Leslie Massey
Monotremes are an unusual group of mammals that lay eggs instead of giving birth to live young. They are considered some of the most primitive living mammals, having split from other mammalian lineages around 150 million years ago. Australia is home to two of the five extant species of monotremes: the platypus and the echidna. Platypuses can be found in freshwater systems on the eastern coast of Australia, while echidnas are found throughout the continent. Both platypuses and echidnas have electroreceptive systems, with platypuses having 40,000 electroreceptors on their bills and echidnas having 400-2,000 electroreceptors on their snouts.
| Characteristics | Values |
|---|---|
| Number of monotreme species | 5 |
| Extant monotreme species | Platypus, Echidna |
| Echidna species | Short-beaked Echidna, Sir David's long-beaked echidna, Eastern long-beaked echidna, Western long-beaked echidna |
| Platypus species | Duck-billed platypus |
| Habitat | Freshwater systems on the eastern coast of Australia, Tasmania, East Gippsland, Atherton Tablelands, Southern Highlands, Kangaroo Island, Flinders Chase, New Guinea |
| Diet | Insects, ants, termites, insect larvae, earthworms, small invertebrates |
| Physical characteristics | Fur, spines, electroreceptors, venomous spurs, duck-like bill, webbed feet, beaver-like tail, strong claws, front limbs, three middle ear bones |
| Behaviour | Flick tongue, curl into a ball when threatened, good swimmers, can tolerate low oxygen levels, hibernate in winter, breed in spring |
| Reproduction | Egg-laying mammals, female monotremes produce milk to feed their young |
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What You'll Learn
Platypuses are found in freshwater systems on Australia's eastern coast
Platypuses are one of the most unusual creatures on Earth, with unique features that make them perfectly adapted for life in the water. Platypuses are found in freshwater systems, from the tropical rainforests of Queensland to the cold, high altitudes of Tasmania and the Australian Alps. They are endemic to eastern Australia, including Tasmania, and are dependent on rivers, streams, and other bodies of freshwater.
Platypuses are semi-aquatic, egg-laying mammals, and are one of the only two monotremes found in Australia, the other being the echidna. Platypuses usually live alone, making their homes in freshwater systems where they hunt for shrimp, swimming beetles, water bugs, and tadpoles. They feed in both slow-moving and rapid parts of streams but show a preference for coarser bottom substrates, particularly cobbles and gravel.
The platypus is a common species, with little apparent change in its historical distribution. However, there is a lack of knowledge about their abundance at local catchment levels, which makes it difficult to predict population trends. Their dependence on established freshwater systems may lead to their decline in the future, as they are vulnerable to changes in water quality from land clearing and irrigation.
Platypuses are found throughout Tasmania, East Gippsland, Atherton Tablelands, and the Southern Highlands, but they are generally shy and elusive creatures. Dawn and dusk are the best times to spot them. They are considered culturally significant to the First Peoples.
Platypuses are easily recognised by their duck-like bills, thick waterproof fur, and webbed feet. They are also known as duck-billed platypuses, and their bills are full of electroreceptors that help them find food. Platypuses are a flagship species, which means that protecting their habitat also supports healthy rivers and waterways, vital for thousands of species that rely on freshwater habitats.
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Echidnas are covered in coarse hair and spines
The spines are an enlarged, tough form of hair, providing a formidable defence mechanism. When threatened, echidnas will roll up into a ball of radiating spines, making them extremely difficult for predators to attack. The spines also provide effective camouflage, especially when combined with the echidna's ability to quickly dig itself into the ground. This combination of spines, strength, and strategy makes the short-beaked echidna a challenging prey animal.
The colour and length of the hair and spines can vary depending on the region. For example, echidnas from colder regions like Tasmania have longer fur that partially obscures the spines, providing extra warmth. In contrast, echidnas from arid zones may have shorter fur, with the spines being more prominent. Echidnas found in different parts of Australia can also vary in colour, from darker shades in South Australia to lighter, almost "blonde" hues in south-east Queensland.
The short-beaked echidna (Tachyglossus aculeatus) is the most common species, known for its forward-pointing beak and heavy coat of spines. It is widely distributed throughout Australia and is well-adapted to various habitats, from snowy conditions to arid deserts. The Zaglossus species, or long-beaked echidnas, are typically found in New Guinea and have varying lengths of fur and spines.
The spines start to develop in young echidnas, known as "puggles", after they hatch and are nursed in a burrow. As the puggles grow and their spines and fur become more prominent, they leave the burrow and start their solitary lives. The spines not only provide physical protection but also help with thermoregulation. The mucous bubbles blown out of the nares in the beak, combined with the spines, aid in cooling the body in hotter temperatures.
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Platypuses have electroreceptors in their bills
Australia is home to two of the world's five extant monotremes: the platypus and the echidna. Platypuses are found in freshwater systems on the eastern coast of Australia, while echidnas are found across the entire continent.
Platypuses are known for their duck-like bills, webbed feet, and beaver-like tails, making them well-adapted for life in the water. They are also known for their electroreceptors, which are densely packed in their bills and assist them in finding prey.
