The koala (Phascolarctos cinereus) is one of Australia's largest arboreal (tree-dwelling) marsupials and is both culturally and ecologically important. The koala is listed as threatened in Queensland, New South Wales and the Australian Capital Territory under the Federal Government’s Environmental Protection and Biodiversity Conservation Act 1999 and vulnerable under Queensland’s Nature Conservation Act 1992.
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Koalas have thick, woolly light grey/brown fur which helps protect them from extreme temperatures and rain. They have muscular bodies, very strong forelimbs and soft, textured gripping pads and sharp long claws to help them grip and climb.
In South East Queensland, adult koalas grow up to around 70 centimetres in length from head to bottom and weigh, on average, between five and seven kilograms. Adult males are generally considerably heavier than females and can reach up to nine kilograms in the Gold Coast area.
Koalas are mainly nocturnal and tend to be most active around dawn and dusk (crepuscular). They spend around 18 to 20 hours of each day resting in order to conserve energy, due to the low-energy content of their main diet of Eucalyptus leaves.
At birth, koala joeys are blind and furless and about the size of a jelly bean (two to three centimetres). The young spend the first six or seven months in the safety of the mother's pouch and then ride on her back, continuing to suckle milk until around 12 months of age. Females are generally sexually mature and capable of breeding from around two years of age and can produce a maximum of one young per year. However, a breeding rate of one young each two years appears to be more common in the wild.
The peak koala breeding season in South East Queensland runs from July to January. During this period, koalas move around considerably more as juvenile males seek their own home range and breeding adults seek a mate. Koalas generally live for about 10 to 14 years in the wild. However, in urban areas their life span can be significantly reduced due to loss of suitable habitat and threats from dogs, cars and disease.
Koalas are widely distributed across eastern Australia, from far north-eastern Queensland to the Eyre Peninsula in South Australia, extending inland to the Brigalow Belt and Mulga Lands of central Queensland and the tablelands and western slopes and plains of New South Wales.
Koala populations depend on large areas of eucalypt forests and woodlands for reproductive success and long-term sustainability. More than 50 per cent of these habitat types have been cleared since European settlement and much of what remains has been fragmented or degraded.
In areas where adequate habitat remains to support a stable breeding population, koalas establish and occupy individual 'home ranges'. These home ranges adjoin or overlap with those of other members of the population and incorporate home range trees that are visited more frequently than others. The home range areas vary in size due to habitat quality and demographic or social factors, with males tending to establish larger home ranges than females.
Habitat quality can be measured by factors such as the abundance and size of preferred food and shelter tree species, soil nutrient availability, and the extent of habitat fragmentation or other disturbance. Research suggests that koalas are likely to remain loyal to their home range area throughout their lives unless there is major disturbance to the habitat or disruption to social structures.
The minimum amount of habitat needed in a landscape to ensure the persistence of a species provides an important target for conservation planning. Landscape ecology research has indicated that habitat thresholds are likely to exist for sustaining koala populations. Below habitat threshold points, a rapid decline in koala occupancy is likely. Estimated threshold points for koalas appear to vary between regions, possibly in response to cross-regional differences in habitat quality, demographic rates, and patterns of land use.
Koalas are obligate folivores, which means they survive exclusively on a diet of leaves. They feed mainly on the leaves of Eucalyptus trees which are high in fibre, low in protein and contain a range of phenolic compounds and cyanide precursors that are unpalatable or toxic to most mammals. Koalas, along with greater gliders (Petauroides Volans) and Common Ringtail Possums (Pseudocheirus peregrinus), are the only mammals that have evolved for survival on a diet primarily of Eucalyptus leaves.
Preferred koala food trees on the Gold Coast include:
- Forest red gum or Queensland blue gum (Eucalyptus tereticornis)
- Tallowwood (E. microcorys)
- Swamp mahogany (E.robusta)
- Grey gums (E. propinqua and E. biturbinata).
Important local supplementary resources include species such as:
- Grey ironbark (E. siderophloia)
- White stringybark (E. tindaliae)
- Brush box (Lophostemon confertus)
- Broad-leaved paperbark (Melaleuca quinquenervia).
Koalas on the Gold Coast
Koala populations continue to survive in a few locations east of the Pacific Motorway (M1), with the majority of Gold Coast koalas occupying habitat west of the motorway. Koalas have been sighted in a number of City Conservation Areas including Pimpama River, Wongawallan (Wilkes Scrub), Clagiraba (Lower Beechmont - Mount Nathan), Coombabah, Elanora, Numinbah Valley, Tugun Hill and Upper Mudgeeraba.
These areas were purchased by the City under the Open Space Preservation Levy Acquisition program, which is funded by ratepayers. Koalas also occur in residential areas where they are particularly at risk from disease, domestic dogs and traffic.
Below is a list of Gold Coast suburbs where koalas have been sighted:
- Burleigh Heads
- Currumbin Valley
- Currumbin Waters
- Highland Park
- Hope Island
- Pacific Pines
- Palm Beach
- Paradise Point
- Pine Ridge
- Reedy Creek
- Runaway Bay
- Tallebudgera Valley
- Upper Coomera
Threats to koalas
As urban expansion continues, koalas face ever-increasing threats to their survival. Koalas regularly move to access food, establish their home range and socialise and are particularly vulnerable during breeding season, when juvenile males are dispersing in search of their own home range and breeding adults are seeking a mate.
The greatest threats to koalas are listed below.
- Fragmentation of habitat, resulting from development, weed invasion and inappropriate fire regimes can lead to isolation of individuals and populations.
- Chlamydial disease can cause a variety of clinical symptoms including:
- eye infections (which can lead to conjunctivitis and blindness)
- urogenital infections in female koalas, which can lead to 'wet bottom' or 'dirty tail' (a brown discoloured rump caused by dripping urine), cystitis and infertility
- respiratory infections (including nasal discharge), leading to pneumonia in some cases.
- Retrovirus (KoRV): Most koalas in Queensland are also believed to be infected with Koala retrovirus (or KoRV), which may cause suppression of the immune system, leukaemia and lymphoma.
- Road fatalities, when koalas are forced to regularly cross busy roads to access food and shelter resources, establish home ranges and seek mates.
- Barriers to movement including fences, roads and cleared land, which alters population dynamics, impedes gene flow and limits population recovery.
- Domestic dog attacks can injure or kill koalas when they enter yards or when dogs roam into nearby bushland.
To find out how you can help reduce threats to our city’s koala population visit Help save koalas.
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