Despite ongoing projects involving the breeding and release of equids into semi-wild and wild environments, insufficient information is available in the literature that describes strategies used by equids to adapt and survive in a novel environment. The aim of this study was to assess the ability of nave, feral Equus caballus (horse) mares to cope in a novel feral horse environment and investigate possible reasons why some may not survive this challenge. Four mares taken from a semi-arid desert environment remained in good health but significantly changed their movement behaviour pattern when surrounded by prime grazing habitat in a mesic temperate grassland. Three of the four mares captured from the prime grazing habitat and released in the semi-arid desert habitat died, apparently due to stress and/or starvation, within 8 weeks of release. The fourth mare survived 4 months but lost considerable weight. The group of mares relocated to the semi-arid desert environment had difficulty adapting to relocation and did not take up the movement behaviour strategy of local horses, which required long distance treks from a central water hole to distant feeding areas at least 15km away. The movement behaviour, range use and health consequences of relocating equids may be of interest to wildlife ecologists, animal behaviourists and horse welfare groups. The observations may be used to guide those intending on relocating managed domestic and native horses to novel habitats.