Ungulate Responses to Unmanned Aerial Vehicles Flying at Different Altitudes in Africa’s Arid Savanna

This paper tests the hypothesis that ungulate-UAV interaction depends strongly on flight altitude, that there may be a lowest altitude range for which the ungulates are not exceedingly disturbed, dictating a practically achievable level of discernibility in flight observation. This question strongly influences the future viability of the UAV in the study and protection of the ungulates in Africa’s arid savanna. This paper examined the behavioral responses of a group of free ranging ungulate species (Oryx, Kudu, Springbok, Giraffe, Eland, Hartebeest, and Impala) found in an animal reserve in Namibia to the presence of different in-flight UAV models. The study included 99 flights (337 passes) at altitudes ranging from 15 to 55 meters. The ungulates were unhabituated to the UAVs and the study was conducted in the presence of stress-inducing events that occur naturally in the environment. The results suggest strong correlations between flight altitude and response across the different ungulates and anecdotal evidence suggests in some cases rapid habituation to the UAVs.


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The highly valued ungulates in Africa's arid savanna, making up more than 25% of its landscape, 42 might be effectively monitored by unmanned aerial vehicles (UAV) [1]. The question of this paper 43 concerns the extent to which ungulate responses might allow aerial wildlife monitoring (AWM) 44 by UAVs. The hypothesis is that ungulate-UAV interaction depends strongly on flight altitude, 45 that flying too low could excessively disturb them, and that there may be a lowest altitude range 46 for which the ungulates are not exceedingly disturbed (putting aside for the moment how  Note that the AWM engineer or designer, when laying out a system of UAVs to monitor a field, 58 would begin by selecting a flight altitude after which vehicles and a communication network would 59 be selected, and in more advanced systems sophisticated data patching methods and graphical 60 interfaces employed [1]. Other preparations, too, would be necessary depending on the application. 61 Indeed, the large number of reported studies and methods preparing for AWM strongly suggests 62 that the potential AWM applications are plentiful. Considering just a few of the papers, studies 63 have focused on the cost savings [5], the management role [1], and more applied work on wildlife  In general, the level of danger that an ungulate perceives strongly influences its response. The 67 perceived danger that a UAV poses could come from the ungulate-UAV distance, sensed by an 68 auditory signal, or it could come from secondarily observing the responses of neighboring species 69 who have already responded to the UAV. In Africa's arid savanna, one finds many ungulates in 70 mixed herds so one could expect neighboring herds to trigger a response. The usual source of the 71 danger to the ungulate comes from the ground, not the air. Therefore, the level of response could 72 be moderate or low depending on flight altitude, while differing from specie to specie. One also expects the responses to depend strongly on the environment. The time of day (before or after 74 eating), the proximity of nearby animals posing a danger, and the passing by of vehicles or other 75 stress inducing events would be expected to influence the responses.

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The method section describes the study site, the wildlife species monitored, the data collection 78 process, the aerial vehicles, and the data collected. The results section gives the ungulate responses, 79 the occurrences of positive responses (no or little discernable reaction) versus altitude, and 80 discusses the data and secondary factors. Finally, the paper summarizes the results and draws 81 conclusions.

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The purpose of this study was to assess ungulate responses to UAVs flying at different altitudes in 84 Africa's arid savanna. Several considerations were vital when setting up the study. First, the 85 protection of ungulate wildlife from human interaction favors human interactions that are 86 sufficiently unobtrusive such that it requires no or a minimal level of habituation. Furthermore, 87 ungulate habituation, when none of the conditioning is negative, would only tend to decrease the 88 altitude that an ungulate tolerates. Therefore, for the purposes of this study, it was reasonable to   The study was conducted at a wildlife sanctuary (N/a'an ku se) located about 40 km east of 104 Windhoek, Namibia's capital city, over a ten-week period in 2017 from September to November.

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The land is 25 km 2 , located on Namibia's central plateau, and its elevation is 1600 to 1800 meters.

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From September to November, the average temperature is 20 to 23 C, and the average rainfall is 107 10 mm in September, 10 mm in October, and 30 mm in November. The land is a semi-closed eco-   As shown, the loudest to quietest vehicles were the Custom X8, Phantom 3, Skyeye and Mavic behavior. Passes were continued until animals were no longer within sight. Table 2 shows the 159 procedure that each of the members of the field unit followed.  As shown, the least populated species were the Impala and the Kuda and the most populated were sound intensity each UAV produces was previously given in Table 1, the least noisy being the the graph on the right, negative response vs altitude, shows the same datasets plotted with altitude.

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The most important takeaway being that the datasets overlap and almost align when plotted against 252 altitude. This shows a stronger correlation to altitude than sound intensity for these two vehicles.

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This was also reinforced after taking the Pearson correlation coefficient for the two data sets. The 254 coefficient was 0.303 for the negative response vs sound intensity for the combined vehicle data.

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The coefficient was -0.836 for the negative response vs altitude. This shows a stronger correlation 256 to negative response vs altitude for these two vehicles. In Fig. 7, the graphs show the Phantom 3 257 and Custom X8 plots with negative response vs sound intensity on the left and negative response 258 vs altitude on the right.  Table 3 shows the negative responses over each set of passes. The period in which this data was collected was 41 days. The 4 sets of passes varied slightly in 298 time, having collected the first set in 11 days, the second set in 17 days, the third set in 8 days, and 299 the fourth set in 5 days. While these numbers are statistically insignificant, there appears to be a 300 trend toward less response over more passes. Although beyond the scope of this study, this 301 anecdotal data suggests that animal habituation to the presence of UAVs is possible. UAVs. Over the suite of UAVs used in the study, the correlation between negative response and 310 flight altitude was most pronounced at low sound intensities (less than 60 dB). At higher sound 311 intensities (above 60 dB), it was found that the negative response has a more discernable parallel 312 to sound intensity. finding only a 5% chance of inducing a negative response when flying at 55 meters and when 318 using a UAV that is quieter than 60 dB. The study was conducted with ungulates that were 319 unhabituated to the presence of UAVs. Further study of habituation to the presence of UAVs could 320 further strengthen the results.