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{{Short description|Arboreal herbivorous marsupial native to Australia}}
{{Other uses|Koala (disambiguation)}}
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{{Use dmy dates|date=January 2020}}
{{Use Australian English|date=February 2012}}
{{Speciesbox
| name = Koala
| fossil_range = {{Fossil range|0.7|0}}<small>Middle [[Pleistocene]] – Recent</small>
| image = Koala climbing tree.jpg
| image_upright = 1.1
| status = VU
| status_system = IUCN3.1
| status_ref =<ref name="iucn status 12 November 2021">{{cite iucn |author=Woinarski, J. |author2=Burbidge, A.A. |date=2020 |title=''Phascolarctos cinereus'' |volume=2020 |page=e.T16892A166496779 |doi=10.2305/IUCN.UK.2020-1.RLTS.T16892A166496779.en |access-date=12 November 2021}}</ref>
| genus = Phascolarctos
| species = cinereus
| authority = ([[Georg August Goldfuss|Goldfuss]], 1817)
| synonyms_ref =<ref name=moyal/>{{rp|45}}<ref name = MSW3>{{MSW3 Diprotodontia | id = 11000005 | page = 43}}</ref>
| synonyms =
  {{plainlist|
* ''Lipurus cinereus'' {{small|Goldfuss, 1817}}
* ''Marodactylus cinereus'' {{small|Goldfuss, 1820}}
* ''Phascolarctos fuscus'' {{small|[[Anselme Gaëtan Desmarest|Desmarest]], 1820}}
* ''Phascolarctos flindersii'' {{small|[[René Primevère Lesson|Lesson]], 1827}}
* ''Phascolarctos koala'' {{small|[[John Edward Gray|J.E. Gray]], 1827}}
* ''Koala subiens'' {{small|[[Gilbert Thomas Burnett|Burnett]], 1830}}
}}
| range_map = Koala Range.jpg
| range_map_upright =
| range_map_caption = Koala range
{{leftlegend|red|Native}}
{{leftlegend|purple|Introduced}}
}}
 	
The '''koala''' ('''''Phascolarctos cinereus'''''), sometimes called the '''koala bear''', is an [[arboreal]] herbivorous [[marsupial]] native to Australia. It is the only [[Extant taxon|extant]] representative of the [[Family (biology)|family]] ''[[Phascolarctidae]]''. Its closest living relatives are the [[wombat]]s. The koala is found in coastal areas of the island's eastern and southern regions, inhabiting [[Queensland]], [[New South Wales]], [[Victoria (state)|Victoria]], and [[South Australia]]. It is easily recognisable by its stout, tailless body and large head with round, fluffy ears and large, dark nose. The koala has a body length of {{cvt|60|-|85|cm}} and weighs {{cvt|4|-|15|kg}}. [[Fur]] colour ranges from silver grey to chocolate brown. Koalas from the northern populations are typically smaller and lighter in colour than their counterparts further south. These populations possibly are separate [[subspecies]], but this is disputed.

Koalas typically inhabit open ''[[Eucalyptus]]'' woodland, as the leaves of these trees make up most of their diet. This eucalypt diet has low nutritional and caloric content and contains toxic compounds that deter most other mammals from feeding on it. Koalas are largely [[Sedentary lifestyle|sedentary]] and sleep up to twenty hours a day. They are asocial, only mothers [[maternal bond|bond]] to dependent offspring. Adult males [[animal communication|communicate]] with bellows that intimidate rivals and attract mates. Males mark their presence with secretions from [[scent gland]]s located on their chests. Like other marsupials, koalas give birth to young known as [[Marsupial#Early development|joeys]] at a very early stage of development. They crawl into their mothers' [[pouch (marsupial)|pouches]], where they live for their first six to seven months. They are fully [[weaned]] around a year old. Koalas have few natural predators and parasites, but are threatened by [[pathogen]]s such as ''[[Chlamydiaceae]]'' bacteria and ''[[koala retrovirus]]''.

Because of their distinctive appearance, koalas, along with [[kangaroo]]s and [[emu]]s, are recognised worldwide as [[National symbols of Australia|symbols of Australia]]. They were hunted by [[Indigenous Australians]] and depicted in [[Australian Aboriginal mythology|myths]] and [[cave art]] for millennia. The first recorded encounter between a European and a koala was in 1798, and an image of the animal was published in 1810 by naturalist [[George Perry (naturalist)|George Perry]]. Botanist [[Robert Brown (Scottish botanist from Montrose)|Robert Brown]] wrote the first detailed scientific [[species description|description]] in 1814, although his work remained unpublished for 180 years. Artist [[John Gould]] illustrated and described the koala, introducing the species to the British public. Further details about the animal's biology were revealed in the 19th century by English scientists. Koalas are listed as a [[vulnerable species]] by the [[International Union for Conservation of Nature]]. Among the many threats to their existence are [[habitat destruction]] caused by agriculture, urbanisation, droughts, and associated [[Bushfires in Australia|bushfires]], some related to climate change. In February 2022, the koala was officially listed as [[Endangered species|endangered]] in the [[Australian Capital Territory]], New South Wales, and Queensland.

==Etymology==
The word "koala" comes from the [[Sydney Language|Dharug]] {{lang|xdk|gula}}, meaning {{gloss|no water}}. Although the vowel "u" was originally written in the [[English orthography]] as "oo" (in spellings such as ''coola'' or ''koolah'' — two syllables), the spelling later became "oa" and the word is now pronounced in three syllables, possibly in error.<ref name=Dixon>{{cite book |first1=R. M. W. |last1=Dixon |first2=B. |last2=Moore |first3=W. S. |last3=Ramson |first4=M. |last4=Thomas |year=2006 |title=Australian Aboriginal Words in English: Their Origin and Meaning |edition=2nd |page=65|publisher=Oxford University Press |isbn=978-0-19-554073-4}}</ref>
Related words include “kula” from [[Georges River]] to Sydney's south and west, and “kulla” (or kūlla) among southeastern [[Queensland]]’s [[Dippil people]].<ref>https://www.studycountry.com/wiki/what-does-the-word-dharug-mean</ref>
Another hypothesis is that koala was an aboriginal name from the [[Hawkesbury River]] district near Sydney.<ref>https://wildlife.org.au/news-resources/educational-resources/species-profiles/mammals/koala/#:~:text=Its%20Australian%20indigenous%20name%20is,River%20district%20(near%20Sydney)</ref>

Adopted by white settlers, the word "koala" became one of hundreds of [[List of English words of Australian Aboriginal origin|Aboriginal loan words in Australian English]], where it was also commonly referred to as "native bear",<ref>{{cite book|author=Edward E. Morris |title=Dictionary of Australian Words ''(orig)'' Austral English |year=1898}} This author strongly deprecated use of another synonym, "sloth".</ref> later "koala bear", for its resemblance to a bear.<ref name="autogenerated1" /> It is one of several Aboriginal words that made it into [[International English]] alongside words like "[[didgeridoo]]" and "[[kangaroo]]".<ref name="autogenerated1">{{cite journal|last1=Leitner|first1=Gerhard|last2=Sieloff|first2=Inke|year=1998|title=Aboriginal words and concepts in Australian English|journal=World Englishes|volume=17|issue=2|pages=153–69|doi=10.1111/1467-971X.00089|quote=Dixon et al. (1990) believe there to be some 400 loans in Mainstream Australian English [...] Some Aboriginal expressions have entered the stock of world English vocabulary; witness kangaroo, didgeridoo, koala, [...] Sometimes popular usage deviated markedly from scientific taxonomies, as in the case of the koala which became known as koala bear. [...] Both mallee and mallee scrub, koala, and koala bear are common today.}}</ref> The [[genus|generic]] name, ''[[Phascolarctos]]'', is derived from the [[Ancient Greek|Greek]] words {{lang|grc|φάσκωλος}} ({{transl|grc|phaskolos}}) {{gloss|pouch}} and {{lang|grc|ἄρκτος}} ({{transl|grc|arktos}}) {{gloss|bear}}. The [[Specific name (zoology)|specific name]], {{lang|la|cinereus}}, is [[Latin]] for {{gloss|ash coloured}}.<ref>{{cite book |title=Collins Latin Gem Dictionary |first=D. A. |last=Kidd |year=1973 |publisher=Collins|page=53|isbn=978-0-00-458641-0}}</ref>

==Taxonomy==
The koala was given its generic name ''Phascolarctos'' in 1816 by French zoologist [[Henri Marie Ducrotay de&nbsp;Blainville]],<ref>{{cite journal |author=de Blainville, H. |title=Prodrome d'une nouvelle distribution systématique du règne animal |journal=Bulletin de la Société Philomáthique, Paris |year=1816 |volume=8 |pages=105–24 |language=fr |url=https://www.biodiversitylibrary.org/page/4439803 |access-date=20 February 2018 |archive-url=https://web.archive.org/web/20181014145245/https://www.biodiversitylibrary.org/page/4439803 |archive-date=14 October 2018 |url-status=dead }}</ref> who did not give it a specific name until further review. In 1819, German zoologist [[Georg August Goldfuss]] gave it the [[Binomial nomenclature|binomial]] ''Lipurus cinereus''. Because ''Phascolarctos'' was published first, according to the [[International Code of Zoological Nomenclature]], it has [[Principle of Priority|priority]] as the official genus name.<ref name=jackson>{{cite book |author=Jackson, S. |year=2010 |title=Koala: Origins of an Icon |publisher=Allen & Unwin |edition=2nd |isbn=978-1-74237-323-2 |url={{google books|plainurl=yes|id=uAic9hHaB1IC}}|access-date=9 November 2015 |archive-date=3 February 2021 |archive-url=https://web.archive.org/web/20210203083713/https://books.google.com/books?id=uAic9hHaB1IC |url-status=live }}</ref>{{rp|58–59}} French naturalist [[Anselme Gaëtan Desmarest]] coined the name ''Phascolarctos fuscus'' in 1820, suggesting that the brown-coloured versions were a different species than the grey ones. Other names suggested by European authors included ''Marodactylus cinereus'' by Goldfuss in 1820, ''P.&nbsp;flindersii'' by [[René Primevère Lesson]] in 1827, and ''P.&nbsp;koala'' by [[John Edward Gray]] in 1827.<ref name=moyal>{{cite book | last=Moyal | first=Ann | title=Koala: a historical biography | publisher=CSIRO Pub | publication-place=Melbourne | year=2008 | isbn=978-0-643-09401-7 | oclc=476194354 | url={{google books|plainurl=yes|id=QGT47L1cbLIC}}| access-date=9 November 2015 | archive-date=2 May 2016 | archive-url=https://web.archive.org/web/20160502165906/https://books.google.com/books?id=QGT47L1cbLIC | url-status=live }}</ref>{{rp|45}}

