Caring for Turtle and Tortoise Eggs
Caring for Turtle and Tortoise Eggs
by Larry N. White, DVM
Nearly all turtles and tortoises deposit their eggs in holes which the female digs in soft soil or sand. The natural moisture of the soil and warmth of the sun will serve to incubate the eggs. For those species which are native to our local area, the simplest method of incubation is to leave the eggs in the ground, and protect the site from marauding dogs, cats, skunks, raccoons, etc. The incubation period is dependent upon the species of turtle and the ambient temperature. Average incubation periods for most native species vary from two to four months.
For those that wish to incubate their eggs, or for those who own turtles and tortoises from several different climates, several methods of incubation have proven successful. the materials needed can range from the very simple and readily available to the complex and costly incubators which can be purchased.
I prefer to place the eggs in some type of medium for the incubation period. My favorite media for this purpose are vermiculite, sphagnum moss, and sand. Vermiculite may be purchased at any nursery. It is usually mixed with water at a rate of one ounce by weight of vermiculite to one fluid ounce of water. For turtles and tortoises from more arid regions the amount of water may be reduced. Sphagnum moss will generally absorb approximately twenty times its weight in water. I generally saturate the moss and wring out the excess water. When sand is used, try to make the mixture damp enough to form a ball which will still fall apart fairly easily.
The container which is used can also vary from a simple tupperware container, a styrofoam cooler, or a commercial incubator for hatching chicken eggs. My favorite is a simple styrofoam cooler. I take a flat piece of styrofoam (such as a lid from a second cooler), and cut it in a way to form a shelf to hold the pan with the eggs. I also cut a hole in the shelf in order to insert an aquarium heater. Fill the bottom part of the cooler with water deep enough to cover the base of the aquarium heater. Place a thermometer on the shelf and put the lid on the cooler. The aquarium heater has a thermostat which can be adjusted to the desired temperature. The heated water in the bottom will keep the humidity high.
The incubation temperature for turtle eggs can vary. Generally, a range of 80 - 88 degrees Fahrenheit is suitable. The sex of the turtle embryos is not determined genetically for the majority of turtle species which have been studied. The incubation temperature determines the sex to a large degree. Eggs which are incubated at the upper end of the acceptable range tend to be females, and those incubated at the lower end of the range tend to be males. In addition, with increased temperature, incubation period s tends to be shorter. Reptile breeders will sometimes use this information in order to produce more of one sex offspring.
After laying, turtle eggs can be safely handled for a few hours, but after the embryo begins development, try not to handle the eggs at all. If this is not possible, try to make sure that the eggs are not rolled or rotated. This type of movement may cause damage to the tiny developing blood vessels in the embryo, and could result in death.
The moisture content of the incubating medium varies depending upon the species of the turtle. Generally, aquatic turtles or those from humid environments require more moisture than those eggs from animals which originate from a more arid environment. Some tortoise eggs will actually absorb so much moisture that the egg will rupture. For these animals try to provide a more dry medium, but keep a container of water in the incubation chamber in order to keep the humidity up. As the eggs develop there should be some swelling. If the eggs appear to be collapsing, the problem may be due to inadequate moisture.
Occasionally, a small amount of mold will be seen on the surface of the eggs. This is usually not a problem. If a large amount of mold is seen, it is usually because the egg is infertile, or the embryo has died. It is not uncommon to have a fairly large clutch with one or more infertile eggs. I have not had a problem with mold growing on an infertile egg spreading to a viable egg and killing the embryo. If embryo death has occurred it is usually due to other factors, such as improper temperature or excessive movement of the eggs.
When hatching begins, small slits will be seen in the egg shells. The baby turtles have a small projection on the tip of the nose known as the egg tooth. This projection allows the hatchling to cut the tough shell in order to make his escape. Usually the hatchling process takes from twelve to forty-eight hours. If any one of the eggs have not slit within forty-eight hours, I generally make a small slit in the shell with a sharp pointed scissors. I have seen instances where perfectly formed embryos have died in the shell without ever having slit the shell. If all the rest of the eggs which are incubating with these contained fully formed embryos, the unslit eggs should be adequately developed also.
On hatching the baby turtles will usually still have a small yolk sac which will provide nutrition for the first few days of life. Normally this yolk sac will rapidly be absorbed, and a small scar will be visible. If a large yolk sac persists, try to suspend the baby and wrap the baby with a damp piece of gauze in order to prevent dessication of the yolk material prematurely, and to prevent the baby turtle from traumatizing the umbilical area. It is possible for the baby to accidentally pull its intestines out if care is not taken to safeguard the sac.
GCTTS Note: Dr. White is one of the foremost reptile veterinarians in the greater Houston area and also has extensive personal experience with chelonians. He is at Briarcrest Veterinary Clinic, 1492 Wilcrest, Houston, TX 77042. Phone 713-789-8320.
Copyright (c) 2007 Gulf Coast Turtle and Tortoise Society
Permission is granted to copy for non-profit use with proper credit given. For any other use you must obtain permission.
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1227 Whitestone Lane
Houston, TX 77073
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