Hollow-using vertebrate fauna of Tasmania: distribution, hollow requirements and conservation status (original) (raw)
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Wildlife Research, 2008
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.
Pacific Conservation Biology
Australia lacks primary excavators of eucalypts (excluding wood-boring insects), and animals using hollows in trees for shelter or nesting are dependent on hollows created by termites (for processes of termite invasion of eucalypts, and hollow formation, see Mackowski 1984; Perry et al. 1985). The abundance of hollows of various sizes has been used to explain why Australia has the largest number of obligate hole-nesting birds, especially the parrots (Saunders et al. 1982). The importance of tree hollows to many small mammals is also well documented (e.g., Mackowski 1984; Dickman 1991). Once the hollowed tree has fallen, it represents an important shelter and bolt hole site for small mammals (e.g., Friend 1990; Abensperg-Traun 1991; Dickman 1991). Logs also provide many invertebrates (e.g., cockroaches, beetles, spiders, isopods) and lizards with shelter, breeding and feeding sites. However, the importance of this habitat for these species has not been documented.
Forest Ecology and Management, 1991
Lindenmayer, D.B., Cunningham, R.B., Tanton, M.T., Smith, A.P. and Nix, H.A., 1991. Character-istics of hollow-bearing trees occupied by arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia. For. Ecol. Manage., 40: 289-308.
Ecological Monographs, 2011
How different are insights based on cross-sectional studies from those of longitudinal investigations? We addressed this question using a detailed case study encompassing a rare suite of interconnected cross-sectional and longitudinal investigations that have spanned the past two decades and included work on: (1) the decay and collapse of large-cavity forest trees (termed ''trees with hollows''), (2) populations of a suite of species of arboreal marsupials that are reliant on trees with hollows as nesting and denning sites, and (3) relationships between the abundance, type, and condition of trees with hollows and the presence, abundance, and species richness of these animals. Our case study was from the montane ash eucalypt forests of the Central Highlands of Victoria, southeastern Australia. Our longitudinal studies led to new insights that either would not have been possible from a cross-sectional study, or which were unexpected because they did not conform, or only partially conformed, to postulated responses made at the outset based on the results of earlier research. These new insights included: (1) a substantial slowing in rates of tree fall between 1997 and 2006, which were significantly lower than predicted from earlier data gathered between 1983 and 1993, (2) no evidence for a decline in populations of almost all species of arboreal marsupials between 1997 and 2007, despite the loss of nearly 14% of the measured population of trees with hollows during that time, (3) changes in nest tree selection by some species of arboreal marsupials in response to these changes in hollow availability, (4) concentration effects, in which populations of animals used the declining tree hollow resource more intensively, and (5) evidence for significant rainfall effects on temporal changes in animal abundance. Our case study underscored the additional ecological insights that can be generated from longitudinal studies, including how relationships between biota and their habitat can change over time. Understanding these temporal changes is essential for informed forest management and biodiversity conservation, and points toward the need for greater use of longitudinal data sets in ecology.
Austral Ecology, 2006
We examined factors affecting roost tree selection by the white-striped freetail bat Tadarida australis (Chiroptera: Molossidae), a large insectivorous bat in suburban Brisbane, Australia. We compared biophysical characteristics associated with 34 roost trees and 170 control trees of similar diameter, height and tree senescence characters. Roost trees used by the white-striped freetail bat had significantly higher numbers of hollows in the trunk and branches (P < 0.003) and were more likely to contain a large trunk cavity with an internal diameter of >30 cm (P < 0.001) than control trees. These trees also accommodated more species of hollow-using fauna (P = 0.005). When comparing roost trees with control trees of similar diameters and heights, roost trees were on average at a later stage of tree senescence (P < 0.001). None of the roost trees were found in the large forest reserves fringing the Brisbane metropolitan area despite these areas being used for foraging by the white-striped freetail bat. Although all tree locations in this study were in modified landscapes, roost trees tended to be surrounded by groups of trees and undergrowth. Roost trees provide important habitat requirements for hollowusing fauna in suburban, rural and forested environments.