Platypus
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{{Taxobox
| name = Platypus<ref name=MSW3>{{MSW3 Groves | pages = 2|id=10300020}}</ref>
| status = LR/lc
| status_system = iucn2.3
| trend = unknown
| status_ref =<ref name="IUCN">{{IUCN2006|assessors=Australasian Marsupial & Monotreme Specialist Group|year=1996|id=40488|title=Ornithorhynchus anatinus|downloaded=9 May 2006}} Database entry includes a brief justification of why this species is of least concern </ref>
| image = Ornithorhynchidae-00.jpg
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Mammal]]ia
| ordo = [[Monotremata]]
| familia = [[Ornithorhynchidae]]
| genus = '''''Ornithorhynchus'''''
| genus_authority = [[Johann Friedrich Blumenbach|Blumenbach]], 1800
| species = '''''O. anatinus'''''
| binomial = ''Ornithorhynchus anatinus''
| binomial_authority = ([[George Shaw|Shaw]], 1799)
| range_map = Platypus Distribution.png
| range_map_caption = Platypus range (indicated by darker shading)<ref name="APC">{{cite web|url=http://www.platypus.asn.au/|title=Platypus facts file|publisher=Australian Platypus Conservancy| accessdate = 2006-09-13}}</ref>
}}
The '''Platypus''' (''Ornithorhynchus anatinus'') is a semi-[[Aquatic animal|aquatic]] [[mammal]] [[Endemic (ecology)|endemic]] to [[Eastern states of Australia|eastern Australia]], including [[Tasmania]]. Together with the four species of [[echidna]], it is one of the five extant species of [[monotreme]]s, the only mammals that lay [[Egg (biology)|eggs]] instead of giving birth to live young. It is the sole living representative of its [[Family (biology)|family]] (''[[Ornithorhynchidae]]'') and [[genus]] ('''''Ornithorhynchus'''''), though a number of [[Monotreme#Fossil Monotremes|related species]] have been found in the fossil record.
The bizarre appearance of this egg-laying, [[venom]]ous, [[duck]]-billed, [[beaver]]-tailed, [[otter]]-footed mammal baffled European naturalists when they first encountered it, 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 that delivers a venom 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 recognisable and iconic symbol of [[Australia]]; it has appeared as a mascot at national events and is featured on the [[Obverse and reverse|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.
== Taxonomy and etymology ==
When the Platypus was first discovered by Europeans in 1798, a [[Pelage|pelt]] and sketch were sent back to the [[Kingdom of Great Britain|United Kingdom]] by [[John Hunter (New South Wales)|Captain John Hunter]], the second Governor of [[New South Wales]].<ref name="Paradox">{{cite journal|journal=BioScience|title=The Paradoxical Platypus|author=Brian K. Hall|volume=49|issue=3|pages=211–218|publisher=American Institute of Biological Sciences|date=1999-03|doi=10.2307/1313511}}</ref> The British scientists were at first convinced that the attributes must have been a hoax.<ref name="APC" /> [[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 [[Taxidermy|taxidermist]].<ref name="hoax">{{cite web|url=http://www.museumofhoaxes.com/hoax/Hoaxipedia/Duckbilled_Platypus/|title= Duck-billed Platypus|publisher =Museum of hoaxes| accessdate = 2008-04-02}}</ref> 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.<ref name="APC" />
The common name, ''Platypus'', is Latin derived from the Greek words πλατύς ("platys", flat, broad) and πους ("pous", foot), meaning "flat foot".<ref> {{cite book|author=Liddell & Scott|year=1980|title=Greek-English Lexicon, Abridged Edition |publisher=Oxford University Press, Oxford, UK|id=ISBN 0-19-910207-4}}</ref> Shaw assigned it as a [[Linnaean taxonomy|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'').<ref name="ABRS">{{cite web|url=http://www.deh.gov.au/biodiversity/abrs/publications/fauna-of-australia/pubs/volume1b/16-ind.pdf#search=%22platypus%20pelt%201700%22|title=Fauna of Australia chap.16 vol.1b|author=J.R.Grant|publisher=Australian Biological Resources Study (ABRS)| accessdate = 2006-09-13}}</ref> It was independently described as ''Ornithorhynchus paradoxus'' by [[Johann Blumenbach]] in 1800 (from a specimen given to him by [[Sir Joseph Banks]])<ref name="NLA">{{cite web|url=http://www.nla.gov.au/pub/gateways/archive/52/p16a01.html|title=Platypus Paradoxes|publisher=National Library of Australia|date=2001–08| accessdate = 2006-09-14}}</ref> and following the rules of priority of nomenclature it was later officially recognised as ''Ornithorhynchus anatinus''.<ref name="ABRS"/>
