The moisture content of the substrate upon which reptile eggs are incubated is a critical factor in hatching success. While certain hardy species fare well under the much-promoted technique of “squeezing water from the substrate until it barely sticks together”, many eggs require closer attention to detail.
I would like to pass along a method that I have used for hundreds of species, both in zoos and in my own collection. All that is required by way of measuring devices is a simple gram scale and a graduated cylinder (marked off in milliliters). Fortunately for me and other mathematically impaired herpers, calculations are simple – it turns out that 1 milliliter of water weighs 1 gram.
First, determine the moisture level required by the eggs that you are incubating (please write in if you need help with this). Then, using the gram scale, weigh out enough substrate contain the eggs. You can now easily set up a ratio of, for example, 1 part substrate to 1 part water, by measuring, in the graduated cylinder, a corresponding volume of water. So, 10 milliliters of water added to 10 grams of vermiculite provides a 1:1 ratio (1:1 works well for many, but not all, reptiles).
Place the eggs (1/2 buried for most reptiles) and moistened substrate into a sealed container, weigh the container and record the weight (and date) on the cover. The cover should not be ventilated – for most reptile eggs, a once- daily check provides enough oxygen exchange (ventilation may need to be increased for large numbers of eggs once hatching time nears – please write in if unsure).
Keeping Track of Moisture Loss
Weigh the container weekly – any weight loss will be the result of evaporation, and should be made up by adding an appropriate volume of water to the substrate. For example, if the container weighs ½ gram less than the previous week, add ½ ml. of water.
The abstract of an interesting article on the conservation of moisture in reptile eggs is posted at: