For many hobbyists, the successful captive breeding of a lizard species is a hallmark of good husbandry. If the lizards are comfortable enough in their surroundings to breed, it indicates that the artificial environment provided is acceptable. In order for this to happen, you have to take care of as many variables as possible. Here are some points to cover:
Know What Your Lizards Need
The artificial environment needs to be large enough, and you'll need to provide at least one hiding area per lizard. You'll need to offer about the same humidity as the homeland of the lizard, so you'll need to find out where your lizards are from.
You wouldn't expect leopard geckos, an aridland species, to feed, much less thrive, if kept in a rainforest environment. But simplify the caging to something leopard geckos are accustomed to - offer a sand/gravel substrate, hiding areas, a shallow water dish that won't add much humidity to the cage - and chances are good that leopard geckos will breed several times annually.
Don't Keep Too Many Lizards in One Cage
In the wild, male lizards stake out their home turf and defend it from other males. When the home turf is as small as a 30-gallon terrarium (or smaller), having just one male per cage becomes even more important. The "turf" issue doesn't seem to arise when you keep more than a single female in a cage; in fact, most lizards do well when kept in trios of one male and two females. With chameleons, you not only have to provide separate caging, but male chameleons of many species should not be allowed to see each other.
Provide Day/Night Cycles
Day/night cycles are also called the photoperiod. These should equate with the breeding cycle in the lizard's area of origin. Some lizard species, like leopard geckos, have been bred in captivity for so many generations that captive breeding takes no special provisions, other than to provide good food, semi-arid housing and both sexes.
Other lizards, particularly those that have been taken from the wild, require at least one year of adjustment to a change in light cycles and the confines of captivity. For example, blue-tongued skinks from Australia/New Guinea (the southern hemisphere) are habituated to hot weather and longer days from November through April. It takes a full year, maybe more, before their circadian rhythms adjust to a reversed cycle of the northern hemisphere.
For most of us, it's simply easier to provide a natural photoperiod and wait for the lizards to adapt than it is to change over the lighting and heat cycles for a single cage or two.
In a nutshell, most lizards breed in the early spring. In North America, the young are generally born or hatched at the beginning of the summer (although many lizards will produce several clutches at intervals throughout the summer), and have two to four months to feed and grow before cooler weather slows down lizard movement and curtails the food supply.
What To Do If They Don't Breed
So what happens if you have a pair of lizards and you've done everything right – but so far there's no breeding? What else can you try? Separate the lizards. Many breeders keep the sexes separate until breeding is desired. Then the sexes are placed together for a week or so or until breeding takes place. Afterward they are again separated.
The addition of a second male to the cage may also create breeding displays between the males, which tends to arouse breeding interest in the female as well.
You may need to provide a period of dormancy/hibernation for lizards that hibernate, such as the collared or leopard lizards. In the fall, or in October or November, decrease cage temperatures and lighting levels for 60 to 90 days but continue to provide fresh water.
Cage temperatures should be about 55 degrees Fahrenheit or 16 degrees Celsius.
If you're unsure of what your lizards need in dormancy length, begin with three weeks to avoid putting too much stress on them (or on their keeper). At the end of the dormancy period, restore lighting and temperature levels and offer food. After the lizards have regained their former activity levels, put the sexes together.
After Your Lizards Breed
Once your lizards have bred, for the egg-laying species, provide an egg
deposition site. A margarine tub, with a layer of damped sphagnum moss and an access hole cut in the lid, is one choice. Incubate the eggs at 80 to 84 degrees, making sure that the sphagnum under the eggs is kept moist (One exception - and there are always exceptions - are eggs from Phelsuma, the day geckos. Their eggs decay if kept on damp substrate, so keep the substrate dry for them).
Most lizard eggs hatch in about 55 days. For live-bearing lizards, like the night lizards or blue-tongued skinks, provide a secluded area where the female can give birth to her young without fear of predation by another lizard. (Most lizards aren't too picky about what tiny animals they consume.) Female may become very aggressive toward cagemates and their keeper before, during and after partuition. Make certain you have an adequate supply of tiny insects available when the young are born or emerge from their eggs. You can buy hatchling crickets and wingless fruit flies from cricket supply houses, but your delivery date will be at least one day, maybe longer, after you order. Some pet stores stock fly-sized crickets, which may be large enough for some of the insectivorous lizards. Provide a variety of insects for the babies.