To hatch painted turtle (Chrysemys picta) eggs, you must keep them in a safe place that provides the appropriate temperatures and moisture levels. In the wild, painted turtles address these needs by depositing their eggs in underground nests dug into sandy areas near their pond or river. However, in captivity, most keepers have better success by digging up the eggs and artificially incubating them inside a climate-controlled box.
If you are not interested in investing a whole lot of time, money or effort, and are willing to accept less-than-ideal hatching rates, you can just leave the eggs where your turtle deposited them and hope for the best. Any of the hatchlings that survive the incubation process will hatch in 72 to 80 days. However, this is only possible if your turtle buried the eggs in a sunny patch of sand near her pond. If she deposited her eggs in an artificial egg box that you have provided, you will need to dig them up and incubate them artificially. Most painted turtle clutches contain between 5 and 15 eggs, and the females bury them about 4 to 6 inches deep.
Recreating the Nest
Carefully excavate the nest, taking care to avoid disturbing or damaging the eggs. Make a mark on the very top of each egg with a pencil -- this will allow you to place the eggs in the egg box in the same orientation in which they were deposited. Rotating turtle eggs may cause the young turtles to drown inside their eggs.
Gently remove the eggs and place them in the egg chamber. Most breeders use plastic storage boxes, partially filled with damp vermiculite, moss or sand as egg chambers. Place the eggs in the substrate so about half of the egg is covered and the other half is open to the air in the chamber. Place the top on the egg chamber once the eggs are inside.
Using an Incubator
You could place the egg chamber in a warm room and cross your fingers. However, you are likely to have more success by incubating the eggs in a specially constructed chamber, known as an incubator. Novices should purchase a commercial model at the outset, as it can be tricky to construct a suitable incubator and have it maintain consistent temperatures. Entry-level, foam incubators are often available at farm supply stores. However, more experienced keepers can make their own by installing heat tape or light bulbs in a well-insulated box and wiring the heating element to a thermostat.
You can make an incubator by placing an aquarium heater in a 10-gallon aquarium and filling the aquarium with a few inches of water. Place a brick in the water, on which the egg chamber will rest, and cover the tank with a glass lid. By adjusting the temperature of the water heater, you can change the air temperature inside the egg chamber. Always place the probe of a digital thermometer inside the incubator to monitor the temperatures. Periodically check the moisture level of the egg box to ensure the eggs are not shrinking or swelling excessively. Swollen eggs indicate excessive moisture, while shrunken eggs indicate that the substrate is too dry.
The Importance of Temperature
Because they are ectothermic, temperature affects a variety of biological functions in painted turtles, including egg development. In fact, temperatures can even affect the growth rate of the individuals after they hatch. To ensure proper development, you must keep painted turtle eggs between 78 and 86 degrees Fahrenheit. Within this range of tolerable temperatures, the eggs develop more quickly in warmer temperatures than cooler temperatures, but incubation temperature also influences other biological process; specifically, the determination of the turtle’s sex.
This phenomenon -- known to scientists as temperature dependent sex determination -- is common to many species, notably turtles and geckos. This means that you can decide which sex you want the hatchlings to be. Those incubated at the upper end of the acceptable range become females, while incubation temperatures at the lower end of the range produce males. Intermediate temperatures of about 84 degrees yield a mix of both sexes.