===Evolution===
The koala is classified with [[wombat]]s (family ''[[Vombatidae]]'') and several extinct families (including [[Palorchestes|marsupial tapirs]], [[Thylacoleonidae|marsupial lions]] and [[Diprotodontidae|giant wombats]]) in the suborder [[Vombatiformes]] within the order [[Diprotodontia]].<ref name="Long">{{cite book|author=Long, J. A.|year=2002|title=Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution|publisher=Johns Hopkins University Press|pages=77–82|isbn=978-0-8018-7223-5}}</ref> The Vombatiformes are a [[sister group]] to a [[clade]] that includes [[Macropodiformes|macropods]] ([[kangaroo]]s and [[Wallaby|wallabies]]) and [[Phalangeriformes|possums]].<ref>{{cite journal|author1=Asher, R. |author2=Horovitz, I. |author3=Sánchez-Villagra, M. |year=2004|title=First combined cladistic analysis of marsupial mammal interrelationships|journal=Molecular Phylogenetics and Evolution|volume=33|issue=1|pages=240–50|doi=10.1016/j.ympev.2004.05.004|pmid=15324852|bibcode=2004MolPE..33..240A }}</ref> The koala's [[Lineage (evolution)|lineage]] possibly branched off around 40&nbsp;million years ago during the [[Eocene]].<ref>{{cite journal|author=Beck, R. M. D.|year=2008|title=A dated phylogeny of marsupials using a molecular supermatrix and multiple fossil constraints|journal=Journal of Mammalogy|volume=89|issue=1|pages=175–89|doi=10.1644/06-MAMM-A-437.1|doi-access=free}}</ref>
[[File:Nimiokoala Litokoala.JPG|thumb|right|upright|Reconstructions of the ancient koalas ''Nimiokoala'' (larger), and ''Litokoala'' (smaller), from the Miocene Riversleigh Fauna]]
The modern koala is the only [[Extant taxon|extant]] member of ''[[Phascolarctidae]]'', a family that includes several extinct genera and species. During the [[Oligocene]] and [[Miocene]], koalas lived in [[rainforest]]s and had broader diets.<ref name=Louysa>{{cite journal|author1=Louys, J. |author2=Aplin, K. |author3=Beck, R. M. D. |author4=Archer, M. |year=2009|title=Cranial anatomy of Oligo-Miocene koalas (Diprotodontia: Phascolarctidae): Stages in the evolution of an extreme leaf-eating specialization|journal=Journal of Vertebrate Paleontology|volume=29|issue=4|pages=981–92|doi=10.1671/039.029.0412|bibcode=2009JVPal..29..981L |s2cid=86356713 |doi-access=free}}</ref> Some species, such as ''Nimiokoala greystanesi'' and some species of ''[[Perikoala]]'', were around the same size as the modern koala, while others, such as species of ''[[Litokoala]]'', were one-half to two-thirds its size.<ref name="Archer">{{cite journal |author1=Archer, M. |author2=Arena, R. |author3=Bassarova, M. |author4=Black, K. |author5=Brammall, J. |author6=Cooke, B. M. |author7=Creaser, P |author8=Crosby, K. |author9=Gillespie, A. |author10=Godthelp, H. |author11=Gott, M. |author12=Hand, S. J. |author13=Kear, B. P. |author14=Krikmann, A. |author15=Mackness, B. |author16=Muirhead, J. |author17=Musser, A. |author18=Myers, T. |author19=Pledge, N. S. |author20=Wang, Y. |author21=Wroe, S. |year=1999 |title=The evolutionary history and diversity of Australian mammals |journal=Australian Mammalogy |volume=21 |pages=1–45 |doi=10.1071/AM99001 |url=https://www.academia.edu/1157777 |access-date=1 November 2017 |archive-date=12 August 2021 |archive-url=https://web.archive.org/web/20210812194648/https://www.academia.edu/1157777 |url-status=live }}</ref> Like the modern species, prehistoric koalas had well developed ear structures, which suggests that they also made long-distance vocalisations and had a relatively inactive lifestyle.<ref name=Louysa/> During the Miocene, the Australian continent began drying out, leading to the decline of rainforests and the spread of open ''[[Eucalyptus]]'' woodlands. The genus ''Phascolarctos'' split from ''Litokoala'' in the late Miocene,<ref name=Louysa/><ref>{{cite journal|author1=Black, K. |author2=Archer, M. |author3=Hand, S. J. |year=2012|title=New Tertiary koala (Marsupialia, Phascolarctidae) from Riversleigh, Australia, with a revision of phascolarctid phylogenetics, paleoecology, and paleobiodiversity|journal=Journal of Vertebrate Paleontology|volume=32|issue=1|pages=125–38|doi=10.1080/02724634.2012.626825|bibcode=2012JVPal..32..125B |s2cid=86152273 }}</ref> and had several adaptations that allowed it to live on a eucalyptus diet: the [[palate]] shifted towards the front of the skull; the upper teeth were lined by thicker bone, [[molar (tooth)|molars]] became relatively low compared to the jaw joint and with more chewing surface; the [[pterygoid fossa]] shrank;<ref name=Louysa/> and a larger [[diastema (dentistry)|gap]] separated the [[incisor]] teeth and the molars.<ref name="Tyndale-Biscoe"/>{{rp|226}}

''P. cinereus'' may have emerged as a dwarf form of the [[giant koala]] (''P.&nbsp;stirtoni''), following the disappearance of several giant animals in the late [[Pleistocene]]. A 2008 study questioned this hypothesis, noting that ''P.&nbsp;cinereus'' and ''P.&nbsp;stirtoni'' were [[Sympatry|sympatric]] during the mid-late Pleistocene, and that  their teeth morphology displayed the major differences.<ref>{{cite journal|author=Price, G. J.|year=2008|title=Is the modern koala (''Phascolarctos cinereus'') a derived dwarf of a Pleistocene giant? Implications for testing megafauna extinction hypotheses|journal=Quaternary Science Reviews|volume=27|issue=27–28|pages=2516–21|doi=10.1016/j.quascirev.2008.08.026|bibcode=2008QSRv...27.2516P|url=https://www.academia.edu/1299583|access-date=1 November 2017|archive-date=13 August 2021|archive-url=https://web.archive.org/web/20210813040512/https://www.academia.edu/1299583|url-status=live}}</ref> The fossil record of the modern koala extends back at least to the middle Pleistocene.<ref name="Price 2012">{{cite book |author=Price, G. J. |chapter=Long-term trends in lineage 'health' of the Australian koala (Mammalia: Phascolarctidae): Using paleo-diversity to prioritize species for conservation |title=Paleontology in Ecology and Conservation |series=Springer Earth System Sciences |editor-last=Louys, J. |year=2013 |publisher=Springer |pages=171–92 |isbn=978-3-642-25037-8}}</ref>

{{clade gallery |style=border:0; |headerstyle=width:325px;height:60px;vertical-align:top;
|header1=Molecular relationship between living Diprotodontia families based on Phillips and collages (2023)<ref>{{cite journal|last1=Phillips|first1=M. J.|last2=Celik|first2=M. A.|last3=Beck|first3=Robin M. D.|year=2023|title=The evolutionary relationships of Diprotodontia and improving the accuracy of phylogenetic inference from morphological data|journal=Alcheringa: An Australasian Journal of Palaeontology|volume=47 |issue=4 |pages=686–698 |doi=10.1080/03115518.2023.2184492|s2cid=257634430 |doi-access=free|bibcode=2023Alch...47..686P }}</ref> 
|cladogram1= 
{{clade
|1={{clade
   |1={{clade
      |1=[[Vombatidae]] (wombats)
      |2=[[Phascolarctidae]] (koalas)
    }}
   |2={{clade
      |1={{clade
         |1=[[Acrobatidae]]
         |2={{clade
            |1=[[Tarsipedidae]] (honey possum)
            |2={{clade
               |1=[[Petauridae]] ([[wrist-winged glider]]s and allies)
               |2=[[Pseudocheiridae]] (ringtail possums and allies)
             }}
          }}
       }}
      |2={{clade
         |1=[[Macropodidae]] (kangaroos, wallabies and allies)
         |2={{clade
            |1=[[Phalangeridae]] ([[brushtail possum]]s and [[cuscus]]es)
            |2=[[Burramyidae]] (pygmy possums)
          }}
       }}
    }}
 }}
}}

|header2=Morphology tree of Phascolarctidae based on Beck and collages (2020)<ref name=Beck2020>{{cite journal|first1=R. M. D.|last1=Beck|first2=J.|last2=Louys|first3=P.|last3=Brewer|first4=M.|last4=Archer|first5=K. H.|last5=Black|first6=R. H.|last6=Tedford|year=2020|title=A new family of diprotodontian marsupials from the latest Oligocene of Australia and the evolution of wombats, koalas, and their relatives (Vombatiformes)|journal=Scientific Reports|volume=10|issue=9741|page=9741 |doi=10.1038/s41598-020-66425-8|pmid=32587406 |pmc=7316786 |bibcode=2020NatSR..10.9741B }}</ref>
|cladogram2=
{{clade
|1={{clade
   |1=[[Thylacoleonidae]] (extinct marsupial lion and allies)
   |2={{clade
      |1=[[Vombatomorphia]] (wombats and fossil relatives)
      |2={{clade
         |label1=[[Phascolarctidae]]&nbsp;
         |1={{clade
            |1=''[[Priscakoala]] lucyturnbullae''
            |2={{clade
               |1={{clade
                  |1=''[[Madakoala]]'' spp.
                  |2=''[[Perikoala]] robustus''
                }}
               |2={{clade
                  |1=''[[Nimiokoala]] greystanesi''
                  |2={{clade
                     |1=''[[Litokoala]] dicksmithi''
                     |2={{clade
                        |1=''Litokoala kutjamarpensis''
                        |2='''''Phascolarctos cinereus'''''
                      }}
                   }}
                }}
             }}
          }}
       }}
    }}
 }}
}}

}}

===Genetics and variations===
Three [[subspecies]] are recognised: the Queensland koala (''Phascolarctos cinereus adustus'', [[Oldfield Thomas|Thomas]] 1923), the New South Wales koala (''Phascolarctos cinereus cinereus'', Goldfuss 1817), and the Victorian koala (''Phascolarctos cinereus victor'', [[Ellis Le Geyt Troughton|Troughton]] 1935). These forms are distinguished by [[pelage]] colour and thickness, body size, and skull shape. The Queensland koala is the smallest, with silver or grey short hairs and a shorter skull. The Victorian koala is the largest, with shaggier, brown fur and a wider skull.<ref name="Martin-Handasyde">{{cite book |author1=Martin, R. W. |author2=Handasyde, K. A. |year=1999 |title=The Koala: Natural History, Conservation and Management |publisher=New South Wales University Press |edition=2nd |isbn=978-1-57524-136-4 |url={{google books|plainurl=yes|id=RdWg_f5UI7cC}} |access-date=9 November 2015 |archive-date=6 April 2015 |archive-url=https://web.archive.org/web/20150406041539/http://books.google.com/books?id=RdWg_f5UI7cC |url-status=live }}</ref>{{rp|7}}<ref name="Houlden 1999">{{cite journal|author1=Houlden, B. A. |author2=Costello, B. H. |author3=Sharkey, D. |author4=Fowler, E. V. |author5=Melzer, A. |author6=Ellis, W. |author7=Carrick, F. |author8=Baverstock, P. R. |author9=Elphinstone, M. S. |year=1999|title=Phylogeographic differentiation in the mitochondrial control region in the koala, ''Phascolarctos cinereus'' (Goldfuss 1817)|journal=Molecular Ecology|volume=8|issue=6|pages=999–1011|doi=10.1046/j.1365-294x.1999.00656.x|pmid=10434420|bibcode=1999MolEc...8..999H |s2cid=36771770 }}</ref> The geographic limits of these variations are based on [[States and territories of Australia|state borders]], and their status as subspecies is disputed. A 1999 genetic study suggests koalas exist as a [[cline (biology)|cline]] within a single [[evolutionarily significant unit]] with limited [[gene flow]] between local populations.<ref name="Houlden 1999"/>

