Editing Common brushtail possum (section)

==Biology and ecology==

===Range and habitat===
{{see also|Common brushtail possum in New Zealand}}

The common brushtail possum is one of the most widespread marsupials of Australia. It is found throughout the eastern and northern parts of the continent, as well as some western regions,<ref name="DPAW2005" /><ref name="Abbott-2012" /> Tasmania<ref name="TasGov" /> and a number of offshore islands, such as [[Kangaroo Island]]<ref name="SAGov" /> and [[Barrow Island (Western Australia)|Barrow Island]].<ref name="Chevron" /><ref name="PerthNow" /> [[Western Australia]] alone has several scattered population groups locally distinguished with given indigenous names: ''nunguin'' in [[Kimberley (Western Australia)|Kimberley]], ''walambari'' in [[Pilbara]], ''wayurta'' in the desert areas, and ''bilda'' in [[Nullarbor Plain]] shared with [[South Australia]] among many others.<ref name="Abbott-2012" />

It is also widespread in New Zealand since its introduction in 1850. The common brushtail possum can be found in a variety of habitats, such as forests, semi-arid areas and even cultivated or urban areas.<ref name="Nowak1991" /><ref name="Cronin2008" /> It is mostly a forest inhabiting species, however it is also found in treeless areas.<ref name="Cronin2008" /> In New Zealand, possums favour broadleaf-podocarp near farmland pastures.<ref name="Efford2000" /> In [[Nothofagus|southern beech]] forests and pine plantations, possums are less common.<ref name="Efford2000" /> Overall, brushtail possums are more densely populated in New Zealand than in their native Australia.<ref name="Tyndale2005" /> This may be because Australia has more fragmented [[eucalypt]] forests and more predators. In Australia, brushtail possums are threatened by humans, [[tiger quoll]]s, [[dog]]s, [[fox]]es,<ref name="Abbott-2012" /> [[cat]]s, [[goanna]]s, [[Morelia spilota|carpet snakes]], and [[powerful owl]]s. In New Zealand, brushtail possums are threatened only by humans and cats.<ref name="Tyndale2005" /> The IUCN highlight the population trend in Australia as decreasing.

The northern subspecies of the common brushtail possum has declined substantially, with one study in Australia's Northern Territory finding a 22% reduction in the extent of occurrence of and a 50% reduction in the breadth of occupied environmental space.<ref name="von Takach-2020">{{Cite journal |last1=von Takach |first1=Brenton |last2=Scheele |first2=Ben C. |last3=Moore |first3=Harry |last4=Murphy |first4=Brett P. |last5=Banks |first5=Sam C. |date=2020 |editor-first= |title=Patterns of niche contraction identify vital refuge areas for declining mammals |url=https://onlinelibrary.wiley.com/doi/10.1111/ddi.13145 |journal=Diversity and Distributions |language=en |volume=26 |issue=11 |pages=1467–1482 |doi=10.1111/ddi.13145 |bibcode=2020DivDi..26.1467V |issn=1366-9516|hdl=1885/286535 |s2cid=221758373 |hdl-access=free }}</ref> Analysis of contemporary occurrence points suggested that the species is contracting towards areas of higher rainfall, lower fire frequency, and higher vegetation cover.<ref name="von Takach-2020" /> Little is known about the distribution of the species in the Pilbara.<ref name="abc 2025-05-14">{{cite news |last1=Adams |first1=Mietta |title=Scientists surprised to find possums in WA's Pilbara region |url=https://www.abc.net.au/news/2025-05-14/pilbara-possum-discovery-surprises-scientists/105290378 |access-date=15 May 2025 |work=ABC News |date=14 May 2025 |language=en-AU}}</ref> However, a paper published in the mid-2020s announced a discovery that the populations in the Pilbara, and in the Mid-West of Western Australia where the species is almost extinct, were genetically closer to the subspecies found on the east coast and South Australia, and the now presumed extinct Central Australian subspecies, than those in the South West of Western Australia.<ref name="abc 2025-05-14"/><ref name="abc 2023-06-13">{{cite news |last1=McManus |first1=Sam |title=Study of brushtail possum population differences could help halt species' decline in parts of WA |url=https://www.abc.net.au/news/2023-06-13/brushtail-possums-population-decline-extinction-study-wa-museum/102462162 |access-date=15 May 2025 |work=ABC News |date=13 June 2023 |language=en-AU}}</ref>
===Food and foraging===
The common brushtail possum can adapt to numerous kinds of vegetation but it is largely [[omnivorous]].<ref name="Tyndale2005" /> It prefers ''[[Eucalyptus]]'' leaves, but also eats flowers, shoots, fruits, and seeds.<ref name="Tyndale2005" /> It may also consume animal matter such as insects, birds' eggs and chicks, and other small vertebrates.<ref name="EoL" /> Brushtail possums may eat three or four different plant species during a foraging trip, unlike some other arboreal marsupials, such as the [[koala]] and the [[greater glider]], which focus on single species. The brushtail possum's rounded molars cannot cut ''Eucalyptus'' leaves as finely as more specialised feeders. They are more adapted to crushing their food, which enables them to chew fruit or herbs more effectively. The brushtail possums' caecum lacks internal ridges and cannot separate coarse and fine particles as efficiently as some other arboreal marsupials.<ref name="Tyndale2005" /> The brushtail possum cannot rely on ''Eucalyptus'' alone to provide sufficient protein.<ref name="Wellard1981" /> Its more generalised and mixed diet, however, does provide adequate nitrogen.<ref name="Harris1985" />

