Gecko Reproduction

Geckos, lovely to look at and fun to watch, are cold-blooded critters you can really warm up to. Of the species widely available in pet stores, leopard geckos are among the most popular for their hardiness, their docility and the variety of patterns and colors they come in. After their habitat is in order, these low-maintenance lizards and their cousins, including crested and tokay geckos, don't need much more from their human families than feeding and routine care. To the uninitiated, some of their breeding habits can look a little brutal.

Geckos have some intriguing reproductive habits. The majority of more than 2,000 identified species reproduce by laying eggs, say Richard D. Bartlett and Patricia Pope Bartlett, authors of the book "Geckos." However, one subfamily native to New Zealand bear live young, and several species, including the Indo-Pacific and mourning geckos, generate fertilized eggs with no help from males, although all offspring are genetic clones of their mothers. Female crested, tokay and leopard geckos can lay eggs without fertilization, but they will be infertile. Leopard geckos are considered fairly easy to breed. Often, all you need for success is a healthy male and female pair.

You might not be able to spot gender differences in very young geckos but, by the age of about 9 months, you should see two bulges at the base of the tail behind the vent on the undersides of a male but only one on a female. Males tend to be larger and have broader heads. A single male gecko can live together in the same habitat with females. But, if given the chance, two males will fight to the death. Even before genitals are mature enough to confirm gender, if two geckos are vibrating their tails and biting at each other, they're probably males and should be separated immediately.

Sacramento herpetologist and leopard gecko breeder Steve Sykes advises exercising caution when putting male and female geckos together for breeding purposes. Males grow faster and get heavier than females, but both geckos should weigh at least 45 grams before reproducing, he says. Even though females may be physically capable of laying eggs at weights of 25 to 30 grams, allowing them to breed at that weight "is often too stressful and can cause health problems, in addition to reducing the female's lifetime reproductive potential," Sykes says.

When a male is placed into a habitat with female, he springs into reproductive overdrive almost immediately, writes leopard gecko breeding expert Ron Tremper in "Reptiles" magazine. The tip of his tail vibrates rapidly, making a rattling sound that sends a message to all males within earshot to stay away and to females that he's ready for romance. But what comes next doesn't look very romantic. While the female stands still, the male starts biting her, working his way up from her tail. When he reaches her neck, he grasps the skin in his mouth, mounts her and, two or three minutes later, it's all over. After that, the female should be separated from the male, Tremper advises.

If mating has been successful, expect to see eggs 16 to 22 days later. From that point, if you're hoping for baby geckos, the temperature of incubation will determine their sex, Tremper says. All hatchlings from eggs incubated at 80 degrees Fahrenheit will be female. If you incubate the eggs at around 87 degrees, you'll get a more equal gender distribution. At 90 degrees, 98 percent of the hatchlings will be male. If you allow the temperature to fall below 74 degrees, though, the eggs might not hatch at all. Typically, female leopard geckos lay two eggs at a time every 15 to 22 days over a four to five-month breeding season. Depending upon incubation temperature, they'll start hatching in 35 to 89 days.