Response of pumas to a population decline of the plains vizcacha

We examined the dietary response of pumas (Puma concolor) to a population decline of the plains vizcacha (Lagostomus maximus), and compared the diet of pumas in semi-arid scrub of Argentina to predicted patterns based on a biogeographic analysis of the diet of this species throughout the Americas, Feces of pumas were collected in Lihue Calel National Park in 1985-1988 and in 1994, and populations of vizcachas were monitored during the same period by direct observation of marked animals and burrow surveys. Vizcachas were the most abundant prey in feces of pumas during all years and composed 51.6-84.9% of the diet, During 1986-1994, the population of vizcachas declined >90% in Lihue Calel National Park, and greater than or equal to 14% on surrounding ranches. The proportion of vizcachas in feces of pumas declined by 33%, and consumption of ungulates increased. Weight of prey and breadth of diet of pumas were lower in our study site than in almost all other areas in North and South America. We hypothesize that pumas are selectively foraging on vizcachas because this species provides a clumped resource that is spatially predictable, easy to handle, and, at times, abundant.