Breeding Leopard Geckos
We get asked countless questions regarding Leopard Gecko breeding and egg incubation. This article will explain how we do it, using methods we've developed at VMS over the last twenty-plus years. Some articles may differ from the methodology presented here, and some may view it as overly simplified. Remember, Leopard Geckos have been breeding in the wild for thousands of years without our help - they'll do it just fine in our cages, no need to make it harder than it is!
Do you really want to breed your Leopard Gecko?
This seemingly simple question is often never considered by the novice. There are several reasons to consider NOT breeding your Leopard Geckos!
First, do you have a market for the offspring once they have been produced? Leopard Geckos can be very prolific. If you don't have a place to sell them, you can quickly tire of feeding all those little mouths and then cleaning up after all those little...well you get the idea.
Second, do you have adequate food supplies and caging for the offspring? A typical Leopard Gecko will produce around a dozen pairs of eggs each season, a total of about two dozen offspring. We've had as many as 20 pairs of eggs from particularly prolific females. That's a lot of babies, all needing their own little cages and gazillions of crickets!
Third, are you willing to risk the life of your Leopard Gecko? Breeding your Leopard Gecko is not without risks. Dystocia (commonly known as egg-binding) is fairly common and poses serious health risks that may require expensive veterinary services. More common is the incredible drain on body resources that egg production places on the female. If not in perfect health, a female can become severely weakened and may succumb to renal failure or disease.
I'm not trying to tell you not to breed your Leopard Geckos, just making sure you are aware of a few of the problems associated with it. If you still want to breed them, read on!
Are your geckos properly sexed?
This seemingly simple question is often overlooked by the novice. They simply take whatever the pet store says to them and consider it correct. Well, it may not be correct! Nine times out of ten when I am questioned by someone unable to breed Leopard geckos, it turns out they have two females. Females may 'cycle' and begin to produce eggs without a male present if conditions are right. This can lead the beginner to believe he or she is incapable of incubating eggs correctly, despite all attempts.
It can be very difficult to sex juvenile Leopard geckos accurately. Most often, they are sold as 'unsexed' meaning the breeder cannot tell, or as 'temperature sexed'. 'Temperature sexed' refers to geckos which hatched from eggs incubated at temperatures known to produce primarily a given sex. This is not a guarantee they will be sexed correctly, however. You still must mature them and verify the sexes visually.
Visual sexing cannot take place accurately until the gecko is about two-thirds grown, usually at about five months of age. This will vary a bit, based on individual growth rate.
A male Leopard Gecko
Figure 1: a male Leopard Gecko
Here's a snapshot of the relevant parts of a mature male Leopard Gecko (Fig. 1). Notice the well developed row of pre-anal pores, hi-lighted here in blue. Under magnification, these pores can be seen as open holes, often capped with a waxy build-up. Sexually mature specimens will exude a waxy substance from these pores which is smeared about the cage. This is a form of scent marking. Many beginners think their gecko is being cute 'wagging his butt all over the cage'. In reality, he is staking out his territory.
Do NOT put another male in with a mature male. They will fight violently, often to the death.
The real giveaway in males is the presence of the two enlarged 'hemipene bulges' at the base of the tail, hi-lighted here in red. If these are evident on your gecko, it is without doubt a male. Juveniles of both sexes will often show a bulge in this area, but it is not neatly divided in two as shown here.
A female Leopard Gecko
Figure 2: a female Leopard Gecko
Here's a snapshot of the important parts of a mature female Leopard Gecko (Fig. 2). Many females will show poorly developed pits in the same location as the pre-anal pores of the male, or sometimes an enlarged row of scales, hi-lighted here in blue. Under magnification, these can be seen to be simple dents or pits in the scales, not true hollow pores, and they'll never have the waxy substance found on males. Many beginners mistake these for the pores of males. Many females also have very slight bulges in the same location as the 'hemipene bulges' as the male, hi-lighted here in red. However, they are never anywhere near as well-defined as those of a male.
It can be very difficult to accurately sex juveniles, ranging from impossible at birth to more and more educated guesses as they grow. Usually, the males will show with absolute certainty at around four months of age (if growing well). Note that this can vary a bit, and a specimen should not be considered female with certainty until about six to eight months of age, when any hope of it's being male can be ruled out safely. To sum up: if a young gecko is obviously male then OK, but if it's not obvious it could be either a female or a male waiting to finish developing. Years of experience sexing hundreds of juveniles each year is a definite plus....
