Editing Koala (section)

===Social life===
{{multiple image
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| image1 = Phascolarctos cinereus Bonorong.jpg
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| 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
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| alt2 = A bellowing male in the [[Lone Pine Koala Sanctuary]]
| caption2 = A bellowing male in the [[Lone Pine Koala Sanctuary]]
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Koalas are asocial and spend just 15 minutes a day on social behaviours. In areas of higher density and fewer trees, home ranges 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 territorial and 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 frequency, these bellows can travel far through the forest.<ref name="Martin-Handasyde"/>{{rp|56}} Koalas may bellow at any time, particularly during the 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 |bibcode=2011JExpB.214.3414C }}</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 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}}