We’ve all thought about this frustrating question: Which came first, the chicken or the egg?
Well, this forever ongoing debate still hasn’t been cracked in this advanced era.
This is proof of how complex and fascinating the egg-laying process is, and many animals utilize this method of reproduction.
Living organisms have distinct reproductive modes that divide animals into two categories: viviparous and oviparous. Viviparous animals give birth directly after a labor process, while oviparous animals lay eggs that hatch and give birth to their offspring. It is fascinating how nature has provided such unique reproductive abilities to different animals, and the reasons behind this division remain largely unknown to us.
So, get ready to explore the top 13 animals that lay eggs and learn about their unique characteristics and egg-laying habits.
1. Crocodiles
When it’s time to lay eggs, crocodiles are quite particular. They lay hard-shelled eggs, which can weigh up to 0.4 pounds each. Depending on the species, the female lays around 12-48 eggs per nest.
Some species dig a hole to deposit their eggs, while others build a nest mound out of plant material and soil.
Interestingly, the temperature of the incubating egg during the first half of incubation determines the sex of the developing embryo. Females protect their eggs from predators until the young are fully developed and ready to hatch.
When the young are ready to emerge, the adult female helps them out of their shells and into the water. In some cases, males have also been seen helping with hatching and caring for hatchlings in captivity.
2. Birds
You probably know birds lay eggs, but did you know how different the development of these chicks can be?
Some are born featherless with their eyes closed, and they rely solely on their parents for food and warmth. These little ones are called altricial hatchlings.
On the other hand, some birds, such as ducks, swans, geese, pheasants, and emus, have highly developed chicks that are ready to leave the nest and forage for food almost immediately after hatching.
These little ones are called precocial birds, and they are mobile within hours of hatching. They have a good covering of feathers, can walk, swim, and even fly in some cases, like the Maleo of Indonesia, almost straight away!
3. Turtle/Tortoise
Turtle and Tortoise both go to the shore to find the perfect spot to dig a nest and lay their eggs. This can take up to three hours before the mother turtle/tortoise slowly returns to the sea.
Around 100 eggs are laid and left to incubate in the warm sand for around 60 days. The gender of the baby turtles is determined by the temperature of the sand, with cooler sand resulting in more males and warmer sand producing more females. This process is called Temperature-Dependent Sex Determination.
However, climate change may increase the number of female sea turtles and impact genetic diversity.
When it’s time to hatch, the baby turtles do so together, creating a frenzy in the nest, often called a “turtle boil.”
4. Snakes
Did you know that 70% of snake species lay eggs, while the remaining 30% give birth to live young, including rattlesnakes, vipers, boas, and most sea snakes?
However, there is one exception: the oviparous Laticauda genus of sea snakes lay their eggs on land instead of giving birth to live young like their counterparts.
Even some of the most venomous snakes, like cobras, adders, mambas, and taipans, lay eggs.
After laying their eggs, most female snakes abandon them, but a few species will coil around the eggs to keep them warm until they are ready to hatch. Surprisingly, the highly venomous king cobra actually builds a nest for its eggs and stays with their offspring for a while after they hatch.
5. Fish
Fish reproduce by laying eggs in water, and the babies hatch after a certain period of time.
The eggs are usually stuck to plants or structures underwater, and some fish even make their own bubble nests to protect their eggs from being eaten by predators.
They can lay their eggs in different places, like open water or among plants, and some fish even secrete glue to keep their eggs in place.
Depending on the season, some fish can lay eggs multiple times.
Fish have developed some pretty clever ways to ensure their babies have the best chance at survival!
6. Frogs
Frogs and toads lay eggs, usually in a warm, wet environment, and males fertilize them externally.
Females can lay hundreds to thousands of eggs in a single clutch. Every spring, they gather to find mates and reproduce.
Frog eggs lack protective shells and are small and fragile, usually laid in water to keep them moist. Vernal pools are a common location for laying eggs.
Depending on the temperature, frog eggs hatch within a few days to three weeks.