The scientific name ''Ornithorhynchus'' is derived from ''ορνιθόρυνχος'' ("ornithorhynkhos"), which literally means "bird snout" in [[Greek language|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" or simply "platypus". Colloquially, "platypi" is also used for the plural, although this is [[pseudo-Latin]];<ref name="APC" /> the Greek plural would be "platypodes". Early [[United Kingdom|British]] [[settler]]s called it by many names, such as '''watermole''', '''duckbill''', and '''duckmole'''.<ref name="APC" /> The name "Platypus" is often prefixed with the adjective "duck-billed" to form '''Duck-billed Platypus''', despite there being only one species of Platypus.<ref name="UT">{{cite web|url=http://www.medicine.utas.edu.au/research/mono/Platpage.html|title=The Platypus|publisher=Department of Anatomy & Physiology, University of Tasmania|date=1997-07-03| accessdate = 2006-09-14}}</ref>
== 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.<ref name="APC" /><ref name="ABRS" /> The Platypus uses its tail for storage of fat reserves (an adaptation also found in animals such as the [[Tasmanian Devil]]<ref name="Guiler">{{cite book|author=Guiler, E.R.|date=1983|chapter=Tasmanian Devil|editor=R. Strahan Ed.|title=The Australian Museum Complete Book of Australian Mammals|pages=27–28|publisher=Angus & Robertson|id=ISBN 0-207-14454-0}}</ref> and [[fat-tailed sheep]]). 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.<ref name="ABRS" /> Unlike a [[bird]]'s [[beak]] (in which the upper and lower parts separate to reveal the 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.<ref name="ABRS" /> Platypuses have been heard to emit a low growl when disturbed and a range of other vocalisations have been reported in captive specimens.<ref name="APC" />
[[Image:platypus-sketch.jpg|left|200px|thumb|A colour print of platypuses from 1863]]<!--[[Image:Platypus.jpg|left|thumb|250px|A platypus in [[Sydney Aquarium]] in 2004]]-->
Weight varies considerably from {{convert|0.7|to|2.4|kg|lb|abbr=on|lk=on}}, with males being larger than females: males average {{convert|50|cm|in|abbr=on|lk=on}} total length while females average {{convert|43|cm|in|abbr=on}}.<ref name="ABRS" /> 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.<ref name="Workshop">{{cite web|url=http://www.medicine.utas.edu.au/research/mono/Taspaper.html|title=Current research on the platypus, Ornithorhynchus anatinus in Tasmania: Abstracts from the 1999 'Tasmanian Platypus WORKSHOP'|author=Sarah Munks and Stewart Nicol|publisher=University of Tasmania|date=1999–05| accessdate = 2006-10-23}}</ref>
The Platypus has an average [[Core temperature|body temperature]] of about {{convert|32|°C|°F|lk=on}} rather than the {{convert|37|°C|°F}} typical of [[placentalia|placental mammals]].<ref name="DC">{{cite web|url=http://www.bio.davidson.edu/courses/anphys/1999/White/thermal.htm|title=Thermal Biology of the Platypus|publisher=Davidson College|date=1999| accessdate = 2006-09-14}}</ref> 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.<ref name="temp">{{cite journal|journal=Australian Journal of Zoology|title=Monotreme Cell-Cycles and the Evolution of Homeothermy|author=J.M. Watson and J.A.M. Graves|volume=36|issue=5|pages=573–584|date=1988|publisher=CSIRO | doi = 10.1071/ZO9880573 <!--Retrieved from CrossRef by DOI bot-->}}</ref><ref name="temp2">{{cite journal|journal=Australian Journal of Zoology|title=Standard Metabolism of Monotremes and the Evolution of Homeothermy|author= T.J. Dawson, T.R. Grant and D. Fanning |volume=27|issue=4|pages=511–515|date=1979|publisher=CSIRO | doi = 10.1071/ZO9790511 <!--Retrieved from CrossRef by DOI bot-->}}</ref>
