Most people know that birds and animals lay eggs, but only a small number of people know that a small group of mammals also lay eggs.
What mammals lay eggs? These interesting animals, called monotremes, are some of the oldest living mammals. They have been around for millions of years.
This article will talk about the five species of egg-laying mammals that still exist, how they are different from other mammals, and how they reproduce and raise their young.
Lacoon will also look at how they have changed over time and think about how to protect and study them now and in the future.
Monotremes – What Mammals Lay Eggs?
Mammals that lay eggs instead of having live babies are called monotremes. They are a subgroup of the class of mammals, and how they reproduce makes them unique.
Monotremes are unique among mammals and are an interesting link between reptiles and mammals in terms of how they evolved.
The Extant (Currently Alive) Species of Egg-laying Mammals Are:
The Duck-Billed Platypus (Ornithorhynchus anatinus)
The duck-billed platypus is perhaps the most well-known monotreme. It is a semiaquatic mammal found in eastern Australia and Tasmania with a unique appearance. The platypus has a duck-like bill, webbed feet, and a furry body.
It hunts for food underwater, using its sensitive bill to detect the electrical signals of its prey.
The platypus is also one of the few venomous mammals; males have a spur on their hind legs that can deliver a painful sting.
The Short-Beaked Echidna (Tachyglossus aculeatus)
The short-beaked echidna is found throughout Australia, including Tasmania, and in parts of New Guinea.
It is a small, burrowing mammal with a rounded body covered in spines and fur. The echidna primarily feeds on ants and termites, using its long, sticky tongue to capture its prey.
The Eastern Long-Beaked Echidna (Zaglossus bartoni)
This rare species of echidna is native to the highlands of New Guinea. It is similar in appearance to the short-beaked echidna but has a longer snout and a more robust body. The eastern long-beaked echidna primarily feeds on earthworms.
Sir David’s Long-Beaked Echidna (Zaglossus attenboroughi)
Sir David’s long-beaked echidna is one of the rarest monotremes, found only in the remote Cyclops Mountains of New Guinea.
It is named in honor of Sir David Attenborough, a renowned naturalist and broadcaster.
This species is larger than the other echidnas and has longer spines. It also feeds on earthworms.
Western Long-Beaked Echidna (Zaglossus bruijni)
The western long-beaked echidna is another rare species native to the highlands of New Guinea.
It is similar in appearance to Sir David’s long-beaked echidna but can be distinguished by its shorter snout and differently-shaped spines. Like other long-beaked echidnas, it feeds on earthworms.
Egg-Laying Mammals are Different From Other Mammals in Several Fascinating Ways
In addition to laying eggs, monotremes have other characteristics that set them apart from other mammals. They have a lower body temperature, typically around 90°F (32°C) compared to the average mammalian temperature of 98.6°F (37°C).
Monotremes also lack nipples, and instead, they secrete milk through specialized patches of skin for their young to lap up.
Also, like snakes and birds, monotremes have a single opening called a cloaca for both pooping and making babies.
How Do Egg-Laying Mammals Raise Their Young?
Female monotremes lay their eggs after a short gestation period. The platypus lays one to three eggs, while echidnas typically lay a single egg. The eggs are leathery rather than hard, similar to reptile eggs.
Monotremes keep their eggs warm after they have laid them. The platypus makes a nest out of leaves and curls around her eggs to keep them warm while they hatch.
Echidnas, on the other hand, lay their eggs in a temporary pouch on their belly, where they stay warm for about ten days.
Once the eggs hatch, the young monotremes, called puggles, are born in a very underdeveloped state.
They are blind, hairless, and extremely vulnerable. Their mother’s milk is crucial for their survival and development.
As previously mentioned, monotremes do not have nipples. Instead, they secrete milk through patches of skin on their abdomen, called mammary patches.
The puggles lap up the milk, which is rich in nutrients and antibodies to help them grow and develop a healthy immune system.
Monotreme mothers provide care and protection for their young during the early stages of their lives.
The platypus mother remains in the nesting burrow with her young, only leaving to forage for food.
Echidna mothers, after the puggle hatches, return the young to a nursery burrow and periodically return to feed it.
Young monotremes remain with their mothers for an extended period before gaining independence.
Platypus puggles typically leave the burrow after about four months, while echidna puggles leave the nursery burrow between six and twelve months of age.
After this time, they are fully independent and will begin to forage and explore their environment on their own.
Monotremes: A Journey Through Time and Evolution
The Past: A Glimpse of Early Mammalian Evolution
Monotremes represent an ancient lineage of mammals, with a fossil record dating back over 110 million years.
They provide valuable insights into the early evolution of mammals and the transition from reptiles.
The unique characteristics of monotremes, such as egg-laying and their lower body temperature, are thought to be remnants of their reptilian ancestors.
The Present: Conservation and Research
Many monotreme species are in danger because of habitat loss, climate change, and human actions.
The duck-billed platypus is considered “Near Threatened,” while the long-beaked echidna is “Critically Endangered” or “Endangered.”
For these unique mammals to stay alive, conservation measures like restoring habitats and breeding them in captivity are vital.
Researchers keep looking into monotremes and learning new things about their biology, behavior, and development.
The Future: Unraveling the Secrets of Monotremes
As more study is done on monotremes, we will learn more about these interesting animals and where they fit in the family tree of mammals.
Understanding the biology and history of the development of monotremes helps protect and preserve these species and helps us learn more about how mammals have changed over time.
Monotremes don’t have a clear future, but ongoing conservation efforts and studies give people hope that these unique mammals that lay eggs will be around for many more generations.
What are some examples of mammals that lay eggs?
The platypus and the echidna are the only two known mammals that lay eggs. Despite their egg-laying ability, they still produce milk to feed their young, which is a characteristic of all mammals.
The platypus is especially unique with its duck-like bill and various other puzzling features.
Do porcupines lay eggs?
No, porcupines do not lay eggs. Like most mammals, porcupines give birth to live young. The only two mammals that lay eggs are the platypus and the echidna.
The echidna, also known as the spiny anteater, has spines similar to those of a porcupine.
Which animals lay eggs?
Many animals lay eggs, not just birds and fish. Insects, turtles, lizards, and reptiles are some examples of egg-laying animals.
Among mammals, only the platypus and the echidna lay eggs. All other mammals give birth to live young.
Despite their egg-laying ability, the platypus and the echidna are still considered mammals because they produce milk to feed their young.
Monotremes are an intriguing group of egg-laying mammals that provide a glimpse into the early stages of mammalian evolution.
The five extant species, including the duck-billed platypus and four species of echidna, exhibit a range of fascinating characteristics and behaviors that set them apart from other mammals.
Their reproductive strategy, lower body temperature, and unique anatomy are just a few examples of the traits that make monotremes so captivating.
As researchers continue studying these remarkable creatures, they will uncover more secrets about their biology, behavior, and evolutionary history.
Conservation efforts are essential to ensure the survival of these unique mammals in a rapidly changing world.
By protecting and preserving these species, we are safeguarding their future and deepening our understanding of the rich tapestry of life on Earth. Monotremes truly embody the wonder and diversity of the natural world, and their continued existence is a testament to the resilience and adaptability of life.