Temporal range: Miocene to Recent
(red – native, yellow – introduced)
The platypus (Ornithorhynchus anatinus),
Together with the four species of
The unique features of the platypus make it an important subject in the study of evolutionary biology, and a recognisable and iconic symbol of Australia. It is culturally significant to several Aboriginal peoples of Australia, who also used to hunt the animal for food. It has appeared as a mascot at national events and features on the reverse of the Australian twenty-cent coin, and the platypus is the animal emblem of the state of New South Wales. Until the early 20th century, humans hunted the platypus for its fur, but it is now protected throughout its range. Although captive-breeding programs have had only limited success, and the platypus is vulnerable to the effects of pollution, it is not under any immediate threat.
As of 2020[update], the platypus is a legally
Taxonomy and naming
When the platypus was first encountered by Europeans in 1798, a
The common name "platypus" literally means 'flat-foot', deriving from the
There is no universally-agreed plural form of "platypus" in the English language. Scientists generally use "platypuses" or simply "platypus". Colloquially, the term "platypi" is also used for the plural, although this is a form of pseudo-Latin; going by the word's Greek roots the plural would be "platypodes". Early British settlers called it by many names, such as "watermole", "duckbill", and "duckmole". Occasionally it is specifically called the "duck-billed platypus".
The scientific name Ornithorhynchus anatinus literally means 'duck-like bird-snout',
In David Collins's account of the new colony 1788–1801, he describes coming across "an amphibious animal, of the mole species". His account includes a drawing of the animal.
The body and the broad, flat tail of the platypus are covered with dense, brown, biofluorescent fur that traps a layer of insulating air to keep the animal warm. The fur is waterproof, and the texture is akin to that of a mole. The platypus uses its tail for storage of fat reserves (an adaptation also found in animals such as the Tasmanian devil). The webbing on the feet is more significant on the front feet and is folded back when walking on land. The elongated snout and lower jaw are covered in soft skin, forming the bill. The nostrils are located on the dorsal surface of the snout, while the eyes and ears are located in a groove set just back from it; this groove is closed when swimming. Platypuses have been heard to emit a low growl when disturbed and a range of other vocalisations have been reported in captive specimens.
Weight varies considerably from 0.7 to 2.4 kg (1 lb 9 oz to 5 lb 5 oz), with males being larger than females. Males average 50 cm (20 in) in total length, while females average 43 cm (17 in), with substantial variation in average size from one region to another. This pattern does not seem to follow any particular climatic rule and may be due to other environmental factors, such as predation and human encroachment.
The platypus has an average
Modern platypus young have three teeth in each of the
While both male and female platypuses are born with ankle spurs, only the spurs on the male's back ankles deliver venom, composed largely of defensin-like proteins (DLPs), three of which are unique to the platypus. The DLPs are produced by the immune system of the platypus. The function of defensins is to cause lysis in pathogenic bacteria and viruses, but in platypuses they also are formed into venom for defence. Although powerful enough to kill smaller animals such as dogs, the venom is not lethal to humans, but the pain is so excruciating that the victim may be incapacitated. Oedema rapidly develops around the wound and gradually spreads throughout the affected limb. Information obtained from case histories and anecdotal evidence indicates the pain develops into a long-lasting hyperalgesia (a heightened sensitivity to pain) that persists for days or even months. Venom is produced in the crural glands of the male, which are kidney-shaped alveolar glands connected by a thin-walled duct to a calcaneus spur on each hind limb. The female platypus, in common with echidnas, has rudimentary spur buds that do not develop (dropping off before the end of their first year) and lack functional crural glands.
The venom appears to have a different function from those produced by non-mammalian species; its effects are not life-threatening to humans, but nevertheless powerful enough to seriously impair the victim. Since only males produce venom and production rises during the breeding season, it may be used as an offensive weapon to assert dominance during this period.
Similar spurs are found on many archaic mammal groups, indicating that this is an ancient characteristic for mammals as a whole, and not exclusive to the platypus or other monotremes.
