Most lizard species, including many small ones, reproduce by laying eggs, a process known as oviparity. However, some lizards give birth to live young. This diversity in reproductive methods allows lizards to thrive in various environments, showcasing their adaptability and survival mechanisms.
Understanding Lizard Eggs
Most lizards reproduce by laying eggs. These eggs have a soft, leathery, and porous shell that expands by absorbing moisture as the embryo develops. While most are white, some species lay brown or light green eggs.
Female lizards carefully select sites for laying their eggs, often seeking dark, moist, and sheltered locations. Common nesting spots include under woodpiles, sheds, decks, beneath shrubs, in tall grass, or within rotting logs.
Some species, like certain geckos, may even lay eggs in cracks or crevices or utilize communal nesting sites. After laying, the incubation period typically ranges from 40 to 60 days, though it varies by species and environmental conditions. Most lizard species provide little to no parental care after egg deposition, abandoning the nest to allow the eggs to develop independently.
Lizards That Give Live Birth
A notable number of lizard species give birth to live young, a reproductive mode called viviparity. This strategy involves the internal development of embryos within the mother’s reproductive tract until they are born fully formed. Some species exhibit ovoviviparity, where eggs hatch internally, and live young emerge shortly after.
Examples of viviparous lizards include approximately one-third of skink species, such as blue-tongued skinks, shingleback skinks, and the common lizard (Zootoca vivipara). Certain chameleons, like Jackson’s chameleon, and some anoles also exhibit live birth. During internal development, the embryos receive nourishment from a yolk sac or through placental-like connections that transfer nutrients from the mother. This internal gestation provides protection and allows the mother to regulate the environmental conditions for the developing young.
Why Lizards Lay Eggs or Give Live Birth
The evolution of different reproductive strategies in lizards is influenced by environmental and ecological factors. Viviparity, or live birth, is often observed in species inhabiting colder environments, such as high altitudes or extreme latitudes. In these conditions, retaining embryos internally protects them from harsh external temperatures that could be detrimental to eggs laid in a nest. The mother can actively thermoregulate, providing a more stable and warmer environment for development.
Conversely, egg-laying (oviparity) is advantageous in warmer, more stable climates, as it reduces the energetic burden on the mother by releasing the developing embryos earlier. It also allows for multiple clutches to be laid within a breeding season, potentially increasing overall reproductive output. Predator avoidance also plays a role, as vulnerable eggs can be hidden in specific nesting microhabitats. The reproductive strategy adopted by a lizard species represents an adaptation that maximizes offspring survival in its specific ecological niche.