GPS tracking reveals koalas Phascolarctos cinereus use mosaics of different forest ages after environmentally regulated timber harvesting

Abstract

An accurate picture of an animal's home range is fundamental for quantifying habitat quality and response to disturbance. When combined with remote sensing of vegetation attributes, there is potential to assess habitat selection at high resolution. We used a high-quality GPS-collaring data set (> 12 500 fixes) from 10 koalas Phascolarctos cinereus and a canopy height model derived from LiDAR in multiple-use forests harvested for timber 5–10 years previously. Our aim was to assess how individual koalas use the forest mosaic created by timber harvesting by quantifying home ranges and habitat selection of different forest age/height classes created by past harvesting. We found that koalas maintained a stable home range over the average of 7 months of tracking. On average, there was 95% overlap for individuals among seasons, illustrating high site fidelity in the regenerating forest. Also, there were no apparent shifts during the intense drought of spring 2019. Male home ranges (64 ha) were three times the size of females (21 ha). Core areas were considerably smaller, ranging from 15 (male) to 6 ha (female). Three forest age/height classes were defined from LiDAR: (i) harvest – regeneration <14 m, (ii) harvest – retained trees ≥14 m and (iii) harvest – exclusion trees ≥14 m (zones excluded from harvesting for environmental protection). Home ranges covered the mosaic of forest classes and mixed models revealed no selection of forest class based on use versus availability. High site fidelity with no clear selection for forest age/height class (i.e. harvested and non-harvested patches) confirms that resource quality in the home range remained sufficient for breeding koalas in the post-harvest landscape. Ongoing monitoring of koalas is required to ensure that environmental protections are effective in maintaining koala populations in the face of additional disturbances from fire and climate change.