Lizards lay their eggs anywhere dark and moist, such as under woodpiles, sheds, and decks. Nesting sites can also be found beneath shrubs and in areas of tall grass. Younger, smaller females produce fewer eggs than older, larger ones, and experienced lizards can instinctually scope out safer nesting sites. Upon selecting a location, females dig holes to carefully bury their eggs.
Lizard hatchlings emerge between May and July, but about 40 percent of them don't make it to adulthood. Opossums and raccoons are able to sniff out and dig up lizard nesting sites with ease. These pests spread diseases like rabies or giardia to humans and leave parasite-infested feces near sidewalks. Newborn lizards are bite-sized morsels in the eyes of snakes, coyotes, foxes, and birds of prey, as well. Whittington and her team study the Australian three-toed skink Saiphos equalis , a lizard with the remarkable distinction of being able to both lay eggs and give birth to live young.
Recently in Molecular Ecology , Whittington and her team describe the differences in gene expression — which genes are switched on or off — between a lizard mother that lays eggs and one that gives birth to live young. Within a single species, there are thousands of such differences between a female with an egg and one without. Crucially, the specific genes that get switched on in these cases are very different. But in three-toed skinks, a lot of the genes that switch on when a mother makes an egg also get switched on in mothers with embryos.
The finding implies that this lizard is in a transitional state between egg laying and live bearing. Which way the lizard is evolving is impossible to say and may still be undetermined.
The idea that the skink could be moving away from live bearing and back to egg laying is a relatively new development in the field. But a growing body of research since then has shown that it may be quite common. Recent analyses of genetic relationships between species revealed that certain egg layers are deeply nested within an evolutionary tree of live-bearing neighbors.
Does it use the same genetic instructions when it evolved? Do [different species] have the same problems? The three-toed skink is not the only remarkable creature she studies as she searches for answers. Get highlights of the most important news delivered to your email inbox. Quanta Magazine moderates comments to facilitate an informed, substantive, civil conversation. Abusive, profane, self-promotional, misleading, incoherent or off-topic comments will be rejected.
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A lizard that both lays eggs and gives birth to live young is helping scientists understand how and why these forms of reproduction evolved. A Strategic Choice Early female animals laid eggs in the sense that they released their ova into the world, often thousands at a time. Lizard eggs can take up to 90 days to hatch but this largely varies dependant on the species on lizard.
When a lizard lays its eggs, they will aim to find a spot that is as hidden as possible, this is usually in a small pit where the ground is moist to stop the eggs from drying out. When fresh there is a small pocket of air within the egg which an embryo attaches so the baby lizard can breathe.
Once this is in place if the egg rolls or moves to far this will go under the fluid in the egg and actually drown the baby lizard. So, as the egg ages, the lizard will grow inside until it is ready to hatch. This is a tooth that is designed to pierce the egg and begin the hatching process.
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