Breeding

The short version

• Do not breed a female under 45 g; most breeders prefer 50 g or more and at least 9–12 months of age [20][21].
• Females lay 2 eggs per clutch, every 15–22 days, for 4–5 months a season [20][21].
• Incubation temperature sets sex: about 80°F (26.7°C) gives females, about 90°F (32°C) gives males [20].
• Give every breeding female extra calcium and pull her from breeding if her weight or tail drops [20][22].
• Never breed Enigma or Lemon Frost morphs (see the Genetics and Morphs chapter).

Sexing

Leopard geckos are sexed by looking at the underside just in front of and behind the vent.

ReptiFiles sexes geckos by inspecting the areas just before and after the vent, and says geckos can usually be sexed once they reach about 5–6 in (13–15 cm) total length [19]. At normal growth rates that is roughly 4–6 months of age (breeder experience, not proven). Hatchlings and small juveniles cannot be sexed reliably by eye. A "pore line" on a 10 g baby is a guess.

Because incubation temperature sets sex (see Incubation below), "temp-sexed" in a listing means "probable," not "proven." Hobby reports say Mack Snow and Super Snow lines are harder to temp-sex than other morphs [26].

Maturity and breeding weight

The most repeated rule in leopard gecko breeding: do not breed a female under 45 g, and most breeders prefer 50 g or more.

• Ron Tremper writes that females are usually sexually mature at 45 g and 9–10 months of age, and that virgin females should be introduced to a male once they reach 45–55 g, or infertility may result [20].
• Leopard Gecko Wiki, a long-running hobby reference, gives at least 50 g for females and at least 45 g for males [21].
• Reptile Advisor repeats the 45 g minimum and gives the reason: females bred below that size are likely to lay infertile or non-viable eggs [22]. Breeders also link underweight females to egg binding (breeder experience, not proven).

The "45–50 g or more" rule is breeder experience, not proven by a published study. It holds up because making eggs pulls calcium and fat from the female's body, and a small or thin female has nothing to draw on.

Weight is not the only test. The female should also be:

• At least 9–12 months old. Tremper gives 9–10 months [20]; many breeders wait for her second spring (breeder experience, not proven).
• Carrying a full, firm tail, which shows good fat reserves.
• Free of mites, stuck shed and any history of impaction.

Males can breed a little smaller: Leopard Gecko Wiki sets the male minimum at 45 g [21]. A male much smaller than the female may struggle to hold and court her (breeder experience, not proven).

Cooling and cycling

Leopard geckos do not strictly need a winter cool-down to breed, but many breeders use one to bring females into sync and sharpen the male's interest.

Tremper's method [20]:

• Do not cool first-year females. They are still growing.
• Stop feeding 10 days before cooling so the gut is empty.
• Hold the geckos at 74–78°F (23–26°C) for six to eight weeks, with water available at all times.
• Warm back up gradually, resume feeding, and wait for females to regain condition before pairing.

In the Northern Hemisphere, the breeding season runs roughly January to September. Late-hatched females from the previous year may not lay until April [20].

Geckos kept at normal temperatures all year will still breed. Cooling mostly affects timing, not whether breeding happens (breeder experience, not proven).

Pairing, ratios and male aggression

Ratios. Tremper describes groups of three to five females sharing one lay box [20]. A common hobby setup is one male rotated through a group of three to five females, or a male introduced to one female at a time for a short visit (breeder experience, not proven). Never house two adult males together. They fight.

Courtship. The male vibrates or rattles his tail, approaches the female, and bites and holds the skin of her neck or flank while mating. Tremper writes that "a male restraining a female in this way is normal" [20]. Mating takes two to three minutes, and the female should be removed soon afterward [20]. Leopard Gecko Wiki agrees that biting is normal courtship, and notes that an unreceptive female will bite back, run or wave her tail [21].