7. Duck-billed Platypus
The platypus is a unique, egg-laying aquatic animal found in Australia. Unlike most mammals, which give birth to live young, platypuses are part of a group called monotremes that lay eggs.
Female platypuses dig underground burrows near water and lay their eggs there. After hatching, the young platypuses nurse for up to four months before leaving to forage on their own.
The platypus babies use a sharp “egg tooth” on their nose, made of keratin-like fingernails, to break out of their eggs. Platypuses are one of the few mammals that lay eggs, while most other animals, including reptiles, amphibians, fish, and birds, reproduce by laying eggs.
8. Lizards
Lizards exhibit a wide range of clutch sizes (number of eggs released), which can depend on various factors such as species, maternal size and age, and environmental conditions.
Smaller species generally lay fewer eggs, while larger species may lay dozens of eggs in a single clutch.
In addition to variation in clutch size, lizard eggs also differ in their shell characteristics. Most lizard eggs have leathery shells that allow for some expansion as the embryos grow. However, some geckos lay eggs with hard shells that do not expand, which may provide greater protection against predation and dehydration.
Overall, the reproductive strategies of lizards have evolved to maximize their reproductive success in different environments and ecological niches.
9. Spiny Ant-Eaters (Echidnas)
Did you know that the echidna, like the platypus, is one of the only egg-laying mammals?
For up to a year, the puggle chills in its den with its mom before heading out on its own. Unlike the hard-shelled eggs we’re used to, echidnas lay a softer, leathery egg that already has a growing embryo inside. Once the egg enters the pouch, it hatches in under two weeks, and the tiny puggle is only around 0.75 inches long.
The puggle stays in the pouch for up to three weeks, slurping on its mom’s milk that comes from the skin inside the pouch.
As it grows, it starts developing spines that eventually get too prickly for the mom’s skin, which signals that it’s time for the puggle to come out of the pouch and see the world.
10. Seahorses
Did you know that seahorses are totally different from most animals when it comes to giving birth?
It’s the male seahorse who carries and gives birth to the babies, not the female! Crazy, right? Have a look at the pregnant male in the picture above.
Here’s how it works: the female seahorse puts up to 2,000 eggs in a pouch on the male’s tummy. Then the dad carries those eggs around for two to four weeks while they grow.
During this time, the father hardly moves at all. After the eggs hatch, the little seahorse babies hang out in the dad’s pouch for a while longer to grow a bit more before they’re ready to face the big, bad ocean.
And when the time is right, the dad gives birth to his tiny offspring under the cover of darkness when the predators are all asleep.
11. Hermit Crabs
Hermit crabs are selective when it comes to reproduction and rarely mate in captivity. They require expansive bodies of saline water to birth their young, and without it, female hermit crabs lose interest in breeding.
After mating, the female can carry up to 50,000 eggs in her belly for a month before depositing them in the ocean. The eggs hatch upon contact with saltwater, and the hatchlings are known as zoea.
Female hermit crabs carry eggs in a sac on the side of their abdomen.
The red color of the sac fades to a deep gray shade as the eggs approach hatching. Once laid, the female hermit crab leaves the hatchlings to fend for themselves.
12. Insects
So, did you know that most insects lay eggs during their adult stage? It’s a common way for them to reproduce, although some can also give birth to live offspring.
A few insects even retain their eggs internally until after they hatch! How cool is that?
Eggs are a handy way for insects to make it through tough times when food is scarce.
Insect eggs come in all sorts of shapes, sizes, and colors, with some even having special structures like anchors or floats. And when it comes to laying eggs, insects are pretty consistent in their pattern. Whether it’s oviparity, viviparity, or ovoviviparity, insects have all sorts of ways to ensure their offspring’s survival.
13. Spiders
When it comes to spiders, females are usually the ones producing the eggs.
They can either create one big egg sac with anywhere from several to a thousand eggs, or they can create multiple egg sacs with progressively fewer eggs.
After producing the last egg sac, females of many species die, while others stick around for a bit to care for their young. The egg sacs themselves are usually made of silk and can be quite elaborate, with many layers of thick silk.
