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Koala Conservation

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About koalas

Click to enlarge Koala sitting in a tree

 

Koala - gripping pads on foot

 

Koala - sharp claws

The koala (Phascolarctos cinereus) is one of Australia's largest arboreal (tree-dwelling) marsupials. They have muscular bodies, very strong forelimbs and soft, textured gripping pads and sharp long claws on their paws to help them grip and climb.

Both the front and hind paws have five digits each. The front paws have two fingers opposing the other three, giving the koala its distinctive “double thumb”. The hind paws have a clawless opposable big toe to help with gripping, while the second and third toes are fused together to form a double-clawed (syndactylus) grooming toe.

Koalas have thick, woolly light grey/brown fur which helps to protect them from extremes in temperature and from the rain.

In South East Queensland, adult koalas grow up to around 70 centimetres in length from head to bottom and weigh on average between five (5) kilograms and seven (7) kilograms. Adult males are generally considerably heavier than females and can reach up to nine (9) 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.

Eucalypt leaves are high in fibre and low in protein. They also contain a range of phenolic compounds and cyanide precursors, making them unpalatable or toxic to most mammals.

The koala has many adaptations to cope with this problem including a large caecum, proportionally longer than that of any other mammal, to assist with microbial fermentation. Leaves that contain significant amounts of cyanide precursors are likely to be avoided. Oils and phenolic compounds are detoxified in the liver.

Koalas normally obtain sufficient water from the leaves they eat, although they do come to the ground to drink from pools and streams when conditions are hot and dry.

Lifecycle

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 and continue 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 koala breeding season in South East Queensland commences around July-August and can extend through until around April-May. This is a time of increased activity and movement on the ground between trees, particularly from around November to January, and extra care should be taken when driving near koala habitat during this time.

Koalas generally live for about 10 - 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.

Habitat and food

Koalas are mainly restricted to the eucalypt forests and woodlands of eastern and southern Australia.

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. Koala populations depend on large areas of eucalypt forests and woodlands for reproductive success and long-term sustainability.

Koalas are obligate folivores, which means they survive exclusively on a diet of leaves. They feed mainly on the leaves of Eucalyptus trees, with a few preferred species making up the bulk of the diet in any given area.

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 and grey gums E. propinqua and E. biturbinata. In areas where the preferred species occur in adequate abundance, koalas will utilise a wide range of other species for supplementary food and shelter including many non-eucalypts.

Important local supplementary resources include species such as grey ironbark E. siderophloia, white stringybark E. tindaliae, brush box Lophostemon confertus and broad-leaved paperbark Melaleuca quinquinervia.

Koalas, 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.

Landscape ecology

The loss and fragmentation of forest habitats associated with human land use is recognised as a significant factor in the decline of forest-dependent fauna. Recent investigation of the importance of forest area and configuration for koala conservation in Noosa Shire (South East Queensland), revealed that:

  • koala occurrence increased with increases in the area of forest habitats, habitat patch size and the proportion of preferred Eucalyptus species; and
  • decreased with increases in the mean nearest neighbour distance between forest patches, density of forest patches, and the density of sealed roads.

The configuration of remnant forest appears to be increasingly important to koalas as the overall area of forest habitat declines. These findings confirm that the area of forest and its configuration, together with the land use matrix, are all important determinants of koala occurrence (see McAlpine et al. 2006a).

 

The minimum amount of habitat needed in a landscape to ensure the persistence of a species provides an important target for conservation planning. Such targets can be determined by identifying thresholds in the amount of habitat, below which persistence, abundance or occupancy declines rapidly. 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.

For example, the research has indicated that minimum targets for native forest cover in areas supporting koalas of around 60 per cent in Noosa Shire, 50 per cent in Port Stephens Shire (Central Coast of NSW) and 30 per cent in the City of Ballarat (Victoria) may be necessary for conserving koala populations (see Rhodes et al. 2008a).

The Koala Planning Guidelines prepared by the University of Queensland, Australian Koala Foundation (AKF) and the NSW Department of Environment and Climate Change (DECC) provide a synthesis of four years research into the conservation and restoration of koala populations in fragmented landscapes of eastern Australia.

The guidelines also capture a decade of practical research and planning experience by the Australian Koala Foundation in mapping koala habitat and developing koala conservation and management plans for local government areas in New South Wales.

They draw on the collective knowledge of researchers who wanted to see their results put into action with practical outcomes for koala conservation.

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