Initial evaluation of a state-wide multi-method survey to estimate koala occupancy and abundance
Knowledge of species distribution and abundance is crucial for effective threatened species management and conservation but is rarely obtained from purpose-built large-scale surveys. The koala (Phascolarctos cinereus) is a nationally threatened species; however, its current distribution is poorly kn...
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| Format: | Article |
| Language: | English |
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Elsevier
2025-07-01
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| Series: | Ecological Indicators |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S1470160X25005849 |
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| author | Graeme R. Gillespie Nicole Gallahar Allen P. McIlwee Benjamin Douglas Hope Elliot B. Webb Matthew Clements Veronica F. Gama Madison Casley Tim S. Jessop |
| author_facet | Graeme R. Gillespie Nicole Gallahar Allen P. McIlwee Benjamin Douglas Hope Elliot B. Webb Matthew Clements Veronica F. Gama Madison Casley Tim S. Jessop |
| author_sort | Graeme R. Gillespie |
| collection | DOAJ |
| description | Knowledge of species distribution and abundance is crucial for effective threatened species management and conservation but is rarely obtained from purpose-built large-scale surveys. The koala (Phascolarctos cinereus) is a nationally threatened species; however, its current distribution is poorly known, and uncertainty has surrounded the most suitable methods to address this at large spatial scales. To implement a state-wide koala survey in New South Wales (NSW), Australia, we sought to address this issue by evaluating and minimising trade-offs between the number of survey sites and site-specific survey effort using a multi-method survey approach. Here, we evaluate the comparative efficacy of three koala survey methods- diurnal transects, drones, and passive acoustic recorders (acoustic recorders) implemented across a wide range of habitats in NSW. We evaluated how these methods, individually and combined, influenced koala detection, occupancy, and relative abundance-related performance criteria to optimise the state-wide koala survey. Under the deployed survey effort, acoustic recorders performed optimally for assessing occupancy, achieving high detection of koalas and avoiding false absences within sites with high certainty (P* ≥ 0.99). To achieve similar performance, drone surveys and diurnal transects required survey effort (and cost) to be increased 19 and 206-fold, respectively. Due to considerable overlap in within-site detection between acoustic recorders and drones and the poor performance of diurnal transects, there is little advantage to using these methods concurrently to estimate koala occupancy. However, drone surveys were highly effective at estimating relative abundance of koalas compared to diurnal transects. Overall, the combined use of acoustic recorders and drones is highly advantageous because, where drones fail to detect koalas, acoustic recorder detections help eliminate false site absences, enhancing the precision of abundance estimates. Their combined use enables interoperability with other survey programs, fostering comparison and standardisation of important koala population measures. Ongoing optimising of koala survey and monitoring methods will improve the capacity to provide important insights for koala management and conservation. |
| format | Article |
| id | doaj-art-2f63eaf746d34c0995229c32adad70bd |
| institution | OA Journals |
| issn | 1470-160X |
| language | English |
| publishDate | 2025-07-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Ecological Indicators |
| spelling | doaj-art-2f63eaf746d34c0995229c32adad70bd2025-08-20T02:07:27ZengElsevierEcological Indicators1470-160X2025-07-0117611365410.1016/j.ecolind.2025.113654Initial evaluation of a state-wide multi-method survey to estimate koala occupancy and abundanceGraeme R. Gillespie0Nicole Gallahar1Allen P. McIlwee2Benjamin Douglas Hope3Elliot B. Webb4Matthew Clements5Veronica F. Gama6Madison Casley7Tim S. Jessop8Koala Science Team, Conservation and Restoration Science, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW). Locked Bag 5022, Parramatta, New South Wales 2124, AustraliaKoala Science Team, Conservation and Restoration Science, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW). Locked Bag 5022, Parramatta, New South Wales 2124, Australia; Corresponding author.Spatial Products and Custom Delivery, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW), Locked Bag 5022, Parramatta, New South Wales 2124, AustraliaKoala Science Team, Conservation and Restoration Science, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW). Locked Bag 5022, Parramatta, New