REPRODUCTIVE BIOLOGY OF BEARDED DRAGONS
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REPRODUCTIVE BIOLOGY OF BEARDED DRAGONS IN CAPTIVITY By Jonathan Rheins
The inland bearded dragon (Pogona vitticeps) of central Australia, has risen from moderate obscurity to become one of the world's favorite pet lizards in the span of only a few decades. Their personable demeanor, manageable size, and attractive appearance have all contributed to their current level of popularity.
In addition to making excellent family pets, bearded dragons are also very easy to breed in captivity. In fact, some would argue that preventing them from reproducing is a more daunting task. Fortunately, there is a constantly high demand for these animals, and many breeders, both professional and not, have found bearded dragons to be a simple and lucrative breeding project.
There are many excellent books available that cover all aspects of keeping and breeding bearded dragons. However, many keepers find that the data given on breeding, egg-laying, and incubation is cursory, at best. Below, you will find a detailed, step-by-step guide to the reproductive management of bearded dragons in captivity.
Because the focus of this article is breeding and not basic husbandry, it shall be assumed that the reader is familiar with the general care of these animals. If not, please refer to one of the many bearded dragon care books mentioned earlier.
Assuming that you have a sexual pair (one male, one female) of mature dragons, reproduction may take place regardless of what measures you take. However, if your goal is to produce the maximum number of viable, healthy babies while placing minimal stress on your breeders, special actions will need to be taken.
First and foremost, it is essential that both your adult dragons are in prime health. The male should be at least 18 months old, and the female closer to 24 months old. While some dragons will mature and become capable of breeding earlier, doing so may prove harmful to them over time. Both animals should have ideal body weight, well hydrated, and show no signs of disease prior to conditioning them for breeding.
To further ensure that breeding occurs, the lizards should be subjected to a pseudo-brumation, that is a brief period of time (typically from mid December to mid February) where both temperature and photoperiod are altered. This action simulates the brief winters that these animals would encounter in nature. The process not only triggers behavioral breeding activity, but the reduced temperatures seem necessary to induce spermatogenesis in males.
During this period of inactivity, basking temperatures should be reduced to around 80 degrees during the day. Night temperatures may drop to as low as 50 degrees, but around 60 degrees is not only sufficient, but slightly safer as well. In addition to reduced temperatures, the photoperiod should be altered so that the animals receive roughly 10 hours of light and 14 hours of darkness. This is an approximate opposite of what they should receive during the rest of the year.
Most bearded dragons will show reduced appetite and activity during the winter months, even if the above actions are not taken. But as mentioned earlier, to ensure viable sperm from the male and receptiveness from the female, these steps are highly recommended.
It should be noted that during their winter cool down, bearded dragons will behave very differently than normal. They may eat very little, spend large amounts of time in hiding, and refuse to bask. These are all normal behaviors. Water should always be made available, and food may be offered occasionally, but there is no need for concern as long as the lizards appear hydrated, and exhibit only minimal weight loss.
By mid to late February, environmental conditions should be returned to normal. After a few days of higher temperatures and longer days, bearded dragons will regain their appetite with a vengeance. During this time, they should be fed heavily, especially the females who will have to support egg development in addition to their own metabolic needs. Calcium supplementation is also particularly important during this time. Female dragons should receive a high quality calcium/vitamin D3 supplement at every feeding in addition to the standard multivitamin regimen. Increased dietary calcium in pre-breeding females is absolutely essential to prevent poorly calcified eggs and/or calcium deficiency post-laying.
Typically within a month of being returned to normal conditions, the keeper will begin to see courtship behavior in the lizards. The throats (beards) of male dragons will darken to nearly jet black. They will also exhibit head bobbing and an obvious interest in their female counterparts. Females will respond to the head bobbing with similar motions, coupled with a rather entertaining arm waving behavior, suspected to be a sign of appeasement and receptiveness to mate.
The actual process of copulation may appear brutal by human standards. The male dragon will chase the female around the enclosure until she fully submits. Male bearded dragons bite the neck of the female during breeding to ensure that she does not run off prior to the act being completed. Copulation will likely occur numerous times over a period of a few months.
Pay close attention to the condition of the female lizard. If the dragons are housed in too small of an enclosure, or if the male is simply over zealous, she may not be able to escape his mating attempts and become stressed. Typically large enclosures, visual barriers (logs, rocks, etc.), and careful observation on the part of the keeper will prevent this from occurring.
Actual egg laying occurs 4 to 6 weeks after a successful mating. Gravid (carrying eggs) females will become very plump prior to laying. In fact, in many cases the outlines of the eggs may be visible through the females abdominal wall, resembling marbles. As the eggs grow inside of her, she will begin to eat less and less, usually fasting completely for a few days right before laying.