The function of these electroreceptors was, until recently, believed to be largely mechanoreceptive. However, research by Scheich et al. provides behavioural and electrophysiological evidence that these receptors are indeed electroreceptors. They recorded evoked potentials in the platypus's somatosensory cortex in response to weak voltage pulses, indicating the animal's ability to detect electric dipoles and locate moving prey through the electrical activity of their muscle contractions.
The electroreceptors in the platypus's bill are similar to the ampullary electroreceptors found in freshwater fish. This discovery offers valuable insights into the ancient evolutionary history of monotremes and their important ecological roles in Australia.
The platypus is considered one of the most extraordinary animals on the planet due to its unique appearance and traits, such as its ability to locate prey using electroreception, as well as its venomous spurs and spiny defences. These features make the platypus a captivating and unusual creature.
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Echidnas are the only mammals found across the entire Australian continent
Monotremes are a unique group of mammals that lay eggs instead of giving birth to live young. They are found primarily in Australia and New Guinea and include just a few species, notably the platypus and the echidna. These creatures represent an evolutionary link between reptiles and mammals, exhibiting traits of both.
The echidna is a monotreme and one of the most unusual and captivating creatures on Earth. Echidnas are medium-sized, solitary mammals covered with coarse hair and spines, which are made of keratin. They are usually black or brown, but albino echidnas with pink eyes and white spines have also been reported. They have long, slender snouts that function as both mouth and nose, with electroreceptors to help them find prey. Echidnas have tiny mouths and toothless jaws, and they feed by tearing open soft logs and anthills, then using their long, sticky tongues to lick up their prey.
The short-beaked echidna (Tachyglossus aculeatus) is the only mammal found across the entire Australian continent. It is smaller than the Zaglossus species and has longer hair. Short-beaked echidnas can be found in almost all Australian environments, from the snowy Australian Alps to the arid Outback deserts. They are also present in Tasmania, where their appearance differs slightly due to longer fur that blends in with their spines. Some of the best regions for spotting short-beaked echidnas include East Gippsland, Kangaroo Island, and Tasmania, including Maria Island.
Echidnas are known for their sharp spines, but they also have a well-developed subcutaneous muscle layer underneath, contributing to their surprising strength. They have a low body temperature of around 29–32 °C (84–90 °F) and cannot tolerate extreme heat or harsh weather, seeking shelter in caves and rock crevices. They are excellent swimmers, having evolved from platypus-like ancestors. Echidnas are important for the environment, with a single individual able to move seven tons of soil each year.
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Platypuses are the only venomous Australian mammal
Monotremes are mammals that lay eggs instead of giving birth to live young. They are found primarily in Australia and New Guinea and include just a few species, notably the platypus and the echidna. Platypuses, also known as duck-billed platypuses, are native to Australia and can be found in freshwater systems on the eastern coast of the country, including Tasmania, East Gippsland, Atherton Tablelands, and the Southern Highlands. They are known for their unusual combination of reptilian and mammalian traits, such as being an egg-laying, lactating, nipple-less, toothless, and stomach-less mammal.
What sets the platypus apart from its mammalian cousins is that males are venomous. They have a crural venom system, with paired venom glands situated on the dorsocaudal side of the pelvic area and ducts that connect to hollow, keratinous spurs on their hind legs. Young females also have vestigial spurs, which are lost within their first year. The crural gland is thought to be a derived sweat gland, and the venom it secretes contains at least 19 proteins belonging to three major toxin groups: C-type natriuretic peptides, nerve growth factor, and defensin-like peptides.
Platypus venom disrupts haemostasis (blood regulation), cell membranes, and nociception (pain regulation) to cause nausea, swelling, and excruciating pain that lasts for weeks and cannot be alleviated by morphine. While platypus venom is lethal, there are no recorded deaths from platypus stings. Male platypuses use their stingers for defence, delivering a strong toxic blow to any approaching foe.
Platypuses are considered a living evolutionary link with their therapsid ancestors, which were likely furry, egg-laying, lactating, reptile-like, endothermic creatures. Platypuses are revered in Australia, even featuring on the country's 20-cent coin. However, their populations are decreasing due to prolonged droughts, bushfires, a changing climate, and deforestation.
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Frequently asked questions
Monotremes are mammals that lay eggs instead of giving birth to live young. They are considered some of the most primitive living mammals, having split from other mammalian lineages approximately 150 million years ago during the Jurassic period.
The platypus and the four species of echidnas are the only monotremes in existence today. The platypus is endemic to eastern Australia, while the short-beaked echidna is the only species of echidna found in Australia.
Platypuses are famous for their duck-like bills and webbed feet. Echidnas are known for their sharp spines and coarse hair, which provide excellent protection from predators.
Platypuses can be found throughout Tasmania, East Gippsland, Atherton Tablelands, and the Southern Highlands. The short-beaked echidna can be spotted in East Gippsland, Kangaroo Island, and Tasmania.
