Koala research in NSW forests

Monitoring Koalas in Hinterland Forests of Northeast NSW

map showing a  koala habitat model for northeast NSW

Monitoring is fundamental to improving the management of threatened species. There is much speculation, but few available data on trends in koala populations. DPI Forest Science has monitored annually the koala metapopulation of the hinterland forests of northeast New South Wales since 2015.

The program evolved out of a three-year study of koala occupancy in hinterland forests between 2015-2017 (Law et al. 2018). This study used novel passive acoustic methods to record koala bellows and site occupancy at 171 sites across a variety of forest types in State forests and National Parks. An extensive area (1.7 million hectares) of better-quality koala habitat was targeted for surveys using a model derived for the study area (Law et al. 2017).

Acoustic monitoring during the spring breeding season continued at a subset of sites (~ 60 sites per year) in 2018 and after extensive bushfires in 2019. The four years of pre-fire data provides a strong baseline for ongoing koala monitoring and assessing the impacts and recovery from the 2019 fires in these forests.

An extensive dataset has accumulated through the program comprising:

  • >20,000 hours of nocturnal recording over >2,000 nights;
  • > 10,000 bellows identified so far
  • koala bellows recorded at 62 % of sites in modelled habitat

Identification of koala bellows was undertaken in collaboration with the Ecoacoustics lab at Queensland University of Technology using an algorithm that identifies the low frequency, oscillating nature of the koala bellow.

Statistical analysis of these data identifies a stable trend in koala occupancy over four years from 2015 to 2018. Occupancy remained high throughout this period with at least one bellowing koala occupying about 67 % of survey sites in modelled better-quality koala habitat. The size of a survey site is a circular zone (~300 m radius) slightly larger than the expected home range of one adult male koala. Additional effects are controlled for in the analysis including nightly temperature, sensor type, elevation, habitat quality and site productivity (NDVI). Interestingly, there was no signal of a decline in koala occupancy in 2018 when the recent NSW drought was well underway.

column graph showing koala occupancy trends


It is important to point out that stable occupancy of a metapopulation can include increasing and decreasing subpopulations. Also, in north-east NSW many koala subpopulations are under threat along the coast from increasing urbanisation. These coastal populations are not part of the hinterland forests monitored in this study.

A subset of burnt and unburnt sites was also monitored post-fire in 2019 and these data are currently being processed to assess the impact of the extensive fires. Continued monitoring in spring 2020 will allow a robust assessment of the early stages of post-fire recovery of this important koala metapopulation.

The 2020 field program is across tenures and will be undertaken by Forestry Corporation of NSW and NSW DPI with funding from the NSW Forest Monitoring and Improvement Program, overseen by the Natural Resources Commission.

Information from the study will be progressively posted on this site.

FAQs

  • What is a metapopulation? A metapopulation consists of a group of spatially separated populations of the same species which interact at some level.
  • What is site occupancy? Site occupancy is a standard population surrogate used by ecologists to compare different areas or trends in populations over time. It differs from presence/absence data in that imperfect detection of the study species is accounted for. Typically, many sites are surveyed to characterise a metapopulation.
  • What are koala bellows? Bellows are primarily produced by adult male koalas both to avoid male-male interactions by functioning as a signal of body size and to attract females, and thus they indicate breeding activity in a population. Given bellows are mostly produced by adult koalas, they are expected to mostly represent resident individuals.

References

Law B, Caccamo G, Roe P, et al. (2017) Development and field validation of a regional, management-scale habitat model: A koala Phascolarctos cinereus case study. Ecology and Evolution 7:7475–7489. https://doi.org/10.1002/ece3.3300

Law BS, Brassil T, Gonsalves L, Roe P, Truskinger A, McConville A (2018) Passive acoustics and sound recognition provide new insights on status and resilience of an iconic endangered marsupial (koala Phascolarctos cinereus) to timber harvesting. PLoS ONE 13(10): e0205075. https://doi.org/10.1371/journal.pone.0205075

Koala tracking research

a koala sitting in a tree

A new koala tracking project began in 2018 and is still is underway in north-east forests of NSW on the mid north-coast.

The project is using GPS collars on koalas to track their movements throughout the forest which will enable DPI researchers to look at the effectiveness of koala protections in State forests and relative use of young regenerating eucalypts after harvesting compared to mature forest that is excluded from harvesting.

Eight Koalas have been collared so far providing outstanding information on what tree species and sizes offer important browse as well as other aspects of habitat use like use of ridges vs gullies.

The DPI Forest Science research is partnered with the Port Macquarie Koala Hospital and Forestry Corporation.

The findings of the research will be considered by the Natural Resources Commission who is independently commissioning and overseeing other research projects investigating how koalas respond to regeneration harvesting on state forests as part of the NSW Koala Strategy.

Status of koalas in north-east NSW forests

an acoustic recording device attached to a tree

Between 2015 and 2017, DPI forest scientists undertook a large-scale study on the status and response of koalas to timber harvesting in the north-east forests of NSW. Koalas are surprisingly difficult to survey due to their low densities and cryptic nature, especially in tall remote forests. Surveys were focused on forests of the hinterland, ranges and tablelands of North East NSW, rather than the coastal strip where urbanisation is the main threat to koala populations.

SongMeters were deployed at nearly 200 sites over 7-14 nights to record male bellows over three breeding seasons (>14,500 hours of recording). The project relied on cutting-edge software developed by the Queensland University of Technology to automate the call detection process from thousands of hours of recordings.

Results showed that, on average, 65 per cent of survey sites (the small zone surrounding each SongMeter) were occupied by at least one koala, which was much higher than expected based on previous surveys using alternative methods. We found that occupancy was influenced by elevation, cover of important browse trees, site productivity and extent of wildfire in the last 10 years.

Occupancy was not influenced by timber harvesting intensity, time since harvesting, land tenure, landscape extent of harvesting or old growth forest extent. The highest bellow rate (23 calls per night) across all sites surveyed was recorded at a site in Kiwarrak State Forest that was recently heavily harvested (though with a mosaic of harvest exclusions). Overall, forest treatment had no statistically significant effect on bellow rate.

Extrapolation of occupancy across modelled habitat indicates that the hinterland forests of north-east NSW support a widespread, though naturally low density koala population that is considerably larger than previously estimated.

A paper detailing the results of this study has been published (Law et al. 2018).

Predictive habitat modelling

Predictive models that map species distributions are a useful management tool for guiding and informing on-ground management of threatened species. Forest scientists at DPI have developed a model for the koala (Phascolarctos cinereus) in North East NSW. The model is used by the Environmental Protection Authority to predict where areas of differing habitat quality for koalas are likely to occur.

The focus was to help guide decisions on timber harvesting in forests by identifying likely koala habitat. Ultimately, this could lead to better on-ground implementation of koala management for public state forests and private forestry areas.

Publications

Media releases