Reproductive biology

Males of some species attract females by calling. This reaches an extreme in the bell geckos (Ptenopus) of southern Africa, in which males participate in choruses. Individual males try to attract mates by calling from their burrow entrances, which serve as resonating chambers to amplify the sound. Less vocal geckos, such as leopard geckos (Eublepharis macularius), can identify members of the opposite sex by chemical cues, and many others identify mates visually at close range. Male geckos rub or lick females before mating and restrain them during copulation by biting them on the nape of the neck or the back. In the mourning gecko (Lepidodactylus lugubris) and a few other species, there are no males. Such unisexual species have arisen from the hybridization of two bisexual parental species and, once established, reproduce clonally by parthenogenesis.

Most geckos and all pygopods lay eggs. In gekkonine geckos the eggs are hard-shelled, but in the remaining subfamilies they are leathery. Females lay eggs in protected sites that often provide a high-humidity microclimate, such as on the axils of leaves, under bark, or in shallow nests in the soil. Desert geckos lay eggs in burrows or rock crevices or lay flattened, adherent eggs on vertical or overhanging rock surfaces. All geckos have fixed clutch sizes. Most species produce two young in a clutch, but a few groups of mostly smaller species produce a single egg at a time. Tropical species may produce several clutches a year, sometimes only during wetter periods, but those in cooler climates often have only a single clutch in a year.

Geckos typically abandon their eggs, and development takes one to six months, depending on temperature. In euble-pharines and some gekkonines, the sex of the offspring is temperature-dependent. The average temperature experienced by developing embryos during the second trimester of development determines what sex the geckos will become, with higher temperatures yielding males and lower temperatures yielding females. Hatchling geckos slit their eggshells with paired egg teeth that are shed shortly after eclosion (hatching). The geckos of New Zealand and one species in neighboring New Caledonia are unique in being viviparous (live-bearing) and possessing a simple placenta. These species always produce twins, which may gestate for four to 14 months.

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