Do Mammals Lay Eggs? Monotremes – Egg-Laying Mammals

Types of Mammals That Lay Eggs

It’s common for mammals to give birth to live young. However, you will be surprised to know that there is a fascinating group of mammals that lay eggs instead.

These unique creatures are called monotremes. You can only find these unique creatures in Australia and New Guinea. These two well-known examples of egg-laying mammals are the platypus and the echidna.

What do you call a mammal that lay eggs?

The Monotremes: Mammals That Lay Eggs

Mammals that lay eggs are called Monotremes. As can be seen, only three types of egg laying mammals exist today.

Echidnas, platypuses and solipugids – although other egg-laying mammal species may have existed at one point during Earth’s evolutionary history.

Despite being oddities among mammals due to their method of reproduction, these animals are remarkable creatures with unique physical characteristics and behaviors that make them stand out from other species within this class of animals!

Do mammals lay eggs? let’s discuss in detail

Ancient egg-laying mammals, called monotremes. They are some of the oldest mammals on the earth. The platypus and echidna, both live only in Australia and New Guinea.

These animals are unique in that they lay eggs and also possess certain reptilian properties, such as the absence of nipples and they produce a leathery eggshell.

Monotremes have been around for over 160 million years, which makes them some of the most ancient mammals on the planet. We can considered them a living fossils, as they have not changed much since they first evolved. One of the unique characteristic that they possess a sense of electroreception, which helps them to detect the electrical signals of prey and predators in the water which is not found in any other mammal.

What Are The Types of Egg-Laying Mammals?

There are only three types of egg-laying mammals in the world known to science today: the echidna (also called the spiny anteater or “spiney”), the platypus, and the “solipugid”.

These animals are monotremes, meaning they are primitive mammals with unique characteristics, such as the ability to lay eggs rather than giving birth to live young like most other mammal species. Let’s discuses more.

NameEgg SizeEgg CharacteristicOriginIncubation PeriodFeeding
PlatypusSmallSoft, leatheryAustralia10-12 daysPlankton, insects
EchidnaSmallHard, spinyAustralia, New Guinea45-55 daysInsects, worms

1. Echidna

The echidna lays one or two leathery eggs into a shallow depression that it digs in the ground with its strong hind legs and front claws. After laying its egg(s), the mother echidna covers it with soil and leaves it there to incubate without her care.

Once hatched, baby echidnas feed off their yolk sack until they’re able to leave the nest and begin eating small invertebrates on their own.

Echidna- Types of Mammals That Lay Eggs

2. Platypus

Platypuses lay between one and three very soft eggs in an underground burrow dug by the mother for incubation. Like all monotreme mammals, platypuses lack nipples and must use their bill to milk food from their mothers. Once born, these platypuses feed off milk from their mothers’ skin before moving onto insects when they’re about three months old.

Platypus- Types of Mammals That Lay Eggs

3. Solipugid

The solipugid is another primitive egg-laying mammal found in Australia but little is known about this species because it is extremely rare. It has been estimated that fewer than 100 solipugids exist today due to destruction of their natural habitat by humans over time.

It is thought that these unusual mammals lay one leathery egg at a time in underground burrows or nest chambers in trees where the female provides care for her offspring until they’re able to hunt on their own.

What Is A Mammal?

A mammal is any animal in the class Mammalia, which includes humans, dogs, cats, bats, dolphins and many others. All mammals share certain traits such as warm-bloodedness (homeothermy), a high metabolic rate, and live birth of their young.

They also have fur or hair on their bodies, produce milk for their offspring, and breathe air through lungs rather than through gills like some fish or amphibians.

Mammals Lay Eggs: A Comprehensive Overview

Mammals are animals that share many common traits such as having hair or fur, warm bloodedness, and the presence of mammary glands.

Mammals are known to give birth to live young but there are some mammals that lay eggs as part of their reproductive cycle. Below is a comprehensive overview of the mammals who lay eggs and the reproductive processes involved in doing so.


The first and most notable group of mammals to lay eggs are known as Monotremes, which are native to Australia and New Guinea.

This group includes the platypus and four species of echidnas (or spiny anteaters). The egg-laying process for monotremes is unique because they are the only mammals whose offspring emerge from the shell fully formed.

Monotreme eggs are relatively large, leathery-shelled eggs resembling those of reptiles. Additionally, monotremes lack nipples; instead, their milk oozes through their skin onto their stomachs where the young can lick it off to nurse.


Unlike Monotremes, Marsupials give birth to relatively undeveloped young after a short gestation period in which they incubate within an eggshell inside their mother’s pouch until they have developed enough to emerge.

