Egg Incubation Techniques
I have written this to provide a starting point for anyone who is not well versed in the methods of egg incubation of colubrids, pythons, turtles and lizards. This is a general starting point and some species may be a bit more exact. Take notes whenever dealing with your success or failures, this helps you identify mistakes and acts as a future point with the eggs of that species for yourself and others. The points here are intended as a point of reference, I write these sheets as I go, I ramble! I take the eggs away from all reptiles including maternally incubating snakes, this allows me a greater level of control over the eggs and the incubating environment.
Incubators - Provide a rigid temperature environment. Most eggs have a fair degree of tolerance for temperature fluctuations for short periods. Since the developing embryo is dependent upon its immediate ambient temps it is critical to keep temperatures stable to provide an ideal situation and avoid the chance of birth defect related to inappropriate incubating temps. Buying an incubator is the easiest and perhaps the best choice if you are breeding any egg laying species. My first choice would be the incubators sold by Neodesha Plastics/Bush Herp. (1(800)451-6178), this one is ideal, I helped provide the concept and design it! This one incorporates a false wall, and a fan where air is passed over the heating element. Hovabators are used with a fair degree of accuracy but I have little knowledge of them.
Incubator Concept - This is a critical point, please read and understand if you wish to have success! The eggs are contained typically in a tupperware style vessel that has a few if not a single vent hole. This container is placed in the incubator. The incubator has a heating source that is controlled by a thermostat; rheostats on incubators are inappropriate since they are not self regulating and you can find thermostats for an inexpensive price. The air around the egg chamber will change as the heat source fluctuates as the thermostat calls it. The egg chamber acts as a buffer and the temperatures inside change slowly, this is the key. If the temperature is immediately effective upon the eggs there will be a greater chance of development mishaps!! The PROBE OF THE THERMOSTAT MUST BE PUT INTO THE EGG CHAMBER, do not put it outside of the egg container since this will create unstable temps. DO NOT LOCATE THE EGG CONTAINER ON THE HEAT SOURCE, this can and will create hot spots that will damage the eggs! Raise the container up to prevent this potential problem. Use two digital thermometers that are first matched by locating the probes in a glass of water to measure the readings. If they vary use a normal accurate thermometer to decide the correct temp and then mark the deviation on each of the digital therms. They can then be used with a greater degree of accuracy in your incubator. I like using two, this ensures I will have no surprises down the road. I strongly suggest using a fan or two (depends upon incubator size and air path) within the incubator, the fan should be controlled by the thermostat. This ensures that the air surrounding the egg container has mixed well with the heat source and there will be less chance of hot spots.
An Ideal Incubator - Will
have the following points.
Egg Substrate - I suggest the use of Vermiculite. It is easy to obtain through and gardening store and very inexpensive. It holds water well and harbors no detrimental organisms at purchase. I also have used perlite for some lizard eggs, this can be tricky stuff to use since if the humidity is not kept properly it can and will draw moisture from the eggs that sit on it. I will not try to explain the incubating technique with this substace because I am not confident that I can explain it well enough for it to work well. Remember reptiles look for a place of high humidity and warmth to lay their eggs. If the substrate is too wet or too dry it will destroy the eggs.
