INCUBATION OF TURTLE AND TORTOISE EGGS - Paula Morris
Copyright © 2003 World Chelonian Trust. All rights reserved
Although applying principally to the incubation of California desert tortoise eggs, the following suggestions are for all turtle and tortoise eggs in general. Always bear in mind that there is no one method that will assure success and that in some cases an entire clutch of eggs will be infertile and not capable of hatching under even ideal conditions.
Unless the area in which captive tortoises and turtles live is very similar in temperature and soil to that of the natural environment, eggs will rarely hatch if left in the nest. They should be dug up very carefully, the top of each egg marked with a pencil (not a marker; the shells are permeable and the ink is toxic) to guard against turning and jarring, and then placed in an incubator.
Incubators may be anything from the commercial type used for chickens (available at some pet stores, feed stores, or by mail-order) to the homemade variety made from bread boxes, cardboard boxes, styrofoam coolers, small glass aquariums, or even margarine tubs (placed in a warm spot with a few small holes in the lid so oxygen can get in). A light for heat control should be in the incubator, plus a thermometer (either hung on inside wall or placed next to eggs) and, in cases where water or box turtle eggs are being incubated, include a small container of water or wetted-down sphagnum moss for necessary humidity. Eggs incubated without minimal humidity tend to cave in, dry out and not hatch. Most eggs require a small container of water near the eggs, replenished regularly (the water evaporates).
Sand, peat moss or other floor covering may be used, but again this is a matter of personal preference. Some fanciers bury eggs in sand to a depth of an inch or two. Others do not. In 1969 the San Diego Zoo incubated its eggs in sand-filled earthenware crocks, covered with sheets of glass to contain condensed moisture. A hazard to sand is that a newly hatched turtle or tortoise may eat it, become impacted and die. Soft, finely sifted, chemical-free dirt works well for most eggs and won’t tear the yolk sac attached to all new hatchlings for the first few days of life.
Regardless of method chosen, temperature is the most important factor. Eggs incubated at between 85° and 90° F will usually hatch if fertile. Experimentation is necessary to determine proper light wattage that will maintain constant temperature. In some incubators, a 7-1/2-Watt light is sufficient; others may need a 40-Watt bulb or more. Distance from the eggs should be 8-10 inches if using a styrofoam cooler so you avoid hot spots on the eggs; this will probably necessitate mounting the bulb in the lid and adjusting the wattage to get a stable interior temperature.
Let the closed incubator heat completely for several hours, checking the thermometer from time to time before finally deciding which size light is best. Always keep a spare light on hand because the original will burn out at some point during the incubation process.
Desert tortoise eggs will hatch anywhere between 76 and 120 days, average time being about 85 to 90 days. Many water turtle eggs require the same length of time. Some of the more exotic species require up to six months (one African Pancake tortoise hatchling appeared after 210 days!); in these cases, it is best to check specific references, look on the internet, or network with other keepers to learn incubation times.
The following incubation times are average ranges: Tortoises, 70-100 days; box turtles, 60-90 days; water turtles, 60-85 days; and exotic tortoises, 100-160 days. Use these times as a guide; remember, there can be exceptions based on external factors.
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