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.

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Monitoring species abundance and distribution is a prerequisite when assessing species status and population viability, a difficult task to achieve for large herbivores at ecologically meaningful scales. Co-occurrence patterns can be used to infer mechanisms of community organization (such as biotic interactions), although it has been traditionally applied to binary presence/absence data. Here, we combine density surface and null models of abundance data as a novel approach to analyze the spatial and seasonal dynamics of abundance and distribution of guanacos (Lama guanicoe) and domestic herbivores in northern Patagonia, in order to visually and analytically compare the dispersion and co-occurrence pattern of ungulates. We found a marked seasonal pattern in abundance and spatial distribution of L. guanicoe. The guanaco population reached its maximum annual size and spatial dispersion in spring-summer, decreasing up to 6.5 times in size and occupying few sites of the study area in fall-winter. These results are evidence of the seasonal migration process of guanaco populations, an increasingly rare event for terrestrial mammals worldwide. The maximum number of guanacos estimated for spring (25951) is higher than the total population size (10000) 20 years ago, probably due to both counting methodology and population growth. Livestock were mostly distributed near human settlements, as expected by the sedentary management practiced by local people. Herbivore distribution was non-random; i.e., guanaco and livestock abundances co-varied negatively in all seasons, more than expected by chance. Segregation degree of guanaco and small-livestock (goats and sheep) was comparatively stronger than that of guanaco and large-livestock, suggesting a competition mechanism between ecologically similar herbivores, although various environmental factors could also contribute to habitat segregation. The new and compelling combination of methods used here is highly useful for researchers who conduct counts of animals to simultaneously estimate population sizes, distributions, assess temporal trends and characterize multi-species spatial interactions.

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Context The use of wild guanacos (Lama guanicoe) through live capture and shearing may contribute to their conservation by providing an economic alternative to rural inhabitants. However, none of the biological impacts of this activity, including the physiological ones, have been addressed. Aims The aim of this work was to characterise the acute response of guanacos to stress after capture and shearing in terms of serum cortisol levels, heart rate, and body temperature. Methods The study was performed during 2006 and 2007 in La Payunia Reserve in western Argentina. In order to determine serum cortisol concentration, 128 blood samples were obtained and the unextracted sera were analysed by radioimmunoanalyses (RIA). Sex, age category, heart rate, body temperature and total restraint time (TRT) were also registered for each animal captured. Key results Serum cortisol levels were higher in guanacos captured and sheared during 2007 than in 2006, and male cortisol levels were consistently lower than female levels. No significant differences were observed in cortisol levels of the different age categories. A positive correlation was observed between TRT and serum cortisol concentration. The analyses of cortisol levels in relation to TRT showed differences between males and females. With handling periods longer than 80 minutes, females showed a delayed stabilisation in cortisol response when compared with males. Heart rate and body temperature showed no differences between year, sex or age categories. Conclusions The present results show that the stress response to capture and shearing in wild guanacos increased significantly with handling time. We recommend avoiding capture of large numbers of animals and keeping roundup duration short to reduce TRT. Implications This work provides new information that can improve guanaco welfare during handling and shearing and may have implications for the conservation of the species.

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