Mini-acoustic sensors reveal occupancy and threats to koalas (Phascolarctos cinereus) in private native forests

1. Forests on private land have a wide range of uses that span activities
such as recreation, primary production and nature conservation.
Traditionally, it has been difficult for researchers to access private
land to undertake systematic surveys. We used mini-acoustic sensors
(Audiomoth) mailed via the postal service to overcome landholder concerns
about researchers accessing private property, with a focus on properties
used for private native forestry. 2. We surveyed koalas, an iconic
threatened marsupial, in north-east New South Wales, Australia using
passive acoustics, with repeat surveys over consecutive nights to account
for imperfect detection in an occupancy modelling framework. 3. Over three
years, we surveyed 128 sites and recorded 2,560 male bellows. Detection
probability over seven nights was high (>0.79), but varied
substantially between years, due to use of different sensors, housings and
weather conditions. After accounting for detection probability, modelling
revealed that koalas commonly occupied private native forests of the study
region (probability of occupancy = 0.58±0.08). 4. Occupancy was modelled
against several covariates and it varied with the landscape extent of
sealed roads (-ve), NDVI (-ve) and a habitat suitability model (+ve, but
minor). There was no support for occupancy in private forests to be
related to a range of other factors including extent of surrounding
cleared land, timber harvesting history, fire and other measured habitat
features. 5. Synthesis and applications. We conclude that mini-acoustic
recorders mailed to landholders were a highly effective method for
assessing koala occupancy on private land and the approach could be
deployed more widely for a range of species. Private native forests in
partly cleared landscapes are commonly occupied by koalas, highlighting
that practices seeking to balance conservation and production should be
encouraged.