Other studies have found that koala populations are highly [[inbreeding|inbred]] with low [[genetic variation]].<ref>{{cite journal|author1=Houlden, B. A. |author2=England, P. R. |author3=Taylor A. C. |author4=Greville, W. D. |author5=Sherwin, W. B. |year=1996|title=Low genetic variability of the koala ''Phascolarctos cinereus'' in south-eastern Australia following a severe population bottleneck|journal=Molecular Ecology|volume=5|issue=2|pages=269–81|pmid=8673272|doi=10.1046/j.1365-294x.1996.00089.x |bibcode=1996MolEc...5..269H |s2cid=22441918 }}</ref><ref>{{cite journal|author1=Wilmer, J. M. W. |author2=Melzer, A. |author3=Carrick, F. |author4=Moritz, C. |year=1993|title=Low genetic diversity and inbreeding depression in Queensland Koalas|journal=Wildlife Research|volume=20|issue=2|pages=177–87|doi=10.1071/WR9930177}}</ref> Such low [[genetic diversity]] may have been caused by population declines during the late Pleistocene.<ref>{{cite journal|author1=Tsangaras, K. |author2=Ávila-Arcos, M. C. |author3=Ishida, Y. |author4=Helgen, K. M. |author5=Roca, A. L. |author6=Greenwood, A. D. |year=2012|title=Historically low mitochondrial DNA diversity in koalas (''Phascolarctos cinereus'')|journal=BMC Genetics|volume=13|pages=92|doi=10.1186/1471-2156-13-92|pmid=23095716|pmc=3518249|issue=1 |doi-access=free }}</ref> Rivers and roads limit gene flow and contribute to the isolation of southeast Queensland populations.<ref>{{cite journal |author1=Lee, K. E. |author2=Seddon, J. M. |author3=Corley, S. |author4=Williams, E. |author5=Johnston, S. |author6=Villers, D. |author7=Preece, H. |author8=Carrick, F. |year=2010 |title=Genetic variation and structuring in the threatened koala populations of Southeast Queensland |journal=Conservation Genetics |volume=11 |issue=6 |pages=2091–103 |doi=10.1007/s10592-009-9987-9|bibcode=2010ConG...11.2091L |s2cid=36855057 }}</ref> In April 2013, scientists from the [[Australian Museum]] and [[Queensland University of Technology]] announced they had [[Whole genome sequencing|fully sequenced]] the koala [[genome]].<ref name="Davey2013">{{cite news |title=Australians crack the code of koala's genetic blueprint |url=http://www.theage.com.au/national/australians-crack-the-code-of-koalas-genetic-blueprint-20130409-2hjfm.html |date=10 April 2013 |author=Davey, M. |newspaper=[[The Age]] |access-date=25 June 2013 |archive-url=https://web.archive.org/web/20130514133101/http://www.theage.com.au/national/australians-crack-the-code-of-koalas-genetic-blueprint-20130409-2hjfm.html |archive-date=14 May 2013 |url-status=live }}</ref>

==Characteristics==
[[File:Koala grooming.ogv|thumb|right|Scratching and grooming]]

The koala is a robust animal with a large head and [[vestigiality|vestigial]] or non-existent tail.<ref name=jackson/>{{rp|1}}<ref name="Nowak 2005">{{cite book|author=Nowak, R.|year=2005|title=Walker's Marsupials of the World|url=https://archive.org/details/walkersmarsupial00nowa|url-access=limited|publisher=Johns Hopkins University Press|pages=[https://archive.org/details/walkersmarsupial00nowa/page/n145 135]–36|isbn=978-0-8018-8211-1}}</ref> It has a body length of {{cvt|60|-|85|cm}} and a weight of {{cvt|4|-|15|kg}},<ref name="Nowak 2005"/> making it among the largest arboreal marsupials.<ref name=captive/> Koalas from Victoria are twice as heavy as those from Queensland.<ref name="Martin-Handasyde"/>{{rp|7}} The species is [[Sexual dimorphism|sexually dimorphic]]: males are 50% larger than females. Males' noses are more curved<ref name="captive" /> and sport chest glands, which are visible as bald patches.<ref name="Martin-Handasyde" />{{rp|55}} The female's [[Pouch (marsupial)|pouch opening]] is secured by a [[sphincter]] which holds the young in.<ref>{{cite journal|last=Smith|first=M|year=1979|title=Notes on reproduction and growth in the koala, ''Phascolarctos cinereus'' (Goldfuss)|journal=Australian Wildlife Research|volume=6|issue=1|pages=5–12|doi=10.1071/WR9790005}}</ref>

The pelage of the koala is denser on the back.<ref name="captive">{{cite book|author=Jackson, S.|year=2003|title=Australian Mammals: Biology and Captive Management|publisher=CSIRO Publishing|pages=147–51|isbn=978-0-643-06635-9}}</ref> Back fur colour varies from light grey to chocolate brown.<ref name="jackson" />{{rp|1–2}} The belly fur is whitish; on the rump it is mottled whitish and dark.<ref name="Nowak 2005" /> The koala has the most effective insulating back fur of any marsupial and is resilient to wind and rain, while the belly fur can reflect solar radiation.<ref>{{cite journal|author1=Degabriele, R. |author2=Dawson, T. J. |year=1979|title=Metabolism and heat balance in an arboreal marsupial, the koala (''Phascolarctos cinereus'')|journal=Journal of Comparative Physiology B|volume=134|issue=4|pages=293–301|doi=10.1007/BF00709996|s2cid=31042136 |issn=1432-1351}}</ref> The koala has curved, sharp claws well adapted for climbing trees. The large forepaws have two [[Thumb#Other animals with opposable digits|opposable digits]] (the first and second, which are opposable to the other three) that allow them to grip small branches. On the hind paws, the second and third digits are [[syndactyly|fused]], a typical condition for members of the ''Diprotodontia'', and the attached claws (which are still separate) function like a comb.<ref name="Martin-Handasyde" />{{rp|5}} The animal has a robust skeleton and a short, muscular upper body with relatively long upper limbs that contribute to its ability to climb. The thigh muscles are anchored further down the [[shinbone]], increasing its climbing power.<ref name="moyal" />{{rp|183}}
[[File:Koala skeleton1.jpg|thumb|upright|left|Mounted skeleton]]
For a mammal, the koala has a [[Brain-to-body mass ratio|disproportionately small brain]],<ref name=jackson/>{{rp|81}} 60% smaller than that of a typical [[diprotodont]], weighing only {{cvt|19.2|g}} on average.<ref>{{cite journal |author1=Carmen de Miguel |author2=Maciej Henneberg |year=1998 |title=Encephalization of the Koala, Phascolarctos cinereus |journal=Australian Mammalogy |volume=20 |issue=3 |pages=315–320 |doi=10.1071/AM98315 |url=https://www.researchgate.net/publication/233726395 |access-date=13 October 2018 |archive-date=17 March 2022 |archive-url=https://web.archive.org/web/20220317214337/https://www.researchgate.net/publication/233726395_1998_koala_brain |url-status=live }}</ref> The brain's surface is fairly smooth and "[[primitive (phylogenetics)|primitive]]".<ref name="Martin-Handasyde"/>{{rp|52}} It does not entirely fill the [[cranial cavity]], unlike most mammals,<ref name=jackson/>{{rp|81}} and is lightened by large amounts of [[cerebrospinal fluid]]. It is possible that the fluid protects the brain should the animal fall from a tree.<ref name="Martin-Handasyde"/>{{rp|52–53}} The koala's small brain may be an adaptation to the energy restrictions imposed by its diet, which is insufficient to sustain a larger brain.<ref name=jackson/>{{rp|81}} Its small brain limits its ability to perform complex behaviours. For example, it will not eat plucked eucalyptus leaves on a flat surface, which does not match its feeding routine.<ref name="Tyndale-Biscoe"/>{{rp|234}}

The koala has a broad, dark nose<ref name=Clode>{{cite book|last=Clode|first=Danielle|year=2023|title=Koala: The Extraordinary Life of an Enigmatic Animal|publisher=W. W. Norton & Company|pages=172–175|isbn=9781324036845}}</ref> with a good sense of smell, and it is known to sniff the oils of individual branchlets to assess their edibility.<ref name=jackson/>{{rp|81}} Its relatively small eyes are unusual among marsupials in that the pupils have vertical slits,<ref name=captive/> an adaptation to living on a more vertical plane. Its round ears provide it with good hearing,<ref name=Clode/><ref name="Martin-Handasyde"/>{{rp|6}} and it has a well-developed [[middle ear]].<ref name=Louysa/> The koala larynx is located relatively low in the vocal tract and can be pulled further down. They possess unique folds in the velum (soft palate), known as velar vocal folds, in addition to the typical [[vocal folds]] of the larynx. These features allow the koala to produce deeper sounds than would otherwise be possible for their size.<ref name=Frey>{{cite journal|last1=Frey|first1=R|last2=Reby|first2=D|last3=Fritsch|first3=G|last4=Charlton|first4=B. D.|year=2018|title=The remarkable vocal anatomy of the koala (Phascolarctos cinereus): insights into low-frequency sound production in a marsupial species|journal=Journal of Anatomy|volume=232|issue=4|pages=575–595|doi=10.1111/joa.12770|pmid=29460389|pmc=5835795|s2cid=3708255}}</ref><ref name="Charlton 2013">{{cite journal |author1=Charlton, B. D. |author2=Frey, R. |author3=McKinnon, A. J. |author4=Fritsch, G. |author5=Fitch, W. T. |author6=Reby, D. |title=Koalas use a novel vocal organ to produce unusually low-pitched mating calls |journal=Current Biology |volume=23 |issue=23 |pages=R1035–6 |year=2013 |doi=10.1016/j.cub.2013.10.069 |pmid=24309276|doi-access=free |bibcode=2013CBio...23R1035C }}</ref>
[[File:Machoires de koala avec dents.png|thumb|right|Teeth of a koala, from left to right: [[molar (tooth)|molars]], [[premolar]]s (dark), [[diastema (dentistry)|diastema]], [[canine tooth|canines]], [[incisor]]s]]
The koala has several adaptations for its low nutrient, toxic, and fibrous diet.<ref name=jackson/>{{rp|76}} The animal's [[dentition]] consists of incisors and [[cheek teeth]] (a single premolar and four molars on each jaw) that are separated by a large gap (a characteristic feature of herbivorous mammals). The koala bites a leaf with the incisors and clips it with the premolars at the [[Petiole (botany)|petiole]], before chewing it to pieces with the [[Cusp (dentistry)|cusped]] molars.<ref name="Martin-Handasyde"/>{{rp|46}} Koalas may store food in their [[cheek pouch]]es before it is ready to be chewed.<ref>{{cite book|author1=Lee, A. L. |author2=Martin, R. W. |year=1988|title=The Koala: A Natural History|publisher=New South Wales University Press|page=20|isbn=978-0-86840-354-0}}</ref> The partially worn molars of koalas in their prime are optimal for breaking leaves into small particles, resulting in more efficient stomach digestion and nutrient absorption in the small intestine,<ref name="Tyndale-Biscoe"/>{{rp|231}} which digests the eucalyptus leaves to provide most of the animal's energy.<ref name="Martin-Handasyde"/>{{rp|47}} A koala sometimes [[regurgitation (digestion)|regurgitates]] the food into the mouth to be chewed a second time.<ref>{{cite journal|author=Logan, M.|year=2001|title=Evidence for the occurrence of rumination-like behaviour, or merycism, in the koala (''Phascolarctos cinereus'', Goldfuss)|journal=Journal of Zoology|volume=255|issue=1|pages=83–87|doi=10.1017/S0952836901001121}}</ref>

Koalas are [[Hindgut fermentation|hindgut fermenters]], and their digestive retention can last 100 hours in the wild or 200 hours in captivity.<ref name="Martin-Handasyde"/>{{rp|48}} This is made possible by their [[caecum]]—{{cvt|200|cm}} long and {{cvt|10|cm}} in diameter—possibly the largest for an animal of its size.<ref name=moyal/>{{rp|188}} Koalas can retain food particles for longer fermentation if needed. They are more likely keep smaller particles as larger ones take longer to digest.<ref name="Martin-Handasyde"/>{{rp|48}} While the hindgut is relatively large, only 10% of the animal's energy is obtained from digestion in this chamber. The koala's [[Basal metabolic rate|metabolic rate]] is only 50% of the typical mammalian rate, owing to its low energy intake,<ref name=jackson/>{{rp|77–78}} although this can vary across seasons and sexes.<ref name="Martin-Handasyde"/>{{rp|49}} They can digest the toxic [[secondary metabolite|plant secondary metabolites]], [[phenolic compound]]s and [[terpene]]s due to their production of [[cytochrome P450]], which neutralises these poisons in the [[liver]].<ref>{{cite journal |last1=Johnson, R. N. |display-authors=etal |year=2018 |title=Adaptation and conservation insights from the koala genome |journal=Nature Genetics |volume=50 |issue=8 |pages=1102–1111 |doi=10.1038/s41588-018-0153-5 |pmid=29967444 |pmc=6197426 |hdl=2440/115861 |hdl-access=free}}</ref> The koala replaces lost water at a lower rate than species such as some possums.<ref name="Tyndale-Biscoe">{{cite book |author=Tyndale-Biscoe, H. |year=2005 |title=Life of Marsupials |publisher=CSIRO Publishing |isbn=978-0-643-06257-3 |url={{google books|plainurl=yes|id=KqtlPZJ9y8EC}}|access-date=9 November 2015 |archive-date=23 January 2016 |archive-url=https://web.archive.org/web/20160123225012/https://books.google.com/books?id=KqtlPZJ9y8EC |url-status=live }}</ref>{{rp|231}} It maintains water by absorbing it in the caecum, resulting in drier faecal pellets packed with undigested fibre.<ref name="Tyndale-Biscoe"/>{{rp|231}}<ref name=moyal/>{{rp|188}}

