Animals move through their environment in response to resource, competitor, and predator distribution. In this dissertation I examine resource and space use in wild golden lion tamarins (GLTs, Leontopithecus rosalia). In chapter one I present the results of a field study exploring factors predicting sleeping site selection. GLTs preferentially slept in tree holes. Each group had a few frequently used sites typically found in large, living trees on hillsides near other large trees. Topography and smallscale forest and tree variables were better than habitat-level classifications in predicting sleeping site use. In my second chapter I evaluated home range calculation methods. Using 19 years of data for 15 groups of GLTs, I calculated a yearly home range for each group with the three most commonly used methods: minimum convex polygon (MCP), grid cell, and kernel density estimates. MCP produced the largest home range estimates, grid cell the smallest, and kernel estimates were intermediary. Kernel estimates were preferred because probability of use may be calculated for any part of the home range, there is high concordance between observation spatial distribution and home range shape, and there is a lack of relationship between sample size and home range size. In my third chapter I tested three hypotheses explaining home range size in group-dwelling animals. First, I tested the dominant hypothesis, which states that home range size is determined by group energetic needs and, therefore, group size. The second and third hypotheses relate to numbers of adult females and males present in groups. More adults may increase ranging because of increased reproduction, search for breeding opportunities, or defense. I also examined how variation in predation affects population density and demography and, thus, mediates space use. I found support for all three hypotheses. Larger ranges were occupied by groups that were large, had two breeding females, and/or more potentially breeding males or adult natal males. Intense predation resulted in lower population densities, smaller groups, only one breeding female per group, and fewer adult natal males. Population density and predation had significant, negative impacts on home range size.