Watch for injuries. Courtship bites look alarming and can break the skin. Check the female after each pairing. Separate a male that chases relentlessly, bites hard enough to draw blood, or will not let go. Reptile Advisor strongly recommends against keeping leopard geckos together for long periods, including breeding pairs [22].

After mating, the male cleans his hemipenis for up to 10 minutes; do not disturb him. If it does not go back in, it may be a prolapse and needs a vet [21].

Re-pairing. If the pair is kept apart, Leopard Gecko Wiki recommends reintroducing the male once every two to three clutches to keep fertility up [21]. Females can store sperm and often lay several fertile clutches from one mating (breeder experience, not proven).

Gravid signs

A gravid (egg-carrying) female shows:

• Two pale, oval shapes through the belly skin when held gently belly-up. They sit low in the belly and look like two white grapes side by side.
• A swollen lower belly.
• Less appetite a few days before laying.
• Digging and restlessness, especially in the lay box corner.

These signs are standard breeder practice. Eggs are laid 16–22 days after mating, according to Tremper [20]. Leopard Gecko Wiki gives a wider two-to-five-week window, and warns that if eggs are not laid within that time, the female may be egg-bound and a reptile vet should be contacted [21].

The lay box

A female without a damp, enclosed place to dig will often hold her eggs too long, scatter them to dry out, or lay them in the water dish.

Tremper's specification [20]:

• At least 6–7 in (15–18 cm) across and 4 in (10 cm) tall. A plastic shoebox works for a group of three to five females.
• A 2 in (5 cm) hole cut in the lid.
• Filled with peat moss, vermiculite or coconut fiber, kept moist but not wet.

Reptile Advisor gives the same design, filled with several inches of slightly damp potting soil or vermiculite, and says to add it within about a week of the first pairing [22].

Check the box daily during the season. Eggs left in a warm lay box for days start developing at whatever temperature the box happens to be, which takes sex control out of your hands (see Incubation).

Clutch size and clutches per season

The references do not state clutches per season outright. Working from Tremper's figures (one clutch every 15–22 days over four to five months), a mature female produces roughly 6–10 clutches a season, or 12–20 eggs, with first-year females at the low end. That is our arithmetic, not the source's, and Reptile Advisor's 8–10 eggs a season [22] suggests many females land lower.

First-time females are less productive than proven breeders [21], and breeders report they lay more infertile ("slug") eggs (breeder experience, not proven). Infertile eggs are yellowish, soft and often dented. Fertile eggs are white, firm and chalky.

Incubation

Medium and moisture

Tremper's method [20]:

• Vermiculite or perlite, 1–2 in (2.5–5 cm) deep.
• Mix equal parts medium and water by weight, not by volume.
• Set the eggs at least 0.5 in (1.3 cm) apart. Most breeders bury them about halfway and keep them in the position they were found in, without rotating (breeder experience, not proven).
• Use a container with a tight lid and five to ten pin-sized air holes.
• If eggs dent, the medium is too dry. Spray the inside walls of the container four or five times, never the eggs.

Many breeders now set eggs on a plastic tray above damp medium so they never touch water. This is a method choice, not a correction (breeder experience, not proven). Humidity in a sealed tub runs near saturation, which is what the eggs want.

Time to hatch

Tremper gives 35–89 days depending on temperature [20]. Reptile Advisor gives one to three months, faster at warmer settings [22]. Expect about 35–45 days at male-producing temperatures and 55–70 days at female-producing temperatures, with extremes beyond that (breeder experience, not proven, within the range in [20]).

Temperature sets sex

Leopard geckos have no sex chromosomes that decide sex. Incubation temperature does. This is one of the best-studied temperature-dependent sex systems in lizards.

A 2026 Tokyo University of Science study found that 79.7°F (26.5°C) produced 100% females and 88.7°F (31.5°C) produced 91% males. It also found that sex could still be switched by moving eggs between temperatures until a late embryonic stage, after which it was fixed [24].