The modern Platypus young have three-cusped [[Molar (tooth)|molars]] which they lose before or just after leaving the breeding burrow;<ref name="MS">{{cite journal|journal=Acta Palaeontologica Polonica |url=http://app.pan.pl/acta47/app47-487.pdf|title=New data on the Paleocene monotreme ''Monotrematum sudamericanum'', and the convergent evolution of triangulate molars|author=Pascual, R., Goin, F.J., Balarino, L., and Udrizar Sauthier, D.E.|volume=47|issue=3|pages=487–492|date=2002|format={{dead link|date=June 2008}} – <sup>[http://scholar.google.co.uk/scholar?hl=en&lr=&q=intitle%3ANew+data+on+the+Paleocene+monotreme+%27%27Monotrematum+sudamericanum%27%27%2C+and+the+convergent+evolution+of+triangulate+molars&as_publication=Acta+Palaeontologica+Polonica&as_ylo=&as_yhi=&btnG=Search Scholar search]</sup>}}</ref><ref name="geowords">{{cite web|url=http://geowords.com/histbooknetscape/f01.htm|title=Living mammals are placentals (eutheria), marsupials, and monotremes|publisher=Geowords|author=Hugh Race| accessdate = 2006-09-19}}</ref> adults have heavily keratinised pads in their place.<ref name="ABRS" /> The Platypus [[jaw]] is constructed differently from that of other mammals, and the jaw-opening muscle is different.<ref name="ABRS" /> 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 [[cynodont]]s and other pre-mammalian [[synapsid]]s. However, the external opening of the ear still lies at the base of the jaw.<ref name="ABRS" /> The Platypus has extra bones in the shoulder girdle, including an [[interclavicle]], which is not found in other mammals.<ref name="ABRS" /> It has a [[Reptile|reptilian]] gait, with legs that are on the sides of the body, rather than underneath.<ref name="ABRS" />
=== Venom ===
{{main|Platypus venom}}
[[Image:Platypus spur.JPG|right|thumb|The calcaneus spur found on the male's hind limb is used to deliver venom.]]
The male Platypus has ankle spurs which produce a cocktail of venom,<ref>[http://www.australianfauna.com/platypus.php Australian Fauna]</ref><ref>[http://www.usyd.edu.au/news/84.html?newsstoryid=2267 The University of Sydney] </ref><ref>[http://rainforest-australia.com/platypus_poison.htm Rainforest Australia]</ref>
composed largely of [[defensin]]-like [[protein]]s (DLPs), which is unique to the Platypus.<ref name="PS">{{cite journal| last = Gerritsen| first = Vivienne Baillie | title = Platypus poison| journal = Protein Spotlight| issue = 29| date = 2002-12| url = http://www.expasy.org/spotlight/back_issues/sptlt029.shtml| accessdate = 14 September|accessyear=2006 }}</ref> Although powerful enough to kill smaller animals,<ref name="PS" /> the venom is not lethal to humans, but is so excruciating that the victim may be incapacitated. [[Edema|Oedema]] rapidly develops around the wound and gradually spreads throughout the affected limb. Information obtained from [[Case study|case histories]] and anecdotal evidence indicates that the pain develops into a long-lasting [[hyperalgesia]] that persists for days or even months.<ref name="JN">{{cite journal|journal= Journal of Neurophysiology|title=Venom From the Platypus, ''Ornithorhynchus anatinus'', Induces a Calcium-Dependent Current in Cultured Dorsal Root Ganglion Cells|author=G. M. de Plater, P. J. Milburn and R. L. Martin|volume=85|issue=3|pages=1340–1345|date=2001-3|publisher=American Physiological Society|url=http://jn.physiology.org/cgi/reprint/85/3/1340}}</ref><ref name="venom">{{cite web|url=http://www.kingsnake.com/toxinology/old/mammals/platypus.html|title=The venom of the platypus (Ornithorhynchus anatinus)| accessdate = 2006-09-13}}</ref> Venom is produced in the [[wiktionary:crural|crural]] glands of the male, which are kidney-shaped [[alveolar gland]]s 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.<ref name="ABRS" />
The venom appears to have a different function from those produced by non-mammalian species: its effects are not 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 theorised that it is used as an offensive weapon to assert dominance during this period.<ref name="PS" />
=== Electrolocation ===
Monotremes (see also [[echidna]] for the other species) 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.<ref name="Electro1">{{cite journal| last = Pettigrew| first = John D.| title = Electroreception in Monotremes| journal = The Journal of Experimental Biology|pages=1447–1454| issue = 202| date = 1999| url = http://jeb.biologists.org/cgi/reprint/202/10/1447.pdf| accessdate = 19 September|accessyear=2006 |format=PDF}}</ref>
The [[electroreceptor]]s are located in rostro-caudal rows in the skin of the bill, while [[mechanoreceptor]]s (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. Both electroreceptors and mechanoreceptors in the bill dominate the [[somatotopic map]] of the platypus brain, in the same way human hands dominate the [[Cortical homunculus|Penfield homunculus map]].<ref name="sensory_platypus">{{cite journal
| last = Pettigrew
| first = John D.
