Department of Natural Resources and Society, University of Idaho, Moscow, ID 83844, UNITED STATES OF AMERICA.
Jaguar predation patterns and spatial organization were studied from 2003 to 2004 in a ranch/wildlife reserve located in the southern region of the Pantanal, Brazil. Through radio-tracking we found that jaguar home-range sizes were comparable between sexes and little overlap was observed between core areas. Jaguars relied mostly on mammalian prey species (61% of prey items and 77% of biomass) and selected large-sized prey species. The most common prey consumed were capybara (Hydrochaeris hydrochaeris) and caiman (Caiman crocodilus). We estimated the wild prey base was adequate to support the resident jaguar population and therefore that jaguars did not require a livestock subsidy to survive. Large prey species were considerably more likely to die from jaguars predation than from other causes, and predation was more likely to occur in jaguar home range core areas than in areas of home range overlap. Spacing patterns seemed to be influenced by a territorial system because regions of exclusiveness occurred for both sexes and predation was more likely in core areas.
Despite the appearance jaguars did not require a livestock subsidy, livestock depredation was one of the most important sources of carnivore-human conflict in the region. We examined patterns of livestock depredation by jaguars to assess the factors contributing to mortality risk. Interactions between jaguars and domestic cattle were examined by recording each death event for the entire ranch and estimating survival and mortality causes of livestock through daily visits to 15 allotments, comprising one third of all livestock holdings in the ranch. Predation mortality was less common than non-predation mortality, and survival in allotments was lower for calves. Forest was the only significant explanatory variable found to explain cause of mortality, because predation increased as distance to forest declined. Cattle movement patterns and grouping behavior did not vary relative to the level of spatial overlap with jaguars. The overall effect of jaguars on cattle was low and cattle likely constitute an alternative prey killed opportunistically. However, despite the higher abundance of non-calves, our results indicate a preponderance of jaguar predation toward calves within a limited range of distance from forest, a pattern that may be explained through selection of substandard individuals.
The importance of food resources on the dynamics of carnivore populations was further investigated through the study of dietary breadth and overlap of sympatric small and medium-sized carnivores from a prairie habitat in central North America. We performed a stomach content analysis of carcasses salvaged as part of a predator control program in southern Saskatchewan, Canada (2000-2001). American badgers (Taxidea taxus), coyotes (Canis latrans), red fox (Vulpes vulpes), raccoons (Procyon lotor), and striped skunks (Mephitis mephitis) consumed a total of 25 separate food items. Dietary breadth varied among the 5 carnivore species, and was narrowest for raccoons and widest for skunks. Overall, dietary overlap tended to be highest for species pairings associated with the highest level of presumed niche similarity, which included raccoon-skunk and coyote-fox dyads. The assessment of a larger assemblage of carnivores within a North American prairie community showed that marked interspecific and temporal variation in dietary breadth and overlap may characterize a guild of sympatric species occupying similar habitat.