Alpha males tend to establish their territories

Alpha males tend to establish their territories close to breeding females, while younger males are subordinate until they mature and reach full size.[61] Adult males occasionally venture outside their home ranges; when they do so, dominant ones retain their status.[59] When a male enters a new tree, he marks it by rubbing his chest gland against the trunk or a branch; HP 532613-001 CPU Fan males have occasionally been observed to dribble urine on the trunk. This scent-marking behaviour probably serves as communication, and individuals are known to sniff the base of a tree before climbing.[62] Scent marking is common during aggressive encounters.[63] Chest gland secretions are complex chemical mixtures—about 40 compoundsHP Envy 14-1080eo CPU Fan were identified in one analysis—that vary in composition and concentration with the season and the age of the individual.[64] Adult males communicate with loud bellows—low pitched sounds that consist of snore-like inhalations and resonant exhalations that sound like growls.[65] ACER TravelMate 5230 CPU Fan Because of their low frequency, these bellows can travel far though air and vegetation.[66]Koalas may bellow at any time of the year, particularly during the breeding season, when it serves to attract females and possibly intimidate other males.[67]They also bellow to advertise their presence to their neighbours when they enter a new tree.[66] Lenovo 3000 G430 CPU Fan These sounds signal the male's actual body size as well as exaggerate it;[68] females pay more attention to bellows that originate from larger males.[69] 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.[65] ASUS EEE PC 1215N CPU Fan Young koalas squeak when in distress. As they get older, the squeak develops into a "squawk" that is produced both when in distress and to show aggression. When another individual climbs over it, a koala makes a low grunt with its mouth closed. Koalas make numerous facial expressions. When snarling, wailing or squawking, the animal curls the upper lip and points its ears forward. Dell Vostro 3750 CPU Fan During screams, the lips retract and the ears are drawn back. Females bring the lips forward and raise their ears when agitated.[70] Agonistic behaviour typically consists of squabbles between individuals climbing over or passing each other. This occasionally involves biting. Toshiba Satellite L500-018 CPU Fan Males who are strangers may wrestle, chase and bite each other.[71] In extreme situations, a male may try to displace a smaller rival from a tree. This involves the larger aggressor climbing up and attempting to corner the victim, who tries either to rush past him and climb down or to move to the end of a branch. COMPAQ Presario CQ42-116TU CPU Fan The aggressor attacks by grasping the target by the shoulders and repeatedly biting him. Once the weaker individual is driven away, the victor bellows and marks the tree.[72]Pregnant and lactating females are particularly aggressive and will attack individuals that come too close.[71] In general, however, koalas tend to avoid energy-wasting aggressive behaviour. HP Pavilion dv6-2115eg CPU Fan Koalas are seasonal breeders, and births take place from October to May. Females in oestrus tend to hold their head further back than usual and commonly display tremors and spasms. However, males do not appear to recognise these signs, and have been observed to mount non-oestrous females. Toshiba Satellite L645D-S4056 CPU Fan Because of his much larger size, a male can usually force himself on a female, mounting her from behind, and in extreme cases the male may pull the female out of the tree. A female may scream and vigorously fight off her suitors, but will submit to one who is dominant, or who is more familiar. HP 646578-001 CPU Fan The bellows and screams that accompany matings can attract other males to the scene, obliging the incumbent to delay mating and fight the intruders off. These fights may allow the female to assess who is dominant.[73] Older males usually have accumulated scratches, scars and cuts on the exposed parts of their noses and on their eyelids.[74] SONY VAIO PCG-6L2L CPU Fan The koala has a gestation period lasting 30–35 days,[75] and gives birth to a single young (although twins occur on occasion). As with all marsupials, the young or joey is born while at the embryonic stage, weighing only 0.5 g (0.02 oz). However, it has relatively well-developed lips, forelimbs and shoulders, as well as functioning respiratory, digestive andurinary systems. The joey crawls into its mother's pouch to continue the rest of its development.[76] Toshiba Satellite X205-S9349 CPU Fan Unlike most other marsupials, the koala does not clean her pouch.[77] A female koala has two teats; the joey attaches itself to one of them and suckles for the rest of its pouch life.[76] The koala has one of the lowest milk energy production rates in relation to body size of any mammal. The female makes up for this by lactating for as long as 12 months.[78]  DELL yy529 CPU Fan At seven weeks of age, the joey's head grows longer and becomes proportionally large, pigmentation begins to develop, and its sex can be determined (the scrotum appears in males and the pouch begins to develop in females). At 13 weeks, the joey weighs around 50 g (1.8 oz) and its head has doubled in size. HP Pavilion dv7-3020es CPU Fan The eyes begin to open and fine fur grows on the forehead, nape, shoulders and arms. At 26 weeks, the fully furred animal resembles an adult, and begins to poke its head out of the pouch.