| coauthors = P R Manger, and S L Fine
| title = The sensory world of the platypus
| journal = Philosophical Transactions of the Royal Society of London
| pages = 1199–1210
| issue = 353
| date = 1998
| url = http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1692312&blobtype=pdf
| accessdate = 8 August
| accessyear = 2007
}}</ref><ref name="Ancestors_Tale">{{cite book
| first = Richard
| last = Dawkins
| authorlink = Richard Dawkins
| title = [[The Ancestor's Tale|The Ancestor's Tale, A Pilgrimage to the Dawn of Life]]
| chapter = The Duckbill's Tale
| publisher = Houghton Mifflin Company
| location = Boston
| year = 2004
| id = ISBN 0-618-00583-8 }}</ref>
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.<ref name="Electro1" />
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).<ref name="Electro1" /> 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.<ref name=Manning>{{cite book | author = Manning, A & Dawkins, M.S. |title = An Introduction to Animal Behaviour Fifth Edition | publisher = Cambridge University Press | year = 1998}}</ref>
== Ecology and behaviour ==
[[Image:Platipus-on-the-surface.jpg|thumb|The platypus is very difficult to spot even on the surface of a river.]]
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 rainforest]]s of coastal [[Queensland]] as far north as the base of the [[Cape York Peninsula]].<ref name="DPIW">{{cite web|url=http://www.dpiw.tas.gov.au/inter.nsf/WebPages/BHAN-53573T?open|title=Platypus|publisher = Department of Primary Industries and Water, Tasmania|date=2006-08-31| accessdate = 2006-10-12}}</ref> Inland, its distribution is not well known: it is extinct in [[South Australia]] (barring an introduced population on [[Kangaroo Island]])<ref name="RKI">{{cite web|url=http://web.archive.org/web/www.ees.adelaide.edu.au/research/fbp/ki_res/|title=Research on Kangaroo Island|publisher=University of Adelaide|date=2006-07-04| accessdate = 2006-10-23}}</ref> 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.<ref name="CSIRO">{{cite web|
url=http://www.clw.csiro.au/publications/technical97/tr23-97.pdf|
title=Impacts of water management in the Murray-Darling Basin on the platypus (''Ornithorhynchus anatinus'') and the water rat (''Hydromus chrysogaster'')|author=Anthony Scott and Tom Grant|publisher=CSIRO Australia|date=1997-11| accessdate = 2006-10-23|format=PDF}}</ref> 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 River|Maribyrnong]], for example).<ref name="APC2">{{cite web|url=http://www.platypus.asn.au/platypus_in_country_areas.html|title=Platypus in Country Areas|publisher=Australian Platypus Conservancy| accessdate = 2006-10-23}}</ref>
In captivity, Platypuses have survived to seventeen years of age and wild specimens have been recaptured at eleven years old. [[Mortality rate]]s for adults in the wild appear to be low.<ref name="ABRS" /> Natural predators include [[snake]]s, [[water rat]]s, [[goanna]]s, [[hawk]]s, [[owl]]s and [[eagle]]s. Low Platypus numbers in northern Australia are possibly due to predation by [[crocodile]]s.<ref name="EPA">{{cite web|url=http://www.epa.qld.gov.au/nature_conservation/wildlife/native_animals/platypus/| title=Platypus|publisher=Environmental Protection Agency/Queensland Parks and Wildlife Service|date=2006| accessdate = 2006-10-24}}</ref> The introduction of [[red fox]]es as a predator for [[rabbit]]s may have had some impact on its numbers on the mainland.<ref name="Workshop" /> The Platypus is generally regarded as [[nocturnal]] and [[crepuscular]], but individuals are also active during the day, particularly when the sky is overcast.<ref name="EC">{{cite web|url=http://www.biology.iastate.edu/intop/1Australia/04papers/CromerMonotrRepro.htm|title=Monotreme Reproductive Biology and Behavior|publisher=Iowa State University|author=Erica Cromer|date=2004-04-14| accessdate = 2006-10-23}}</ref><ref name="HCP">{{cite journal|journal=Philosophical Transactions: Biological Sciences|title=Field Biology of the Platypus (Ornithorhynchus Anatinus): Historical and Current Perspectives|publisher=The Royal Society|volume=353|issue=1372|author=T.G. Grant and P. D. Temple-Smith|date=1998-07-29|pages=1081–1091 | doi = 10.1098/rstb.1998.0267 <!--Retrieved from CrossRef by DOI bot-->}}</ref> 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.<ref name="HCP" /> It may have a range of up to {{convert|7|km|mi|abbr=on|lk=on}}, with male's home ranges overlapping with those of 3 or 4 females.<ref name="AJZ4">{{cite journal|journal=Australian Journal of Zoology|title=Spatial-Organization and Movement Patterns of Adult Male Platypus, Ornithorhynchus-Anatinus (Monotremata, Ornithorhynchidae)
