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Incubation of Reptile Eggs - By Jonathan Rheins
There is no doubt as to the booming popularity of reptiles and amphibians in the United States. People are becoming more aware of their qualities as pets, and are gaining further understanding of their special captive needs. The current trend among reptile enthusiasts is to not simply have "pets" but to obtain breeding pairs of their favorite species and strive to have them reproduce in captivity.
When done responsibly, this is a great way for us to expand the scope of our hobby. It allows breeders to work on developing healthier, more colorful animals, and helps to alleviate the demand for wild-caught animals. While some species are being bred in captivity in huge numbers, others are only occasionally produced, while still others still pose problems that we must figure out and overcome. Regardless of the species in question, proper care and successful mating are only half of the equation. With the exception of viviparous (true live-bearing) species, the end result of captive breeding is eggs. Eggs which in most cases will require artificial incubation to ensure proper embryonic development and eventual hatching.
All egg-laying reptiles have adapted strategies that allow them to lay their eggs in suitable areas in the wild. Even desert species know that in order to prevent their eggs from quickly desiccating, the eggs must be laid in deep, moist burrows, protected from the blazing sun. Likewise tropical animals must find suitable nesting spots that will provide constant temperature, but without allowing the eggs to become to moist. In this article, I intend to present the reader with basic guidelines to follow when the time comes to incubate a clutch of reptile eggs. Actual husbandry and cycling regimens are far too variable to be included here, yet should be researched carefully by the interested breeder.
Gravid females should be fed an exceptionally well-balanced diet, including increased calories to support the increased energy expenditure associated with egg development and laying. Additionally, dietary calcium intake should be closely monitored, as the calcification of the eggs within the female requires large amounts of calcium, which if not present, will be pulled from the blood, and in turn from the skeletal tissue.
Every species is slightly different, but as a general rule, females that are known or suspected to be gravid should be provided with a suitable egg-laying area. This can be as simple as a small tupperware container filled with moist sand or soil. Most females will instinctively seek out these more suitable (as compared with the rest of the enclosure) areas to deposit there eggs. By allowing the female to lay her eggs directly in a moist medium, you greatly lessen the likelihood of the eggs drying out and dying before you can recover them and transfer them to a suitable incubator. In fact, some reptiles will actually postpone egg-laying if a suitable area is not provided. In the best case scenario this will result in reabsorption of the eggs, and in the worst case, lead to post-ovulatry egg-binding, which may require veterinary assistance.
Recovering the Eggs
Shortly after laying, reptile embryos begin developing. In addition to the embryo, each egg contains a nutrient rich yolk, amniotic fluid, and an airspace. Typically within 3-4 days (but as soon as 24 hours) of being laid, the egg "sets," that is, the embryo settles to the bottom of the egg with the air space at the top. After this has occurred, the eggs should not be turned, and should be moved as little as possible, as disrupting this interior arrangement can quickly lead to death of developing herps.
Luckily, most eggs are recovered by keepers shortly after laying, but nonetheless, to be on the safe side I recommend being very careful about turning eggs as they are removed from where they were laid and set-up in an incubator. When you excavate the eggs (assuming they were buried) you should mark the top of each egg with a pencil, so that you can ensure they remain in the same orientation during incubation. Many experienced keepers forgo this step, but until you get the feel for dealing with eggs, it is a good idea to mark your eggs.
There is another concern when it comes to collecting freshly laid eggs. In some species (most notably with snakes) the eggs are laid in a pile and will adhere to each other about 12 hours after laying. If the eggs are freshly laid when you encounter them, and they separate easily, then do so. By separating the eggs, you can ensure that should one egg go bad later during incubation, any mold or fungi will not necessarily affect the other healthy eggs. If they do not come apart very easily, then DO NOT FORCE THEM. Doing so may result in rupture of one or both eggs and the loss of two babies! Usually, these "clump" clutches can be incubated successfully just as they are. You will just have to use a larger container to hold the eggs during incubation.
There are a variety of products that have proven successful as incubator mediums, that is, the substance that the eggs rest directly in as they develop. When choosing a medium, there are a handful of factors that must be considered. You need something that will retain water and maintain humidity within the egg container, something sterile (or close to it) and something that will not promote excessive growth of molds or fungi. Most breeders and hobbyists turn to either perlite or vermiculite as their medium of choice. Both have proven highly successful, and render high hatch rates. Both of these substances are examples of naturally occurring siliceous rock. When heated to a proper temperature, they expand to many times their original volume, producing a very light, absorbent material that naturally resists molding.
There are arguments on both sides regarding which product is better. Some say perlite provides better airflow, others insist vermiculite has better mold-resistant qualities. Still others mix the two to get the best of both worlds. My honest opinion is that if all other conditions are proper, either one will serve perfectly.
