Animals are my friends, and I don't eat my friends - George Bernard Shaw

Platypus

The Platypus (Ornithorhynchus anatinus) is a semi-aquatic mammal endemic to eastern Australia and Tasmania. Together with the four species of echidna, it is one of the five species of monotremes, the only mammals that lay eggs instead of giving birth to live young. It is the sole living representative of its family (Ornithorhynchidae) and genus (Ornithorhynchus), though a number of related species have been found in the fossil record.
 

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The bizarre appearance of this egg-laying, duck-billed mammal baffled naturalists when it was first discovered, with some considering it an elaborate fraud. It is one of the few venomous mammals; the male Platypus has a spur on the hind foot which delivers a poison capable of causing severe pain to humans. The unique features of the Platypus make it an important subject in the study of evolutionary biology and a recognizable and iconic symbol of Australia; it has appeared as a mascot at national events and is featured on the reverse of the Australian 20-cent coin.

Until the early 20th century it was hunted 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.

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Taxonomy and etymology

When the Platypus was first discovered by Europeans in the late 1700s, a pelt and sketch were sent back to the United Kingdom by Captain John Hunter, the second Governor of New South Wales.[4] The British scientists were at first convinced that the odd collection of physical attributes must have been a hoax.[3] George Shaw, who produced the first description of the animal in the Naturalist's Miscellany in 1799 stated that it was impossible not to entertain doubts as to its genuine nature, and Robert Knox believed it may have been produced by some Asian taxidermist.[5] It was thought that somebody had sewn a duck's beak onto the body of a beaver-like animal. Shaw even took a pair of scissors to the dried skin to check for stitches.[3]

The common name, Platypus, is Latin derived from the Greek words πλατύς ("platys", flat, broad) and πους ("pous", foot), meaning "flat foot".[6] Shaw assigned it as a Linnaean genus name when he initially described it, but the term was quickly discovered to already belong to the wood-boring ambrosia beetle (genus Platypus).[7] It was independently described as Ornithorhynchus paradoxus by Johann Blumenbach in 1800 (from a specimen given to him by Sir Joseph Banks)[8] and following the rules of priority of nomenclature it was later officially recognised as Ornithorhynchus anatinus.[7] The scientific name Ornithorhynchus is derived from ορνιθόρυγχος ("ornithorhynkhos"), which literally means "bird snout" in Greek, and anatinus which means "duck-like" in Latin.

There is no universally agreed upon plural of "platypus" in the English language. Scientists generally use "platypuses", "platypoda", or simply "platypus". Colloquially, "platypi" is also used for the plural, although this is pseudo-Latin.[3] Early British settlers called it by many names, such as watermole, duckbill, and duckmole.[3] The name "Platypus" is often prefixed with the adjective "duck-billed" to form Duck-billed Platypus, despite there being only one species of Platypus.

Description

The body and the broad, flat tail of the Platypus are covered with dense brown fur that traps a layer of insulating air to keep the animal warm.[3][7] The Platypus uses its tail for storage of fat reserves, an adaptation it shares with the Tasmanian Devil.[9] It has webbed feet and a large, rubbery snout; these are features that appear closer to those of a duck than to those of any known mammal. The webbing is more significant on the front feet and is folded back when walking on land.[7] Unlike a bird's beak (in which both the upper and lower parts of the beak separate to reveal its mouth), the snout of the Platypus is a sensory organ with the mouth on the underside. 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.[7] Platypuses have been heard to emit a low growl when disturbed and a range of other vocalisations have been reported in captive specimens.[3]

Weight varies considerably from 700 g (1.54 lb) to 2.4 kg (5.3 lb) with males being larger than females: males average 50 cm (20 in) total length while females average 43 cm (17 in).[7] There is substantial variation in average size from one region to another, and 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.[10]

The Platypus has an average body temperature of 31–32 °C (88–90 °F) rather than the 38 °C (100 °F) typical of placental mammals.[11] Research suggests this has been a gradual adaptation to harsh environmental conditions on the part of the small number of surviving monotreme species rather than a historical characteristic of monotremes.[12][13]