We get a gazillion questions on this subject. Temperature cycling is a critical part of breeding most reptiles. Most will not breed unless rather exact parameters are met. Fortunately, temperature cycling is not very important in breeding Leopard Geckos. We do not provide any special changes in temperature in our colonies. However, in most temperate climates (this means most of the US) a natural drop in temperature will occur in the home during winter. If it didn't, the furnace industry would not exist. This is usually more than adequate to cycle your Leopard geckos and nothing special need be done if you are just providing an undertank heat source of some type to a cage located in a typical living room. The natural drop in ambient air temperature during winter will be sufficient.
Light cycling (photoperiod)
Here's another one we get a lot of questions about. These nocturnal animals may be somewhat affected by shortening photoperiods, but it's more likely that slight temperature changes are what really triggers reproductive cycles. For years, we bred these geckos in rooms with the only available light coming from a small basement window. This proved sufficient to trigger reproductive behavior (if that's what was triggering it). In later years, we've provided artificial light controlled by timers. Changes to settings of the timers has not seemed to make any difference at all in our colonies' reproductive behavior.
Mating can be a somewhat violent affair in geckos, and we get many questions about separation of the sexes as a result. At VMS, we have NEVER separated the sexes at any time. We maintain our colonies in groups of one male and up to five females together year-round with few problems. In fact, we believe most of these aggression problems occur when the geckos are first introduced. So separating them and periodically re-introducing them may actually make the situation endlessly repeat itself!
Usually, when a male is confronted by a female ready to breed, he will begin to stalk her. He may rapidly vibrate his tail, or begin waving it about and scent marking. He'll slowly get near and will then bite the female, often at the base of the tail. He'll then take rapid nips, moving forward a little with each bite in hopes of achieving a neck hold on the back or side of the neck.
If the female accepts him, he'll curl his tail under that of the female and copulation will take place. This usually lasts a very short time, and the male can usually be seen cleaning himself immediately after they separate. While I'm not sure how she does it, sometimes a female will reject the male. Usually the male understands this 'NO' signal and releases the female. Don't worry if this happens, he'll try again later and eventually she will be ready. In fact, he'll mate with the female several times during the breeding season, fertilizing many sets of eggs.
Many sets of eggs? How can I tell when my gecko is gravid?
That's correct. These geckos produce eggs many times during one breeding season. Usually they are laid two at a time, although a single egg is often produced at the beginning or end of the reproductive cycle. Each clutch will be laid at approximate three week intervals, although this can vary a bit based on conditions. The average female will lay about seven or eight pairs, although we've had females that produced eleven pairs in a single season!
In most US collections, mating and egg-laying will begin in February or March and continue through July or August. Please note that this may vary a bit based on your particular conditions. Timing of the breeding season may also vary a bit based on the particular strain you are working with, and the timing used by the breeder who produced them. Geckos produced 'off-season' tend to try to reproduce 'off-season' as well.
Figure 3: eggs very early in development
Here is a female Leopard gecko just starting to develop eggs (Fig. 3). We've circled them in red, so you know where to look. At this early stage, the eggs are spherical and just under 1/2 inch in diameter. Gently bending the gecko backwards will push the eggs towards the thin belly skin, where they are easily seen. The eggs are surrounded by the pink glow of blood vessels nourishing the developing egg.
Eggs are always located at the positions shown, but other white materials may also be present further down in the belly. We have hi-lighted this material in blue. This can include whitish urates (the white parts of gecko poop) and calcium or eggshell (being stored for use in eggshell-production). While this sort of material can be present year round, remembering the location of the eggs shown here will help you to determine when you are actually seeing eggs.
Figure 4: eggs later in development
Here is another female, with a more developed pair of eggs (Fig. 4). The eggs are still in the same locations, and the eggs are now much larger and elliptical in shape. They are nearly an inch long, and she will lay them soon!
Provide a good laying site
Figure 5: a female in the laying cup
We utilize a standard 16oz deli cup as a combination moist hide area and laying site. A hole large enough to permit access by the geckos is cut in the top or side. The cups are filled with lightly dampened sphagnum moss. Our gravid females always select them as their egg-laying site. On very rare occasions, eggs have been laid on the floor of the cage, but these have almost always proven infertile.
Here you can see a Blazing Blizzard Leopard Gecko just finishing laying her eggs (Fig. 5). In most cases, the female will burrow down and lay the eggs on the bottom of the cup. After she finishes, she will spend a bit of time pulling all the moss back over the eggs to cover them. Some females will spend a great amount of time using the back feet to rotate the eggs. We believe this is an effort to get bits of lay site medium to adhere all over the surfaces of the egg - providing camouflage.