Humidity - This is a critical point and varies from species to species. I will not discuss this in terms of a gauge, I never use one but depend on reading the eggs and the level of moisture within the egg chamber. We are typically thinking of levels of 90-100% ambient humidity. Some lizards(Uromastyx, beardies etc. arid region critters) will suffice with lower levels. Some eggs may demand more moisture while others will die if the humidity is excessive. Remember, we are imitating what the adult animal and nature naturally provide. We often tend to go overboard on the moisture content that we provide. General rule of thumb is to add small amounts of water to the vermiculite as you mix it. Make sure it is mixed well. Typically for pythons and colubrids add enough water to clump the vermiculite slightly when you squeeze it into a clump. No water should come out and it should flake apart. After the eggs have set up in a day or so note the amount of water condensation within the container and its lid. It should be slight if at all, not dripping!!! A wet egg box will KILL the eggs, they will turn green, smell and mold up. Eggs do not have a method of dealing with too much moisture, the eggs will absorb whatever they are in contact with. For lizards such as monitors I use the same technique as with pythons. I like to bury monitor eggs completely as they are buried by the nesting feamel and water dripping on some species eggs can destroy the eggs. For lizards such as dragons, uros, and frills I tend to go a bit drier. I have noticed that many lizard eggs will not tolerate being directly moistened and may actually die if hit with water spray. I moisten the substrate and not the egg and then cover the egg. Perlite as an incubating substrate is used with a good deal of success but I am not well versed on the exact techniques of this substrate. Be careful a substrate if kept too dry can extract prescious moisture from the egg! IMPORTANT - it is easier to save an egg that has dried out a bit from low humidity than to save one that has been exposed to too much!! Don't go overboard! A white egg that is dimpled or caved in is acceptable and can easily be fixed by wetting some of the medium and putting it over the eggs for a day or two. An egg that appears a bit dimpled(snake) is nothing to worry about, some eggs may fill out while others look a bit caved in. A living healthy egg will absorb the extra direct moisture. If the eggs are turning foul, moldy, green, yellow or blue this is a dead or dying egg. This is also a good indication that it is too moist. Remove all bad eggs whenever possible, do not damage an attached egg by the removal of a bad one. Many eggs if healthy and provided the proper environment will exist attached to a shriveled dead egg. If they go moldy and turn colors they will often damage the attached egg and are typically easy to remove as they decay!! If this occurs you may want to rethink if the eggs are too wet. Tortoise eggs in my opinion are the hardest to read and candling is the best method of checking, time will tell! look for blood vessels attached to the egg wall after 10 -20 days in a developing egg to see if it is fertile. I often see gorgeous white tortoise eggs that are sterile and will never develop into a baby tortoise.
Hatching Green Tree
python eggs (Chondropython viridis)
As an egg matures - As an egg grows it often grows in mass and draws its moisture from its environment and nourishment from its yolk. We often notice that snake eggs will often cause the egg chamber to sweat as they prepare to hatch. They are warming up! They are actually creating a bit of their own heat which may be several degrees in larger clutches. At some point in the incubation process large clutches may create too much heat and actually cause embryo death and deformaties. Watch out for this on large clutches, check your temps as time passes. I generally incubate all python eggs at 90F but it seems a bit wiser to incubate large clutches at lower temps such as 88F. I learned this the hard way when incubating a clutch of blood python eggs. They generated too much heat since it was a massive clutch and the babies hatched with an unusual number of birth defects. I had kept them too warm! This whole event can be observed by using two digital thermometers or a raytec gun to measure the egg box temp and the temps of the egg mass! Be careful with too much heat.
Close to hatch - the eggs shell becomes soft or brittle as the animal releases enzymes to break down the shell. This enables the baby to cut or break free from its shell. With pythons I often seperate the eggs from each other a few days before they are due to hatch, this prevents snakes from slitting into another egg and possibly drowning. The eggs are easier to seperate at this point and can be done with relative safety if care is taken and the eggs are not rotated.
Egg handling - Rule of thumb is not to rotate the eggs from their original position. As an egg develops it attaches blood vessels to the walls of the egg for oxygen absorption. If the egg is rotated there is a chance of the vessels pulling free and a resulting death of the embryo. I use a pencil to mark the tops of eggs and number them with large clutches. The lead graphite is harmless and works well.
After taking the Eggs
away - Pythons
Egg Viability - Are the eggs viable?
looking eggs are typically a good sign of a viable egg. Some eggs may
have transparent spots that are not calcified, this is fairly common and not
a great worry. I have had eggs (snakes) that are nearly half this way with a
nippled end and have hatched a perfect but smaller baby. They are more
likely to die in the incubation process than perfect looking eggs. After
7-10 days the eggs can be candled with a mag lite to observe for the
presence of blood vessels along the egg wall. Shine a bright light into the
egg and look for the red blood vessels attached to the egg wall. If you see
them you have fertile eggs!
What should they look
Placement of eggs on the
How long should they take
Temperature Examples (I
need to update, off the top of my head!)
Here are some pictures showing the steps in order of one way you may make your own egg incubator!!