Are there habitat thresholds in koala occupancy in the semiarid landscapes of the Mulgalands Bioregion?

Smith, Andrew G., McAlpine, Clive, Rhodes, Jonathan, Seabrook, Leonie, Lunney, Daniel and Baxter, Greg (2013) Are there habitat thresholds in koala occupancy in the semiarid landscapes of the Mulgalands Bioregion?. Wildlife Research, 40 5: 413-426. doi:10.1071/WR13010

Author Smith, Andrew G.
McAlpine, Clive
Rhodes, Jonathan
Seabrook, Leonie
Lunney, Daniel
Baxter, Greg
Title Are there habitat thresholds in koala occupancy in the semiarid landscapes of the Mulgalands Bioregion?
Journal name Wildlife Research   Check publisher's open access policy
ISSN 1035-3712
Publication date 2013-01-01
Year available 2013
Sub-type Article (original research)
DOI 10.1071/WR13010
Open Access Status Not Open Access
Volume 40
Issue 5
Start page 413
End page 426
Total pages 14
Place of publication Collingwood, VIC Australia
Publisher C S I R O Publishing
Language eng
Formatted abstract
Context: Habitat thresholds are the critical point(s), below which the probability of occurrence of a species declines. Identifying thresholds assists land managers to decide how much habitat is needed to conserve a species. However, for any given species, a threshold may not exist, or might occur at one scale but not at others, and it may differ across regions. The use of critical habitat thresholds can negatively affect populations if simplified conservation targets for habitat retention are prescribed. This problem is relevant to the koalas where there is evidence of habitat thresholds in mesic regions, but no studies of thresholds in semiarid regions.

Aims: The aim of the present study was to investigate whether a threshold exists between the occupancy of a site by koalas and habitat variables at both the site and at four landscape scales in the semiarid Mulgalands Bioregion of Queensland, Australia.

Methods: We modelled habitat relationships using standard and piece-wise logistic regression, and an information-theoretic approach, to determine whether the best model that explained the occupancy–habitat relationships was linear or had a distinct threshold. The site-scale variable was the percentage of primary eucalypt species. The landscape-scale variables included the amount of primary and secondary habitat, and an interaction between them.

Key findings: There was a threshold relationship between the occurrence of koalas and the percentage of primary trees at the site scale. At the landscape scale, most threshold models failed to converge, and evidence pointed to a linear relationship between habitat amount and koala occupancy.

Conclusions: Conservation actions for koalas in the Mulgalands Bioregion should concentrate on protecting the primary tree resource for koalas, namely, river red gums (E. camaldulensis). However, the maintenance or restoration of primary and secondary habitat to distances of 1000 m from the creek is important because of the linear relationship between koala presence and habitat amount.

Implications: As habitat is lost in the semiarid Mulgalands Bioregion, koala occupancy declines. If known thresholds from mesic regions are used to define a minimum amount of habitat to be retained for koalas, conservation of local koala populations may well fail.
Keyword Piece wise logistic regression
River red gum
Species distributions
South West Queensland
Phascolarctos Cinereus Populations
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID 0882090
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Geography, Planning and Environmental Management Publications
Official 2014 Collection
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