Animals that lay eggs are called oviparous animals and form entirely inside of the egg shell with no other development. Such animals may be reptiles, birds, sea creatures and even some mammals. Most mammals do not lay eggs, however. While oviparous animals lay eggs, the way in which they protect their eggs may vary from species to species.
Birds are the most commonly thought of animal that lay eggs. A bird egg has four components, which are the yolk, germinal disc, white part and shell. Birds may lay their eggs in nests or in other areas away from predators. Birds may use sticks, leaves and other debris found in nature to construct their nest. Birds generally sit on their eggs to protect and keep them warm until they hatch.
While some reptiles like some varieties of lizards, snakes and chameleons give birth to their young live, many species of reptiles lay eggs. All turtles, tortoises and crocodiles lay eggs in addition to some snakes and lizards. These reptiles lay their eggs out of water. Similar to birds, oviparous reptiles seek to hide their eggs from predators. To accomplish this, they will often dig holes in moist soil and bury their eggs there. Reptile eggs can incubate from 45 days to one year and the temperature of the incubation site can influence the sex of the hatchling in some cases.
Most fish lay eggs underwater. Fish will generally lay millions of eggs, which will develop without parental involvement. Males may also fertilize these eggs externally. When fish hatch, they survive off of the yolk of their egg until they learn to hunt and feed themselves. Amphibians, like toads and frogs, may also lay eggs in water, which later hatch on their own. Rays and sharks, on the other hand, fertilize and nurture their eggs internally before giving birth to live young.
While most all mammals give birth to live young, other species of mammals lay eggs. These species are called monotremes and are limited to just five animal species. These species are the duck-billed platypus and four species of spiny anteaters. Unlike other egg-laying creatures, however, monotremes produce milk for their young and have high metabolic rates. As of 2011, monotremes are only found in Australia and New Zealand.
- Photo Credit Jupiterimages/BananaStock/Getty Images
What Is Digging 4-Inch-Deep Holes in My Potted Plants?
Holes that begin appearing as soon as the container is planted may signal a hungry animal. Browsing mammals cause holes all season...
What Time of Year Do Wild Birds Lay Eggs?
Wild birds lay eggs when environmental conditions are best for providing adequate shelter and food for building nests and feeding their young....
Where Do Reptiles Typically Lay Their Eggs?
Not all reptiles lay eggs, but those that do typically choose loose earth or sand in order to lay their clutch of...
How Many Eggs Does a Water Turtle Lay?
The number of eggs a turtle lays at one time varies by species. Some turtles can lay over 200 eggs at a...
Reptiles that Give Live Birth
While it's true that almost all mammals give live birth to their offspring, it is rare to find a reptile who gives...
What Kind of Leaves Do Butterflies Lay Their Eggs On?
The life cycle of a butterfly begins with the egg. According to the University of Rhode Island, butterflies can lay from 200...
Which Reptiles Do Not Lay Eggs?
Birthing live young, as opposed to laying eggs, seems to fall almost completely in the domain of mammals. With only two exceptions,...
What Are the Only Two Mammals That Lay Eggs Rather Than Give Live Birth?
Mammals are separated from other animal classes by characteristics such as milk-producing mammary glands, for feeding their young, and live birth. Animals...
Where Do Reptiles Lay Their Eggs?
Reptiles lay their eggs in different places depending on the species, with lizards looking for sandy or moist soil. Find out how...
When Do Ticks Lay Eggs?
Ticks lay eggs by getting fully engorged on blood, climbing up a tree, shrub or building, and laying between 1,000 and 3,000...
Do Catfish Lay Eggs?
Catfish are not live bearers. They lay their eggs in cavities. Look for places with lots of nooks and crannies in shallow...