Lizards, a diverse group of reptiles, exhibit varied reproductive strategies. While most lizard species lay eggs, a significant number give birth to live young. This adaptability in reproduction allows lizards to thrive in numerous environments across the globe. Understanding these different methods provides insight into the life cycles of these common reptiles.
The Egg-Laying Majority
Most lizards reproduce through oviparity, or egg-laying. After internal fertilization, females typically deposit eggs in suitable locations. These nesting sites are often hidden, moist, and dark, such as under woodpiles, beneath sheds, in crevices, or buried in soil or leaf litter. The number of eggs in a clutch varies widely depending on the species, the mother’s size, age, and condition. For instance, small anoles may lay a single egg, while large iguanas can lay 50 or more at one time.
Lizard eggs differ from bird eggs. Their shells are typically soft and leathery, rather than hard and brittle. This porous shell allows for the absorption of moisture, enabling the eggs to expand as the embryo develops inside. While most lizard species exhibit minimal parental care after the eggs are laid, some, like certain skinks, remain with their eggs throughout the incubation period to guard them from predators and prevent fungal growth. Incubation periods generally range from 35 to 89 days, influenced by factors like temperature and humidity.
Lizards That Bear Live Young
While egg-laying is common, some lizard species give birth to live young, an adaptation known as viviparity. This reproductive strategy includes two main forms: ovoviviparity and true viviparity. In ovoviviparity, the eggs develop and hatch inside the mother’s body, with the young nourished primarily by the yolk sac within the egg. The mother’s body provides a protective environment, and the young emerge alive.
True viviparity involves a more direct connection, where the developing embryos receive nutrients from the mother through a placenta-like structure. This allows for substantial nutrient transfer beyond the yolk, often resulting in larger, more developed offspring. Live birth is particularly common in lizard species inhabiting colder climates or high altitudes, as the mother can regulate the internal temperature of the developing young, providing a stable environment that eggs laid externally might not have. Examples of live-bearing lizards include some skinks, such as the blue-tongued skink, and the viviparous lizard (Zootoca vivipara), found in colder regions of Eurasia. The ability to give live birth can also increase offspring survival by protecting them from external predators and environmental hazards.
Identifying Lizard Eggs
Distinguishing lizard eggs from bird or snake eggs involves specific traits. Lizard eggs are generally small, often ranging from the size of a fingernail to a small grape. They are typically oval or slightly elongated in shape, though some species lay more spherical or uniquely shaped eggs. While commonly white or off-white, some lizard eggs can appear light brown or even greenish, and some may have speckles.
Their texture is a distinguishing feature; most lizard eggs have a soft, leathery, and pliable shell, unlike the hard, brittle shells of bird eggs. This flexibility allows them to absorb moisture and expand. Snake eggs also share this soft, leathery texture, but are often larger and more elongated, while lizard eggs are typically smaller than an inch.
If you discover suspected lizard eggs, it is best to leave them undisturbed. Moving or rotating them can harm the developing embryos. If relocation is necessary due to immediate danger, move them carefully, maintaining their original orientation.