Influences on koala habitat selection across four local government areas on the far north coast of NSW

Abstract

Conserving habitats crucial for threatened koala (Phascolarctos cinereus) populations requires rating habitat quality from a fine spatial scale to patches, landscapes and then regions. The koala has a specialized diet focused on the leaves of a suite of Eucalyptus species. We asked: what are the key regional influences on habitat selection by koalas in the far north coast of New South Wales? We addressed this question by investigating the multi‐scale factors, and within‐scale and cross‐scale interactions, that influence koala habitat selection and distribution across four local government areas on the far north coast of New South Wales. We assembled and analysed a large data set of tree selection, identified by the presence of scats, in a wide range of randomly selected 5 × 5 km grids across the region. This resulted in more than 9000 trees surveyed for evidence of koala use from 302 field sites, together with associated biophysical site features. The dominant factor influencing habitat use and koala occurrence was the distribution of five Eucalyptus species. Koalas were more likely to use medium‐sized trees of these species where they occurred on soils with high levels of Colwell phosphorous. We also identified new interactions among the distribution of preferred tree species and soil phosphorous, and their distribution with the amount of suitable habitat in the surrounding landscape. Our study confirmed that non‐preferred species of eucalypts and non‐eucalypts are extensively used by koalas and form important components of koala habitat. This finding lends support to restoring a mosaic of koala‐preferred tree species and other species recognized for their value as shelter. Our study has provided the ecological foundation for developing a novel regional‐scale approach to the conservation of koalas, with adaptability to other wildlife species.

Broad‐scale acoustic monitoring of koala populations suggests metapopulation stability, but varying bellow rate, in the face of major disturbances and climate extremes

“…Koalas have been associated previously with regrowth forest (Kavanagh et al, 1995), especially if uneven age (Radford Miller, 2012;Smith, 2004), which is a typical outcome of selective harvesting. In addition, radio-tracking and scat searches have confirmed medium-sized trees are the preferred-size class used by koalas in the study area (Law, Slade, et al, 2022;McAlpine et al, 2023), perhaps because they are closely spaced, and the canopy is not as high as old growth, also noting tree hollows are not used by koalas. Other factors such as tenure, topography, site precipitation and temperature (though the latter is negatively correlated with elevation), soil phosphorus and moisture as well as disturbance variables (timber harvesting) had no detectable effect on initial occupancy, confirming koalas occur across a broad range of environments in the region (see also Goldingay et al, 2022).…”

“…Other factors such as tenure, topography, site precipitation and temperature (though the latter is negatively correlated with elevation), soil phosphorus and moisture as well as disturbance variables (timber harvesting) had no detectable effect on initial occupancy, confirming koalas occur across a broad range of environments in the region (see also Goldingay et al., 2022 ). Other studies suggest soil phosphorus, water availability and/or tree species influence habitat use at a more local scale (Gardiner et al., 2023 ; McAlpine et al., 2023 ).…”

“…Other studies suggest soil phosphorus, water availability and/or tree species influence habitat use at a more local scale (Gardiner et al, 2023;McAlpine et al, 2023).…”