===Behaviour===
{{Listen|filename=Brushtail Possum.flac|title=Hissing and growling vocalisations}}
The common brushtail possum is largely arboreal and nocturnal. It has a mostly solitary lifestyle, and individuals keep their distance with scent markings (urinating) and vocalisations. They usually make their dens in natural places such as tree hollows and caves, but also use spaces in the roofs of houses.  While they sometimes share dens, brushtails normally sleep in separate dens. Individuals from New Zealand use many more den sites than those from Australia.<ref name="Green1984" /> Brushtail possums compete with each other and other animals for den spaces, and this contributes to their mortality. This is likely another reason why brushtail possum population densities are smaller in Australia than in New Zealand.<ref name="Tyndale2005" /> Brushtail possums are usually not aggressive towards each other and usually just stare with erect ears.<ref name="Tyndale2005" /> They vocalise with clicks, grunts, hisses, alarm chatters, guttural coughs, and screeching.<ref name="Nowak1991" /><ref name="Cronin2008" />

<gallery mode = packed heights = 180px>
Trichosurus vulpecula brown form.jpg|In a tree (dark brown form)
Common brushtail possum (Trichosurus vulpecula) climbing with joey Scottsdale.jpg|Climbing with joey (light brown form)
Common brushtail possum (Trichosurus vulpecula) with joey Triabunna.jpg|Feeding with joey
</gallery>

===Reproduction and life history===

The common brushtail possum can breed at any time of the year, but breeding tends to peak in spring, from September to November, and in autumn, from March to May, in some areas. Mating is promiscuous and random; some males can sire several young in a season, while over half sire none.<ref name="Tyndale2005" /> In one Queensland population, males apparently need a month of consorting with females before they can mate with them.<ref name="Winter1976" /> Females have a gestation period of 16–18 days, after which they give birth to single young.<ref name="Nowak1991" /><ref name="Cronin2008" /> A newborn brushtail possum is only {{Convert|1.5|cm|abbr=on|sigfig=1}} long and weighs only {{Convert|2|g|abbr=on|sigfig=1}}. As usual for marsupials, the newborn may climb, unaided, through the female's fur and into the pouch and attach to a teat. The young develops and remains inside the mother's pouch for another 4–5 months. A preliminary study inducing [[ovulation]] through exposure of [[Hormone|hormones]] resulted in changes to the appearance of [[Mammary gland|mammary glands]] in females suggesting that mammary glands provide immunological protection to [[Infant|neonates]] through [[milk]] secretions.<ref>{{Cite journal |last1=Old |first1=Julie M. |last2=Irving |first2=M. |last3=Deane |first3=Elizabeth M. |date=2005-07-04 |title=BRIEF COMMUNICATION: Histology of the pouch epithelium and the mammary glands during chemically induced oestrus in the brushtail possum (Trichosurus vulpecula) |url=http://dx.doi.org/10.1111/j.1469-7580.2005.00424.x |journal=Journal of Anatomy |volume=207 |issue=1 |pages=97–102 |doi=10.1111/j.1469-7580.2005.00424.x |pmid=16011549 |issn=0021-8782|pmc=1571494 }}</ref> When older, the young is left in the den or rides on its mother's back until it is 7–9 months old.<ref name="Nowak1991" /><ref name="Cronin2008" /> Females reach sexual maturity when they are a year old, and males do so at the end of their second year.<ref name="Nowak1991" /><ref name="Cronin2008" /> Brushtail possums can live up to 13 years in the wild.<ref name="Nowak1991" /><ref name="Cronin2008" />

Female young have a higher survival rate than their male counterparts due to establishing their home ranges closer to their mothers, while males travel farther in search of new nesting sites, encountering established territories from which they may be forcibly ejected. In New Zealand's [[Ōrongorongo River|Ōrongorongo]] population, female young have been found to continue to associate with their mothers after weaning, and some inherit the prime den sites.<ref name="Brockoe1992" /> A possible competition exists between mothers and daughters for dens, and daughters may be excluded from a den occupied by the mother.<ref name="Johnson2001" /> In forests with shortages of den sites, females apparently produce more sons, which do not compete directly for den sites, while in forests with plentiful den sites, female young are greater in number.<ref name="Johnson2001" />
[[File:Brushtail possum exudative dermatitis.jpg|thumb|Brushtail possum exhibiting exudative dermatitis, a condition that often results from stress associated with overcrowding, particularly in young males attempting to assert territory]]