Eggstravagance: Like other reptiles, most snakes lay eggs (70%). Egg-laying allows mamas to be done quickly with their motherly responsibilities and go back to feeding. This also allows them to lay another batch more quickly.
Although egg-laying snakes appear to just lay ‘em and leave ‘em, all mama snakes care for their babies and are very particular about where they lay their eggs. They search for a spot which is damp and warm, and predator proof. A female may travel long distances to use her regular personal nest site. Where only a few spots are suitable, many different snakes, and even other reptiles, lay eggs in the same spot. Some popular spots are used year after year and are piled deep with egg shells.
Some females, although they don’t coil around their eggs, will stay near the spot where they laid their eggs, keeping away predators.
Are snake eggs like bird eggs? Snake eggshells are soft leathery parchment-like and not hard like birds’ eggs. So while snake eggshells are permeable, allowing gases to exchange so the embryo can breathe, water is also lost. While birds' eggs have a harder more watertight shell and a fatty yolk that produces metabolic water, a reptile egg yolk provides little water. So snake’s eggs are susceptible to drying out. Snake eggs also must be kept within a temperature range. Eggs kept too warm or too cold result in deformed or dead babies.
Snake eggs may not be egg-shaped like birds', some look like long bumpy potatoes.
Most live-bearing mothers actually retain their eggs. These develop in transparent egg membranes like beads on a string. The embryos are not connected to the mother’s tissues. When the young are ready to "hatch", the mother lays them. Each live young emerges encased in a clear membrane, and have to break out of it by themselves. In a few snakes, the embryos do develop functional placentas attached to the mother (some pit vipers, and the Garter Snake Thamnophis sirtalis). But the exchange of nutrients through the placenta is not as extensive as in mammals.
Do snakes give birth to live young? Some give birth to live young. This minimises the exposure to the elements and predators. All snakes which live in cool climates give birth to live young because laid eggs will not be warm enough to develop properly. Live birth is also common among terrestrial snakes in warmer areas. Tree-dwelling snakes get too heavy carrying eggs and so lay them. Snakes that give birth to live young can produce as many young as those that lay eggs: the Garter Snake (Thamnophis sirtalis) can produce 40 or more at one time!
A snake which retains her eggs is looking after them and sacrifices much. The eggs take up body space so she doesn't’t eat much, if at all. She is also more vulnerable to predators; the eggs make her slow and clumsy, and she exposes herself by actively shuttling between basking and shady spots to ensure an ideal body temperature. Some females group together when they are pregnant, perhaps to share a more conducive microclimate and for protection against predators.
Some outstanding mums include ...
The Common Grass Snake (Natrix natrix) of Europe is an egg-layer that lives in temperate climates. Its eggs survive the cool climate because females travel long distances to find suitable laying sites, in particular piles of cow manure which generate heat as they decompose. The babies hatch before the first frost of winter.
The Mud Snake (Farancia abacura) a harmless snake, often lays in an alligator nest so her eggs have a fierce guardian from predators.
Nesting snake? The female King Cobra (Ophiophagus hannah) constructs an elaborate nest. She uses her coils to scrape together leaves, twigs and vegetation, deposits her eggs and covers them with vegetation which generates heat as it decays. She makes another chamber above the nest where she and her mate rest. They actively patrol the area around the nest chasing off predators. A favourite nest site is bamboo groves.
The warmth of mama: Pythons are among the best egg-laying mamas. They not only coil around their eggs, but if the temperature falls, will “shiver” to raise the body temperature and keep the eggs warm. Their eggs need to stay within a narrow 5 degrees C range in order to develop properly. Only large pythons and/or with powerful muscles can do this: Carpet Python (Morelia spilota), Indian Rock Python (Python molurus). The Diamond Python (Morelia s. spilota), in addition to shivering, also builds a nest for herself by burrowing slightly in sandy soil at the base of a tree or bush and pushing leaf litter into a small mound. "Shivering" uses up precious energy and a female may lose half her body weight by the time the eggs hatch, and it may take 2-3 years before she builds up enough energy to breed again. Other python moms choose well-insulated burrows. Yet others bask in the sun and quickly return to their eggs to warm them.
Other pythons which stay with their eggs don’t shiver. Their presence nevertheless keeps away egg predators and reduces the surface area of the eggs exposed to air, keeping them warm and preventing them from drying out. If it gets too dry, females have been known to drink water and then urinate over their eggs.
Baby snakes use their egg tooth to break out of their eggs. They make a slit in the leathery shell with the tooth. This tooth falls off shortly after hatching. Most snakes don’t look after their babies after they are born. But some which give birth to live young stay with their babies for a while. Some pit vipers stay with their babies until after their first moult.
Baby snakes: Babies don’t rush out of the eggshell but look around first. Sometimes a baby may stay in its shell for a few days before moving out. In some snakes, when the surroundings become too dry, babies can hatch “prematurely” with the remaining yolk in their tummies so they can move to a more conducive microclimate. Babies are capable of defending themselves, and are often more venomous and aggressive than adults.
More about snakes
- What are snakes?
- Are snakes cold?
- Why are snakes long?
- What do snakes eat? Do they drink?
- How do snakes swallow?
- How do snakes hunt?
- Why and how do snakes kill?
Snake predators and how do snakes protect themselves?
Snake mating, eggs and babies
Where are snakes found?
Fascinating snake adaptations to various habitats
Snake bites and first aid
Snakes in danger: role and conservation and snakes in human culture
Snake records: biggest, smallest, deadliest and more
- More snakes
- More animals
- General snake links and references
Further informations in german can be found here!