Discover 5 Mammals That Lay Eggs

Key Points

• Monotremes are mammals that lay eggs.
• There are only 5 monotremes on Earth today, the duck-billed platypus and four species of echidna.
• Sir David’s long-beaked echidna is critically endangered and one of the 25 most wanted “lost species” on the planet.

Mammals are defined as warm-blooded vertebrate animals that have hair or fur, provide milk to their offspring, and typically give birth to live young. Giving birth to live young is widespread for land and sea mammals alike, but there is a ridiculously small group of mammals that do not share this quality.

Nature never ceases to surprise when there are mammals who lay eggs instead of giving live birth. There are not many of them left, with several being critically endangered and one practically missing or extinct.

Let’s dig into these five unique mammals to understand why they can lay eggs and where they live.

What Mammals Lay Eggs?

The majority of mammals like humans, primates, dogs, cats, dolphins, whales, tigers, etc. give birth to live young. A tiny and select group of mammals lay eggs when giving birth.

Monotremes are mammals that lay eggs. In Greek, it translates as “one opening” which refers to the single duct (cloaca) the animal uses to urinate, defecate, and reproduce. This specific trait is common in reptiles and birds.

Why Can Mammals Lay Eggs?

Scientists theorize these mammals have a common ancestor which gave them the specific trait to continue laying eggs, while other mammals give live birth. Amniotes are animals whose embryo develops inside an egg without the need for water. Snakes and birds possess this dominant gene, allowing them to reproduce with eggs, while most mammals adapted to live births.

5 Mammals They Lay Eggs

The five mammals that lay eggs are the duck-billed platypus and four related species of echidna.

Each animal lives in a small section of the world and the echidnas share many similar traits like diet, defense mechanisms, and conservation status.

Duck-Billed Platypus

The duck-billed platypus is infamous for being the strangest creature that waddles and swims on Earth. Its unusual features are the perfect example of a real-life chimera (several animal parts fused to create a new animal.) They are the amalgam of a beaver, a duck, and a snake into one animal.

Fun fact, platypuses are venomous (thus the snake portion). They have a small claw at the edge of their webbed feet which can inject a venomous toxin into predators. The venom is excruciatingly painful to humans and deadly to small mammals. Thankfully, the venom is non-lethal to humans.

Platypus Reproduction

A female platypus reaches maturity at two years old and will lay a clutch of one to three eggs at a time. Baby platypus (puggles) stay with the mother, living in a protective pouch on her body for several weeks. As they age, the mother will move them to a small burrow along the shore and bring them food. When the puggles are four or five months old, they start swimming on their own and forage for their food.

Platypus Diet

The platypus consumes a diet of worms, fish, and insect larvae.

They swim to the bottom of the river or lake, digging around in the mud to find food. They grab what they can with their bills and bring it up to the surface where they can eat it without ingesting water.

When puggles are hiding in a burrow, the mother platypus will carry food to her young and teach them how to find food.

Platypus Habitat

Duck-billed platypus only live in rivers in eastern Australia along the Great Dividing Range. This makes these animals exceptionally rare because they cannot be found anywhere else in the world.

Scientists theorize the platypus adapted to living in the water when marsupials migrated to the region 71 million to 54 million years ago. Platypus were easy prey for the larger predators, seeking shelter in water and burrows.

Platypus Conservation Status

Because of their limited habitat, they are “near threatened.” They are protected by Australian legislation against poaching, but the animals are still hunted by predatory animals. Habitat loss from agriculture and logging reduces their already restrictive habitat.

Western Long-Beak Echidna

The western long-beak echidna is one of four echidnas that make up the remaining four mammals that lay eggs. It is the largest monotreme in the world, weighing 40 pounds. Their name is a direct description of the animal itself, being an echidna with a long beak, and living in the western highland forests of Australia, New Guinea, and Tasmania.

Western Echidna Reproduction

Unlike the platypus and other mammals that have a couple of kids, the western echidna only lays one egg. The egg hatches in 10 days, after which, the mother will carry the young pup in her pouch for protection.

After several weeks of carrying the infant in her pouch, the mother will dig a deep burrow with her strong paws and place the infant there while she forages for food.

