Most geckos lay small, white, oval eggs in hidden crevices, bark gaps, rock fissures, or gaps behind human-made structures, and the eggs themselves range from soft and leathery to hard and calcified depending on the species. A typical gecko clutch is just one or two eggs, far fewer than most other lizards. The details vary in fascinating ways across the roughly 2,000 gecko species worldwide, from the tropical house geckos tucking eggs behind picture frames to New Zealand species that skip egg-laying entirely and give live birth.
What Gecko Eggs Look Like
Gecko eggs come in two distinct types, and which one you encounter depends on the species. The majority of geckos produce parchment-shelled eggs, which are soft, flexible, and leathery when first laid. These eggs look somewhat translucent and feel rubbery, and they absorb moisture from the surrounding environment as the embryo develops, swelling noticeably over the incubation period. They resemble tiny deflated beads when fresh and become plumper as they take on water.
One large group of geckos does something different. Species in genera like Hemidactylus (house geckos), Lepidodactylus, and Gekko produce rigid, calcified eggshells that are white, brittle, and hard to the touch. These look more like miniature bird eggs than typical reptile eggs. The shell is mineralized with calcium carbonate, giving it that distinctive chalky hardness. Researchers have shown that this rigid shell is an example of convergent evolution, where geckos arrived at hard shells independently from birds and other archosaurs through a completely different developmental pathway.1PLOS ONE. A comparative study of eggshells of Gekkota with morphological, chemical compositional and crystallographic approaches and its evolutionary implications
Size varies with the gecko. A Mediterranean house gecko egg might be about the size of a jellybean, while a tokay gecko egg can be closer to the size of a large grape. The eggs are usually pure white or off-white, and hard-shelled eggs sometimes appear slightly glossy when freshly laid. Over time, hard-shelled eggs may develop a slightly chalky texture as the outer surface dries.
Where Geckos Choose to Lay
Geckos are particular about laying sites, but the specifics they care about are not always what you would guess. The most consistent preference across species is for enclosed, sheltered spaces. In the wild, this means rock crevices, spaces behind loose bark, hollow tree limbs, and gaps in leaf litter. Arboreal species that live in forests are especially dependent on finding suitable cavities in trees and branches, and the availability of these microhabitats can actually be the main factor limiting how large a gecko population can grow in a given area.2PubMed. How habitat disturbance benefits geckos: Conservation implications
In human environments, geckos adapt readily. House geckos lay eggs behind wall hangings, inside electrical boxes, beneath roof tiles, in cracks in masonry, and in gaps behind furniture. A study of invasive house geckos found that the width of the cavity opening, height above the ground, and even temperature variation inside the hiding spot did not strongly influence which sites the geckos preferred. The factor that did matter was humidity stability: cavities where humidity stayed more consistent were used more often for egg-laying.3Biotropica. Low Requirement on the Nest Site Selection Influencing the Invasion Success of House Geckos This flexibility in everything except moisture conditions helps explain why house geckos have been so successful as invasive species around the world. They do not need a perfect spot. They just need a sheltered one that stays reasonably humid.
Hard-shelled egg layers have an additional advantage here. Because their eggs lose very little water to evaporation, rigid-shelled species can use drier nesting spots that would be fatal for species with parchment-shelled eggs. Research on Hemidactylus and Lepidodactylus eggs showed that hard-shelled gecko eggs have extremely low rates of water loss in dry air, with water vapor conductance values actually lower than those predicted for bird eggs of the same size.4Journal of Experimental Zoology. Low water vapor conductance of hard‐shelled eggs of the gecko lizards Hemidactylus and Lepidodactylus Normal embryo development in these species does not require absorbing liquid water from the environment at all, which means females can lay in sites that might seem too dry for reptile eggs.
Why Geckos Only Lay One or Two Eggs
If you find a gecko nest, you will almost certainly count either one or two eggs. This is not a coincidence or a sign that the gecko was interrupted. Geckos have an essentially fixed clutch size, which is unusual among reptiles. Most lizards and snakes vary their clutch sizes considerably based on body size, food availability, and age, but geckos are locked into this one-or-two pattern.5PubMed. One or two eggs: what underlies clutch size variation within a gecko species?
Instead of adjusting how many eggs they lay, geckos modify their reproductive output in other ways. A well-fed female in good condition may lay multiple clutches per season rather than one large clutch. She can also invest more resources per egg, producing larger eggs with bigger hatchlings. Some gecko species do show variation between one-egg and two-egg clutches, and research on these species found something interesting: eggs from single-egg clutches were similar in size to individual eggs from two-egg clutches, but the hatchlings from single-egg clutches actually had lower body condition than those from two-egg clutches.5PubMed. One or two eggs: what underlies clutch size variation within a gecko species? In other words, laying just one egg does not seem to give that single offspring an extra advantage in size or health.
Part of the reason for this tight clutch-size constraint is anatomy. Gecko females produce eggs in alternating ovaries and are physically built for a one-or-two-egg payload. Species that lay hard-shelled eggs face an additional constraint: the eggs are rigid and cannot deform during passage through the oviduct, which limits how large or numerous they can be.
