is gradually enlarged over the next few hours. The hatchling may then sit in the egg for quite some time whilst its egg sac is absorbed. Until this is absorbed, the hatchling remains especially vulnerable as movement is seriously impaired. There can certainly be a considerable delay between emergence of the first hatchling and the last - in the case of Mediterranean tortoises we have experienced periods of up to 18 days and even longer may be possible.
With some tropical species the time scale can be very extended indeed. This effect is noted even in highly accurate and stable incubators, and only seems to happen occasionally. By far the best sort of incubator uses an electronic proportional thermostat and ultra-reliable heating element combination. Commercial reptile-egg incubators are available. You can however make do with less. What we do not recommend is relying upon airing cupboards or light bulbs as your heat source.
Whilst these can work, they are in reality far too unpredictable and unreliable to guarantee a secure incubation environment for on average a continuous period of operation lasting weeks or more.
When light bulbs are used as the heat source they invariably fail during the most critical phase, just as the egg is about to hatch!. Stability and reliability are the two key precepts to adhere to when incubating tortoise eggs. A basic incubator is shown in the diagram below. The average is weeks for most turtle and tortoise species, however the lower the temp, the longer it takes. So if you are temp sexing, looking for mostly males, it will take you longer to hatch your eggs than if you are looking for mixed or all females.
The temperature gradient for incubating tortoise eggs is very large- anwyere from 85 degrees F to 90 degrees F should do the trick. Humidity is much more important for soft shelled eggs than for hard shelled eggs. Since most tortoise eggs are of the hard shelled variety, we will focus more on that here.
Many breeders report that they don't use a hygrometer, but for someone who is less experienced at understanding the signs of humidity that is too low pitting, collapsing of the eggs or humidity that is too high excess moisture, bacteria growth , we definitely recommend picking up a hygrometer to monitor and maintain your humidity. As with any incubation project, we encourage you to set-up your incubator atleast hours prior to placing eggs inside.
This gives you the opportunity to make sure your unit is thoroughly cleaned and sterilized, as well as make sure all components are working properly. You should double check your temperature and humidity and let the device regulate before placing your eggs inside. You will then need to periodically check your eggs, about once an hour for the first few hours, as the temp and humidity will change with the addition of the eggs to the unit. You may then need to dial your temp up or down slightly to account for more mass inside the unit.
For the first time breeder, incubating tortoise eggs can be ominous, but it is extremely rewarding. Over time, a network of blood vessels may be seen above it. The time taken for eggs to hatch depends upon both the type of turtle and the incubation temperature.
The eggs may not all hatch at once, so be sure to leave any unhatched eggs to incubate longer, just in case. When the female has finished laying, open the nest and carefully remove the eggs. A clean paintbrush is a useful tool for uncovering the eggs.
If the nest has been filled in, dig out the soil using a spoon, paintbrush or other small utensil. The dirt may be packed down tightly, and caution is needed to avoid breaking the eggs. After carefully removing the eggs from the nest, lightly mark a cross or number on the top of each one with a pencil. At some stages in the their development, turning a turtle or tortoise egg can result in the death of the growing embryo, and the pencil mark makes it easier to maintain the eggs in the same orientation as they were laid.
Gently brush off soil and debris from the eggs with a tissue or paper towel, and transport them to the incubator. A variety of incubation set-ups have been used to successfully incubate turtle and tortoise eggs. The important factor is that the incubator be able to maintain the appropriate temperature and humidity.
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