In order to conserve mammalian top predators in human-dominated landscapes, large scale habitat requirements and food habits of the Japanese weasel (Mustela itatsi) were studied using 237 faecal samples, from a 901 km² area in the vicinity of Mito City, Ibaraki Prefecture, Japan between 1999 and 2001. Findings show a significant difference in the faeces distribution among the nine biotope types surveyed, with a marked preference for rice fields and conifer plantations, coupled with an avoidance of farming and urban areas. In terms of weasel diet, mammals occured most frequently in relative volume and single occupancy in faeces and most often observed in conifer plantations along river banks. Second, Orthoptera insects, crustaceans, fruits, Coleoptera insects and fish were also found both in high frequency and relative volume, most often in rice fields and riparian habitats along river banks. Third, a high frequency of occurrence among combinations of (1) mammals with Coleoptera insects and (2) crustaceans with Orthoptera insects suggests the necessity of interaction among habitats. Artificial items were rare. These patterns provide evidence that weasels require diverse landscapes and further suggest weasels do not use urban areas because of their predatory preference for fresh animal food. This has implications for weasel conservation strategies.