The platypus can determine the direction of an electric source, perhaps by comparing differences in
Feeding by neither sight nor smell, the platypus closes its eyes, ears, and nose each time it dives. Rather, when it digs in the bottom of streams with its bill, its electroreceptors detect tiny electric currents generated by muscular contractions of its prey, so enabling it to distinguish between animate and inanimate objects, which continuously stimulate its mechanoreceptors. Experiments have shown the platypus will even react to an "artificial shrimp" if a small electric current is passed through it.
Monotreme electrolocation probably evolved in order to allow the animals to forage in murky waters, and may be tied to their tooth loss. The extinct Obdurodon was electroreceptive, but unlike the modern platypus it foraged pelagically (near the ocean surface).
In recent studies it has been suggested that the eyes of the platypus are more similar to those of Pacific hagfish or Northern Hemisphere lampreys than to those of most tetrapods. The eyes also contain double cones, which most mammals do not have.
Although the platypus's eyes are small and not used under water, several features indicate that vision played an important role in its ancestors. The
In 2020, research in biofluorescence revealed that the platypus glows a bluish-green color when exposed to black light.
Distribution, ecology, and behaviour
The platypus is semiaquatic, inhabiting small streams and rivers over an extensive range from the cold highlands of Tasmania and the Australian Alps to the tropical rainforests of coastal Queensland as far north as the base of the Cape York Peninsula.
Inland, its distribution is not well known. It was considered extinct on the
The platypus is no longer found in the main part of the
In captivity, platypuses have survived to 17 years of age, and wild specimens have been recaptured when 11 years old.
The platypus is an excellent swimmer and spends much of its time in the water foraging for food. It has a very characteristic swimming style and no external ears. Uniquely among mammals, it propels itself when swimming by an alternate rowing motion of the front feet; although all four feet of the platypus are webbed, the hind feet (which are held against the body) do not assist in propulsion, but are used for steering in combination with the tail. The species is endothermic, maintaining its body temperature at about 32 °C (90 °F), lower than most mammals, even while foraging for hours in water below 5 °C (41 °F).
Dives normally last around 30 seconds, but can last longer, although few exceed the estimated aerobic limit of 40 seconds. Recovery at the surface between dives commonly takes from 10 to 20 seconds.
When not in the water, the platypus retires to a short, straight resting burrow of oval cross-section, nearly always in the riverbank not far above water level, and often hidden under a protective tangle of roots.
The average sleep time of a platypus is said to be as long as 14 hours per day, possibly because it eats
The platypus is a carnivore: it feeds on annelid worms, insect larvae, freshwater shrimp, and freshwater yabby (crayfish) that it digs out of the riverbed with its snout or catches while swimming. It uses cheek-pouches to carry prey to the surface, where it is eaten. The platypus needs to eat about 20% of its own weight each day, which requires it to spend an average of 12 hours daily looking for food.
When the platypus was first encountered by European naturalists, they were divided over whether the female lays eggs. This was finally confirmed by William Hay Caldwell's team in 1884.
The species exhibits a single
Outside the mating season, the platypus lives in a simple ground burrow, the entrance of which is about 30 cm (12 in) above the water level. After mating, the female constructs a deeper, more elaborate burrow up to 20 m (65 ft) long and blocked at intervals with plugs (which may act as a safeguard against rising waters or predators, or as a method of regulating humidity and temperature). The male takes no part in caring for his young, and retreats to his year-long burrow. The female softens the ground in the burrow with dead, folded, wet leaves, and she fills the nest at the end of the tunnel with fallen leaves and reeds for bedding material. This material is dragged to the nest by tucking it underneath her curled tail.
