How Many Reindeer? UAV Surveys as an Alternative to Helicopter or Ground Surveys for Estimating Population Abundance in Open Landscapes

Conservation of wildlife depends on precise and unbiased knowledge on the abundance and distribution of species. It is challenging to choose appropriate methods to obtain a sufficiently high detectability and spatial coverage matching the species characteristics and spatiotemporal use of the landscape. In remote regions, such as in the Arctic, monitoring efforts are often resource-intensive and there is a need for cheap and precise alternative methods. Here, we compare an uncrewed aerial vehicle (UAV; quadcopter) pilot survey of the non-gregarious Svalbard reindeer to traditional population abundance surveys from ground and helicopter to investigate whether UAVs can be an efficient alternative technology. We found that the UAV survey underestimated reindeer abundance compared to the traditional abundance surveys when used at management relevant spatial scales. Observer variation in reindeer detection on UAV imagery was influenced by the RGB greenness index and mean blue channel. In future studies, we suggest testing long-range fixed-wing UAVs to increase the sample size of reindeer and area coverage and incorporate detection probability in animal density models from UAV imagery. In addition, we encourage focus on more efficient post-processing techniques, including automatic animal object identification with machine learning and analytical methods that account for uncertainties.

Automated summary

Conservation of wildlife requires precise and unbiased knowledge on species abundance and distribution. However, choosing appropriate methods for obtaining accurate data is challenging, especially in remote regions like the Arctic. In this study, we compared the use of a quadcopter survey to traditional ground and helicopter surveys to assess its efficiency as an alternative technology. The results showed that the quadcopter survey underestimated the abundance of Svalbard reindeer compared to traditional surveys. Future studies should explore long-range fixed-wing UAVs and improve post-processing techniques to increase sample size and coverage, as well as account for uncertainties.