Which Animals Lay Eggs?
Which Animals Lay Eggs?
Animals that lay eggs are called oviparous. These animals are usually Birds, fish, reptiles, amphibians, and insects. But some mammals lay eggs as well – the Platypus and the echidna.
Animals that produce live young are called viviparous. Mammals such as rabbits, horses, and humans give birth to their young ones, who can survive outside the mother’s body right after they are born.
Some animals have the characteristics of both oviparity and viviparity. They produce eggs, but their young will hatch inside of their body, and then the mother will give birth to live young. These types of animals are called ovoviviparous.
Platypus and Echidna.
Monotremes are the only mammals that lay eggs! The Platypus has two or three eggs at a time lain into a pouch on its stomach, while echidnas have one egg per clutch. These animals have milk glands and feed their babies with mother milk as soon as they hatch.
Birds lay eggs. One or both parents will make a nest out of grasses, twigs, and feathers. Then she will lay one or more eggs in the nest. It is not uncommon for birds to use some other animal’s abandoned home as their own. Sometimes birds even reuse nests that they built themselves! For example, some birds will lay eggs in a hole in a tree.
Besides the Platypus and the Echidna, birds are the only egg-laying animals that care for their young. Why? Because fish, reptiles, amphibians, and insects are cold-blooded and don’t produce enough body heat to keep their young warm.
Reptiles and Amphibians
Reptiles and amphibians all fall under the category of invertebrates. They are closely related, and both types must go into a metamorphosis state to become adult organisms (frogs or reptiles). This is when the creatures change shape to become what they will be as adults.
Lizards, turtles, crocodilians, and snakes all come from eggs.
Reptiles lay eggs because they can’t provide warmth to their eggs as they are cold-blooded (ectothermic), and their internal body temperature depends on their environment. Because of this, reptiles cannot provide warmth to the eggs or babies. Therefore, for baby reptiles to develop in an egg outside of a mommy reptile’s body, the eggs must incubate – meaning they need heat!
Reptiles may lay dozens of eggs, but it doesn’t mean that all the eggs will hatch, as they often get eaten by predators before they’re ready to hatch. Also, if the conditions aren’t right while the eggs are developing, they won’t survive.
Not all reptiles lay eggs in the sand. Some use soft mud or a bed of leaves instead.
The only way cold-blooded parents can provide heat to their eggs is by placing the eggs into sand that has been warmed up by the sun. This way, they can stay warm while still developing! In fact, of all animals that lay eggs, only birds and Monotreme can sit on their eggs to keep them warm.
Amphibians must find a safe place for their eggs until the young can hatch on their own. They lay their eggs in a pond or similar body of water where their young will develop and can later swim to land. Some salamanders lay the eggs on land and then carry them to water on their backs to hatch there.
Most amphibians go through metamorphosis – which means their body changes as they grow – so when a hatchling comes out of its’ egg, it has gills like a fish! Then, as it grows into adulthood and starts living on land, it loses the gills and changes in other ways to allow it to move around better on land.
There are thought to be more than 24,000 species in the world. These cold-blooded vertebrates produce and lay eggs. Some fish, such as salmon and trout, have traveled 60 miles upstream before depositing eggs for breeding purposes. Most fish eggs are fertilized externally by males releasing sperm into the water or onto eggs found on stream bottoms. But some fish don’t lay eggs! Like sharks, who give birth to live young.
Almost all insects, including beetles, bees, butterflies, and ants, hatch from eggs, but some come out as live births (called ovoviviparous – those animals produce eggs as well, but their young hatch inside their body before they are fully developed.)
In a nutshell
Animals that lay eggs are oviparous. The types of animals that lay eggs include:
Birds, Amphibians, Reptiles, Fish, Insects, Platypus, and Echidna (Monotremes).
Lizards and turtles (Reptiles) lay their eggs in nests or under rocks on land. Salamanders (Amphibians), such as newts and axolotls, deposit their eggs into the water, where they will hatch internally and develop into tiny aquatic larva before emerging to live on land. Birds lay their eggs in nests often made of grass, leaves, or feathers, sea birds building nests out of seaweed or cliff swallows using mud! Fish usually deposit their eggs on the bottoms of streams, rivers, ponds, lakes, or oceans.
The only mammals that lay eggs are the Platypus and Echidna. Plus, unlike most other animals that lay eggs, platypuses actually have nipples to feed their young with mother milk.
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