|publisher=CSIRO|volume=43|issue=1|author= J.L. Gardner and M. Serena |date=1995|pages=91–103 | doi = 10.1071/ZO9950091 <!--Retrieved from CrossRef by DOI bot-->
}}</ref>
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.<ref name="parks">{{cite web|url=http://www.parks.tas.gov.au/factsheets/wildlife/Platypus.pdf|title =Platypus|publisher=Parks and Wildlife Service Tasmania|date=2003-12| accessdate = 2006-10-23|format=PDF}}</ref> 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.<ref name="Rowing">{{cite journal|journal=The Journal of Experimental Biology|volume=200|issue=20|pages=2647–2652|title=Energetics of Swimming by the Platypus ''Ornithorhynchus Anatinus'': Metabolic Effort Associated with Rowing|publisher=The Company of Biologists Limited|author=F.E. Fish, R.V. Baudinette, P.B. Frappell, and M.P. Sarre|date=1997-07-28|url=http://jeb.biologists.org/cgi/reprint/200/20/2647.pdf}}</ref> The species is [[Warm-blooded|endothermic]], maintaining its body temperature about {{convert|32|°C|°F}}, lower than most mammals, even while foraging for hours in water below {{convert|5|°C|°F}}.<ref name="ABRS" />
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.<ref name="Bethge">{{cite web|url=http://www.bethge.org/BethgePhD.pdf|title=Energetics and foraging behaviour of the platypus|publisher = University of Tasmania|author=Philip Bethge|date=2002-04| accessdate = 2006-10-23|format=PDF}}</ref><ref>{{cite journal|journal=The Journal of Applied Ecology|title=The Diving Behaviour of the Platypus (''Ornithorhynchus anatinus'') in Waters with Different Trophic Status|author=H. Kruuk|volume=30|issue=4|date=1993|pages=592–598 | doi = 10.2307/2404239 <!--Retrieved from CrossRef by DOI bot-->}}</ref> The Platypus is a [[carnivore]]: it feeds on [[annelid]] worms and [[Larva|insect larvae]], freshwater [[shrimp]]s, and [[yabbie]]s (freshwater crayfish) that it digs out of the riverbed with its snout or catches while swimming. It utilises cheek-pouches to carry prey to the surface where they are eaten.<ref name="parks" /> 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.<ref name="Bethge" /> 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 [[Camouflage|hidden]] under a protective tangle of roots.<ref name="parks" />
=== 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.<ref name="ABRS"/><ref name="PS"/> 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, and the eggs are similar to those of reptiles in that only part of the egg divides as it develops. <!--Suggest moving this to article on Caldwell when written. A bit of historical footnote that better belongs to zoology or a person-->
The species exhibits a single [[breeding season]]; mating occurs between June and October, with some local variation taking place in populations across the extent of its range.<ref name="EPA" /> 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 [[Polygyny|polygynous]] mating system.<ref name="AJZ2">{{cite journal|journal=Australian Journal of Zoology|title=Aspects of Lactation in the Platypus, ''Ornithorhynchus anatinus'' (Monotremata), in Waters of Eastern New South Wales|author=T.R. Grant, M. Griffiths and R.M.C. Leckie|volume=31|issue=6|pages=881–889|publisher=1983|doi=10.1071/ZO9830881|year=1983}}</ref> 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.<ref name="AJZ2"/>
Outside the mating season, the Platypus lives in a simple ground burrow whose entrance is about {{convert|30|cm|in|abbr=on}} above the water level. After mating, the female constructs a deeper, more elaborate burrow up to {{convert|20|m|ft|abbr=on|lk=on}} 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).<ref name="ADW">{{cite web | url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Ornithorhynchidae.html | title=Family Ornithorhynchidae (platypus) | author = Anna Bess Sorin and Phil Myers |publisher = University of Michigan Museum of Zoology|date=2001|accessdate=2006-10-24}}</ref> 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.<ref name="APC" />