When a female bearded dragon is ready to lay her eggs, she will begin searching for a suitable spot to deposit them. She may be observed digging at the corners of the enclosure and seem hyperactive. At this point, a suitable place for her to deposit her eggs should be provided, and the water dish removed from the cage. Some keepers opt to simply place a box or deep pan of moist, sandy soil into the enclosure. This is a popular and proven technique, however, with this practice, there is still a chance of the eggs being laid elsewhere in the habitat, in which case they will likely desicate and perish before they can be retrieved by the keeper.
A second option is to procure a plastic tub or similar container with an 8 to 10 gallon capacity and a secure lid. The container, which will become the egg laying box, should be filled nearly to the top with at least 8 inches of moist, sandy soil. The soil mixture should be damp enough to barely clump when squeezed. As soon as digging behavior within the primary enclosure is observed, place the female into the box. Typically, instinct will take over, and she will dig a burrow and lay her eggs within a few hours.
If the eggs have still not been deposited after several hours in a lay chamber, the female should be returned to her normal enclosure and the process repeated the following day. Most bearded dragons lay their eggs in the afternoon or early evening, and if possible, place the female into the lay box during this time of day. Regardless of when or for how long the female remains in the box, every effort should be made to maintain the chamber around 80 degrees. Cooler temperatures may lead to lethargy and failure to lay.
RETRIEVING THE EGGS
Once a female bearded dragon has laid her eggs, she will bury them well. The exception would be among animals not given a suitable laying area, in which case they may be scattered throughout the cage or even in a water receptacle. More often than not, the only evidence that egg laying has occurred will be the deflated appearance taken on by the female.
While freshly laid bearded dragon eggs are rather stable, they should still be handled gingerly. The eggs should be carefully dug up with the hands or a plastic spoon. If the eggs have been successfully deposited in an appropriate container, begin by excavating the corners of the box, as these are the most likely places for the eggs to have been laid.
Clutch size will depend on the age and condition of the female, as well as how many times she has reproduced in the past. Average clutch size for Pogona vitticeps is between 16 and 24 eggs. However, clutches both drastically larger and smaller have been recorded.
After the eggs have been laid, and successfully unearthed, they should be moved to an incubator to ensure proper growth and development. As mentioned earlier, freshly laid eggs are not nearly as fragile as those that have begun embryonic development. Nonetheless, every effort should be made to keep them in the same orientation as they were discovered. Some keepers choose to mark the upper side of the egg with a pencil as to better prevent the eggs being turned during transfer to the incubator.
The actual type of incubator used for bearded dragon eggs is of little importance. While poultry incubators (Hovabators) are most commonly used, any thermostatically controlled container will work. It is advisable to purchase a pre-made unit as opposed to constructing your own in an effort to reduce the likelihood of malfunction.
Bearded dragon eggs should be incubated at 84 degrees, plus or minus 2 or 3 degrees. Sustained temperatures above 90 degrees can quickly kill developing embryos, so the use of an accurate and trustworthy digital thermometer is highly recommended. The incubator should be calibrated to the proper temperature prior to the actual laying of the eggs. Most incubator models take at least 12 hours, if not more, to be properly and accurately set.
The eggs themselves should not be placed directly into the incubator. Instead they will be placed in squat deli cups or tupperware pans filled with vermiculite, which are then in turn placed into the incubator. Vermiculite is an all natural product used in gardening. It is essentially heat expanded mica, a naturally occurring mineral. It is perfectly suited as an incubation medium due to its ability to hold nearly it's own weight in water, and it's natural resistance to mold and fungus.
There are alternatives to using vermiculite as an incubation medium. Some breeders use a similar product called perlite with excellent results. Others simply use damp soil or sand. In fact, there are now some commercially available products designed specifically for reptile use. However, vermiculite is by far the most popular choice, and remains a favorite of the author.
Optimally, the containers in which the eggs are placed should have ventilation holes and a snug lid. These features make controlling the humidity of the eggs much easier than having to manipulate the humidity within the entire incubator. The container should be half filled with vermiculite mixed with water until a specific consistency is reached. The vermiculite should clump when squeezed, but should not drip. This moisture level should be maintained throughout the incubation process.
Each egg should be individually placed into the vermiculite, approximately half buried. The thumb can be used to create depressions into which the eggs may be gently placed. Bearded dragon eggs will grow considerably during incubation, so avoid overcrowding the eggs or allowing any two eggs to touch.