[79] As the young koala approaches six months, the mother begins to prepare it for its eucalyptus diet by pre-digesting the leaves, HP G62-369TX CPU Fan producing a faecal pap that the joey eats from her cloacum. The pap is quite different in composition than regular faeces, resembling instead the contents of the caecum, which has a high concentration of bacteria. Eaten for about a month, the pap provides a supplementary source of protein at a transition time from a milk to a leaf diet.[80] HP 13.V1.BJ195.F.GN CPU Fan The joey fully emerges from the pouch for the first time at six or seven months of age, when it weighs 300–500 g (11–18 oz). It explores its new surroundings cautiously, clinging to its mother for support. By nine months, it weighs over 1 kg (2.2 lb) and develops its adult fur colour. Toshiba Satellite L675D-S7016 CPU Fan Having permanently left the pouch, it rides on its mother's back for transportation, learning to climb by grasping branches.[81] Gradually, it spends more time away from its mother and at 12 months it is fully weaned, weighing around 2.5 kg (5.5 lb). When the mother becomes pregnant again, her bond with her previous offspring is permanently severed. HP Pavilion dv7-1451nr CPU Fan Newly weaned young are encouraged to disperse by their mother's aggressive behaviour towards them. Females become sexually mature at about three years of age and can then become pregnant; in comparison, males reach sexual maturity when they are about four years old,[83] although they can produce sperm as early as two years.[82] HP G62-a57SG CPU Fan While the chest glands can be functional as early as 18 months of age, males do not begin scent-marking behaviours until they reach sexual maturity.[64] Because the offspring have a long dependent period, female koalas usually breed in alternate years. Favourable environmental factors, such as a plentiful supply of high-quality food trees, allow them to reproduce every year. SONY Vaio VGN-NR31S/S CPU Fan Koalas may live from 13 to 18 years in the wild. While female koalas usually live this long, males may die sooner because of their more hazardous life.[85] Koalas usually survive falls from trees and immediately climb back up, but injuries and deaths from falls do occur, particularly in inexperienced young and fighting males.[86] IBM 91P9252 CPU Fan At around six years of age, the koala's chewing teeth begin to wear down and their chewing efficiency decreases. Eventually, the cusps will disappear completely and the animal will die of starvation.[87] Koalas have few predators; dingos and large pythons may prey on them, Toshiba Satellite M70-122 CPU Fan while birds of prey (such as Powerful Owls and Wedge-tailed Eagles) are threats to young. They are generally not subject to external parasites, other than ticks in coastal areas. Koalas may also suffer mange from the mite Sarcoptes scabiei, and skin ulcers from the bacterium Mycobacterium ulcerans, but neither are common. SONY UDQFWPH22FQU CPU Fan Internal parasites are few and largely harmless.[86] These include the tapeworm Bertiella obesa, commonly found in the intestine, and thenematodes Marsupostrongylus longilarvatus and Durikainema phascolarcti, which are infrequently found in the lungs.[88] HP Pavilion dv6-2150ei CPU Fan In a three-year study of almost 600 koalas admitted to the Australian Zoo Wildlife Hospital in Queensland, 73.8% of the animals were infected with at least one species of the parasitic protozoal genus Trypanosoma, the most common of which was T. irwini.[89] Koalas can be subject to pathogens like Chlamydiaceae bacteria,[86] HP G42-367TU CPU Fan which can cause keratoconjunctivitis, urinary tract infection and reproductive tract infection.[90] Such infections are widespread on the mainland but absent in some island populations.[91] The koala retrovirus (KoRV) may cause Koala Immune Deficiency Syndrome (KIDS), Toshiba Satellite P100-238 CPU Fan which is similar to AIDS in humans. Prevalence of KoRV in koala populations suggests a trend spreading from the north to the south of Australia. Northern populations are completely infected, while some southern populations (including Kangaroo Island) are free.[92] The animals are vulnerable to bushfires due to their slow movements and the flammability of eucalypt trees.[93] ACER Aspire 5739 CPU Fan The koala instinctively seeks refuge in the higher branches, where it is vulnerable to intense heat and flames. Bushfires also fragment the animal's habitat, which restricts their movement and leads to population decline and loss of genetic diversity.[94] Dehydration and overheating can also prove fatal.[95] Consequently, IBM ThinkPad T40 2678 CPU Fan the koala is vulnerable to the effects of climate change. Models of climate change in Australia predict warmer and drier climates, suggesting that the koala's range will shrink in the east and south to more mesic habitats.[96] Droughts also affect the koala's well-being. For example, a severe drought in 1980 caused many Eucalyptus trees to lose their leaves. IBM Thinkpad T43 CPU Fan Subsequently, 63% of the population in southwestern Queensland died, especially young animals that were excluded from prime feeding sites by older, dominant koalas, and recovery of the population was slow.[39] Later, this population declined from an estimated mean population of 59,000 in 1995 to 11,600 in 2009, IBM ThinkPad T43 2668 CPU Fan a reduction attributed largely to hotter and drier conditions resulting from droughts in most years between 2002 and 2007.