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Sound management of flying-foxes is reliant on accurate and precise monitoring information. In Australia, flying-fox monitoring has traditionally been carried out using ‘on-ground’ methods, where animals are counted by human observers, such as, until recently, under the umbrella of the National Flying-Fox Monitoring Program (NFFMP; Westcott et al., 2015). However, that program was highly logistically complex and expensive, and, importantly, the lack of precision of monitoring practices meant that significant population trends could only be detected with sufficient power after more than a decade of range-wide monitoring, limiting the program’s utility for conservation managers to respond with immediacy to emergent population threats (McCarthy et al., 2022; Westcott et al., 2012).
Our team has demonstrated that drone-based thermal remote sensing provides a highly accurate and precise new tool for monitoring the abundance of vulnerable grey-headed flying-foxes in their roosts (McCarthy et al., 2021, 2022). In addition, we have recently shown that thermal drone-based observations of crèched young in roosts at night can give meaningful quantification of flying-fox productivity (Meade et al., 2025).
Drone-based thermal remote sensing of flying-fox roosts thus holds great promise for improving the accuracy and precision of current monitoring practices, thereby greatly enhancing the capacity for flying-fox monitoring to detect significant population trends over shorter timeframes, allowing management to respond more quickly and proactively to threats.
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AIM: The aim of this project is to maximise the utility of drones for monitoring flying-foxes in their roosts.
CURRENT RESEARCH:
- Testing the utility of drones under a range of environmental conditions, including at times of the year (ie. summer) and in locations (e.g., Christmas Island) where thermal contrast is minimal and so hampers detection.
- Fusing thermal roost surveys with surveys obtained from other drone-mounted sensors for improved accuracy and species identification.
TEAM: Prof Justin Welbergen, Dr Jessica Meade, A/Prof Chris Turbill, Prof Matthias Boer, Dr John Martin; Annabel Dorrestein; Samantha Yabsley; Eliane McCarthy
FUNDING: Regional Bushfire Recovery for Multiregional Species and Strategic Projects Program; Western Sydney University (ongoing).
References
- DORRESTEIN, A., MCCARTHY, E.M., MARTIN, J.M., YABSLEY, S.H. & WELBERGEN, J.A. (in press) Batmobile – using nocturnal drone imagery to assess the habitat use and population size of a tropical island-endemic flying-fox. Austral Ecology
- MEADE, J., MCCARTHY, E.D., YABSLEY, S.H., GRADY S.C., MARTIN, J.M. & WELBERGEN J.A. (2025). Using night-time drone-acquired thermal imagery to monitor flying-fox productivity – a proof of concept. Remote Sensing
- MCCARTHY, E. D., MARTIN, J. M., BOER, M. M. & WELBERGEN (2022). Ground-based counting methods underestimate true numbers of a threatened colonial mammal: an evaluation using drone-based thermal surveys as a reference. Wildlife Research, doi: 10.1071/WR21120
- MCCARTHY, E. D., MARTIN, J. M., BOER, M. M. & WELBERGEN (2021). Drone-based thermal remote sensing provides an effective new tool for monitoring the abundance of roosting fruit bats. Remote Sensing in Ecology and Conservation, 7: 461-474
- DORRESTEIN, A., RUST, H.P.R., MACGREGOR, N.A., TIERNAN, B., JANKOWSKI, A., WOINARSKI, J.C.Z., JAMES, D., FLAKUS, S., SCHULZ, M., PAHOR, S., MANN, A., DESMOND, B. & WELBERGEN, J.A. (2025). Factors affecting the detection probability of a critically endangered flying-fox: consequences for monitoring and conservation. Wildlife Research, DOI: 10.1071/WR24030
- MEADE, J., MARTIN, J.M., MCKEOWN, A., TURBILL, C., WALKER, M.J., BOARDMAN, W.S.J & WELBERGEN J.A. (2025) Flight behaviour and short-distance homing by nomadic grey-headed flying-foxes: a pilot study. Movement Ecology, DOI: 10.1186/s40462-025-00532-x
- YABSLEY, S. H., MEADE, J., HIBBURT, T., MARTIN, J. M., BOARDMAN, W. S. J., NICOLLE, D., WALKER, M., TURBILL, C & WELBERGEN, J. A. (2022). Variety is the spice of life: flying-foxes exploit a variety of native and exotic food plants in an urban landscape mosaic. Frontiers in Ecology and Evolution, 10:907966
- MEADE, J., MARTIN, J. M., & WELBERGEN, J. A. (2021). Fast food in the city? Nomadic flying-foxes commute less and hang around for longer in urban areas. Behavioral Ecology, 32: 1151-1162
- YABSLEY, S. H., MEADE, J., MARTIN, J. M., & WELBERGEN, J. A. (2021). Human-modified landscapes provide key foraging areas for a threatened flying mammal: The grey-headed flying-fox. Plos One, 16: e0259395.
- WELBERGEN, J. A., MEADE, J., FIELD, H., EDSON, D., McMICHAEL, L., SHOO, L. P., PRASZCZALEK, J., SMITH, C., MARTIN, J. (2020) Extreme mobility of the world's largest flying mammals creates key challenges for management and conservation. BMC Biology, 18: 101
- MEADE, J., VAN DER REE, R., STEPANIAN, P. M., WESTCOTT, D. A. & WELBERGEN, J. A., 2019. Using weather radar to monitor the number, timing and directions of flying-foxes emerging from their roosts. Scientific Reports, 9(1):10222.