Modern Platypus young have three-cusped molars which they lose before or just after leaving the breeding burrow;[14][15] adults have heavily keratinised pads in their place.[7] The Platypus jaw is constructed differently from that of other mammals, and the jaw opening muscle is different.[7] As in all true mammals, the tiny bones that conduct sound in the middle ear are fully incorporated into the skull, rather than lying in the jaw as in cynodonts and other pre-mammalian synapsids. However, the external opening of the ear still lies at the base of the jaw.[7] The Platypus has extra bones in the shoulder girdle, including an interclavicle, which is not found in other mammals.[7] It has a reptilian gait, with legs that are on the sides of the body, rather than underneath.[7]

Venom

The male Platypus has venomous ankle spurs which produce a cocktail of venom, composed largely of defensin-like proteins (DLPs), which is unique to the Platypus.[16] Although powerful enough to kill smaller animals,[16] the venom is not lethal to humans, but does produce excruciating pain; so intense 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 that the pain develops into a long-lasting hyperalgesia that persists for days or even months.[17][18] 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 which do not develop (dropping off before the end of their first year) and lack functional crural glands.[7]

The venom appears to have a different function from those produced by non-mammalian species: its effects are non-life threatening but nevertheless powerful enough to seriously impair the victim. Since only males produce venom and production rises during the breeding season it is theorized that it is used as an offensive weapon to assert dominance during this period.[16]

Electrolocation

Monotremes are the only mammals known to have a sense of electroreception: they locate their prey in part by detecting electric fields generated by muscular contractions. The Platypus' electroreception is the most sensitive of any monotreme.[19]

The electroreceptors are located in rostro-caudal rows in the skin of the bill, while mechanoreceptors (which detect touch) are uniformly distributed across the bill. The electrosensory area of the cerebral cortex is contained within the tactile somatosensory area, and some cortical cells receive input from both electroreceptors and mechanoreceptors, suggesting a close association between the tactile and electric senses. The Platypus can determine the direction of an electric source, perhaps by comparing differences in signal strength across the sheet of electroreceptors. This would explain the animal's characteristic side-to-side motion of its head while hunting. The cortical convergence of electrosensory and tactile inputs suggests a mechanism for determining the distance of prey items which, when they move, emit both electrical signals and mechanical pressure pulses, which would also allow for computation of distance from the difference in time of arrival of the two signals.[19]

The Platypus feeds by digging in the bottom of streams with its bill. The electroreceptors could be used to distinguish animate and inanimate objects in this situation (in which the mechanoreceptors would be continuously stimulated).[19] When disturbed, its prey would generate tiny electrical currents in their muscular contractions which the sensitive electroreceptors of the Platypus could detect. Experiments have shown that the Platypus will even react to an 'artificial shrimp' if a small electrical current is passed through it.[20]

Ecology and behaviour

The Platypus is semi-aquatic, 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.[21] Inland, its distribution is not well known: it is extinct in South Australia (bar an introduced population on Kangaroo Island)[22] and is no longer found in the main part of the Murray-Darling Basin, possibly due to the declining water quality brought about by extensive land clearing and irrigation schemes.[23] Along the coastal river systems, its distribution is unpredictable; it appears to be absent from some relatively healthy rivers, and yet maintains a presence in others that are quite degraded (the lower Maribyrnong, for example).[24]

In captivity Platypuses have survived to seventeen years of age and wild specimens have been recaptured at eleven years old. Mortality rates for adults in the wild appear to be low.[7] Natural predators include snakes, water rats, goannas, hawks, owls and eagles, and low Platypus numbers in the northern Australia are possibly due to predation by crocodiles.[25] The introduction of red foxes as a predator for rabbits may have had some impact on its numbers on the mainland.[10] The Platypus is generally regarded as nocturnal and crepuscular, but individuals are also active during the day, particularly when the sky is overcast.[26][27] Its habitat bridges rivers and the riparian zone for both a food supply of prey species and banks where it can dig resting and nesting burrows.[27] It may have a range of up to 7 km (4.4 mi) with male's home ranges overlapping with those of 3 or 4 females.[28]