Sand, soil, and pulverized coconut husk are a few other mediums that have been experimented with. However, these mediums provide much more egg to medium contact and less airflow, possibly resulting in rotting or drowned eggs.
Regardless of what you choose, it should remain moist throughout the incubation period. Different sources will give varying ratios of medium to water that will produce the "perfect blend." Luckiliy, there is a rule of thumb that can be followed and provide you with an acceptable medium without the use of mathematics or weights. Just add water to your dry medium until it barely clumps, but does not drip when squeezed. You will want to maintain this consistency until the incubation period is complete.
This is fairly straight forward. Small eggs can easily be placed in deli cups or tupperware containers with ventilation holes added. I usually incubate my eggs covered, that is that the containers in which they sit have tight fitting lids, but air holes as well. Different species will require different levels of humidity, not to mention that each incubator will function slightly differently. It is up to you to decide what measures are necessary to set-up your particular eggs.
Keep in mind, if you choose to use standard lidded-deli cups in which to incubate your eggs, be certain that the level of incubation medium is below the ventilation holes in the sides of the cups.
Choosing an Incubator
Incubators can technically be any device that maintains a constant temperature. Ideally you want one that is well insulated (to cut down on temperature fluctuations) and that allows for easy visual inspection of your eggs. Incubators can be home made or purchased. Building a home-made incubator is beyond the scope of this article, but information exists if you choose to take this route.
Realistically, purchasing an incubator is probably a safer option for those new to the reptile breeding world. There is a much lower chance of failure if you start with a device that was specifically designed for your purposes, rather than rigging up an old aquarium or cooler.
Hovabators, are by far the most commonly used models being used by hobbyists. They are reasonably priced, easy to use, and available with a variety of options. I have had success hatching a wide variety of eggs using these incubators including bearded dragons, various geckos, various colubrids, as well as both ball python and carpet python clutches.
Hovabators are available from www.LLLReptile.com starting at under $50.
Whatever type of incubator you end up using, be certain that you are doing so in conjunction with an accurate thermometer. Knowing the temperature of the chamber containing your eggs is very important, although the exact temperature required will vary from species to species.
Monitoring the Eggs
During incubation, you should regularly check not only the temperature in the incubator, but the condition of the eggs as well. Eggs that are too hot, cold, wet, or dry can all go bad at different stages of incubation, and you need to be aware if this starts to happen. Eggs that are beginning to grow mold may be too wet, although excessive moisture is not always the cause. Similarly, eggs that do not have enough moisture may begin to collapse, although this should not be confused with the normal dimpling that occurs right before hatching.
If your eggs or medium seem to wet, you can leave the container uncovered for a day or so allowing excessive moisture to evaporate. For dry eggs (indicated by collapse or dry medium) you can add water. Do so slowly, as it is easier to add more water than to remove it later. Add the water by dripping it around the perimeter of the egg container, avoiding getting the eggs directly wet.
Incubation times will differ from one animal to another, so be certain to research the specifics of the species you are working with, and always mark the cup with the date the eggs were laid. Depending on your temps and humidity, incubation time may be shorter or longer than the average specified in books or elsewhere. Do not discard of eggs unless you are absolutely certain they are dead, or if they pose an immediate threat to the existing healthy eggs.
With the vast majority of species (namely those with soft-shelled eggs) the egg will dimple and then begin to collapse shortly before hatching. This is a sign that hatching is eminent, and you should prepare facilities for the babies at this time if you have not already done so.
Actual hatching typically begins with the neonate making a slit in the egg (known as pipping). They may then poke their heads out, or remain in the egg with just the nostrils exposed while they take their first breathes of air. Some animals will only take a few hours to emerge completely, while other may remain in the egg, even after pipping, for days. Do not rush them. They will emerge when they are ready. If you are concerned that you have a healthy baby that is simply unable to leave the egg for one reason or another, consult a local herp veterinarian or a more experienced breeder for advice.
I usually recommend leaving the babies in the incubator for 24 hours post-hatching. This allows them to recover from the stress of hatching without the added shock of a significant temperature change. Additionally, the movement of already hatched siblings may stimulate the unhatched babies to leave the egg. If you are dealing with milksnakes or other potentially cannibalistic species, then you may want to remove the neonates to their own quarters as they emerge.
Despite the intricacy of the matter being dealt with, incubating reptile eggs is really not that difficult if you take the proper measures and do adequate research. Keep in mind that this article is merely an introductory guide, and should not be mistaken for an exhaustive reference. Make sure to carefully research the specific needs of the animals you are breeding, as they may differ in one way or another from the guidelines provided herein.
Most importantly, never give up! Even the most experienced breeders have clutches go bad or incubator malfunctions. It happens. We are not dealing with a perfect science here. In the end, it is well worth the time and effort involved to produce your own clutch of happy, healthy, baby reptiles.