[97] Another predicted negative outcome of climate change is the effect of elevations in atmospheric CO2 levels on the koala's food supply: increases in CO2 cause Eucalyptus trees to reduce protein and increase tannin concentrations in their leaves, reducing the quality of the food source. IBM ThinkPad T43 1871 CPU Fan The first written reference of the koala was recorded by John Price, servant of John Hunter, the Governor of New South Wales. Price encountered the "cullawine" on 26 January 1798, during an expedition to the Blue Mountains,[99] although his account was not published until nearly a century later in Historical Records of Australia.[100] ACER Travelmate 8104WLMI CPU Fan 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. DELL Latitude E4300 CPU Fan Similar to Price, Barrallier's notes did not get published until 1897.[101] Reports of the "Koolah" appeared in the Sydney Gazette in late 1803, and helped provide the impetus for King to commission the artist John Lewin to paint watercolours of the animal. Lewin painted three pictures, ASUS F80S CPU Fan one of which was subsequently made into a print that was reproduced inGeorge Culver's The Animal Kingdom (first published in 1827) and several European works on natural history.[102] Botanist Robert Brown was the first to write a detailed scientific description of the koala in 1814, HP Pavilion dv5-1058eo CPU Fan based on a female specimen captured near what is now Mount Kembla in the Illawarra region of New South Wales. Austrian botanical illustrator Ferdinand Bauerdrew the animal's skull, throat, feet and paws. Brown's work remained unpublished and largely unnoticed, however, as his field books and notes remained in his possession until his death, IBM 13N5182 CPU Fan when they were bequeathed to the British Museum of Natural History. They were not identified until 1994, while Bauer's koala watercolours were not published until 1989.[103] British surgeon Everard Home included details of the koala based on eyewitness accounts of William Paterson, who had befriended Brown and Bauer during their stay in New South Wales.[104] IBM Thinkpad T30 2366-AA3 CPU Fan Home, who in 1808 published his report in the journal Philosophical Transactions of the Royal Society,[105] gave the animal the scientific name Didelphis coola.[106] The first published image of the koala appeared in George Perry's (1810) natural history work Arcana.[107] IBM Thinkpad T30 CPU Fan Perry called it the "New Holland Sloth" on account of its perceived similarities to the Central and South American tree-living mammals of genus Bradypus. His disdain for the koala, evident in his description of the animal, was typical of the prevailing early 19th-century British attitude about the primitiveness and oddity of Australian fauna: HP 535438-001 CPU Fan 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 ... they have little either in their character or appearance to interest the Naturalist or Philosopher. As Nature however provides nothing in vain, DELL Inspiron N3010 CPU Fan 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 ...". Naturalist and popular artist John Gould illustrated and described the koala in his three-volume work The Mammals of Australia(1845–63) and introduced the species, HP Pavilion dv6-3070tx CPU Fan as well as other members of Australia's little-known faunal community, to the general British public.[110] 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.[111] IBM 41W5269 CPU Fan In this widely cited publication he provided the first careful description of its internal anatomy, and noted its general structural similarity to the wombat.[112] 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. ASUS A8H CPU Fan He identified similarities between it and its fossil relatives Diprotodon and Nototherium, which had been discovered just a few years before.[113] Similarly, Gerard Krefft, curator of the Australian Museum, noted evolutionary mechanisms at work when comparing the koala to its ancestral relatives in his 1871 The Mammals of Australia.[114] SONY UDQFRZH13CF0 CPU Fan The first living koala in Britain arrived in 1881, purchased 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 used the opportunity to dissect the fresh female specimen, HP COMPAQ 2510P CPU Fan and thus was able to provide explicit anatomical details on the female reproductive system, the brain, and the liver—parts not previously described by Owen, who had access only to preserved specimens.[115] Scottish embryologist William Caldwell—well known in scientific circles for determining the reproductive mechanism of the platypus—described the uterine development of the koala in 1884,[ APPLE 661-4951 CPU Fan and used the new information to convincingly place the koala and the monotremes into an evolutionary time frame.[117] Prince Henry, Duke of Gloucester, visited the Koala Park Sanctuary in Sydney in 1934[118] and was "intensely interested in the bears". HP Pavilion dv6-3034ca CPU Fan His photograph, with Noel Burnet, the founder of the park, and a koala, appeared in the Sydney Morning Herald. After World War II, when tourism to Australia increased and the animals were exported to zoos overseas, the koala's international popularity rose. Several political leaders and members of royal families had their pictures taken with koalas, HP G56-126NR CPU Fan 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.