==Distribution and habitat==
[[File:Koala (Phascolarctos cinereus) female Mount Lofty 4.jpg|thumb|right|Koala with joey in a tree in South Australia]]
The koala's range covers roughly {{cvt|1000000|km2}}, and 30 [[ecoregion]]s.<ref name="McGregor 2013"/> It ranges throughout mainland eastern and southeastern Australia, including the states of Queensland, New South Wales, Victoria, and [[South Australia]]. The koala was [[introduced species|introduced]] to several nearby islands.<ref name="iucn status 12 November 2021" /> The population on [[Magnetic Island]] represents the northern limit of its range.<ref name="McGregor 2013">{{cite journal |author=McGregor, D. C. |author2=Kerr, S. E. |author3=Krockenberger, A. K. |title=The distribution and abundance of an island population of koalas (''Phascolarctos cinereus'') in the far north of their geographic range |journal=PLOS ONE |year=2013 |volume=8 |issue=3 |page=e59713 |doi=10.1371/journal.pone.0059713 |pmc=3601071 |editor1-last=Festa-Bianchet |editor1-first=Marco |pmid=23527258|bibcode=2013PLoSO...859713M |doi-access=free }}</ref>

Fossil evidence shows that the koala's range stretched as far west as southwestern [[Western Australia]] during the late Pleistocene. They were likely driven to extinction in these areas by environmental changes and hunting by [[Indigenous Australians]].<ref name="Martin-Handasyde"/>{{rp|12–13}} Koalas were introduced to Western Australia at [[Yanchep]] in 1938 but that population was reduced to 4 individuals by 2022.<ref name="AFD2022">{{cite web |title=Species ''Phascolarctos cinereus'' (Goldfuss, 1817) |url=https://biodiversity.org.au/afd/taxa/e9d6fbbd-1505-4073-990a-dc66c930dad6 |website=[[Australian Faunal Directory]] |publisher=Australian Government |access-date=12 February 2022 |archive-date=12 February 2022 |archive-url=https://web.archive.org/web/20220212204015/https://biodiversity.org.au/afd/taxa/e9d6fbbd-1505-4073-990a-dc66c930dad6 |url-status=live }}</ref> Koalas can be found in both tropical and temperate habitats ranging from dense [[woodland]]s to more spaced-out forests.<ref name=captive/> In [[semi-arid climate]]s, they prefer [[riparian habitat]]s, where nearby streams and creeks provide refuge during times of drought and extreme heat.<ref>{{cite journal |author1=Smith, A. G. |author2=McAlpine, C. A. |author3=Rhodes, J. R. |author4=Lunney, D. |author5=Seabrook, L. |author6=Baxter, G. |title=Out on a limb: Habitat use of a specialist folivore, the koala, at the edge of its range in a modified semi-arid landscape |journal=Landscape Ecology |year=2013 |volume=28 |issue=3 |pages=418–26 |doi=10.1007/s10980-013-9846-4|bibcode=2013LaEco..28..415S |s2cid=8031502 }}
</ref>

==Behaviour and ecology==
===Foraging and activities===
[[File:Koala eating.jpg|thumb|left|Foraging]]
Koalas are [[herbivorous]], and while most of their diet consists of [[eucalypt]] leaves, they can be found in trees of other genera, such as ''[[Acacia]]'', ''[[Allocasuarina]]'', ''[[Callitris]]'', ''[[Leptospermum]]'', and ''[[Melaleuca]]''.<ref name=jackson/>{{rp|73}} Though the foliage of over 600 species of ''Eucalyptus'' is available, the koala shows a strong preference for around 30.<ref name="Macdonald">{{cite book|author=Martin, R.|year=2001|contribution=Koala|title=Encyclopedia of Mammals|editor=Macdonald, D.|publisher=Oxford University Press|edition=2nd|pages=852–854|isbn=978-0-7607-1969-5}}</ref> They prefer plant matter with higher [[Protein (nutrient)|protein]] than fibre and [[lignin]].<ref name="Tyndale-Biscoe"/>{{rp|231}} The most favoured species are ''[[Eucalyptus microcorys]]'', ''[[Eucalyptus tereticornis|E.&nbsp;tereticornis]]'', and ''[[Eucalyptus camaldulensis|E.&nbsp;camaldulensis]]'', which, on average, make up more than 20% of their diet.<ref name="Osawa 1993">{{cite journal |author=Osawa, R. |title=Dietary preferences of Koalas, ''Phascolarctos cinereus'' (Marsupiala: Phascolarctidae) for ''Eucalyptus'' spp. with a specific reference to their simple sugar contents |journal=Australian Mammalogy |url={{google books|plainurl=yes|id=RF-PjvKUo3AC|page=87}} |volume=16 |issue=1 |year=1993 |pages=85–88 |doi=10.1071/AM93020 |s2cid=239130362 |access-date=9 November 2015 |archive-date=24 April 2016 |archive-url=https://web.archive.org/web/20160424110434/https://books.google.com/books?id=RF-PjvKUo3AC&pg=PA87 |url-status=live }}</ref> Despite its reputation as a picky eater, the koala is more [[Generalist and specialist species|generalist]] than some other marsupial species, such as the [[greater glider]]. The koala does not need to drink often as it can get enough water from the leaves,<ref name=jackson/>{{rp|73–74}} though larger males may additionally drink water found on the ground or in tree hollows.<ref name="Tyndale-Biscoe"/>{{rp|231}} When feeding, a koala reaches out to grab leaves with one forepaw while the other paws hang on to the branch. Depending on the size of the individual, a koala can walk to the end of a branch or must stay near the base.<ref name=jackson/>{{rp|96}} Each day, koalas eat up to {{convert|400|g}} of leaves, spread over four to six feeding periods.<ref name=moyal/>{{rp|187}} Despite their adaptations to a low-energy lifestyle, they have meagre [[adipose tissue|fat reserves]].<ref name=moyal/>{{rp|189}}

Their low-energy diet limits their activity and they sleep 20 hours a day.<ref name=jackson/>{{rp|93}}<ref name="Grand 2001">{{cite journal |author1=Grand, T. I. |author2=Barboza, P. S. |title=Anatomy and development of the koala, ''Phascolarctos cinereus'': An evolutionary perspective on the superfamily Vombatoidea |journal=Anatomy and Embryology |year=2001 |volume=203 |issue=3 |pages=211–223 |doi=10.1007/s004290000153 |pmid=11303907|s2cid=11662113 }}</ref> They are predominantly active at night and spend most of their waking hours foraging. They typically eat and sleep in the same tree, possibly for as long as a day.<ref name="Martin-Handasyde"/>{{rp|39}} On warm days, a koala may rest with its back against a branch or lie down with its limbs dangling.<ref name=jackson/>{{rp|93–94}} When it gets hot, the koala rests lower in the canopy and near the trunk, where the surface is cooler than the surrounding air.<ref>{{cite journal|last1=Briscoe|first1=N. J.|last2=Handasyde|first2=K. A.|last3=Griffiths|first3=S. R.|last4=Porter|first4=W. P.|last5=Krockenberger|first5=A|last6=Kearney|first6=M. R.|year=2014|title=Tree-hugging koalas demonstrate a novel thermoregulatory mechanism for arboreal mammals|journal=Biology Letters|volume=10 |issue=6 |doi=10.1098/rsbl.2014.0235|pmid=24899683 |pmc=4090547 }}</ref> It curls up when it gets cold and wet.<ref name="Martin-Handasyde"/>{{rp|39}} It resorts to a lower, thicker, branch during high winds. While it spends most of the time in the tree, the animal descends to the ground to move to another tree, with either a walking or leaping gait.<ref name=jackson/>{{rp|93–94}} The koala usually grooms itself with its hind paws, with their double claws, but sometimes uses its forepaws or mouth.<ref name=jackson/>{{rp|97–98}}

===Social life===
{{multiple image
| align = right
| direction = horizontal
| header =
| image1 = Phascolarctos cinereus Bonorong.jpg
| width1 = 140
| alt1 = Koala resting in a tree between branch and stem
| caption1 = Resting
| image2 = Perception-of-Male-Caller-Identity-in-Koalas-(Phascolarctos-cinereus)-Acoustic-Analysis-and-pone.0020329.s001.ogv
| width2 = 270
| alt2 = A bellowing male in the [[Lone Pine Koala Sanctuary]]
| caption2 = A bellowing male in the [[Lone Pine Koala Sanctuary]]
}}

Koalas are asocial and spend just 15 minutes a day on social behaviours. In areas of higher density and fewer trees, [[home range]]s are smaller and more clumped.<ref name=jackson/>{{rp|98}} Koala society appears to consist of "residents" and "transients": the former are mostly adult females and the latter are males. Resident males appear to be [[Territory (animal)|territorial]] and [[Dominance (ethology)|dominant]].<ref>{{cite journal|author1=Ellis, W. A. |author2=Hale, P. T. |author3=Carrick, F. |year=2002|title=Breeding dynamics of koalas in open woodlands|journal=Wildlife Research|volume=29|issue=1|pages=19–25|doi=10.1071/WR01042}}</ref> The territories of dominant males are found near breeding females, while younger males must wait until they reach full size to challenge for breeding rights.<ref name=moyal/>{{rp|191}} Adult males occasionally venture outside their home ranges; when they do, dominant ones retain their status.<ref name=jackson/>{{rp|99}} As a male climbs a new tree, he rubs his chest against it and sometimes dribbles urine. This scent-marking behaviour probably serves as communication, and individuals are known to sniff the bottom of a newly found tree.<ref name="Martin-Handasyde"/>{{rp|54–56}}<ref>{{cite journal|author=Smith, M.|year=1980|title=Behaviour of the Koala, ''Phascolarctos cinereus'' (Goldfuss), in captivity IV. Scent-marking|journal=Australian Wildlife Research|volume=7|issue=1|pages=35–40|doi=10.1071/WR9800035}}</ref> Chest gland secretions are complex chemical mixtures — about 40 compounds were identified in one analysis — that vary in composition and concentration across season and age.<ref name="Tobey 2009">{{cite journal |author1=Tobey, J. R. |author2=Nute, T. R. |author3=Bercovitch, F. B. |title=Age and seasonal changes in the semiochemicals of the sternal gland secretions of male koalas (''Phascolarctos cinereus'') |journal=Australian Journal of Zoology |year=2009 |volume=57 |issue=2 |pages=111–18 |doi=10.1071/ZO08090}}</ref>

[[File:A364, Lone Pine Koala Sanctuary, Queensland, Australia, koala, 2007.png|thumb|left|upright|Scent gland on the chest of an adult male. Lone Pine Koala Sanctuary]]

