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

Ingrid Marie Garfelt Paulsen; Åshild Ønvik Pedersen; Richard Hann; Marie-Anne Blanchet; Isabell Eischeid; Charlotte Van Hazendonk; Virve Tuulia Ravolainen; Audun Stien; Mathilde Le Moullec

doi:10.20944/preprints202210.0295.v2

Comment 1

Received: 2 December 2022
Commenter: Ingrid Paulsen
Commenter's Conflict of Interests: Author

Comment: Generally, we have rewritten and restructured all parts of the manuscript with the aim to make results and conclusions more accessible to the scientific community and of greater interest for readers of Remote Sensing. We have put greater emphasis on issues related to detection probability of reindeer in open heterogenous landscape and key concepts that need to be addressed regarding methodological development and future use of UAV to ensure precise and unbiased counts of wildlife in open landscapes. We have detailed these issues in the replies to reviewer 2 and 3. We had someone proofread the English language in our manuscript as requested.

In addition, we have taken these actions:
We have increased the focus on observer variability and bias of reindeer detection based on UAV imagery in the abstract, results and discussion, which contributes to the remote sensing aspect of the manuscript (as addressed by reviewer 2).
We have added a paragraph in the introduction with a rationale of why we use distance sampling (DS) and total counts (TC) as reference for how well the UAV survey predicts population estimates in Sassendalen. We now use the terms of precision and bias in an appropriate way, making our interpretation of the results related to UAV survey more accurate.
We have clarified the methods section of the paper by reducing the number of sections, restructuring the methods, clarifying the fourth method “independent total counts” from the neighboring valley Adventdalen and explained clearer how we use the maximum normalized vegetation index (maxNDVI) (concern by reviewer 2 and 3).
We have improved the figures and restructured the order according to the order they appear in the results section. We have also added several details in the results section and added details to the figures:
Figure 1: Removed A and B. Figure 2: We have added a grey line between the Helicopter and Independent. ground TC method to show that there are two separate survey methods in the workflow.
Figure 3: To focus on the detection probability of reindeer from UAV imagery, we have put the detection probability curves into the main results from the appendix. We have included individual detection curves and raw covariate values. Figure 4: We have added confidence intervals on the Independent total counts and ground distance sampling from the previously named Figure 3.
Table 1:We have corrected a mistake on how we calculated the reindeer abundance for the ground distance sampling at one specific spatial scale. We apologize for the mistake but note that it does not change any of the conclusions of the paper. The uncertainty of abundances is now presented as standard error instead of confidence intervals in Table 1.
We have excluded Table 2 (feasibility of survey methods) according to reviewer 2’s comment. We do believe it was informative but have instead added information to the discussion that was related to this table.
During our revision we found that the drone area extent was incorrectly calculated (16.2 km² instead of 23.4 km²). We apologize for this mistake and have corrected this in all parts of the manuscript and checked the calculation of all other area extents.
We have restructured the discussion and added a paragraph explaining the accuracy of the drone methods compared to other studies (page 3, line 31-47). We have also added a paragraph where we discuss and compare other results in relation to similar studies using UAV imagery as a method to monitor wildlife. We have reordered the Appendix according to the order they appear in methods and results, and re-formatted Appendix B.

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

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