Pilot Study: Effects of Human Presence on Guanaco Spatial Ecology
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The guanaco, or Lama guanicoe, plays an important role in maintaining Patagonian ecosystems: it is a main food source for apex and meso predators and its movement and grazing patterns preserve vegetation and insect biodiversity (Cheli et al. 2016, Baldi et al. 2016). Throughout South America, grazing competition with sheep and widespread hunting almost drove the guanaco to extinction (Baldi et al. 2001). In Argentina, guanaco populations have recovered to levels of “Least Concern,” but they are still regarded as a pest species by ranchers and their populations are highly fragmented and vulnerable to reduced genetic diversity and local extinction (Baldi et al. 2016, Schroeder et al. 2014). It is still unclear the extent to which human activities or competition with sheep affect guanaco spatial preferences, and previous studies have generally not separated impacts due to hunting and competition. The purpose of this study is to look at whether human presence alters guanaco spatial distributions more than current research suggests in unprotected areas. I looked at the spatial patterns of guanacos at a ranch in the Patagonian province of Chubut, Argentina, using camera traps to count the presence/absence of guanacos in different areas of the property. I created two null models in ArcGIS based on expert and local knowledge and scientific literature to predict guanaco spatial patterns; and performed statistical comparisons between predicted guanaco encounter rates and observed guanaco encounter rates at each camera site. Over 90% of observed guanaco encounters occurred in the areas of the property that were farthest away from human residences, regardless of sheep presence and density, the location and quality of water, and the presence of roads or natural landscape features. Neither model adequately predicted the spatial pattern of guanaco encounters displayed by the observed results. This indicates that the parameters used to inform the models do not represent guanaco behavior at the study site, and, likely, that guanacos behave similarly in other unprotected areas of Argentina. This has important implications not only for connectivity and management of guanaco populations, but also for the broader health of the Patagonian ecosystem.