Adult males communicate with loud bellows — "a long series of deep, snoring inhalations and belching exhalations".<ref name="vocal">{{cite journal|author=Smith, M.|year=1980|title=Behaviour of the Koala, ''Phascolarctos cinereus'' (Goldfuss), in captivity III*. Vocalisations|journal=Australian Wildlife Research|volume=7|issue=1|pages=13–34|doi=10.1071/WR9800013}}</ref> Because of their low [[audio frequency|frequency]], these bellows can travel far through the forest.<ref name="Martin-Handasyde"/>{{rp|56}} Koalas may bellow at any time, particularly during the [[seasonal breeder|breeding season]], when it serves to attract females and possibly intimidate other males.<ref>{{cite journal |author1=Ellis, W. |author2=Bercovitch, F. |author3=FitzGibbon, S. |author4=Roe, P. |author5=Wimmer, J. |author6=Melzer, A. |author7=Wilson, R. |title=Koala bellows and their association with the spatial dynamics of free-ranging koalas |journal=Behavioral Ecology |year=2011 |volume=22 |issue=2 |pages=372–77 |doi=10.1093/beheco/arq216 |doi-access=free }}</ref> They also bellow to advertise their presence when they change trees.<ref name="Martin-Handasyde"/>{{rp|57}} These sounds signal and exaggerate the male's body size;<ref>{{cite journal|author1=Charlton, B. D. |author2=Ellis, W. A. H. |author3=McKinnon, A. J. |author4=Cowin, G. J. |author5=Brumm, J. |author6=Nilsson, K. |author7=Fitch, W. T. |year=2011|title=Cues to body size in the formant spacing of male koala (''Phascolarctos cinereus'') bellows: Honesty in an exaggerated trait|journal=Journal of Experimental Biology|volume=214|issue=20|pages=3414–22|doi=10.1242/jeb.061358 |pmid=21957105|doi-access=free }}</ref> females pay more attention to bellows by larger males.<ref>{{cite journal |author1=Charlton, B. D. |author2=Ellis, W. A. H. |author3=Brumm, J. |author4=Nilsson, K. |author5=Fitch, W. T. |title=Female koalas prefer bellows in which lower formants indicate larger males |journal=Animal Behaviour |year=2012 |volume=84 |issue=6 |pages=1565–71 |doi=10.1016/j.anbehav.2012.09.034|s2cid=53175246 }}</ref> Female koalas bellow, though more softly, in addition to making snarls, wails, and screams. These calls are produced when in distress and when making defensive threats.<ref name=vocal/> Younger animals squeak and older ones squawk when distraught. When another individual climbs over it, a koala makes a low closed-mouth grunt.<ref name=jackson/>{{rp|102–03}}<ref name="vocal"/> Koalas also communicate with facial expressions. When snarling, wailing, or squawking, the animal curls the upper lip and points its ears forward. Screaming koalas pull their lips and ears back. Females form an oval shape with their lips when annoyed.<ref name=jackson/>{{rp|104–05}}

[[Agonistic behaviour]] typically consists of quarrels between individuals who are trying to pass each other on a tree. This occasionally involves biting. Strangers may wrestle, chase, and bite.<ref name=jackson/>{{rp|102}}<ref name="aggression">{{cite journal|author=Smith, M.|year=1980|title=Behaviour of the Koala, ''Phascolarctos cinereus'' (Goldfuss), in captivity VI*. Aggression|journal=Australian Wildlife Research|volume=7|issue=2|pages=177–90|doi=10.1071/WR9800177}}</ref> In extreme situations, a larger male may try to displace a smaller rival from a tree, chasing, cornering and biting it. Once the individual is driven away, the victor bellows and marks the tree.<ref name=jackson/>{{rp|101–02}} Pregnant and [[lactation|lactating]] females are particularly aggressive and attack individuals who come too close.<ref name=aggression/> In general, however, koalas tend to avoid fighting due to energy costs.<ref name=moyal/>{{rp|191}}

===Reproduction and development===
[[File:Koala Foetus Almost At Birth.jpg|thumb|right|upright|A young joey, preserved at Port Macquarie Koala Hospital]]
Koalas are seasonal breeders, and give birth from October to May. Females in [[oestrus]] lean their heads back and shake their bodies. Despite these obvious signals, males try to copulate with any female during this period, mounting them from behind. Because of his much larger size, a male can overpower a female. A female may scream and vigorously fight off her suitors but will accede to one that is dominant or familiar. The commotion can attract other males to the scene, obliging the incumbent to delay mating and fight off the intruders. A female may learn who is more dominant during these fights.<ref name="Martin-Handasyde"/>{{rp|58–60}} Older males typically accumulate scratches, scars, and cuts on the exposed parts of their noses and their eyelids.<ref name=moyal/>{{rp|192}}

Koalas are [[Induced ovulation (animals)|induced ovulator]]s.<ref name="Johnston 629–634">{{Cite journal|last1=Johnston|first1=S. D.|last2=O'Callaghan|first2=P.|last3=Nilsson|first3=K.|last4=Tzipori|first4=G.|last5=Curlewis|first5=J. D.|date=2004-11-01|title=Semen-induced luteal phase and identification of a LH surge in the koala (''Phascolarctos cinereus'')|journal=Reproduction|language=en|volume=128|issue=5|pages=629–634|doi=10.1530/rep.1.00300|issn=1470-1626|pmid=15509709|doi-access=free}}</ref> The [[gestation]] period lasts 33–35 days,<ref>{{cite journal |author1=Gifford, A. |author2=Fry, G. |author3=Houlden, B. A. |author4=Fletcher, T. P. |author5=Deane, E. M. |title=Gestational length in the koala, ''Phascolarctos cinereus'' |journal=Animal Reproduction Science |year=2002 |volume=70 |issue=3 |pages=261–66 |doi=10.1016/S0378-4320(02)00010-6 |pmid=11943495}}</ref> and a female gives birth to one [[Joey (marsupial)|joey]] or occasionally, twins. The young are born tiny and barely formed, weighing no more than {{cvt|0.5|g}}. However, their lips, forelimbs, and shoulders are relatively advanced, and they can breathe, defecate and urinate. The joey crawls into its mother's pouch to continue its development.<ref name="Martin-Handasyde"/>{{rp|61}} Female koalas do not clean their pouches, an unusual trait among marsupials.<ref name=moyal/>{{rp|181}}

The joey latches on to one of the female's two teats and suckles it.<ref name="Martin-Handasyde"/>{{rp|61}} The female [[lactation|lactates]] for as long as a year to make up for her low energy production. Unlike in other marsupials, koala milk becomes less fatty as the joey grows.<ref name="Martin-Handasyde"/>{{rp|62}} After seven weeks, the joey has a proportionally large head, clear edges around its face, more colouration, and a visible pouch (if female) or scrotum (male). At 13 weeks, the joey weighs around {{cvt|50|g}} and its head doubles in size. The eyes begin to open and hair begins to appear. At 26 weeks, the fully furred animal resembles an adult and can look outside the pouch.<ref name="Martin-Handasyde"/>{{rp|63}}
[[File:Koala and joey.jpg|thumb|left|Mother with joey on back]]
At six or seven months, the joey weighs {{cvt|300|-|500|g}} and fully emerges from the pouch for the first time. It explores its new surroundings cautiously, clutching its mother for support.<ref name="Martin-Handasyde"/>{{rp|65}} Around this time, the mother prepares it for a eucalyptus diet by producing a faecal pap that the joey eats from her cloaca. This pap comes from the cecum, is more liquid than regular faeces, and is filled with bacteria.<ref>{{cite journal|last1=Osawa|first1=R|last2=Blanshard|first2=W. H.|last3=O'Callaghan|first3=P. G.|year=1993|title=Microbiological studies of the intestinal microflora of the koala, ''Phascolarctos-Cinereus'' .2. pap, a special maternal feces consumed by juvenile koalas|journal=Australian Journal of Zoology|volume=41|issue=6|pages=611–620|doi=10.1071/ZO9930611}}</ref> A nine month old joey has its adult coat colour and weighs {{cvt|1|kg}}. Having permanently left the pouch, it rides on its mother's back for transportation, learning to climb by grasping branches.<ref name="Martin-Handasyde"/>{{rp|65–66}} Gradually, it becomes more independent. The mother becomes pregnant again after a year, when the offspring reaches around {{cvt|2.5|kg}}. She permanently severs her bond with her previous offspring and no longer allows it to suckle, but it remains nearby until it is one-and-a-half to two years old.<ref name="Martin-Handasyde"/>{{rp|66–67}}

Females become [[sexual maturity|sexually mature]] at about three years of age; in comparison, males reach sexual maturity at about age four,<ref>{{cite journal |author=Ellis, W. A. H. |author2=Bercovitch, F. B. |title=Body size and sexual selection in the koala |journal=Behavioral Ecology and Sociobiology |year=2011 |volume=65 |issue=6 |pages=1229–35 |doi=10.1007/s00265-010-1136-4|s2cid=26046352 }}</ref> although they can experience [[spermatogenesis]] as early as two years.<ref name="Martin-Handasyde"/>{{rp|68}} Males do not start marking their scent until they reach sexual maturity, though their chest glands become functional much earlier.<ref name="Tobey 2009"/> Koalas can breed every year if environmental conditions are good, though the long dependence of the young usually leads to year-long gaps in births.<ref name="Tyndale-Biscoe"/>{{rp|236}}

===Health and mortality===
Koalas live from 13 to 18 years in the wild, although males may die sooner because of their more risky lives.<ref name="Martin-Handasyde"/>{{rp|69}} Koalas usually survive falls from trees, but they can get hurt and even die, particularly inexperienced young and fighting males.<ref name="Martin-Handasyde"/>{{rp|72–73}} Around age six, the koala's chewing teeth begin to wear down and their chewing efficiency decreases. Eventually, the cusps disappear completely and the animal dies of starvation.<ref>{{cite journal | last1=Lanyon | first1=Janet M. | last2=Sanson | first2=G. D. | title=Koala (''Phascolarctos cinereus'') dentition and nutrition. II. Implications of tooth wear in nutrition | journal=Journal of Zoology | publisher=Wiley | volume=209 | issue=2 | year=1986 | issn=0952-8369 | doi=10.1111/j.1469-7998.1986.tb03573.x | pages=169–181| doi-access=free }}</ref> Koalas have few predators. [[Dingo]]s and large [[Pythonidae|pythons]] and some [[bird of prey|birds of prey]] may take them. Koalas are generally not subject to external [[parasite]]s, other than [[tick]]s around the coast. The [[mite]] ''[[Sarcoptes scabiei]]'' gives koalas [[mange]], while the bacterium ''[[Mycobacterium ulcerans]]'' [[Ulcer (dermatology)|skin ulcers]], but these are uncommon. Internal parasites are few and have little effect.<ref name="Martin-Handasyde"/>{{rp|71–74}} These include the ''Bertiella obesa'' [[tapeworm]], commonly found in the intestine, and the ''[[Marsupostrongylus longilarvatus]]'' and ''[[Durikainema phascolarcti]] [[nematode]]s'', which are infrequently found in the lungs.<ref>{{cite journal |author1=Spratt, D. M. |author2=Gill, P. A. |title=''Durikainema phascolarcti'' n. sp. (Nematoda: Muspiceoidea: Robertdollfusidae) from the pulmonary arteries of the koala ''Phascolarctos cinereus'' with associated pathological changes |journal=Systematic Parasitology |year=1998 |volume=39 |pages=101–06 |doi=10.1023/A:1005957809179 |issue=2|s2cid=26037401|url=https://link.springer.com/content/pdf/10.1023/A:1005957809179.pdf }}</ref> In a three-year study of almost 600 koalas taken to the Australia Zoo Wildlife Hospital in Queensland, 73.8% of the animals were infected with parasitic [[protozoa]]l genus ''[[Trypanosoma]]'', the most frequent of which was ''[[Trypanosoma irwini|T.&nbsp;irwini]]''.<ref>{{cite journal | last1=McInnes| first1=L. M. | last2=Gillett| first2=A. | last3=Hanger| first3=J. | last4=Reid| first4=S. A. | last5=Ryan | first5=U. M. | title=The potential impact of native Australian trypanosome infections on the health of koalas (''Phascolarctos cinereus'') | journal=Parasitology | publisher=Cambridge University Press (CUP) | volume=138 | issue=7 | date=27 April 2011 | issn=0031-1820 | doi=10.1017/s0031182011000369|doi-access=free | pages=873–883| pmid=21524321 }}</ref>

