Reproduction in chameleons typically begins with ritualistic courtship displays by males. In many species this entails the display of bright colors and a series of jerking or bobbing head movements while advancing on a female. Some males advance slowly with a halting or jerky gait, but others move very quickly and can be aggressive toward females. Females that are unreceptive or gravid may flee or may face the suitor with gaping mouth while hissing, rearing up on the hind legs, and rocking to discourage the male's advances. Females are known to approach males and grasp their forelegs or horns
to stop their pursuit. In some cases, unreceptive or gravid females attack males and inflict bite wounds that can be fatal.
If the female remains passive to the courtship of the male, he will mount the female by grasping her flanks and position himself on the right or left side of her body. He then everts the nearest of his two sexual organs while inserting it in her cloaca, the common chamber into which the intestinal, urinary, and generative canals discharge in reptiles, and copulation ensues. Some species copulate for a few minutes and others for as long as several hours, after which they usually go their separate ways. A few species form pair bonds for a period of time during the mating season.
The majority of chameleon species are oviparous, meaning they produce offspring by laying eggs in tunnels or pits in the ground or under rocks or leaves after a gestation period that can last a few weeks or several months, depending on the species. Females excavate tunnels and pits by digging with their front feet and then back into them to deposit eggs. When they are finished, they bury the eggs, fill in the tunnel or pit, and stomp the soil down to conceal the location of the nest. Some females drag leaves and twigs over the site. This is the final act of motherhood for a chameleon, and her young will be independent at birth. Incubation times vary according to species and according to the stage of embryonic development at the time the eggs are deposited. The shortest known incubation period is around one month, and the longest is 18 months. The young emerge by slitting a star-shaped opening in the end of the eggshell with the egg tooth, a sharp, calcified protrusion on the tip of the upper jawbone that later falls off.
Ovoviviparous species (those with eggs that hatch within the mother's body, or immediately after being laid) are found primarily in climates that experience greater extremes of cold and likely represent a reproductive strategy to increase the survival rate of neonates where eggs deposited in the ground might not hatch. Basking gravid females often position themselves so that sunlight is directed on their swollen abdomens to warm the developing babies. A female paces nervously while giving birth to her young, which emerge encased in thin, transparent membranes. The neonates wriggle free of the membrane and begin moving and climbing about immediately, usually seeking food within 24 hours. They instinctively disperse, perhaps to avoid predation by the mother; this rarely occurs, however, in the confines of a cage in captive births. While live-bearing females are in contact with their offspring at birth (unlike egg-laying females), they do not nurture them in any way.
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