Food habits of jaguar and puma were studied in two regions of the Para
guayan Chaco. Biochemical analysis of 280 seats attributed 106 to jagu
ar and 35 to puma. Overall dietary overlap was 65 percent and they sha
red six oi seven main prey types. For both cats 43 percent of prey ite
ms and 15 percent of prey biomass taken were mammal species <1 kg, 23
percent of items and 29 percent of the biomass were from species 1-15
kg, and 27 percent of items and 53 percent of the biomass were from la
rger species. Birds, reptiles, and insects made up the remainder. In a
developed region no significant differences between their diets were
found, while in an undeveloped area more small mammals were taken by b
oth species, and jaguar took more large prey than puma. The potential
roles of competition and of differences in habitat structure and prey
availability between the two areas on these species' diets are discuss
ed.