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Habitat

Characteristics of arboreal marsupial habitat in the semi-arid woodlands of northern Queensland

Munks, SA, Corkrey, R, & Foley, WJ 1996, Wildlife Research, vol. 23, pp. 185-195.

Koalas and common brushtail possums utilise a range of different land types in the semi-arid woodlands of northern Queensland but exhibit higher preferences for habitats characterised by high tree basal area and nearness to creek-lines. It appears, therefore, that foliar moisture rather than foliar nutrients has a high influence on arboreal marsupials’ habitat preferences in semi-arid woodlands.

  The semi-arid woodlands of the Desert Uplands in north-western Queensland have not been subject to land clearing; however, they may be subject to future clearing as suitable land for conversion is becoming scarce and these woodlands provide fertile soil.  The koala and the common brushtail possum are two arboreal marsupials that are commonly found in these woodlands and would be affected by habitat alteration, thus it is important for their conservation to understand the distribution and characteristics of their preferred habitat types.  In this study, both species appeared to use a wide range of land types, but the highest pellet counts were found in areas near creek-lines and in areas where total tree basal area was the highest.  Furthermore, pellet counts of both species were low where the contribution of Acacia species to tree basal area was high. Some findings appeared to conflict with previous findings from the moist eucalypt forests of south-eastern Australia, as in the present study nutrient levels of foliage did not correlate with the occurrence of koalas or common brushtail possums.  Instead, foliar moisture level was found to be positively correlated with the occurrence of koalas, which coincides with other studies conducted in arid central Australia.

  An explanation for the high preferences of koalas and common brushtail possums for habitats associated with creek-lines is that in arid and semi-arid regions where water is limited, both species rely on foliage with high water content to meet their moisture requirements.  Trees situated near creek-lines are most likely to offer this higher water content.  Faster tree growth can also be expected where there is high availability of water. This, in turn, prevents the accumulation of toxic compounds in the foliage, which may also explain why koalas and common brushtail possums prefer these areas.  Moreover, enhanced growth rates and unlimited water resources near creek-lines also allow larger trees to persist, and these older, larger trees are particularly important for koalas and common brushtail possums for food and shelter.

  Although this study revealed a higher preference for habitats that are in close proximity to creek-lines by koalas and common brushtail possums, it is important to consider that other land types are also used by these animals to varying degrees as they serve not only as dispersal corridors to surrounding forest patches, but also as spill over areas to prevent overcrowding and enable social behaviour. For these reasons, conservation and land managers must consider the values offered by a variety of different potential habitat types.

 

Summarised by Cherie Chan

 

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