In particular, for culpeo foxes, livestock predation is significantly affected by both, livestock and native prey densities (Pia et al. 2003). In contrast, for livestock predation by pumas the type of habitat, prey densities (both, native and livestock), and livestock management practices are important factors (Polisar et al. 2003). Most human communities across the Bolivian Altiplano, including the SNP, have commonly managed the livestock predation conflict by simply killing carnivores. As a consequence, several populations have been eradicated, or severely depleted, including carrion eaters such as the Andean condor (Vultur gryphus), with marked ecological consequences at the community and ecosystem levels, as reported by similar functional losses in other study sites (Mech 1998; Johnson et al. 2001; Blejwas et al. 2002; Treves et al. 2002; Athreya et al. 2004). Although Gallardo et al. (2009) estimated that puma population at SNP was around 10 individuals (~1 puma/100 km 2), retaliation hunting due to livestock depredation was common in the area (GG, JEJ, pers. obs.). There is no local abundance estimate for culpeo foxes, but we infer that their numbers may be lower than in other regions of their distribution, given the high probability of retaliation hunting by locals and the large home range size (35.9 km 2) of a radio-tracked female for ~1 year at SNP (Olarte et al. 2009). This was the second largest estimate for this species, only below the 896 km 2 home range reported by Jiménez et al. (2001) and much larger than the 13.9 km 2 maximum home range size reported for females in Fray Jorge Reserve (Salvatori et al. 1999), both in northern Chile. Therefore, SNP is under a scenario of intense conflict between carnivores and livestock, which is worrisome giving that this protected area harbors protected populations of two of the largest carnivores occurring in the highlands of South America. Consequently, a muchneeded contribution to managing the problem entails an analysis of environmental factors that may influence livestock attack. Specifically, in this study we assessed the relative contribution of socio-ecological variables influencing the probability of an attack at the ranch level within SNP. We predicted that the probability of a carnivore attack on a ranch would increase with a) higher livestock densities, b) lower abundance of wild prey, c) good habitat characteristics for carnivores, such as dense vegetation cover, and a rocky structure, and d) low vigilance by ranchers and their watchdogs. Likewise, we predicted that fewer attacks would be associated with e) smaller ranch areas and f) livestock foraging in areas closer to the nearest human settlement. To examine the relative importance of livestock deaths caused directly by carnivores, we also considered new information on other non-predation related factors affecting livestock mortality at the SNP.