The use of hollow-bearing trees by vertebrate fauna in wet and dry Eucalyptus obliqua forest, Tasmania

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

Does hollow occurrence vary with forest types? A case study in wet and dry Eucalyptus obliqua forest

The distribution of hollow-using fauna is frequently related to forest type. If hollow occurrence varies with forest type, the use of generic prescriptions for managing the hollow resource may be inappropriate. This study examined the relationship between the occurrence and abundance of tree hollows and site and tree attributes in wet and dry Eucalyptus obliqua forest in Tasmania, Australia. A total of 388 trees at 39 sites were examined before and after being felled. Evidence of invertebrate damage contributing to hollow formation was more common in wet forest than either dry or damp forest. Evidence of hollow formation by fire and fungi was more prevalent in drier than wetter forest. There was no difference among forest types in the proportion of hollows showing evidence of limb breakage. Examination of the site and tree factors related to hollow presence and abundance was done using Classification Trees, Random Forests and generalised linear models. The variables found to be most practical for predicting hollow occurrence were the number of hollows observed before the tree was felled, tree diameter and the amount of dead wood in the canopy. Tree age, an important variable to consider when planning harvest rotations, was strongly associated with hollow presence but had less bearing on hollow abundance. The size of hollows that were found in a tree was related to greater senescence. Although significantly more hollows of all sizes were found in wet forest than either dry or damp forest, the age at which trees began to produce hollows was similar among the different forest types. The models predicted that trees needed to be at least 100 years old before they are likely to contain a hollow and that medium-sized hollows rarely occur in trees younger than 140 years old. Trees grow slightly more slowly in dry forest than wet which means that smaller diameter trees were found to contain hollows in dry forest than wet and that even the largest trees may not contain large hollows in wet forest. Despite this, no differentiation between the forest types was found in the predictive models. It is recommended that trees retained for faunal habitat be at least 100 cm in diameter

Distribution, habitat and conservation status of the eastern pygmy-possum \u3cem\u3eCercartetus nanus\u3c/em\u3e in Tasmania

We review literature pertaining to the distribution, habitat and conservation status of the eastern pygmy-possum Cercartetus nanus in Tasmania. Records from fauna surveys, museum specimens, and the Tasmanian Natural Values Atlas database, suggest that although C. nanus is widespread, it occurs in low numbers in Tasmania. From 51 fauna surveys examined, only 19 C. nanus were detected in a total of 47,087 Elliott trap-nights, 5,665 pitfall trap-nights, 196 scats or owl pellets, 899 spotlight hours, and 86 predator stomachs. A total of 102 Tasmanian C. nanus specimens was located in Australian and overseas museums. These records combined with 23 from the Natural Values Atlas database and 61 from an earlier published collation represent 99 of 679 grid squares (10 km x 10 km) overlaid across Tasmania (including King Island and Flinders Island). The patchy distribution of these records may be a reflection of low survey effort, low population numbers, low detectability or a combination of these and other factors. The highest number of records for a single locality was only four. Available data suggest that Tasmanian populations may be small and therefore potentially at risk from habitat loss, inappropriate fire regimes, and firewood collection. We believe there is a pressing need for further surveys to more clearly define the conservation status of C. nanus in Tasmania

The distribution and abundance of an island population of koalas (Phascolarctos cinereus) in the far north of their geographic range

Koalas are an iconic species of charismatic megafauna, of substantial social and conservation significance. They are widely distributed, often at low densities, and individuals can be difficult to detect, making population surveys challenging and costly. Consequently, koala population estimates have been limited and the results inconsistent. The aims of this study were to estimate the distribution, relative abundance and population size of the koalas on Magnetic Island, far north Queensland. Population densities were estimated in 18 different vegetation types present on the island using a Fecal Standing Crop Method. Koala density ranged from 0.404 ha−1, recorded in forest red gum and bloodwood woodland, to absence from eight of the vegetation types surveyed. The second highest density of 0.297 koalas ha−1 was recorded in mixed eucalypt woodland, which covers 45% of the island. The total abundance of koalas on Magnetic Island, not including those present in urban areas, was estimated at 825±175 (SEM). The large variation in koala density across vegetation types reinforces the need for sampling stratification when calculating abundance over large areas, as uniformity of habitat quality cannot be assumed. In this context, koala populations also occur in low densities in areas generally regarded as poor quality koala habitat. These results highlight the importance of protecting vegetation communities not traditionally considered to have high conservation value to koalas, as these habitats may be essential for maintaining viable, widespread, low-density populations. The results from this study provide a baseline to assess future trends in koala distribution, density and abundance on Magnetic Island