Jaguar on 2 small ranches in southwest Brazil had a density of about 1 animal/25 km2. Females ranged over at least 25-38 km2 and males over twice that much terrain. The ranges of females overlapped, and the range of a resident male included the ranges of several females. Jaguar and puma ranges also overlapped, but each species favored parts not much used by the other. Day-and-night radio tracking revealed precise travel and activity patterns of 2 female jaguar. The social system of jaguar is in most respects similar to that of other large solitary cats such as puma, leopard and tiger.