I would like to provide some further facts to your readers in response to Mr Jeayes’ letter, ‘Koala audio study a farce’ on 31 August.
The recent NSW Department of Primary Industries (DPI) acoustic study of koalas in the hinterland forests of the north-east found very high koala occupancy rates across the majority of the 171 surveyed sites.
These sites were spread across the entire north-east region, so sites were spread well beyond an individual koala’s home range.
On average, 65 per cent of sites were occupied, which is much higher than previous systematic surveys have found in the north-east forests using techniques such as spotlighting, scat searches and call playback (though not passive acoustic recording).
Timber harvesting intensity and time since harvesting did not have an effect on site occupancy, indicating that koalas are persisting after harvesting.
Koalas could be remaining in, on average, the 40 per cent of the landscape that is excluded from harvesting in State forests or perhaps in the young trees regenerating after logging.
At the study sites, these young trees were often grey gums and tallowwoods, which are koala browse trees.
The acoustic method does not yet reveal where the koalas are in the landscape or the density of koalas at each site, which are therefore questions that require further research to answer.
However, given an estimated 1.67 million hectares of modelled habitat for koalas in the north-east forest, the research clearly indicates that the overall population of koalas is far larger than previously understood – even if only one koala was detected at each of the occupied sites.
This is just one of the positive outcomes of the extensive three-year study.
Dr Brad Law
Principal Research Scientist,
Forest Science Unit
NSW Department of Primary Industries