The loss of hollow-bearing trees in production forest areas can have large impacts on animal populations that rely on them for shelter. This study facilitates the selection of appropriate trees for retention by examining the proportion and type of trees that were used by vertebrate fauna in mature wet and dry Eucalyptus obliqua forest in Tasmania. Felled trees were searched for hollows and secondary evidence of use by fauna. Classification Trees and Bayesian logistic regression modelling were used to examine the site and tree attributes that best explained the use of a tree by fauna. We did two separate analyses: one using attributes expected to be causally related to hollow use, and a second using attributes that might be correlated with hollow use and could be easily assessed in standing trees. In all, 28% of hollow-bearing trees examined showed evidence of use, which is at the lower end of the scale found in other areas of Australia. The variables most strongly related to the use of a tree were hollow abundance, tree size and senescence. Random Forest modelling indicated that the likelihood of a hollow being used increased with hollow size, particularly hollow depth. Counting the number of hollows in standing trees was the best way to identify a tree that is likely to be used by fauna and this was particularly important for younger and healthier trees. It was recommended that trees to be retained should contain at least one large hollow. It was estimated that 8–15 trees per hectare were used by hollow-using fauna in mature wet and dry E. obliqua forest in Tasmania.
In Tasmania, a considerable proportion of the forested landscape is available for land clearance and production forestry, which has and will continue to result in a decline in hollow availability unless managed appropriately. All hollow-using species are listed as having priority status under the Tasmanian Regional Forest Agreement. To ensure the habitat for hollow-using fauna is managed effectively, we first have to understand the requirements of the species involved. This paper is a review of the distribution, hollow requirements and conservation status of the five species of arboreal marsupials, eight species of bats and 29 bird species that use hollows in Tasmania. The number of species that use hollows is lower than in many other areas of Australia, but these species represent a large proportion of the vertebrate fauna of Tasmania. Three of these species and nine subspecies are endemic to Tasmania and seven are exotic. Four bird species are listed as Threatened at the state and/or national level. Twenty-five of Tasmania’s hollow-using species are capable of using small hollows, 14 can use medium-sized hollows and three bird species are limited to using large hollows. Current records indicate that the highest diversity of hollow-using species is associated with dry forest areas.
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