We learn early on in school that what one of the distinguishing characteristics of mammals is that unlike birds, reptiles, and fish they bear live young. There are exceptions to every rule, some reptiles and fish bear live young, and some mammals lay eggs.
Egg-laying mammals belong to a group called monotremes. Beside egg-laying, monotremes possess other traits that separate them from other mammals. They do not have teats to nurse their young. They instead excrete milk through pores that their young lap from. Their bodies maintained some reptilian traits such as a cloaca.
Their legs are on the sides of their bodies, unlike other mammals, whose legs are positioned under their bodies. There are only 5 known species of monotremes still in existence. Keep reading for some fun facts about these fascinating animals.
5 mammals that lay eggs
1. Duck-billed Platypus
Scientific name: Ornithorhynchus anatinus
Where they’re found: Australia
The platypus has a squat beaver-like body, with webbed feet. They have dense fur that traps a layer of air to provide insulation while in the water. Their most distinguishing feature is a long snout and lower jaw, which is covered in soft leathery skin. This form the bill from which they get their name. They are aquatic and feed by scooping worms, and insects from the water bottom and store it in cheek pouches to eat when they come out of the water.
Duck-billed Platypus facts
- Duck-billed platypus are the only venomous mammals. Males have sharp spurs on their rear feet, which deliver a toxin to competing males during mating season.
- Platypus use electroreception to find food. They have around 40,000 electroreceptors in their bill and can detect weak electrical fields. When hunting they sweep their heads back and forth to locate their prey.
- Platypus are knuckle walkers. To protect the webbing between their toes when walking on the land, they curl their toes under and walk on their knuckles.
- They were originally thought to be a hoax. Since the duck-billed platypus looks like a patchwork of other animals, when scientists were first presented with a specimen, they thought they were being subjected to a ruse.
2. Short-beaked echidna
Scientific name: Tachyglossus aculeatus
Where they’re found: Australia, New Guinea
The short-beaked echidna resembles a small anteater. It has a round body, with a short snout. It’s covered in a thin layer of insulating hair and a layer of long keratin spikes. Unlike the spiny anteater, these spikes are not barbed. Their snout is elongated and covered in a layer of skin resembling a bird’s beak. They have a long tongue which they use to lick up ants and termites, this tongue is where their scientific name “Tachyglossus” comes from.
Short-beaked echidna facts
- The Short-beaked echidna uses its spikes as protection. When threatened it curls into a ball, allowing its spines to protrude.
- Echidnas don’t just lay eggs, they also have pouches. Males and females both have pouches, which are not permanent features, but muscles that form a fold which they contract, making a pouch. Since echidnas are still a bit of a mystery, the reasons the male also possesses a pouch are unclear.
- Short-beaked echidnas are burrowers and have developed a tolerance for very low levels of oxygen, and high levels of carbon dioxide to compensate.
- All monotremes have very low body temperatures. When the short-beaked echidna hibernates, it’s temperature can drop to as low as 41 degrees F.
- Short-beaked echidnas do not have sweat glands. This makes them intolerant to heat, and in hot weather, they will change their typical diurnal behavior to become more active at night.
3. Sir David’s long-beaked echidna
Scientific name: Zaglossus attenborroughi
Where they’re found: New Guinea
This is the smallest echidna species and closely resembles the short-beaked echidna, with the exception of the longer snout. Like the short-beaked echidna, it is covered in a combination of hair and spines.
Sir David’s long-beaked echidna facts
- This little fellow was named after the naturalist Sir David Attenborough. It is one of 18 species, including a dinosaur, that was named in his honor.
- There has only been one specimen of Sir David’s echidna identified. This specimen was found in 1961, and it has not been spotted by naturalists since.
- It was thought to be extinct. On an exhibition to its known habitat in 2006, burrows and echidna activity were spotted in its range, and local people reported seeing it as recently as 2005.
4. Western long-beaked echidna
Scientific name: Zaglossus bruijni
Where they’re found: West Papau, Papau, Indonesia
This is the largest of the echidnas, weighing up to 36lbs. Like the other echidna species, the Western Long-beaked echidna has a stout body with a mixture of fur and specialized hairs that form spines, however, the spikes blend in with the fur. It has a long beak that turns down, and instead of ants, it feeds on earthworms. Unlike other echidnas in the long-beaked group, this fellow has only 3 claws on its feet.
Western long-beaked echidna facts
- Due to hunting and loss of habitat, the Western long-beaked echidna is listed as critically endangered.
- Their tongues are specialized for eating worms, with backward-facing barbs that help them hook and hold onto their prey.
- In captivity, the Western long-beaked echidna can live and astonishing 30 years!
5. Eastern long-beaked echidna
Scientific name: Zaglossus bartoni
Where are they found: New Guinea
The Eastern long-beaked echidna is distinguishable from its cousins by the number of claws on its feet. It has 5 claws on its front feet and 4 on the back. This echidna is in the mid-size range, weighing in at about 22 pounds. Their snout makes up about 2/3 the length of their head.
Eastern long-beaked echidna facts
- The Eastern Long-beaked echidna is currently listed as vulnerable due to overhunting, with estimates that there are only around 10,000 individuals left.
- Instead of teeth, they have a boney plate in the back of their mouth that helps them mash up insects.
- It is suspected they are nocturnal. Due to their elusive nature, and remote location not much is known about these bizarre creatures.