The Platypus is an excellent swimmer and spends much of its time in the water foraging for food. When swimming it can be distinguished from other Australian mammals by the absence of visible ears.[29] Uniquely among mammals it propels itself when swimming by alternate rowing motion with the front two 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.[30] The species is endothermic, maintaining its low body temperature, even while foraging for hours in water below 5 °C (41 °F).[7]

Dives normally last around 30 seconds, but can last longer although few exceed the estimated aerobic limit of 40 seconds. 10 to 20 seconds are commonly spent in recovery at the surface.[31][32] The Platypus is a carnivore: it feeds on annelid worms and insect larvae, freshwater shrimps, and yabbies (freshwater crayfish) that it digs out of the riverbed with its snout or catches while swimming. It utilizes cheek-pouches to carry prey to the surface where they are eaten.[29] The Platypus needs to eat about 20% of its own weight each day. This requires the Platypus to spend an average of 12 hours each day looking for food.[31] 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.[29]

Reproduction

When the Platypus was first discovered scientists were divided over whether the female laid eggs. This was not confirmed until 1884 when W.H. Caldwell was sent to Australia where, after extensive searching assisted by a team of 150 aborigines, he managed to discover a few eggs.[7][16] Mindful of the high cost of wiring England based on the cost per word, Caldwell famously but tersely wired London,"Monotremes oviparous, ovum meroblastic." That is, monotremes lay eggs. The yolk is absorbed by the developing young.[33]

The species exhibits a single breeding season, with mating occurring between June and October, with some local variation taking place in populations across the extent of its range.[25] Historical observation, mark and recapture studies and preliminary investigations of population genetics indicate the possibility of resident and transient members of populations and suggest a polygynous mating system.[34] Females are thought likely to become sexually mature in their second year, with breeding confirmed to still take place in animals over nine years old.[34]

Outside the mating season, the Platypus lives in a simple ground burrow whose entrance is about 30 cm (1 ft) above the water level. After mating, the female constructs a deeper, more elaborate burrow up to 20 m (66 ft) long and blocked with plugs at intervals (which may act as a safeguard against rising waters or predators, or as a method of regulating humidity and temperature).[35] The male takes no part in caring for its young, and retreats to its yearlong 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.[3]

The female Platypus has a pair of ovaries but only the left one is functional.[26] It lays one to three (usually two) small, leathery eggs (similar to those of reptiles), that are about 11 mm (7/16 inches) in diameter and slightly rounder than bird eggs.[36] The eggs develop in utero for about 28 days with only about 10 days of external incubation (in contrast to a chicken egg which spends about 1 day in tract and 21 days externally).[26] After laying her eggs, the female curls around them. The incubation period is separated into three parts. In the first, the embryo has no functional organs and relies on the yolk sac for sustenance. During the second, the digits develop, and in the last, the egg tooth appears.[37]

The newly hatched young 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. There are grooves on her abdomen that form pools of milk, allowing the young to lap it up.[3][25] After they hatch, the offspring are suckled for three to four months. During incubation and weaning, the mother initially only leaves the burrow for short periods to forage. When doing so, she creates a number of thin soil plugs along the length of 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.[38] 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.[25]

In mammalian evolution

The Platypus and other monotremes were very poorly understood for many years and some of the 19th century myths that grew up around them, for example, that the monotremes were "inferior" or quasi-reptilian, still endure.[39] It is now generally accepted that modern monotremes are the survivors of an early branching of the mammal tree; a later branching is thought to have led to the marsupial and placental groups.[40][39] Although in 1947, William King Gregory had theorized that placental mammals and marsupials may have diverged earlier with a subsequent branching dividing the monotremes and marsupials, later research and fossil discoveries have suggested this is incorrect.[39][41]

The oldest discovered fossil of the modern Platypus dates back to about 100,000 years ago, during the Quaternary period. The extinct monotremes (Teinolophos and Steropodon) were closely related to the modern Platypus.[41] The fossilised Steropodon was discovered in New South Wales and is composed of an opalised lower jawbone with three molar teeth (whereas the adult contemporary Platypus is toothless). The molar teeth were initially thought to be tribosphenic which would have supported a variation of Gregory's theory, but later research has suggested while they have three cusps they evolved under a separate process.[14] The fossil is thought to be about 110 million years old, which means that the Platypus-like animal was alive during the Cretaceous period, making it the oldest mammal fossil found in Australia. Monotrematum sudamericanum, another fossil relative of the Platypus has been found in Argentina, indicating that monotremes were present in the supercontinent of Gondwana when the continents of South America and Australia were joined via Antarctica (up to about 167 million years ago).[14][42]