Some examples include Kangaroos, Opossums, Koalas and Tasmanian Devils who are all well known marsupials that lay eggs. These animals typically give birth to several offspring at once from a single egg sac inside the pouch but unlike other species of egg-laying mammals; marsupial eggs do not hatch into fully formed offspring until after emerging from the pouch and usually require additional parental care.


The Sirenia order comprises two extant families: Dugongs and Manatees – both of which are aquatic creatures that live exclusively in coastal regions or freshwaters throughout tropical areas.

As members of this order, these animals do not give live birth but rather produce small elliptical eggs encased within a thick layer of mucous that act as an external protective covering while floating on the surface waters until hatching time arrives.

Interestingly enough, some species such as Manatees have been known to show signs of parental care following the hatching process – even though the newborns can swim immediately upon exiting their shells!

What Is The Difference Between Egg-Laying And Live Birth In Mammals

The most noticeable difference between egg-laying animals and mammals is the method by which they reproduce. While some reptile and bird species still exhibit traditional nesting behaviors such as brooding over the nest or burying the eggs for protection; most of them simply leave them in an open space for incubation by sun or external warmth sources until hatching time arrives.

This stands in stark contrast to the internal development process used by mammals where fertilization occurs internally within female reproductive organs until the young emerge alive from their mother’s body after gestational period ends.

Additionally unlike eggs that require external temperature for incubation, embryos inside a mammal are kept at a constant body temperature thanks to a layer of muscle tissue around it that helps regulate heat production known as “uterine thermal inertia”.

Are Any Other Mammals Known to Lay Eggs?

In addition to the three living species of monotreme, some fossil evidence suggests that several extinct species of mammals also laid eggs instead of giving birth to live young.

These include species like tecophorhynchids, multituberculates and haramiyidans – all prehistoric relatives of modern mammals who lived millions of years ago during the Mesozoic Era.

While we know these animals were egg layers based on fossil evidence, not much else is known about how they reproduced or how similar they were to modern day monotremes.

Are There Any Exceptions?

Although the majority of mammals do not lay eggs, there are some exceptions. Monotremes—which include the platypus and echidna—are special because they lay eggs instead of giving birth to live young like other mammals.

Furthermore, monotremes use external fertilization rather than internal; therefore their reproductive strategy resembles that of reptiles more than other mammals. Other unusual mammal groups also utilize oviparity (egg-laying), such as three species of African mole rats and some shrews native to New Zealand and South America.

How Do Monotremes Reproduce?

Monotremes reproduce differently than other mammals. When it’s time to mate, male monotremes will pursue a female and “tackle” her into submission so she will accept his advances!

The female will then store sperm in an organ known as a shell gland where it can remain viable for months until she ovulates and lays an egg. This egg will usually contain genetic material from both parents.

What Is Internal Fertilization?

Most mammals reproduce by internal fertilization, a process where sperm meets egg inside the female’s body to create an embryo.

This process is distinct from external fertilization, where sperm and eggs mix outside of the body, often in water or moist soil. Internal fertilization ensures greater protection for the embryo until it can be born as a live baby.

The Evolutionary Connection

By studying oviparous (egg-laying) species among different animal classes, scientists have gained insight into evolutionary trends over time.

Many researchers believe that the ancestors of all placental mammals evolved from primitive egg-layers hundreds of millions of years ago before switching over to internal fertilization as a more effective way to produce young.

So while it’s true that most modern mammals don’t lay eggs anymore, they still carry remnants of this ancient egg-laying heritage with them today!

Classification of Mammals

Mammals are vertebrate animals classified in the scientific order known as Mammalia. This group of animals includes all species of rodents (such as mice and rats), primates (such as monkeys and apes), and even aquatic creatures like whales and dolphins.

All these creatures share certain characteristics such as hair or fur, three middle ear bones, mammary glands for nourishing offspring, and sweat glands.

Final Words

It’s clear that while most mammals no longer lay eggs like their ancient ancestors did millions of years ago, there are some species alive today who still use this ancient method for reproducing. It may come as a shock that many mammal species don’t give birth to live young, but the fact is that egg-laying has been around for thousands of years and is still used by some animals today.

The evolutionary pressures surrounding food availability are likely behind this fascinating adaptation, although more research is needed to confirm these theories and further explain the mechanics behind egg-laying mammals.

Imran Khan is a professional in marketing and information technology, and he shares unbiased and informative content on the science, nutrition, and types of eggs through Egg Encyclopedia. With 15 years of experience in content writing, he specializes in creating SEO-optimized content for websites and publications.

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