The female Platypus has a pair of [[Ovary|ovaries]] but only the left one is functional.<ref name="EC" /> It lays one to three (usually two) small, leathery eggs (similar to those of reptiles), that are about {{convert|11|mm|in|abbr=on|lk=in}} in diameter and slightly rounder than bird eggs.<ref name="BSED">{{cite journal|journal= Philosophical Transactions of the Royal Society B: Biological Sciences|title=Early development and embryology of the platypus|author=R. L. Hughes and L. S. Hall|volume=353|issue=1372|pages=1101–1114|publisher=The Royal Society|date=1998-07-29 | doi = 10.1098/rstb.1998.0269 <!--Retrieved from CrossRef by DOI bot-->}}</ref> The eggs develop ''[[in utero]]'' for about 28 days with only about 10 days of external [[Incubate|incubation]] (in contrast to a chicken egg, which spends about 1 day in tract and 21 days externally).<ref name="EC" /> 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. The yolk is absorbed by the developing young.<ref>{{cite web|title=Ockhams Razor|work=The Puzzling Platypus|url=http://www.abc.net.au/rn/science/ockham/stories/s332655.htm|accessdate=2006-12-02}}</ref> During the second, the digits develop, and in the last, the [[egg tooth]] appears.<ref name="RS2">{{cite journal|journal=Philosophical Transactions: Biological Sciences|title =The Development of the External Features of the Platypus (''Ornithorhynchus Anatinus'')|author=Paul R. Manger, Leslie S. Hall, John D. Pettigrew|volume=353|issue=1372|pages=1115–1125|date=1998-07-29|publisher=The Royal Society|doi =10.1098/rstb.1998.0270}}</ref>
The newly hatched young are vulnerable, blind, and hairless, and are fed by the mother's milk. Although possessing [[mammary gland]]s, 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.<ref name="APC" /><ref name="EPA" /> 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.<ref name="QM">{{cite web|url=http://www.qm.qld.gov.au/inquiry/leaflets/leaflet0010.pdf|title=Egg-laying mammals|publisher=Queensland Museum|date=2000-11| accessdate = 2006-10-24|format=PDF}}</ref> 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.<ref name="EPA" />
== Evolution ==
[[Image:Platypus skeleton Pengo.jpg|left|thumb|200px|Platypus skeleton]]
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 quasi-[[Reptile|reptilian]] — still endure.<ref name="Rodent">{{cite journal|journal=Philosophical Transactions: Biological Sciences|title=The Platypus is not a Rodent: DNA Hybridization, Amniote Phylogeny and the Palimpsest Theory|author=John A. W. Kirsch and Gregory C. Mayer|volume=353|issue=1372|pages=1221–1237|date=1998-07-29|doi=10.1098/rstb.1998.0278}}</ref> In fact, 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.<ref name="JME">{{cite journal|journal=Journal of Mammalian Evolution|publisher=Springer Netherlands|title=Evolution of the Monotremes: Phylogenetic Relationship to Marsupials and Eutherians, and Estimation of Divergence Dates Based on α-Lactalbumin Amino Acid Sequences|author=M. Messer, A.S. Weiss, D.C. Shaw and M. Westerman|volume=5|issue=1|pages=95–105|date=1998-03 | doi = 10.1023/A:1020523120739 <!--Retrieved from CrossRef by DOI bot-->}}</ref><ref name="Rodent" /> Although in 1947, [[William King Gregory]] had theorised that placental mammals and marsupials may have diverged earlier and a subsequent branching divided the monotremes and marsupials, later research and fossil discoveries have suggested this is incorrect.<ref name="Rodent" /><ref name="JM">{{cite web|url=http://www.nature.com/nature/journal/v416/n6877/extref/416165a-s1.doc|title=The first Jurassic mammal from South America|author=O. W. M. Rauhut, T. Martin, E. Ortiz-Jaureguizar and P. Puerta|publisher=Nature| accessdate = 2006-10-24|date=2001-12-11|format=DOC}}</ref>
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.<ref name="JM" /> 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 molar|tribosphenic]], which would have supported a variation of Gregory's theory, but later research has suggested that, while they have three cusps, they evolved under a separate process.<ref name="MS" /> 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).<ref name="MS" /><ref name="patagonia">{{cite web|url=http://www.findarticles.com/p/articles/mi_m1511/is_n1_v14/ai_13670058|title=A platypus in Patagonia — Ancient life|author=Tim Folger|publisher=Discover|date=1993-01| accessdate = 2006-10-17}}</ref>