Because of the early divergence from the therian mammals and the low numbers of extant monotreme species, it is a frequent subject of research in evolutionary biology. In 2004, researchers at the Australian National University discovered the Platypus has ten sex chromosomes, compared to two (XY) found in most other mammals (for instance, a male Platypus is always XYXYXYXYXY). Furthermore, one of the Platypus' Y chromosomes shares genes with the ZZ/ZW sex chromosomes found in birds. This news further pronounced the individuality of the Platypus in the animal kingdom.[43] However it lacks the mammalian sex-determining gene SRY, meaning that the process of sex determination in the Platypus remains unknown.[44]

Conservation status

Except for its loss from the state of South Australia, the Platypus occupies the same general distribution as it did prior to European settlement of Australia. However, local changes and fragmentation of distribution due to human modification of its habitat are documented. Its current and historical abundance, however, is less well known and it has probably declined in numbers, although still being considered as common over most of its current range.[27] The species was extensively hunted for its fur until the early years of the 20th century and, although protected throughout Australia in 1905,[38] up until about 1950 it was still at risk of drowning in the nets of inland fisheries.[23] The Platypus does not appear to be in immediate danger of extinction thanks to conservation measures, but it could be impacted by habitat disruption caused by dams, irrigation, pollution, netting and trapping.[2] The IUCN lists the Platypus on its Red List as Least Concern.[2]

A fungal infection poses a possible threat to Platypuses in Tasmania. The fungus, Mucor amphiborum causes ulceration on the body that can lead to problems with thermoregulation and death from secondary infections. The same fungus so far causes no problems to the Platypus on the Australian mainland. The Tasmania Parks and Wildlife Service and Biodiversity Conservation Branch Department of Primary Industries and Water are collaborating to monitor the effects of the infection on the Platypus population in Tasmania.[45] Platypuses in Tasmania tend to be larger than those found in the mainland of Australia, possibly because of the lack of introduced predators. The failure to establish the red fox in particular is theorized to be a contributing factor to both the greater average size and abundance of the Platypus in the state.[10]

Much of the world was introduced to the Platypus in 1939 when National Geographic magazine published an article on the Platypus and the efforts to study and raise it in captivity. This is a difficult task, and only a few young have been successfully raised since — notably at Healesville Sanctuary in Victoria. The leading figure in these efforts was David Fleay who established a platypussary — a simulated stream in a tank — at the Healesville Sanctuary and had a successful breeding in 1943. In 1972, he found a dead baby of about 50 days old, which had presumably been born in captivity, at his wildlife park at Burleigh Heads on the Gold Coast, Queensland.[46] Healesville repeated its success in 1998 and again in 2000 with a similar stream tank. Taronga Zoo in Sydney bred twins in 2003, and had another birth in 2006.[47]

In popular culture

The Platypus is sometimes jokingly referred to as proof that God has a sense of humour (at the beginning of the film Dogma for example). Its unusual appearance has led to it featuring in many media, particularly in its native Australia. The Platypus has been used several times as a mascot: "Syd" the Platypus was one of the three mascots chosen for the Sydney 2000 Olympics along with an echidna and a Kookaburra,[48] while Hexley the Platypus is the mascot for Apple Computer's BSD-based Darwin operating system, Mac OS X.[49] A Platypus named Phyl appears in several of the books written by Timothy Budd. Phyl is used to illustrate two important principles of object-oriented programming: inheritance and overriding.[50] The satirist Barry Humphries exhibited the box of a mock pesticide product called "Platytox" during his early surrealist period.[51] Experimental rock band Mr. Bungle has a track named after the creature on their second major album, Disco Volante,[52] and Green Day have a song called Platypus (I Hate You) on their 1997 album, Nimrod.