The female platypus has a pair of
Most mammal zygotes go through
There is no official term for platypus young, but the term "platypup" sees unofficial use, as does "puggle". Newly hatched platypuses are vulnerable, blind, and hairless, and are fed by the mother's milk. Although possessing mammary glands, the platypus lacks teats. Instead, milk is released through pores in the skin. The milk pools in grooves on her abdomen, allowing the young to lap it up. After they hatch, the offspring are milk-fed for three to four months. During incubation and weaning, the mother initially leaves the burrow only for short periods, to forage. When doing so, she creates a number of thin soil plugs along the length of the burrow, possibly to protect the young from predators; pushing past these on her return forces water from her fur and allows the burrow to remain dry. After about five weeks, the mother begins to spend more time away from her young, and at around four months, the young emerge from the burrow. A platypus is born with teeth, but these drop out at a very early age, leaving the horny plates it uses to grind food.
|Evolutionary relationships between the platypus and other mammals|
The platypus and other monotremes were very poorly understood, and some of the 19th century myths that grew up around them – for example, that the monotremes were "inferior" or quasireptilian – still endure. In 1947, William King Gregory theorised that placental mammals and marsupials may have diverged earlier, and a subsequent branching divided the monotremes and marsupials, but later research and fossil discoveries have suggested this is incorrect. In fact, modern monotremes are the survivors of an early branching of the mammal tree, and a later branching is thought to have led to the marsupial and placental groups. Molecular clock and fossil dating suggest platypuses split from echidnas around 19–48 million years ago.
The oldest discovered fossil of the modern platypus dates back to about 100,000 years ago, during the
Because of the early divergence from the
Status and threats
Except for its loss from the state of South Australia, the platypus occupies the same general distribution as it did prior to
The platypus is not considered to be in immediate danger of extinction, because conservation measures have been successful, but it could be adversely affected by habitat disruption caused by
Researchers have worried for years that declines have been greater than assumed.
A November 2020 report by scientists from the
Platypuses generally suffer from few
Much of the world was introduced to the platypus in 1939 when
As of 2019, the only platypuses in captivity outside of Australia are in the San Diego Zoo Safari Park in the U.S. state of California. Three attempts were made to bring the animals to the Bronx Zoo, in 1922, 1947, and 1958; of these, only two of the three animals introduced in 1947, Penelope and Cecil, lived longer than eighteen months.
Aboriginal Australians used to hunt platypuses for food (their fatty tails being particularly nutritious), while, after colonisation, Europeans hunted them for fur from the late 19th century and until 1912, when it was prohibited by law. In addition, European researchers captured and killed platypus or removed their eggs, partly in order to increase scientific knowledge, but also to gain prestige and outcompete rivals from different countries.
The platypus has been a subject in the
According to one story of the upper Darling River, the major animal groups, the land animals, water animals and birds, all competed for the platypus to join their respective groups, but the platypus ultimately decided to not join any of them, feeling that he did not need to be part of a group to be special,: 83–85 and wished to remain friends with all of those groups. Another Dreaming story emanate of the upper Darling tells of a young duck which ventured too far, ignoring the warnings of her tribe, and was kidnapped by a large water-rat called Biggoon. After managing to escape after some time, she returned and laid two eggs which hatched into strange furry creatures, so they were all banished and went to live in the mountains.
The platypus is also used by some
The platypus has often been used as a symbol of Australia's
Platypuses have been used several times as mascots: Syd the platypus was one of the three mascots chosen for the
Since the introduction of
In the American animated series Phineas and Ferb (2007–2015), the title characters own a pet bluish-green platypus named Perry who, unknown to them, is a secret agent. Such choices were inspired by media underuse, as well as to exploit the animal's striking appearance; additionally, show creator Dan Povenmire, who also wrote the character's theme song, said that its opening lyrics are based on the introductory sentence of the Platypus article on Wikipedia, copying the "semiaquatic egg-laying mammal" phrase word for word, and appending the phrase "of action". As a character, Perry has been well received by both fans and critics. Coincidentally, real platypuses show a similar cyan color when seen under ultraviolet lighting.
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- Platypus facts (archived 10 September 2019)
- View the platypus genome in Ensembl
- IUCN Red List near threatened species
- Semiaquatic mammals
- Electroreceptive animals
- Mammals of New South Wales
- Mammals of Queensland
- Mammals of South Australia
- Mammals of Tasmania
- Mammals of Victoria (state)
- Venomous mammals
- Extant Miocene first appearances
- Quaternary animals of Australia
- Quaternary animals of Oceania
- Mammals described in 1799
- Taxa named by George Shaw