South Wales 2124, AustraliaKoala Science Team, Conservation and Restoration Science, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW). Locked Bag 5022, Parramatta, New South Wales 2124, AustraliaKoala Science Team, Conservation and Restoration Science, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW). Locked Bag 5022, Parramatta, New South Wales 2124, AustraliaKoala Science Team, Conservation and Restoration Science, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW). Locked Bag 5022, Parramatta, New South Wales 2124, AustraliaKoala Science Team, Conservation and Restoration Science, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW). Locked Bag 5022, Parramatta, New South Wales 2124, AustraliaKoala Science Team, Conservation and Restoration Science, Science and Insights Division, Department of Climate Change, Energy, the Environment and Water (DCCEEW). Locked Bag 5022, Parramatta, New South Wales 2124, AustraliaKnowledge of species distribution and abundance is crucial for effective threatened species management and conservation but is rarely obtained from purpose-built large-scale surveys. The koala (Phascolarctos cinereus) is a nationally threatened species; however, its current distribution is poorly known, and uncertainty has surrounded the most suitable methods to address this at large spatial scales. To implement a state-wide koala survey in New South Wales (NSW), Australia, we sought to address this issue by evaluating and minimising trade-offs between the number of survey sites and site-specific survey effort using a multi-method survey approach. Here, we evaluate the comparative efficacy of three koala survey methods- diurnal transects, drones, and passive acoustic recorders (acoustic recorders) implemented across a wide range of habitats in NSW. We evaluated how these methods, individually and combined, influenced koala detection, occupancy, and relative abundance-related performance criteria to optimise the state-wide koala survey. Under the deployed survey effort, acoustic recorders performed optimally for assessing occupancy, achieving high detection of koalas and avoiding false absences within sites with high certainty (P* ≥ 0.99). To achieve similar performance, drone surveys and diurnal transects required survey effort (and cost) to be increased 19 and 206-fold, respectively. Due to considerable overlap in within-site detection between acoustic recorders and drones and the poor performance of diurnal transects, there is little advantage to using these methods concurrently to estimate koala occupancy. However, drone surveys were highly effective at estimating relative abundance of koalas compared to diurnal transects. Overall, the combined use of acoustic recorders and drones is highly advantageous because, where drones fail to detect koalas, acoustic recorder detections help eliminate false site absences, enhancing the precision of abundance estimates. Their combined use enables interoperability with other survey programs, fostering comparison and standardisation of important koala population measures. Ongoing optimising of koala survey and monitoring methods will improve the capacity to provide important insights for koala management and conservation.http://www.sciencedirect.com/science/article/pii/S1470160X25005849Adaptive survey practicesSpecies detectionOptimal survey effortSystematic state-wide samplingMulti-metric population inference |
| spellingShingle | Graeme R. Gillespie Nicole Gallahar Allen P. McIlwee Benjamin Douglas Hope Elliot B. Webb Matthew Clements Veronica F. Gama Madison Casley Tim S. Jessop Initial evaluation of a state-wide multi-method survey to estimate koala occupancy and abundance Ecological Indicators Adaptive survey practices Species detection Optimal survey effort Systematic state-wide sampling Multi-metric population inference |
| title | Initial evaluation of a state-wide multi-method survey to estimate koala occupancy and abundance |
| title_full | Initial evaluation of a state-wide multi-method survey to estimate koala occupancy and abundance |
| title_fullStr | Initial evaluation of a state-wide multi-method survey to estimate koala occupancy and abundance |
| title_full_unstemmed | Initial evaluation of a state-wide multi-method survey to estimate koala occupancy and abundance |
| title_short | Initial evaluation of a state-wide multi-method survey to estimate koala occupancy and abundance |
| title_sort | initial evaluation of a state wide multi method survey to estimate koala occupancy and abundance |
| topic | Adaptive survey practices Species detection Optimal survey effort Systematic state-wide sampling Multi-metric population inference |
| url | http://www.sciencedirect.com/science/article/pii/S1470160X25005849 |
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