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Ecology, management and conservation in natural and modified habitats
RESEARCH ARTICLE

Tree use by koalas after timber harvesting in a mosaic landscape

Bradley Law https://orcid.org/0000-0002-3991-3865 A * , Chris Slade B , Leroy Gonsalves https://orcid.org/0000-0002-2757-4560 A , Traecey Brassil A , Cheyne Flanagan C and Isobel Kerr A
+ Author Affiliations
- Author Affiliations

A NSW Primary Industries, Forest Science, Parramatta, NSW, Australia.

B Forestry Corporation of NSW, Wauchope, NSW, Australia.

C Port Macquarie Koala Hospital, PO Box 236, Port Macquarie, NSW, Australia.

* Correspondence to: brad.law@dpi.nsw.gov.au

Handling Editor: Shannon Dundas

Wildlife Research 50(7) 581-592 https://doi.org/10.1071/WR22087
Submitted: 20 May 2022  Accepted: 12 September 2022   Published: 27 September 2022

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing

Abstract

Context: A better understanding of how individual animals use their habitat after disturbance can help optimise management practices for their conservation. Forestry is one such disturbance for koalas that operates under regulations based on best available information to minimise impacts.

Aims: This study aimed to investigate tree use by koalas in a mosaic of young, regenerating trees after timber harvest and mature trees in adjacent exclusion zones.

Methods: Tracking collars using very high frequency radio and Global Positioning System transmitters were used to track 10 koalas (five males, five females) across all seasons in three forests, 5–10 years after timber harvesting as regulated by practices current at that time. Tree use was compared to availability based on basal area in different parts of the forest.

Key results: We tracked koalas to 429 day-trees and 70 night-trees during this time. Males and females displayed little difference in tree use. Blackbutt Eucalyptus pilularis and turpentine Syncarpia glomulifera were the most commonly used species during the day, but blackbutt was ranked with the highest preference relative to tree availability. Tallowwood Eucalyptus microcorys was by far the most commonly used tree at night. Koalas used a broad range of tree sizes during the day and night, but most often used medium-sized trees, with preferences for a diameter of 30–60 cm (slightly smaller at night). Koalas used all topographic positions in the landscape, but more than half of the trees used were in lower topographic areas (gullies and lower slopes). Areas mapped as having previous heavy timber harvesting were the most used forest category, followed by riparian exclusion zones.

Conclusions: Our results demonstrate that koalas commonly used trees regenerating after harvest, although preferences for medium-sized trees and tallowwood as a night browse tree suggest current forestry regulations can be fine-tuned by retaining a greater proportion of these features.

Implications: Because most trees were used only once, our results support the view and current practice of retaining habitat patches, such as exclusion zones and wildlife clumps (triggered by a koala habitat model), to provide a mix of species and size classes for both food and shelter. A review of tree size and species retention is recommended.

Keywords: browse trees, forestry, forests, GPS-tracking, habitat selection, koala, timber harvesting, tree-use.


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