Koalas can be subject to [[pathogen]]s such as ''[[Chlamydiaceae]]'' bacteria,<ref name="Martin-Handasyde"/>{{rp|74–75}} which can cause [[keratoconjunctivitis]], [[urinary tract infection]], and [[reproductive tract infection]].<ref name=jackson/>{{rp|229–30}} Such infections are common on the mainland, but absent in some island populations.<ref name="Martin-Handasyde"/>{{rp|114}} The [[koala retrovirus]] (KoRV) may cause koala immune deficiency syndrome (KIDS) which is similar to AIDS in humans. [[Disease prevalence|Prevalence]] of KoRV in koala populations suggests it spread from north to south, as only southern populations have virus-free individuals.<ref>{{cite journal |author=Stoye, J. P. |title=Koala retrovirus: A genome invasion in real time |journal=Genome Biology |volume=7 |pages=241 |year=2006 |doi=10.1186/gb-2006-7-11-241 |pmid=17118218 |issue=11 |pmc=1794577 |doi-access=free }}</ref>

The animals are vulnerable to [[Bushfires in Australia|bushfires]] due to their slow speed and the [[Eucalyptus#Fire hazard|flammability of eucalypt trees]].<ref name="Martin-Handasyde"/>{{rp|26}} The koala instinctively seeks refuge in the higher branches, where it is vulnerable to heat and fire. Bushfires divide the animal's habitat, which isolates them, decreases their numbers and creates [[genetic bottleneck]]s.<ref name=moyal/>{{rp|209–11}} [[Dehydration]] and overheating can prove fatal.<ref name=jackson/>{{rp|80}} Consequently, the koala is vulnerable to the [[Effects of climate change in Australia|effects of climate change]]. [[Global climate model|Models]] of [[climate change in Australia|climate change]] predict warmer and drier climates, suggesting that the koala's range will shrink in the east and south to more [[mesic habitat]]s.<ref>{{cite journal |author1=Adams-Hosking, C. |author2=Grantham, H. S. |author3=Rhodes, J. R. |author4=McAlpine, C. |author5=Moss, P. T. |title=Modelling climate-change-induced shifts in the distribution of the koala |journal=Wildlife Research |year=2011 |volume=38 |issue=2 |pages=122–30 |doi=10.1071/WR10156}}</ref>

==Relation to humans==

===History===
[[File:Koalo.jpg|thumb|upright|left|George Perry's illustration in his 1810 ''Arcana'' was the first published image of the koala.]]
The first written reference to the koala was recorded by John Price, servant of [[John Hunter (Royal Navy officer)|John Hunter]], the [[Governor of New South Wales]]. Price encountered the "cullawine" on 26 January 1798, during an expedition to the [[Blue Mountains (New South Wales)|Blue Mountains]],<ref>{{cite book | last=Phillips | first=Bill | title=Koalas : the little Australians we'd all hate to lose | publisher=Australian Government Publishing Service| publication-place=Canberra | year=1990 | isbn=978-0-644-09697-3 | oclc=21532917 | page=13}}</ref> but his remarks would first be published in ''[[Historical Records of Australia]]'', nearly a century later.<ref name=moyal/>{{rp|8}} In 1802, French-born explorer [[Francis Louis Barrallier]] encountered the animal when his two Aboriginal guides, returning from a hunt, brought back two koala feet they were intending to eat. Barrallier preserved the appendages and sent them and his notes to Hunter's successor, [[Philip Gidley King]], who forwarded them to [[Joseph Banks]]. Similar to Price, Barrallier's notes were not published until 1897.<ref name=moyal/>{{rp|9–10}} Reports of the "Koolah" appeared in the Sydney Gazette in late 1803, and helped provide the impetus for King to send artist [[John Lewin]] to create watercolours of the animal. Lewin painted three pictures, one of which was [[printmaking|printed]] in [[Georges Cuvier]]'s ''[[Le Règne Animal]] (The Animal Kingdom)'' (1827).<ref name=moyal/>{{rp|12–13}}

Botanist [[Robert Brown (Scottish botanist from Montrose)|Robert Brown]] was the first to write a formal scientific description in 1803, based on a female specimen captured near what is now [[Mount Kembla]] in the [[Illawarra]] region of New South Wales. Austrian botanical illustrator [[Ferdinand Bauer]] drew the animal's skull, throat, feet, and paws. Brown's work remained unpublished and largely unnoticed, however; his field books and notes remained in his possession until his death, when they were bequeathed to the [[Natural History Museum, London|British Museum]] in London. They were not identified until 1994, while Bauer's koala watercolours were not published until 1989.<ref name=moyal/>{{rp|16–28}} [[William Paterson (explorer)|William Paterson]], who had befriended Brown and Bauer during their stay in New South Wales, wrote an eyewitness report of his encounters with the animals and this would be the basis for British surgeon [[Everard Home]]'s anatomical writings on them.<ref name=moyal/>{{rp|33–36}} Home, who in 1808 published his report,<ref>{{cite journal |author=Home, E. |title=An account of some peculiarities in the anatomical structure of the wombat, with observations on the female organs of generation |journal=Philosophical Transactions of the Royal Society |year=1808 |volume=98 |pages=304–12 |url=https://archive.org/stream/philtrans02276790/02276790#page/n0/mode/2up |doi=10.1098/rstl.1808.0020 |s2cid=108450983 |access-date=9 November 2015 |archive-url=https://web.archive.org/web/20151015004016/https://archive.org/stream/philtrans02276790/02276790#page/n0/mode/2up |archive-date=15 October 2015 |url-status=live }}</ref> coined the scientific name ''Didelphis coola''.<ref name=moyal/>{{rp|36}}

[[George Perry (naturalist)|George Perry]] officially published the first image of the koala in his 1810 natural history work ''Arcana''.<ref name=moyal/>{{rp|37}} Perry called it the "New Holland Sloth", and his dislike for the koala, evident in his description of the animal, was reflected in the contemporary British attitudes towards Australian animals as strange and primitive:<ref name=moyal/>{{rp|40}} <blockquote>...&nbsp; the eye is placed like that of the Sloth, very close to the mouth and nose, which gives it a clumsy awkward appearance, and void of elegance in the combination&nbsp;... they have little either in their character or appearance to interest the Naturalist or Philosopher. As Nature however provides nothing in vain, we may suppose that even these torpid, senseless creatures are wisely intended to fill up one of the great links of the chain of animated nature&nbsp;...<ref>{{cite journal |author=Perry, G. |title=Koalo, or New Holland Sloth |journal=Arcana; or the Museum of Natural History |page=109 |url=https://archive.org/stream/arcanaormuseumof00perr#page/n109/mode/2up |year=1811 |access-date=9 November 2015 |archive-url=https://web.archive.org/web/20151015004010/https://archive.org/stream/arcanaormuseumof00perr#page/n109/mode/2up |archive-date=15 October 2015 |url-status=live }}</ref></blockquote>
[[File:Phascolarctus cinereus 2 Gould.jpg|thumb|upright|Natural history illustrator John Gould popularised the koala with his 1863 work ''The Mammals of Australia''.]]

Naturalist and popular artist [[John Gould]] illustrated and described the koala in his three-volume work ''[[The Mammals of Australia]]'' (1845–1863) and introduced the species, as well as other members of Australia's little-known faunal community, to the public.<ref name=moyal/>{{rp|87–93}} Comparative anatomist [[Richard Owen]], in a series of publications on the physiology and anatomy of Australian mammals, presented a paper on the anatomy of the koala to the [[Zoological Society of London]].<ref>{{cite journal |author=Owen, R. |title=Richard Owen, esq., in the chair |journal=Proceedings of the Zoological Society of London |year=1836 |volume=4 |issue=1 |pages=109–13 |url=https://www.biodiversitylibrary.org/page/30570836 |doi=10.1111/j.1096-3642.1836.tb01376.x |access-date=20 February 2018 |archive-url=https://web.archive.org/web/20170814024831/http://www.biodiversitylibrary.org/page/30570836 |archive-date=14 August 2017 |url-status=live }}</ref> In this widely cited publication, he provided an early description of its internal anatomy, and noted its general structural similarity to the wombat.<ref name=moyal/>{{rp|94–96}} English naturalist [[George Robert Waterhouse]], curator of the Zoological Society of London, was the first to correctly classify the koala as a marsupial in the 1840s, and compared it to fossil species ''[[Diprotodon]]'' and ''[[Nototherium]]'', which had been discovered just recently.<ref name=moyal/>{{rp|46–48}} Similarly, [[Gerard Krefft]], curator of the [[Australian Museum]] in Sydney, noted [[evolution]]ary mechanisms at work when comparing the koala to fossil marsupials in his 1871 ''The Mammals of Australia''.<ref name=moyal/>{{rp|103–105}}

Britain received its first living koala in 1881, which was obtained by the [[Zoological Society of London]]. As related by prosecutor to the society, [[William Alexander Forbes]], the animal suffered an accidental demise when the heavy lid of a [[washstand]] fell on it and it was unable to free itself. Forbes dissected the specimen and wrote about the female reproductive system, the brain, and the liver — parts not previously described by Owen, who had access only to preserved specimens.<ref name=moyal/>{{rp|105–06}} Scottish [[Embryology|embryologist]] [[William Hay Caldwell|William Caldwell]] — well known in scientific circles for determining the reproductive mechanism of the [[platypus]] — described the uterine development of the koala in 1884,<ref>{{cite journal |author=Caldwell, H. |title=On the arrangement of the embryonic membranes in marsupial mammals |journal=Quarterly Journal of Microscopical Science |year=1884 |volume=s2–24 |issue=96 |pages=655–658 |url=https://journals.biologists.com/jcs/article-abstract/s2-24/96/655/61975/Memoirs-On-the-Arrangement-of-the-Embryonic?redirectedFrom=fulltext |access-date=14 June 2013 |archive-url=https://web.archive.org/web/20160304051224/https://journals.biologists.com/jcs/article-abstract/s2-24/96/655/61975/Memoirs-On-the-Arrangement-of-the-Embryonic?redirectedFrom=fulltext |archive-date=4 March 2016 |url-status=live }}</ref> and used this new information to convincingly map out the evolutionary timeline of the koala and the [[monotreme]]s.<ref name=moyal/>{{rp|111}}

===Cultural significance ===
{{main|Koala emblems and popular culture}}
{{multiple image
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| header =
| image1 = Koala_souvenirs.JPG
| width1 = 220
| alt1 = Koala souvenir soft toys
| caption1 = Koala souvenir soft toys are popular with tourists
| image2 = Amy and Oliver (5156253878).jpg
| width2 = 200
| alt2 = Amy and Oliver the bronze koalas (by artist Glenys Lindsay)
| caption2 = Amy and Oliver the bronze koalas (by Glenys Lindsay)
}}
The koala is known worldwide and is a major draw for Australian zoos and wildlife parks. It has been featured in popular culture and as [[plush toy|soft toys]].<ref name=jackson/>{{rp|ix}} It benefited the Australian tourism industry by over $1 billion in 1998, and subsequently grown.<ref name=moyal/>{{rp|201}} Its international popularly rose after [[World War II]], when [[Tourism in Australia|tourism]] increased and the animals were exported to zoos overseas.<ref name=jackson/>{{rp|156}} In 1997, about 75% of European and Japanese tourists placed the koala at the top of their list of animals to see.<ref name=moyal/>{{rp|216}} According to biologist Stephen Jackson: "If you were to take a straw poll of the animal most closely associated with Australia, it's a fair bet that the koala would come out marginally in front of the kangaroo".<ref name=jackson/>{{rp|ix}} Factors that contribute to the koala's enduring popularity include its [[teddy bear]]-like appearance with childlike body proportions.<ref name="Martin-Handasyde"/>{{rp|3}}

