Editing Koala (section)

==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 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 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 it sometimes uses its forepaws or mouth.<ref name=jackson/>{{rp|97–98}}

===Social life===
{{multiple image
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| 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 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}}

===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 they 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=1 November 2004|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, while 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 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 after 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 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|bibcode=2011BEcoS..65.1229E |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, yet 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 parasites other than ticks around the coast. The mite ''[[Sarcoptes scabiei]]'' gives koalas [[mange]], while the bacterium ''[[Mycobacterium ulcerans]]'' 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}} {{As of|2024}}, efforts are underway to use [[vaccination]] to try to stem the koala chlamydia epidemic.<ref>{{Cite web |last=Turnbull |first=Tiffanie |date=December 2024 |title=Chlamydia could kill off koalas. Can a vaccine save them in time? |url=https://www.bbc.com/news/articles/cjdnkdg1l8do |access-date=31 December 2024 |website=www.bbc.com |language=en-GB}}</ref> The [[koala retrovirus]] (KoRV) may cause [[koala immune deficiency syndrome]] (KIDS) which is similar to [[HIV/AIDS|AIDS]] in humans. Prevalence of KoRV in koala populations suggests it spread from north to south, for 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 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. Models of 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>