In this paper alternative explanations for observed patterns of sexual segregation by giraffes are examined at two spatial scales: within-habitats and within-landscape. Habitats are defined as recognizable plant associations and the landscape as the collection of all available habitat types. The study was conducted in Mikumi National Park, Tanzania. At the within-landscape level, all sex and age classes of giraffes exhibited high degrees of preference for riverine habitats. Sex differences in habitat selection were mostly due to females with young, who tended to select open floodplain habitats in which their vigilance time was lowest. Males, and females without young, preferred more heavily-wooded habitat. Habitat preferences were not related to observed habitat-specific forage intake rates for either males or females. Within habitats, male and female giraffes selected different feeding heights, males feeding higher in the canopy than females. Females showed a strong tendency to generalize with respect to feeding height. It is suggested that a sexual dimorphism–body size hypothesis provides a parsimonious explanation for the observed feeding height selection patterns, whereas a reproductive strategy hypothesis can explain sex-differences in habitat selection patterns within the landscape.