The koala features in the [[Dreamtime]] stories and [[Australian Aboriginal mythology|mythology]] of Indigenous Australians. The [[Tharawal people]] believed that the animal helped them get to Australia by rowing the boat.<ref name=jackson/>{{rp|21}} Another myth tells of a tribe that killed a koala and used its long intestines to create a bridge for people from other parts of the world.<ref name="Martin-Handasyde"/>{{rp|17}} How the koala lost its tail is the subject of many tales. In one, a kangaroo cuts it off to punish the koala for uncouth behaviour.<ref name=jackson/>{{rp|28}} Tribes in Queensland and Victoria regarded the koala as a wise animal that gave valuable guidance. [[Bidjara language|Bidjara]]-speaking people credited the koala for making trees grow in their arid lands.<ref name=jackson/>{{rp|41–43}} The animal is depicted in [[Petroglyph|rock carvings]], though less so than some other species.<ref name=jackson/>{{rp|45–46}}

Early European settlers in Australia considered the koala to be a creeping [[sloth]]-like animal with a "fierce and menacing look".<ref name=jackson/>{{rp|143}} At the turn of the 20th century, the koala's reputation took a positive turn. It appears in [[Ethel Pedley]]'s 1899 book ''[[Dot and the Kangaroo]]'', as the "funny native bear".<ref name=jackson/>{{rp|144}} Artist [[Norman Lindsay]] depicted a more [[anthropomorphic]] koala in ''[[The Bulletin (Australian periodical)|The Bulletin]]'' cartoons, starting in 1904. This character also appeared as Bunyip Bluegum in Lindsay's 1918 book ''[[The Magic Pudding]]''.<ref name=jackson/>{{rp|147}} The most well known fictional koala is [[Blinky Bill]]. Created by [[Dorothy Wall]] in 1933, the character appeared in books, films, TV series, merchandise, and a 1986 environmental song by [[John Williamson (singer)|John Williamson]].<ref name=jackson/>{{rp|149–52}} The koala first appeared on an [[Postage stamps and postal history of Australia|Australian stamp]] in 1930.<ref name=moyal/>{{rp|164}} 
[[File:President Obama holding a koala 3.jpg|thumb|right|upright|US President [[Barack Obama]] with a koala in [[Brisbane]], Australia]]
The song "Ode to a Koala Bear" appears on the [[B-side]] of the 1983 [[Paul McCartney]]/[[Michael Jackson]] duet single ''[[Say Say Say]]''.<ref name=jackson/>{{rp|151}} A koala is the main character in animated cartoons in the early 1980s: [[Hanna-Barbera]]'s ''[[The Kwicky Koala Show]]'' and [[Nippon Animation]]'s ''[[Noozles]]''. Food products shaped like the koala include the [[Caramello Koala]] chocolate bar and the bite-sized cookie snack [[Koala's March]]. [[Dadswells Bridge]] in Victoria features a tourist complex shaped like a giant koala<ref name=jackson/>{{rp|155–58}} and the [[Queensland Reds]] rugby team has a koala as its icon.<ref name=jackson/>{{rp|160}}

===Koala diplomacy===
Political leaders and members of royal families had their pictures taken with koalas, including [[Queen Elizabeth II]], [[Prince Harry]], [[Crown Prince Naruhito]], [[Crown Princess Masako]], [[Pope John Paul II]], US President [[Bill Clinton]], Soviet premier [[Mikhail Gorbachev]] and South African President [[Nelson Mandela]]<ref name=jackson/>{{rp|156}} At the [[2014 G20 Brisbane summit]], hosted by Prime Minister [[Tony Abbott]], many world leaders, including Russian President [[Vladimir Putin]] and US President [[Barack Obama]], were photographed holding koalas.<ref>{{cite web |last=Donnison |first=Jon |date=16 November 2014 |url=https://www.bbc.com/news/world-australia-30075241 |archive-url=https://web.archive.org/web/20201112020848/https://www.bbc.com/news/world-australia-30075241 |archive-date=12 November 2020 |title=G20 summit: Koalas and 'shirtfronting' |work=BBC News |access-date=23 February 2021}}</ref><ref>{{Cite web |title=President Obama, Putin Cozy Up With Koalas at G20 Summit |url=https://abcnews.go.com/News/president-obama-putin-cozy-koalas-g20-summit/story?id=26937335 |website=ABC News |language=en |last=Dimitrova |first=Kami |date=16 November 2014 |archive-url=https://web.archive.org/web/20210303131537/https://abcnews.go.com/News/president-obama-putin-cozy-koalas-g20-summit/story?id=26937335 |archive-date=3 March 2021 |access-date=23 February 2021 }}</ref> The event gave rise to the term "koala diplomacy",<ref>{{Cite web |last=Rimmer |first=Susan Harris |date=2014-11-17 |title=Koala diplomacy: Australian soft power saves the day at G20 |url=http://theconversation.com/koala-diplomacy-australian-soft-power-saves-the-day-at-g20-34147 |access-date=2024-06-16 |website=The Conversation |language=en-US|archive-url=https://web.archive.org/web/20210227214645/https://theconversation.com/koala-diplomacy-australian-soft-power-saves-the-day-at-g20-34147 |archive-date=27 February 2021}}</ref><ref>{{Cite web |last=Arup |first=Tom |date=2014-12-26 |title=The rise and influence of koala diplomacy |url=https://www.smh.com.au/politics/federal/the-rise-and-influence-of-koala-diplomacy-20141224-12dj2b.html |access-date=2024-06-16 |website=The Sydney Morning Herald |language=en|archive-url=https://web.archive.org/web/20210117011938/https://www.smh.com.au/politics/federal/the-rise-and-influence-of-koala-diplomacy-20141224-12dj2b.html |archive-date=17 January 2021}}</ref> which became the Oxford Word of the Month for December 2016.<ref>{{cite web|url=https://www.oup.com.au/__data/assets/pdf_file/0027/89127/WotM_December_2016.pdf |title=Oxford Word of the Month – December: koala diplomacy|archive-url=https://web.archive.org/web/20220317214341/https://www.oup.com.au/__data/assets/pdf_file/0027/89127/WotM_December_2016.pdf |archive-date=17 March 2022 |publisher=Oxford University Press|date=28 November 2016|access-date=23 February 2021 }}</ref> The term also includes the loan of koalas by the Australian government to overseas zoos in countries such as Singapore and Japan, as a form of "soft power diplomacy", like the "[[panda diplomacy]]" practised by China.<ref>{{Cite web |duplicate_date=2016-02-10 |title=Koala diplomacy as furry envoys return to Australia {{!}} Australian Government Department of Foreign Affairs and Trade |url=https://www.dfat.gov.au/news/news/Pages/koala-diplomacy-as-furry-envoys-return-to-australia,%20https://www.dfat.gov.au/news/news/Pages/koala-diplomacy-as-furry-envoys-return-to-australia |duplicate_access-date=2024-06-16 |website=www.dfat.gov.au |language=en|archive-url=https://web.archive.org/web/20210613211243/https://www.dfat.gov.au/news/news/Pages/koala-diplomacy-as-furry-envoys-return-to-australia |archive-date=13 June 2021 |publisher=Australian Department of Foreign Affairs and Trade |date=10 February 2016|access-date=23 February 2021}}</ref><ref>{{Cite web |last1=Markwell |first1=Kevin |last2=Cushing |first2=Nancy |date=2015-05-20 |title=Koalas, platypuses and pandas and the power of soft diplomacy |url=http://theconversation.com/koalas-platypuses-and-pandas-and-the-power-of-soft-diplomacy-42051 |access-date=16 June 2024 |website=The Conversation |language=en-US|archive-url=https://web.archive.org/web/20210305111551/https://theconversation.com/koalas-platypuses-and-pandas-and-the-power-of-soft-diplomacy-42051 |archive-date=5 March 2021 }}</ref>

==Conservation==
<!-- Please do not add any more examples to this section. This subject already has its own article -->
{{main article|Koala conservation}}
{{Wikinews|Koalas labeled as 'endangered' in eastern states of Australia}}
[[File:Panneaux koala kangourou.jpg|thumb|Road sign depicting a koala and a kangaroo]]
The koala was originally classified as [[least-concern species|Least Concern]] on the [[IUCN Red List|Red List]], and reassessed as [[Vulnerable species|Vulnerable]] in 2014.<ref name="iucn status 12 November 2021" /> In the Australian Capital Territory, New South Wales and Queensland, the species was listed under the EPBC Act in February 2022 as endangered by extinction.<ref name="SPRAT2022">{{cite web |title=Phascolarctos cinereus (combined populations of Qld, NSW and the ACT) — Koala (combined populations of Queensland, New South Wales and the Australian Capital Territory) |url=https://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=85104 |website=SPRAT |publisher=Australian Government |year=2022 |access-date=12 February 2022 |archive-date=11 February 2022 |archive-url=https://web.archive.org/web/20220211004226/http://environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=85104 |url-status=live }}</ref><ref name="Guardian2022">{{cite news |last1=Cox |first1=Lisa |title=Koala listed as endangered after Australian governments fail to halt its decline |url=https://www.theguardian.com/environment/2022/feb/11/koala-listed-as-endangered-after-australian-governments-fail-to-halt-its-decline |access-date=11 February 2022 |work=The Guardian |date=11 Feb 2022 |archive-date=10 February 2022 |archive-url=https://web.archive.org/web/20220210231836/https://www.theguardian.com/environment/2022/feb/11/koala-listed-as-endangered-after-australian-governments-fail-to-halt-its-decline |url-status=live }}</ref> The described population was determined in 2012 to be "a species for the purposes of the EPBC Act 1999" in Federal legislation.<ref>{{Cite web |title=Determination that a distinct population of biological entities is a species for the purposes of the Environment Protection and Biodiversity Conservation Act 1999 (132) |author=[[Tony Burke|Burke, Tony]] |work=Australian Government - Federal Register of Legislation |date=27 April 2012 |url=https://www.legislation.gov.au/Details/F2012L00960 |access-date=12 February 2022 |archive-date=12 February 2022 |archive-url=https://web.archive.org/web/20220212195138/https://www.legislation.gov.au/Details/F2012L00960 |url-status=live }}</ref>