How Females Build an Egg
Producing a calcified eggshell requires a substantial amount of calcium, and geckos have a specialized system for stockpiling it. Many gecko species use their endolymphatic sacs, small structures near the inner ear, as calcium reservoirs. These sacs fill with calcium carbonate crystals during the early reproductive phase, appearing as visible white deposits on the sides of the neck in some smaller species. As the egg develops and the shell mineralizes, those calcium stores get depleted. Research on a Caribbean gecko species confirmed this pattern: females had larger endolymphatic sacs than males, and females without visible developing eggs had more calcium stored than those actively forming eggs.6Bulletin of the Peabody Museum of Natural History. Endolymphatic Sac Use and Reproductive Activity in the Lesser Antilles Endemic Gecko Gonatodes antillensis (Gekkota: Sphaerodactylidae)
If you keep geckos and notice chalky white patches on the neck of a female, that is not a disease. It is calcium being stored for egg production. In captive geckos, calcium supplementation in the diet becomes especially important for breeding females because of this demand. A female who cannot build up adequate calcium stores may produce eggs with thin, fragile shells or resorb eggs entirely.
Incubation and How Temperature Shapes Hatchlings
Gecko eggs incubate for anywhere from about 45 to over 100 days depending on species and temperature. The mother provides no parental care after laying in most species; she deposits the eggs and leaves, and the environment does the rest. For hard-shelled species, females sometimes glue eggs to surfaces, meaning you cannot remove them without cracking the shell. Parchment-shelled eggs are not adhered and can be gently moved, which matters for captive breeders who incubate eggs in controlled settings.
Temperature during incubation has a surprisingly large effect on how hatchlings turn out. A study on Woodworthia maculata geckos compared eggs incubated at warmer versus cooler temperatures. Eggs in the warm treatment hatched about 15 days earlier, but hatchlings from the cooler treatment were larger, longer-tailed, and heavier.7PubMed Central. Consequences of Oviposition Site Choice for Geckos in Changing Environments Hatch success was similar between treatments, with about 69% hatching in the warm group and about 71% in the cool group. So cooler incubation does not kill the embryos; it produces bigger but slower-developing babies.
This trade-off has real ecological consequences. In a warming climate, gecko eggs in sun-exposed nesting sites may hatch faster but produce smaller offspring. Whether those smaller hatchlings survive as well as their larger, cool-incubated counterparts is an open question that researchers are still investigating.
The Hard Shell Advantage
One of the more interesting findings in gecko egg biology is just how much the rigid shell helps in certain environments. Research on the barking gecko Chondrodactylus turneri, a hard-shelled species, showed survival above 90% when eggs were incubated under dry conditions. In contrast, the same eggs incubated under high-moisture conditions fared poorly, and so did parchment-shelled leopard gecko eggs under the same wet conditions. The main killer in both cases was fungal infection, which thrives when humidity is high.8PubMed. Rigid shells enhance survival of gekkotan eggs
The rigid shell essentially makes survival independent of environmental moisture. The egg does not need external water to develop, and it resists fungal colonization because there is no soft, moist surface for fungi to exploit. Researchers have also suggested that hard shells may protect eggs from small invertebrate predators that could puncture a softer egg.8PubMed. Rigid shells enhance survival of gekkotan eggs This helps explain why hard-shelled gecko species dominate in arid and semi-arid habitats, and why they thrive in the dry crevices of human buildings.
The trade-off cuts both ways, though. A rigid-shelled egg that gets exposed to standing water or a very wet microhabitat is in trouble. Experiments showed that Chondrodactylus turneri eggs lost about 14% of their mass over a 68-day incubation at moderate humidity, with water loss occurring in a characteristic pattern: rapid at first, slow and steady in the middle, and rapid again toward the end as the shell structure changed during embryo growth.9PubMed. Water vapor permeability of the rigid-shelled gecko egg The shells are designed to slowly lose moisture, not gain it. Too much external water disrupts that balance.
Temperature and Sex in Leopard Geckos
Leopard geckos are among the best-studied geckos in captivity, and they have a reproductive quirk that surprises many keepers: incubation temperature determines whether hatchlings become male or female. At around 26°C, essentially all hatchlings are female. At 32.5°C, about 75% are male. And at 34°C, the ratio flips back to predominantly female, around 95%.10Physiology & Behavior. Incubation temperature affects the behavior of adult leopard geckos (Eublepharis macularius) This temperature-dependent sex determination (TSD) means that breeders can influence the sex ratio of their hatchlings simply by adjusting their incubator.
The mechanism works through differential gene expression during a critical window of embryonic development. Research on leopard gecko embryos incubated at female-producing (26°C) and male-producing (32.5°C) temperatures found that key sex-related genes were expressed at different levels depending on the temperature. Genes associated with male development were more active at the warmer male-producing temperature, while a receptor linked to female-associated pathways was more expressed at the cooler temperature.11PubMed Central. Temperature Incubation Influences Gonadal Gene Expression during Leopard Gecko Development
Temperature-dependent sex determination is not universal among geckos. Many species have genetic sex determination instead, where chromosomes decide sex regardless of incubation temperature. Leopard geckos and a handful of other species are the exceptions that have been most thoroughly studied, and they have become important model organisms for understanding how environment can override what we usually think of as genetic destiny.