The practical lesson: the first few weeks of incubation decide sex, so a warm lay box or a wobbly incubator early on can give you males when you wanted females. Keep the incubator steady. Breeders link swings of a few degrees to mixed-sex and deformed clutches (breeder experience, not proven).

"Hot females"

Females hatched at male-producing temperatures (around 90.5°F, 32.5°C) behave differently from females hatched at 78.8°F (26°C). Flores and Crews (1995) found that females from the male-biased temperature were more likely to be aggressive, and the difference held even after hormone treatment [25].

In the hobby these are called "hot females." They tend to have larger heads, be more aggressive toward cage-mates and sometimes toward males, and can be less willing to breed. The aggression finding is from [25]; the breeding part is breeder experience, not proven. If a batch of "males" from a hot incubator includes a female, house her alone and do not count on her as a breeder.

Hatchling care, first shed and first feed

• Leave the hatchling in the incubator tub for a few hours until it is fully out and active, then move it to a small nursery tub.
• Tremper keeps hatchlings in a 12 x 6 x 4 in (30 x 15 x 10 cm) shoebox setup, with the hide end near 90°F (32°C) and the cool end at 73°F (23°C), until they reach about 7 in (18 cm) [20]. Reptile Advisor runs a nursery at about 80°F (27°C) with slightly higher humidity than for adults [22]. Either works. What matters is a warm side, a cool side, a humid hide and paper towel on the floor.
• First shed comes after about the first three days according to Tremper [20], or around one week according to Reptile Advisor [22]. Hatchlings eat their shed. A humid hide prevents stuck shed on toes and eyes.
• First feed comes after the first shed. Tremper offers five to ten 1 in (2.5 cm) mealworms in a jar lid every other day [20]; Reptile Advisor uses very small crickets [22]. Do not panic if a hatchling refuses food for the first week; its yolk reserve covers it.
• Keep hatchlings singly or in small, size-matched groups. Tail nipping is common.
• Weigh weekly. Sources disagree on starting weight: LafeberVet gives 6–8 g for hatchlings [1], while breeders often report 3–4 g (breeder experience, not proven).

Calcium for breeding females

Every eggshell is built from the female's calcium. A female laying 12–20 eggs a season can strip her own bones if her intake does not keep up. The first signs are a shrinking tail, a soft jaw, tremors and lethargy.

• Tremper offers extra calcium with vitamin D3 loose in a jar lid in a corner of the enclosure, rather than dusting feeders, so the gecko can take what she needs [20]. We do not recommend a free-choice dish of D3 calcium: a gecko that licks it often on top of dusted feeders can take in too much D3, so keep the loose dish to plain calcium.
• Leopard Gecko Wiki recommends dusting feeders with calcium and gut-loading insects to support egg production and prevent metabolic bone disease in laying females [21].
• Reptile Advisor gives calcium during conditioning and keeps a dish of plain calcium available at all times after each clutch [22].

What we recommend: dusted feeders plus a dish of plain calcium (no D3) in every breeding female's enclosure, a D3 product on a set schedule, and pulling any female whose weight drops below about 45 g or whose tail thins. Separate her from the male; she will lay what she is carrying and stop.

Egg binding (dystocia) is the emergency to watch for. A female visibly carrying eggs well past five weeks, straining, or off food for more than a few days needs a reptile vet [21]. Low calcium is one of the common contributors (breeder experience, not proven).

Retirement

None of the references gives a retirement age. Most breeders retire females around 6–8 years, or earlier if they stop regaining weight between seasons or lay mostly infertile eggs (breeder experience, not proven). A retired female often lives another 8–12 years as a pet.

A female with a hard season, such as weight loss, an egg-binding scare, or more than about 10 clutches, should sit out the next season.

How many babies to expect

Hatch rates for fertile eggs in a steady incubator are usually 80–90% (breeder experience, not proven). Planning on about 10 healthy hatchlings per proven female per year is conservative and realistic. Make sure you have homes lined up before you pair.