Abstract
Recent technological innovations have led to an upsurge in the availability of unmanned aerial vehicles (also known as drones and hereafter referred to as UAVs)—aircraft remotely operated from the ground—which are increasingly popular tools for ecological research, and the question of this study concerns the extent to which wildlife responses might allow aerial wildlife monitoring (AWM) by UAVs. Our experiment tests the hypothesis that the wildlife-UAVs 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, for this question might influence the future viability of the UAVs in the study and protection of the other wildlife in China’s semiarid ecosystem. We examined the behavioral responses of a group of enclosed Przewalski’s horses (Equus ferus przewalskii) to the presence of different in-flight UAVs models by conducting flights at altitudes ranging from 1 to 52 meters and recorded the heights at which each horse reacted to (noticed and fled) the UAVs. All horses exhibited a stress response to UAVs flights as evidenced by running away. The results suggest strong correlations between flight altitude and response across the different subjects that adults generally noticed the UAVs at the larger heights (20.58 ± 10.46 m) than the immature (4.67 ± 0.87 m). Meanwhile, reaction heights of females (15.85 ± 6.01 m) are smaller than that of males (26.85 ± 18.52 m). Supported by their biological roles in herds (e.g., males must give protection to his entire herd while females are purely responsible for their offspring), our results also show that age, closely followed by gender, are the two most significant elements that determine a horse’s level of alertness to the UAVs. This research will help future scientists to better gauge the appropriate height to use a drone for animal observation in order to minimize disturbance and best preserve their natural behavior.
Highlights
Notice that the positive responses increases with altitude, while the negative responses decrease with altitude. e results help us illustrate the general pattern of less negative response at higher altitudes supporting the hypothesis that altitude plays a large role in animal response from Unmanned aerial vehicles (UAVs)
Notice that the degree of response varied with respect to age and gender: the alert height and run away height of adult horses ranged 11–52 and 1–36 meters while that of immature ranged 3–6 and 1–2 meters, respectively. e result showed that immature compared to adults showed a greater effect in males than in females (Table 1)
Hypothesis 3 was strongly supported by our result. e strength of the responses varied among sex and age, and our results suggest that age and gender are the significant determining factors of a horse’s reaction to UAVs
Summary
E last recorded sighting of a wild Przewalski’s horse occurred in the Dzungarian Gobi of Mongolia in 1969 [4], and since this species has been extinct in the wild with only a few remnant populations existing in small captive breeding herds in Western countries, making the survival of the taxon possible [5,6,7]. All Przewalski’s horses alive today are descendants from only 13 individuals that were the nucleus for captive breeding [1, 3, 6, 8, 9]. After another 20 years of captive breeding on four different continents, including Asia, the total number of horses rose to almost 1000 individuals [3, 6, 7, 10,11,12,13,14], and many organizations have since attempted to release the horses in semiwild habitats such as the International Journal of Zoology
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