Geckos That Skip Eggs Entirely
Not all geckos lay eggs. New Zealand’s native geckos are viviparous, meaning they give birth to live young. These species retain developing embryos inside the body rather than depositing them in the environment. This adaptation is thought to be a response to New Zealand’s cool climate, where ambient temperatures in many habitats are too low for successful external egg incubation.
The trade-off is reduced reproductive output. Unlike egg-laying geckos elsewhere in the world that may produce multiple clutches per breeding season, New Zealand’s viviparous geckos typically produce only one litter per year, and litter sizes are small. This low annual reproductive output reflects the energetic cost of carrying developing young internally in a cool environment, and it makes these populations particularly vulnerable to predation and habitat loss.12New Zealand Journal of Zoology. Low annual reproductive output in female reptiles from New Zealand A species that can only replace itself slowly is much harder to conserve when facing threats from introduced mammals.
Eggs Without Males
A few gecko species have eliminated the need for males altogether. The mourning gecko (Lepidodactylus lugubris) is an all-female species that reproduces through parthenogenesis, producing viable eggs without fertilization. These eggs develop into genetic clones of the mother, though the process is more sophisticated than simple copying. Researchers have mapped the full embryonic development of this species, documenting how a complete gecko develops from an unfertilized egg through the same developmental stages seen in sexually reproducing species.13PubMed. Embryonic development of a parthenogenetic vertebrate, the mourning gecko (Lepidodactylus lugubris)
The cellular trick that makes this work involves premeiotic endoreplication, where the germ cells duplicate their entire genome before the division process that normally halves the chromosome count. This ensures the resulting egg has the full chromosome number without needing sperm to supply the missing half. The fidelity of this process is maintained by the formation of chromosome pairs made from identical copies rather than the mix of maternal and paternal chromosomes that sexual reproduction produces.14Development. Premeiotic endoreplication is essential for obligate parthenogenesis in geckos
Mourning geckos lay hard-shelled eggs that look identical to those of sexually reproducing species in the same genus. If you found one in a crack behind your porch light, you would have no way to tell it was produced without a father. This parthenogenetic ability, combined with the mourning gecko’s tolerance of human-modified habitats, has helped it colonize islands and coastal areas across the Pacific and beyond.
Gecko Eggs in the Fossil Record
Hard-shelled gecko eggs preserve well as fossils, and for a long time paleontologists assumed that rigid eggshells among squamates (the group that includes lizards and snakes) were a gecko-only innovation. That assumption was challenged by the discovery of fossilized hard-shelled eggs from the Early Cretaceous of Thailand, roughly 100 million years old, which contained beautifully preserved embryos of anguimorph lizards rather than geckos.15PLOS ONE. Evidence of Egg Diversity in Squamate Evolution from Cretaceous Anguimorph Embryos Anguimorphs are the group that includes monitor lizards and, in the distant past, the marine mosasaurs.
This finding reshuffled the picture of how hard eggshells evolved in lizards. Rather than being an exclusive gecko trait, rigid shells appear to have evolved multiple times in different lizard lineages, and then been lost in some of them. The gecko lineages that still produce hard-shelled eggs today are not the only squamates to have ever done so; they are simply the ones that kept doing it. This plasticity in the organs responsible for shell mineralization suggests that the genetic toolkit for building a hard egg is more widely available across lizards than the current distribution of the trait would suggest. Most living lizard species have soft-shelled eggs, but the capacity to mineralize a shell may be dormant rather than absent in many of them.
Finding and Identifying Gecko Eggs at Home
If you live in a warm climate with house geckos, you will probably encounter eggs at some point. They turn up during renovations, behind appliances, inside sheds, under roof tiles, and in electrical junction boxes. Here is what to look for and what to do.
Hard-shelled gecko eggs are white, round to slightly oval, and about the size of a small candy. They are often glued firmly to a surface, and trying to pry them off usually cracks the shell. If you find a pair of white, hard eggs stuck to a wall or ceiling inside a cabinet, they are almost certainly gecko eggs. Soft-shelled gecko eggs are less common in household settings (since the common house gecko species tend to have hard-shelled eggs) but look like small, slightly translucent white capsules that give when pressed gently.
Fertile eggs often develop a pinkish tint or visible veining after a week or two as the embryo grows. Infertile eggs stay uniformly white or yellow and may collapse or mold over. If you want to leave them alone, they will either hatch in roughly two to three months or dry out and crumble if infertile. Hatchlings are tiny, usually under an inch long excluding the tail, and will find their way out of whatever crevice the eggs were in.
Communal nesting is common in house geckos, so finding a pile of old eggshells in one spot is not unusual. Multiple females may use the same protected crevice over and over, year after year, resulting in accumulations of hatched shell fragments. If you find what looks like dozens of tiny broken eggshells in a gap behind an exterior wall panel, that spot has likely been a gecko nursery for multiple seasons.