Because of the early divergence from the [[Theria|therian mammals]] and the low numbers of extant monotreme species, it is a frequent subject of research in evolutionary biology. In 2004, [[research]]ers at the [[Australian National University]] discovered the Platypus has ten [[sex chromosome]]s, compared with two (XY) in most other mammals (for instance, a male Platypus is always XYXYXYXYXY).<ref name="discover">{{cite web|url=http://discovermagazine.com/2005/apr/sex-ys-platypuses0425/|title=Sex, Ys, and Platypuses|publisher=Discover|author=Jocelyn Selim|date=2005-04-25| accessdate = 2008-05-07}}</ref> Although given the XY designation of mammals, the sex chromosomes of the Platypus are more similar to the ZZ/ZW sex chromosomes found in [[bird]]s.<ref name="draft_genome">{{cite journal| journal = Nature| volume = 453| issue = 7192| pages = 175–183| title = Genome analysis of the platypus reveals unique signatures of evolution| date = 2008-05-08| doi = 10.1038/nature06936| author = Warren, Wesley C.}}</ref> It also lacks the mammalian sex-determining gene [[SRY]], meaning that the process of sex determination in the Platypus remains unknown.<ref>{{cite web|url=http://pre.ensembl.org/Ornithorhynchus_anatinus/index.html|title=Explore the Platypus genome|publisher=Ensembl|date=2006-11| accessdate = 2007-01-19}}</ref> A draft version of the platypus genome sequence was published in ''[[Nature (journal)|Nature]]'' on [[8 May]] [[2008]], revealing both reptilian and mammalian elements, as well as two genes found previously only in birds, amphibians and fish.<ref name="draft_genome" /> More than 80% of the Platypus' genes are common to the other mammals whose genomes have been sequenced.
== 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.<ref name="HCP" /> The species was extensively hunted for its fur until the early years of the 20th century and, although protected throughout Australia in 1905,<ref name="QM" /> up until about 1950 it was still at risk of drowning in the nets of inland fisheries.<ref name="CSIRO" /> 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.<ref name="IUCN" /> The [[IUCN]] lists the Platypus on its [[Red List]] as Least Concern.<ref name="IUCN" />
[[Image:platypus-plate.jpg|right|200px|thumb|A depiction of a Platypus from a book for children published in Germany in 1798]]
Platypuses generally suffer from few diseases in the wild; however, there is widespread public concern in Tasmania about the potential impacts of a disease caused by the fungus ''[[Mucor amphibiorum]]''. The disease (termed ''[[Mucormycosis]]'') only affects Tasmanian platypuses, and has not been observed in platypuses in mainland Australia. Affected platypuses can develop ugly skin lesions or ulcers on various parts of the body, including their backs, tails and legs. Mucormycosis can kill platypuses, death arising from secondary infection and by affecting the animals' ability to maintain body temperature and forage efficiency. The Biodiversity Conservation Branch at the Department of Primary Industries and Water are collaborating with NRM north and [[University of Tasmania]] researchers to determine the impacts of the disease on Tasmanian Platypus, as well as the mechanism of transmission and current spread of the disease.<ref name="DPIW2">{{cite web|url=http://www.dpiw.tas.gov.au/inter.nsf/WebPages/SSKA-7AH66E?open|title=Platypus Fungal Disease |publisher = Department of Primary Industries and Water, Tasmania|date=2008-08-29| accessdate = 2008-02-29}}</ref> Until recently, the introduced [[Red Fox]] (''Vulpes vulpes'') was confined to mainland Australia, but growing evidence now indicates that it is present in low numbers in Tasmania.<ref>http://www.dpiw.tas.gov.au/inter.nsf/ThemeNodes/LBUN-5K438G?open.</ref>
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 (Australia)|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 [[David Fleay Wildlife Park|wildlife park]] at [[Burleigh Heads, Queensland|Burleigh Heads]] on the [[Gold Coast, Queensland|Gold Coast]], Queensland.<ref name="DF">{{cite web|url=http://www.epa.qld.gov.au/nature_conservation/wildlife/david_fleay_wildlife_park/50_years_wild/david_fleays_achievements/|title= David Fleay's achievements|publisher=Queensland Government|date=2003-11-23| accessdate = 2006-09-13}}</ref> 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.<ref name="catalyst">{{cite web|url=http://www.abc.net.au/catalyst/stories/s988946.htm|title=Platypus|publisher=Catalyst|date=2003-11-13| accessdate = 2006-09-13}}</ref>
== Cultural references ==
[[Image:Oz20cent.jpg|thumb|left|The Australian 20 cent coin features a Platypus.]]