Removing the eggs
Figure 6: a freshly laid Leopard Gecko egg
Here we've pulled back the sphagnum moss to reveal an egg (Fig. 6). This one has been laid against the side of the cup. Since it's smooth plastic, the eggs do not adhere well to the surface and may simply be pulled off if they should stick a bit.
Be sure to maintain the orientation of the egg, keeping the top surface up. We sometimes mark the top lightly with a sharpie marker or soft lead pencil to help keep track of which way is up. Within a few hours of laying, the embryo will adhere to the inner wall surface of the shell - placing the egg upside down after this time will cause the embryo to die.
A healthy egg
Figure 7: a typical fertile Leopard Gecko egg
We rarely have any problems incubating eggs, provided they are healthy to begin with. Here's a pretty typical fertile egg (Fig. 7). It's about an inch long, has a good solid heft or weight to it and feels dry and firm. Small particles of sphagnum moss adhere to the surface.
Eggs which feel very soft or are wet to the touch are most likely infertile. But don't discard them yet, there's always a chance they are good! Set them up for incubation and check them at a later date by 'candling' them. We'll show you how to do this farther down in this page.
This is the number one subject of inquiry for us. Yet it is really the simplest thing in the world to do! After all, Leopard geckos have been doing it out in the uncontrolled wild places for thousands of years. So why should it be hard inside your nice climate controlled house?
We have used a plain vermiculite medium for almost thirty years now, and it has worked well for us. I know there's a thousand formulas out there for water/vermiculite ratios. Believe it or not, we've NEVER weighed or measured it at all! We use a simple method: Mix a bucket of vermiculite with water trickling from your tap, stirring as you go. Stop frequently and stir it all up well. Try making a snowball out of it. If it packs nicely into a snowball, giving just a drop of water when squeezed hard in your fist, that's it. The snowball should fall apart easily, with just a touch of your finger tip. If it's more like a solid mudball, you've got things way too wet. It's best to err on the side of being too dry - most beginners tend to make things too moist.
Figure 8: incubating Leopard Gecko eggs
We place about a two inch layer into the bottom of a plastic shoebox, as shown here (Fig. 8) or 16 oz deli cup for just a pair or two. Embed the eggs (right side up) into the medium about half way. Put on the lid and stick it in your incubator. Leopard Gecko eggs will hatch at any temperature (even fluctuating) from 77 to 92 degrees Fahrenheit. If you don't have an incubator, you can just put the deli cup in a corner of your cage as long as the temps are within this range. Put a rock on it to keep the adults from knocking it over or pushing it around.
You don't need to put air holes in the cup, that just lets out all the moisture you so carefully measured. We open the lid about once week for inspection and blow a little puff of air in. This provides plenty of oxygen for the developing embryos. Any bad eggs are disposed of promptly if they show signs of bacteria or fungus.
By the way, all of this should be done BEFORE your gecko lays her eggs. This will allow you to get everything ready before a developing baby gecko needs it!
Oh, and about that 'temperature sexing' thing, if you want females - stay near the bottom of that range. If you want males, incubate at 90 or over. In between, you'll get a mix!
Now for the hard part of the process....waiting almost two months (exact time varies with temperature).
How to 'candle' an egg.
Figure 9: candling a typical fertile Leopard Gecko egg
Candling refers to the process of illuminating the contents of an egg. It's a relatively simple process. Here we are using a commercially available egg-candler, but a small penlight type flashlight will suffice. This can be done on eggs from about two to four weeks of age. A few tips: Keep the egg in it's normal upright position and don't overheat it with the light bulb! A few seconds is long enough to see what you need. So if you just can't stand it, you can have a look inside...
A healthy egg will glow a rosy pink, as you see here (Fig. 9). The presence of blood vessels developing under the surface of the egg (arrow) is a sure sign that the egg contains an embryo. It's busily developing these veins to carry nutrients from inside the egg to inside it's rapidly developing body! An infertile egg will usually be a yellowish color, or may be nearly solid looking dark inside if it has begun to decompose. Don't confuse this with an older egg which is filled with a developing baby! The egg must be young for candling to work.
Figure 10: hatching Leopard Gecko eggs
You don't have to do a thing. They know how. If you are lucky, you'll get to see it (Fig. 10) - but most times you look in and nothing. An hour later, you look again and two babies are running around in there. Pretty cool stuff.
We setup fresh babies in simple shoebox style cages (see our How to Keep Leopard Geckos page) and don't bother feeding them for three to four days until they have shed their first skins. After that, it's a few 1/3 grown crickets and within a couple weeks you have strong and fat little geckos!