The eggs should be monitored regularly until they hatch. Temperature within the incubator should be checked daily, and humidity levels once or twice a week. Condensation on the lids of the egg containers may be an indication of too much moisture. In this case, the lid should be removed for 24 hours to allow the vermiculite to dry out slightly. Conversely, if the eggs appear dimpled, or begin to collapse, they may be too dry. If this should occur, manually check the moisture level of the vermiculite, and if it seems overly dry, room temperature water may be carefully added to the vermiculite. Avoid getting the eggs themselves wet.
Healthy, fertilized bearded dragon eggs will turn chalk white as they incubate, and will grow up to twice their original size. These signs are good indicators that the eggs are viable and will produce healthy lizards. Yellow, green, or pink eggs that fail to grow may be infertile. However, it is recommended to allow them to incubate to term, just in case. Eggs should only be removed from incubation and discarded if they become moldy and pose a threat to other nearby, healthy eggs.
Incubation time will vary depending on a number of factors, including but not limited to temperature and humidity. Typically, bearded dragon eggs will take between 50 and 80 days to hatch, with 2 months being average.
24 to 48 hours prior to hatching, the eggs may begin to deflate. This should not be confused with a symptom of insufficient humidity. Rather, this is a signal to the keeper that hatching is imminent. During this time the eggs may appear to "sweat" with small droplets of moisture appearing on the egg surface. Again, this is normal.
Baby bearded dragons possess a small egg tooth on the tip of their snout that they will use to slice open the egg. Typically, a small slit appears, followed by the emergence of the lizards nose and head. Often times, neonate dragons will rest for up to a day with only their heads out.
It is recommended to allow the lizards to emerge on their own. Never pull or force a baby bearded dragon from it's egg. Healthy dragons will make it out on their own within 24 to 36 hours of the initial opening of the egg. Babies should remain in the incubator for 24 hours after completely emerging. This will allow time for them to adjust to our atmosphere, avoid temperature shock, and perhaps stimulate any remaining babies to hatch out.
Within a given clutch, most babies will emerge within a day or two of each other. However, in some cases a few days may pass between the hatching of the first and last dragon. Be patient, and allow at least a week before assuming that any neonates are dead within the egg.
Hatchlings should be set-up much like adult dragons. Moist paper towel is the substrate of choice during their first few weeks of life. The added moisture will prevent rapid dehydration of the tiny (4 inch) animals, as well as make it easier for them to move about and find food. They should be lightly misted once or twice a day with water to allow for drinking until they begin eating regularly.
Some newly hatched dragons will have a small amount of their umbilicus still showing. This pinkish mass, located where their belly button would be, is the remains of the lizard's link to the yolk within the egg. It should be completely absorbed after a day or two.
Bearded dragon hatchlings are often full of yolk when they hatch, and can thrive off of these nutritional reserves for up to a week. Begin offering food (tiny crickets, finely chopped greens) when the lizards are 2 or 3 days old. If they seem uninterested, the food should removed and reintroduced the next day. By a week of age, the young dragons should be going strong, and behave exactly like miniature versions of their parents.
Hatchlings may be housed communally, but they will require a lot of food to prevent tail and toe nips among siblings. They should be segregated by size and/or dominance if their appears to be problems. Larger animals should be removed to allow the smaller more submissive dragons to feed equally.
As long as all basic husbandry needs are met (proper heating, lighting, nutrition), the hatchlings will prove extremely hardy, and grow quickly.
It should be briefly noted that bearded dragons often lay two or three clutches of eggs during any given breeding season. This can occur even after a single successful mating due to the female's ability to store sperm.
To avoid health problems with female dragons, they must be carefully monitored after egg laying, and quickly nursed back to a healthy body weight prior to the arrival of the next set of eggs. Subsequent clutches are typically laid 4 to 6 weeks apart, and during that time, the females must be fed heavily, with special attention paid to foods high in caloric and calcium content.
While the general husbandry of Pogona vitticeps is beyond the scope of this article, they are, without a doubt, one of the easiest lizard species to maintain in a captive environment. As friendly and beautiful lizards, it is easy to see why they have skyrocketed to the forefront of American herpeteculture.
The goal of this article has bee to introduce the reader to the next logical step in bearded dragon keeping. While many simply keep these animals as pets, an equal number strive to reproduce them in captivity, for fun, profit, or both. With many new and exciting color and pattern morphs being produced annually, there is simply no telling what exciting changes bearded dragons breeders will see in the years to come.
The information provided herein is by no means intended to be the best or only way to breed these animals. As with many aspects of the hobby, there are many "right" ways to accomplish many things. However, the steps outlined above have proven successful for both the author and many other accomplished breeders of this species.