Platypuses are frequently seen in children's programs. The Platypus Family (Dr. Bill, his wife Elsie Jean and daughter Ana) were prominent characters on Mister Rogers’ Neighborhood. A Platypus named Ovide was the star of the cartoon Ovide and the Gang.[53] Two Platypuses appear in the cartoon Taz-Mania. a young Platypus named Flap is a regular character in each of the Blinky Bill cartoon series. In the animated show Camp Lazlo, the character of Edward is a Platypus. In 1995, United Paramount Network broadcast a short-lived television series entitled Platypus Man, starring comedian Richard Jeni. The title was derived from one of Jeni's stand-up routines, in which he compared various aspects of his own lifestyle to that of the Platypus.

References and Notes

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Comments

omg it is the most amazing thing ive ever seen before
platypuses r awesome
I love the platypus, I'm writing a report and can't find any books who doesn't like the platypus? Obviously a lot of book writers
I'm doing a report on platypus' and I loved them before I started :) they are soooo cute I love them on more then ever!!!!!!!!!
Duck billed Platypuses are the weirdest animals i have seen but i think they are really funny and i love them.
Platypus' rule! They are cool!
Platypusus RULE!!!
i love platypuses i have to do it on a project in GATE!
I LOVE THE PLATYPUS!! IT IS AN AWESOME ANIMAL! THERE SOO CUTE AND DIFFERENT. I HAVE DEFINITELY PUT HOLDING A DUCK-BILLED PLATYPUS ON MY LIST OF THINGS TO  DO BEFORE I DIE =] =] LOVEE 'EMM!! XOX

(Reply : yes but the venom in it's ankle spurs can be extremely painful and therefore the platypus is not suitable for holding)

i love platypus'. - Their sooo... cute!! They are my favourite animal in the world, and by the way to me the video did work. But anyways I think people should do this thing where you save over 100 000 Platypus' and I'll definitely be part of it. I also think people should make a group where you talk about Platypus' and learn more about it from like an adult or an expert. I'll also definitely be part of that too. - I Love You Platypus'<3
I want a pet Platypus soooo badly. I get giddy every time I see one

(Reply: The venom of a platypus is very painful and would not be suitable as a pet, sorry)

Platypuses! I LOVE them so Much. I saw the cutest BABY platypus Picture!!!!
i am doing a project on platypus' and I just find them very interesting!
i am doing a spider diagram on platypuses and i never knew they had venom and all that it is really fun doing this project on platypuses.
SAVE THE PLATYPUSES!!!!!!!
 I love those amazing animals
I REALLY LOVE THESE THINGS
they are sooo cute and gorgeous and they look so friendly and and lovely long nails from becca
I looooooove platypuses
I'm studying how the platypus evolved. it is really quite interesting to discover how a monotreme from today had evolved from something found in Australia over 110 million years ago. fascinating.
dude they are so awesome man do they rock
i think the real question is, who doesn't like platypuses
This Is My Bestest Friend In The World Briiiiittany!
i think the platypus is the most unique animal in the world and they are so cute i think i will be a platypus preserver when i grow up and here is a question: how many animals is the platypus made up of ? i know some people that want to know and i'm doing everything i can to learn about the platypus and i would love to make a platypus preserve/farm to take care of them keep up the good preserving of that awesome platypus!
Wow! I looooove platypuses
Platypuses are cute!

**STAR COMMENT**

I'm doing a report on platypuses for a school report and they are really starting to grow on me! They are so unique. It seems like someone combined 10 animals and came up with a platypus! Platypuses=awesome!!!!!!!

**STAR COMMENT**

OMG I LOVE PLATYPUSES <3 THEY ARE THE CUTEST THINGS IN THE WORLD!!!:):)

I think platypuses are cool!!!!1:) By: Abdi:)

I love platypuses and I think you guys did a great job on this but you could make it better by having a platypus video that works. I want to say you should have more people know about platypusus or you should save them because they are the greatest animal and if they go bye bye i will be mad and so so so so so sad so please save them go on to national tv and do a video about platypusus and how they are so cool thank you. mother of 12.


 

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