Research on the use of unmanned aircraft systems (UAS) in wildlife has made remarkable progress recently. Few studies to date have experimentally evaluated the effect of UAS on animals and have usually focused primarily on aquatic fauna. In terrestrial open arid ecosystems, with relatively good visibility to detect animals but little environmental noise, there should be a trade-off between flying the UAS at high height above ground level (AGL) to limit the disturbance of animals and flying low enough to maintain count precision. In addition, body size or social aggregation of species can also affect the ability to detect animals from the air and their response to the UAS approach. To address this gap, we used a gregarious ungulate, the guanaco ( Lama guanicoe ), as a study model. Based on three types of experimental flights, we demonstrated that (i) the likelihood of miscounting guanacos in images increases with UAS height, but only for offspring and (ii) higher height AGL and lower UAS speed reduce disturbance, except for large groups, which always reacted. Our results call into question mostly indirect and observational previous evidence that terrestrial mammals are more tolerant to UAS than other species and highlight the need for experimental and species-specific studies before using UAS methods.

The impact of predation by wolves on prey populations was analysed in a portion of the western Alps characterized by a rich wild ungulate community. The number of wolves ranged from 7 to 15 (1.7-2.9 wolves/100 km 2 ) during the study period (2000)(2001). The diet of wolves mainly consisted of wild ungulates. Red deer and roe deer were the staple prey, while chamois was consumed less despite its high density. From 2000 to 2002, wolves annually removed 20-34 red deer, 21-58 roe deer, and 7-14 chamois per 100 km 2 . These amounts were equivalent to 19-51% of the annual mortality of red deer, 6-28% of roe deer and 6-9% of chamois. Additionally, hunting accounted for 58-94% of the annual mortality of red deer, 18-29% of roe deer and 22-43% of chamois. Other mortality factors (i.e. traffic accidents, disease, poaching) constituted a small percentage of the annual mortality of red deer (5-6%), roe deer (6-9%) and chamois (1%). During the study period, the density of prey animals was stable. Wolf predation did not seriously affect ungulate populations. The role of wolves on wild ungulate populations in the Susa Valley seemed to be compensatory.