Australian policymakers declined a 2009 proposal to include the koala in the [[Environment Protection and Biodiversity Conservation Act 1999]].<ref name="Price 2012"/> A 2017 [[World Wildlife Fund|WWF]] report found a 53% decline per generation in Queensland, and a 26% decline in New South Wales.<ref>{{cite report |title=Current status of the koala in Queensland and New South Wales |author=Christine Adams-Hosking |publisher=WWF Australia |date=May 2017 |url=https://www.wwf.org.au/ArticleDocuments/353/pub-current-status-of-the-koala-in-queensland-and-new-south-wales-19may17.pdf.aspx |access-date=3 November 2019 |archive-url=https://web.archive.org/web/20190409071936/https://www.wwf.org.au/ArticleDocuments/353/pub-current-status-of-the-koala-in-queensland-and-new-south-wales-19may17.pdf.aspx |archive-date=9 April 2019 |url-status=live }}</ref> The koala population in South Australia and Victoria appear to be abundant; however, the [[Australian Koala Foundation]] (AKF) argued that the exclusion of Victorian populations from protective measures was based on a misconception that the total population was 200,000, whereas they believed in 2012 that it was probably less than 100,000.<ref name="abc120430">{{cite news |url=http://www.abc.net.au/news/2012-04-30/koala-listed-as-vulnerable/3980216/?site=sydney |title=Koalas added to threatened species list |date=30 April 2012 |publisher=ABC |access-date=2 May 2012 |archive-url=https://web.archive.org/web/20120510145419/http://www.abc.net.au/news/2012-04-30/koala-listed-as-vulnerable/3980216/?site=sydney |archive-date=10 May 2012 |url-status=live }}</ref> AKF estimated in 2022 that there could be 43,000–100,000.<ref>{{cite news |title=Koala declared endangered as disease, lost habitat take toll |date=11 February 2022 |url=https://apnews.com/article/health-australian-capital-territory-new-south-wales-queensland-environment-f38e062d7ae4806f9d4f7f67dd538968 |work=AP News |access-date=13 February 2022 |archive-date=13 February 2022 |archive-url=https://web.archive.org/web/20220213152057/https://apnews.com/article/health-australian-capital-territory-new-south-wales-queensland-environment-f38e062d7ae4806f9d4f7f67dd538968 |url-status=live }}</ref> This compares with 8 to 10 million at the start of the 20th century.<ref>{{Cite web |title=Infographic: The Worrying Decline of Koala Populations |last=Buchholz |first=Katharina |work=Statista Infographics |date=27 November 2019 |url=https://www.statista.com/chart/20124/decline-of-koala-populations-in-australian-states/ |access-date=14 February 2022 |archive-date=14 February 2022 |archive-url=https://web.archive.org/web/20220214121514/https://www.statista.com/chart/20124/decline-of-koala-populations-in-australian-states/ |url-status=live }}</ref><ref>{{cite news |title=Koala (Phascolarctos cinereus) Fact Sheet: Population & Conservation Status |url=https://ielc.libguides.com/sdzg/factsheets/koala/population |work=San Diego Zoo Wildlife Alliance |date=June 2021 |access-date=14 February 2022 |archive-date=14 February 2022 |archive-url=https://web.archive.org/web/20220214205336/https://ielc.libguides.com/sdzg/factsheets/koala/population |url-status=live }}</ref> The Australian Government's Threatened Species Scientific Committee estimated that the 2021 koala population was 92,000, down from 185,000 two decades prior.<ref>{{cite web|date=11 February 2022|title=Australia warns koalas 'endangered' as numbers plunge|website=Phys.org|url=https://phys.org/news/2022-02-australia-koalas-endangered-plunge.html#:~:text=The%20koala%2C%20a%20globally%20recognised,coast%20just%20a%20decade%20earlier.&text=Conservationists%20said%20it%20was%20hard,in%20the%20affected%20eastern%20states|access-date=19 December 2022}}</ref>

The koala was heavily hunted by European settlers in the early 20th century,<ref name=moyal/>{{rp|121–128}} largely for its fur. Australia exported as many as two million pelts by 1924. Koala furs were used to make rugs, coat linings, [[muff (handwarmer)|muffs]], and on women's garment trimmings.<ref name=moyal/>{{rp|125}} The first successful efforts at conserving the species were initiated by the establishment of Brisbane's [[Lone Pine Koala Sanctuary]] and Sydney's [[Koala Park Sanctuary]] in the 1920s and 1930s. Its owner Noel Burnet created the first successful breeding program.<ref name=moyal/>{{rp|157–159}}

One of the biggest [[wikt:anthropogenic|anthropogenic]] threats to the koala is [[habitat destruction]] and [[Habitat fragmentation|fragmentation]]. Near the coast, the main cause of this is urbanisation, while in rural areas, habitat is [[Land clearing in Australia|cleared for agriculture]]. Its favoured trees are harvested for wood products.<ref name="Martin-Handasyde" />{{rp|104–107}} In 2000, Australia had the fifth highest rate of land clearance globally, stripping {{convert|564800|ha}} of native plants.<ref name=jackson/>{{rp|222}} The koalas' distribution has shrunk by more than 50% since European arrival, largely due to habitat fragmentation in Queensland.<ref name="McGregor 2013"/> Nevertheless, koalas live in many [[protected area]]s.<ref name="iucn status 12 November 2021" />

While urbanisation can pose a threat to koala populations, the animals can survive in urban areas given enough trees.<ref name="Holtcamp 2007">{{cite web|author=Holtcamp, W.|date=5 January 2007|title=Will Urban Sprawl KO the Koala?|publisher=National Wildlife|access-date=22 March 2013|url=http://www.nwf.org/News-and-Magazines/National-Wildlife/Animals/Archives/2007/Will-Urban-Sprawl-KO-the-Koala.aspx|archive-url=https://web.archive.org/web/20131113173601/http://www.nwf.org/News-and-Magazines/National-Wildlife/Animals/Archives/2007/Will-Urban-Sprawl-KO-the-Koala.aspx|archive-date=13 November 2013|url-status=live}}</ref> Urban populations have distinct vulnerabilities: [[roadkill|collisions with vehicles]] and attacks by domestic dogs.<ref>{{Cite web|date=2006-02-14|title=Cars and dogs threaten koala future|url=https://www.uq.edu.au/news/article/2006/02/cars-and-dogs-threaten-koala-future|access-date=2021-04-22|website=University of Queensland News|language=en|archive-date=22 April 2021|archive-url=https://web.archive.org/web/20210422073105/https://www.uq.edu.au/news/article/2006/02/cars-and-dogs-threaten-koala-future|url-status=live}}</ref> Cars and dogs kill about 4,000 animals every year.<ref name="Foden 2009">{{cite report |author1=Foden, W. |author2=Stuart, S. N. |title=Species and Climate Change: More than Just the Polar Bear |publisher=IUCN Species Survival Commission |year=2009 |pages=36–37 |url=https://portals.iucn.org/library/sites/library/files/documents/2009-051.pdf |access-date=10 November 2016 |archive-url=https://web.archive.org/web/20160315144637/https://portals.iucn.org/library/sites/library/files/documents/2009-051.pdf |archive-date=15 March 2016 |url-status=live }}</ref> To reduce road deaths, government agencies have been exploring various [[wildlife crossing]] options,<ref>{{Cite book|title=How to keep koalas off the road - Koala Vehicle Strike Fact sheet 2|url=https://www.environment.nsw.gov.au/-/media/OEH/Corporate-Site/Documents/Animals-and-plants/Threatened-species/koala-vehicle-strike-fact-sheet-2-how-to-keep-koalas-off-roads-200230.pdf|via=NSW Government|date=June 2020|isbn=978-1-922431-20-2|access-date=22 April 2021|archive-date=22 April 2021|archive-url=https://web.archive.org/web/20210422073105/https://www.environment.nsw.gov.au/-/media/OEH/Corporate-Site/Documents/Animals-and-plants/Threatened-species/koala-vehicle-strike-fact-sheet-2-how-to-keep-koalas-off-roads-200230.pdf|url-status=live }}</ref><ref>{{Cite web|title=Koalas and resilient habitat in the Sutherland Shire|url=https://www.ssec.org.au/our-campaigns/koalas-and-resilient-habitat-in-the-sutherland-shire/|date=September 2021<!--undated, but in Feb22 includes references dated September 2021 & copyr. 2021-->|website=Sutherland Shire Environment Centre|access-date=22 April 2021|archive-date=22 April 2021|archive-url=https://web.archive.org/web/20210422034249/https://www.ssec.org.au/our-campaigns/koalas-and-resilient-habitat-in-the-sutherland-shire/|url-status=live}}</ref> such as the use of fencing to channel animals toward an underpass, in some cases adding a walkway to an existing culvert.<ref>{{Cite web|last=Moore|first=Tony|date=2016-07-26|title=Koalas tunnels and bridges prove effective on busy roads|url=https://www.brisbanetimes.com.au/national/queensland/koalas-tunnels-and-bridges-prove-effective-on-busy-roads-20160726-gqdsi2.html|access-date=2021-04-22|website=Brisbane Times|language=en|archive-date=22 April 2021|archive-url=https://web.archive.org/web/20210422073104/https://www.brisbanetimes.com.au/national/queensland/koalas-tunnels-and-bridges-prove-effective-on-busy-roads-20160726-gqdsi2.html|url-status=live}}</ref><ref>{{Cite news|date=2016-07-27|title=Clever koalas learn to cross the road safely|language=en-GB|work=BBC News|url=https://www.bbc.com/news/world-australia-36891868|access-date=2021-04-22|archive-date=22 April 2021|archive-url=https://web.archive.org/web/20210422073103/https://www.bbc.com/news/world-australia-36891868|url-status=live}}</ref> Injured koalas are often taken to wildlife hospitals and [[Wildlife rehabilitation|rehabilitation centres]].<ref name="Holtcamp 2007"/> In a 30-year [[retrospective cohort study|retrospective study]] performed at a New South Wales koala rehabilitation centre, [[Trauma (medicine)|trauma]] was found to be the most frequent cause of admission, followed by symptoms of [[chlamydia infection|''Chlamydia'' infection]].<ref>{{cite journal |author1=Griffith, J. E. |author2=Dhand, N. K. |author3=Krockenberger, M. B. |author4=Higgins, D. P. |title=A retrospective study of admission trends of koalas to a rehabilitation facility over 30 years |journal=Journal of Wildlife Diseases |year=2013 |volume=49 |issue=1 |pages=18–28 |doi=10.7589/2012-05-135 |pmid=23307368 |hdl=2123/14628 |s2cid=32878079 |url=https://ses.library.usyd.edu.au/bitstream/2123/14628/2/a-retrospective-study-pdf-2013.pdf |access-date=24 September 2019 |archive-url=https://web.archive.org/web/20180721041418/https://ses.library.usyd.edu.au/bitstream/2123/14628/2/a-retrospective-study-pdf-2013.pdf |archive-date=21 July 2018 |url-status=live |hdl-access=free }}</ref>

==See also==
* [[Drop bear]] – A predatory and dangerous version of the koala in popular folklore
* [[Fauna of Australia]]
* [[List of monotremes and marsupials of Australia]]
* [[Sam (koala)]], a female koala known for being rescued during the [[Black Saturday bushfires]] in 2009

==References==
{{Reflist|30em}}

==External links==
{{Wikispecies|Phascolarctos cinereus}}
{{Commons|Phascolarctos cinereus}}
{{Americana Poster|Koala|year=1920}}
{{Wiktionary|koala}}
* Archive – [https://web.archive.org/web/20130204185547/http://www.arkive.org/koala/phascolarctos-cinereus/ images and movies of the koala ''Phascolarctos cinereus'']
* [http://animaldiversity.ummz.umich.edu/accounts/Phascolarctos_cinereus/ Animal Diversity Web – ''Phascolarctos cinereus'']
*iNaturalist crowdsourced [https://www.inaturalist.org/taxa/42983-Phascolarctos-cinereus koala sighting photos] (mapped, graphed)
* [https://koala.org Koala Science Community] {{Webarchive|url=https://web.archive.org/web/20200505230729/https://koala.org/ |date=5 May 2020 }}
* [http://www.abc.net.au/4corners/stories/2012/08/16/3569231.htm "Koala Crunch Time"] – an [[Australian Broadcasting Corporation|ABC]] documentary (2012)
* [http://www.abc.net.au/environment/articles/2012/08/21/3571830.htm "Koalas deserve full protection"]
* [https://www.pbs.org/wnet/nature/episodes/cracking-the-koala-code/full-episode/7721/ Cracking the Koala Code] – a [[Nature (TV series)|PBS Nature]] documentary (2012)
* [https://www.aussieark.org.au/koala-ark/ The Aussie Koala Ark Conservation Project] {{Webarchive|url=https://web.archive.org/web/20210512093727/https://www.aussieark.org.au/koala-ark/ |date=12 May 2021 }}

{{Diprotodontia|V.}}
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{{Taxonbar|from=Q36101}}

[[Category:Koalas| ]]
[[Category:Articles containing video clips]]
[[Category:Clawed herbivores]]
[[Category:Extant Middle Pleistocene first appearances]]
[[Category:Herbivorous mammals]]
[[Category:Mammals described in 1817]]
[[Category:Mammals of New South Wales]]
[[Category:Mammals of Queensland]]
[[Category:Mammals of South Australia]]
[[Category:Mammals of Victoria (state)]]
[[Category:Marsupials of Australia]]
[[Category:Vombatiforms]]
[[Category:Symbols of Queensland]]
[[Category:Taxa named by Georg August Goldfuss]]