The Platypus is sometimes jokingly referred to as proof that [[God]] has a sense of humour (at the beginning of the film ''[[Dogma (film)|Dogma]]'', for example). Its unusual appearance has led to its 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 [[2000 Summer Olympics|Sydney 2000 Olympics]] along with an echidna and a [[kookaburra]],<ref>{{cite web|url=http://en.beijing2008.com/31/87/article211928731.shtml|title=A Brief History of the Olympic and Paralympic Mascots|publisher=Bejing2008|date=2004-08-05| accessdate = 2006-10-25}}</ref> "Expo Oz" the Platypus was the mascot for [[Expo '88]], which was held in [[Brisbane]] in 1988,<ref>{{cite web|url=http://www.foundationexpo88.org/aboutcontents.html|title=About World Expo '88|publisher=Foundation Expo '88|date=1988| accessdate = 2007-12-17}}</ref> and [[Hexley]] the Platypus is the mascot for [[Apple Computer]]'s [[BSD]]-based [[Darwin (operating system)|Darwin]] operating system, Mac OS X.<ref>{{cite web|url=http://www.hexley.com/|title=The Home of Hexley the Platypus| accessdate = 2006-10-25}}</ref>
The Platypus has also been featured in songs, such as [[Green Day|Green Day's]] ''Platypus (I Hate You)'', and frequently appears as a character in children's programs, for example, the Platypus Family on [[Mister Rogers' Neighborhood]],[[Perry the Platypus]] on the show [[Phineas and Ferb]] and Ovide, the star of the cartoon ''[[Ovide and the Gang]]''.<ref>{{cite web|url=http://www.imdb.com/title/tt0388631/|title=Ovide and the Gang|publisher=IMDB| accessdate = 2006-10-25}}</ref>
== See also ==
* [[Australian fauna]]
* [[List of venomous mammals]]
* [[Henry Burrell]]
== Notes ==
{{reflist|2}}
== References ==
;Books
<div class="references-small">
* Augee, Michael L. ''Platypus''. World Book Encyclopedia. 2001 ed.
* Burrell, H. ''The Platypus''. Adelaide: Rigby, 1974.
* Marshall, Ben "The Amazing Duckbilled Platypus" New York Publishers Inc. 2002 ed
* Grant, Tom. ''The platypus: a unique mammal''. Sydney: University of New South Wales Press, 1995. ISBN 0-86840-143-9.
* Griffiths, Mervyn. ''The Biology of the Monotremes''. Academic Press, 1978.
* Michael Hutch, Melissa C. McDade, eds. ''Grzimek's Animal Life Encyclopedia; Volume 12.'' Detroit: Gale, 2004.
* Moyal, Ann. ''Platypus: The Extraordinary Story of How a Curious Creature Baffled the World''. Smithsonian Books, 2001. ISBN 1-56098-977-7.
* Strahan, R. ''The Mammals of Australia''. New South Wales: Reed Books, 1995.
</div>
;Documentary
<div class="references-small">
* ''Eye of the Storm''. Documentary by the [[Australian Broadcasting Corporation]].
</div>
== External links ==
{{commons|Ornithorhynchidae}}
{{wikispecies|Ornithorhynchus anatinus}}
* [http://www.nature.com/news/2008/080507/full/453138a.html Nature.com "Top billing for platypus at end of evolution tree" [[7 May]] [[2008]]]
* [http://www.pbs.org/kratts/world/aust/plat/ PBS.org]
* [http://www.amonline.net.au/factsheets/platypus.htm Platypus-Evolution and Conservation]
{{Monotremata}}
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[[Category:Mammals of Tasmania]]
[[Category:Mammals of Queensland]]
[[Category:Mammals of South Australia]]
[[Category:Monotremes]]
[[Category:Venomous animals]]
[[Category:Mammals of New South Wales]]
[[Category:Mammals of Victoria]]
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