Western Echidna Diet

Echidnas are insectivores, eating assorted insects and insect larvae. However, their primary diet consists of earthworms and grubs.

By using their long snout, they sniff out worms, insects, and grubs in the ground or under logs. Then, they use their snouts to lick up tasty morsels. Western echidnas spend most of their day foraging for food.

Fun Fact, echidnas are also called “spiny anteaters” because of their similar shape, long noses, and similar diet. The difference is that normal anteaters are much larger and have hair, while echidnas have spines to protect them from predators.

Western Echidna Conservation

Western echidnas are critically endangered due to habitat loss from mining, agriculture, and logging. Feral dogs and other predators hunt echidnas as an easy meal, reducing their numbers further. Additionally, they only reproduce one egg at a time, they are a high-risk species for extinction.

Eastern Long-Beak Echidna

The eastern echidna is nearly identical to its western counterpart, just living in a different direction.

Eastern echidnas and the western echidna both:

• Have the same diet.
• Reproduce only one offspring at a time.
• Cares for the young directly with a pouch and provides it a burrow later.
• Located in the highlands of Australia and New Guinea.
• Hunted by feral dogs and other predators.

However, the eastern echidna has a conservation status of “vulnerable,” meaning there are more of them roaming the lands. The species still requires dedicated efforts to protect their lands as their population is steadily decreasing.

Short-Beaked Echidna

The third echidna and fourth monotreme is the short-beaked echidna. This little critter is affectionately called the spiny anteater because it is a delightful combination of an anteater and a hedgehog, with an echidna’s body.

The short echidna has sharp quills that lay flat against its body when relaxed but will point up to prevent predators from attacking it. They do not have the power to shoot their quills like porcupines, but they can curl up in a ball to protect their soft underbelly from attack.

Short Echidna Reproduction

The short echidna mom lays a single egg, watching it carefully until it hatches within a few days. The mother will carry the infant in her pouch for seven weeks, before moving it to a burrow nearby. Infants are born without quills, making it safe for the mother to carry in her pouch. When the quills start coming in within a few weeks, then she moves her young to prevent accidental poking.

After six months of tending to her child, the young echidna will leave the burrow and fend for itself.

Short Echidna Diet

Like other echidnas, the short echidna is an insectivore, finding protein in worms and other insects. However, the short echidna uses its long and sticky tongue to slurp ants and termites from their mounds like an anteater.

Their heightened sense of smell allows them to find anthills, termite mounds, and insects buried in the ground. It also helps them learn of predators in the area to find shelter.

Short Echidna Habitat

The short echidna is found across Australia, Tasmania, and parts of New Guinea. Being spread out across the islands gives them more space to roam and reproduce. They love living in heavy forest areas with plenty of termite mounds available, as well as grasslands, and outer suburbs.

Short Echidna Conservation

Short echidnas are currently a “least concern” species, but every year their population decreases due to habitat loss, predators, and parasites.

Sir David’s Long-Beaked Echidna

Finally, Sir David’s long-beaked echidna is the most elusive and possibly extinct monotreme. It is also called the Cyclops long-beaked echidna.

Fun fact, Sir Attenborough did not discover the species. It was an honorary title for his work in biology and his great achievements in his dedication to research, documentation, and advocacy for nature restoration and protection.

Unfortunately, there is extraordinarily little information on this species because it is considered one of the “most wanted species” for wildlife conservation. They are critically endangered from hunting and habitat loss, so they were considered extinct for many years.

Recently, scientists found evidence of unique nose prints in the ground that match the anatomy of the Cyclops echidna, giving hope the species is still alive.

What little information is available on the species is that:

• They live in the Cyclops Mountains in Papua, New Guinea.
• Eat earthworms, grubs, termites, ants, and larvae.
• They are nocturnal.

The small niche of mammals capable of laying eggs is one of nature’s wonders, which are possibly going extinct. Several of these animals are critically endangered, one being possibly extinct. It will take a lot of effort to ensure these animals are safe and protected for future generations. If not, we will lose out on some of the rarest mammals to date.