Northern brown bandicoot (Isoodon macrourus) and common brushtail possum (Trichosurus vulpecula) density on the Tiwi Islands: insights and implications
Hugh F. Davies
A D , Tiwi Land Rangers B , Emily Nicholson C and Brett P. Murphy A
+ Author Affiliations
- Author Affiliations
A NESP Threatened Species Recovery Hub, Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina, NT 0810, Australia.
B Tiwi Land Rangers, Winnellie, NT 0810, Australia.
C Deakin University, Centre for Integrative Ecology, School of Life and Environmental Sciences, Burwood, Vic. 3125, Australia.
D Corresponding author. Email: hugh.davies@cdu.edu.au
Pacific Conservation Biology 28(3) 224-230 https://doi.org/10.1071/PC21020
Submitted: 29 March 2021 Accepted: 10 June 2021 Published: 6 July 2021
Journal Compilation © CSIRO 2022 Open Access CC BY-NC-ND
Abstract
Despite the ongoing collapse of native mammal populations across northern Australia, the paucity of robust estimates of population density limits our capacity to identify and understand population change. Here we aimed to provide the first estimates of native mammal density on the Tiwi Islands – one of Australia’s largest remaining refuge areas for native mammals. We conducted intensive live-trapping at four sites that represent varying combinations of fire frequency, feral cat density and feral herbivore presence. We used spatially-explicit capture-recapture models to investigate the density of common brushtail possum (Trichosurus vulpecula) and northern brown bandicoot (Isoodon macrourus). Compared with mainland northern Australia, populations of common brushtail possum and northern brown bandicoot have remained relatively healthy on the Tiwi Islands. Common brushtail possum density was significantly higher on Bathurst Island (1.06 possum ha−1) compared with Melville Island (0.32 possum ha−1), whereas northern brown bandicoot density varied across all four sites (ranging from 0.04 to 0.34 bandicoot ha−1). Unexpectedly, the very frequently burnt Ranku site (Bathurst Island) continues to support healthy populations of both species. These density estimates provide critical information for identifying and understanding future population change for two species that have suffered marked declines across the Australian monsoon tropics. Although the lack of replication limits our ability to draw conclusions regarding the ecological constraints of these mammal populations, our density observations align with a recent conceptual model postulating that the persistence of native mammal populations across northern Australian savannas reflects a complex, but spatially-variable interplay of ‘bottom-up’ and ‘top-down’ processes.
Keywords: Bathurst Island, capture-recapture, common brushtail possum, decline, habitat refuge, mammal extinction, Melville Island, monsoon tropics, native mammals, northern Australia, northern brown bandicoot, savannas, Tiwi Islands.
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