Abstract We investigated the Swift fox (Vulpes velox) food habits during an autumn (October) and winter month (December and January) in a sagebrush-grassland habitat in south-eastern Wyoming in 1996 and 1997. The percentage of occurrence of various food items was determined from 63 scat samples of 6 radio-collared foxes (3 pairs). Mammals, especially rodents, and insects were the most common prey (24.5% and 19.1%, respectively). 49 scat contained plant material. Ungulate carrion was an important part of the Swift fox's diet. No significant difference between autumn and winter diet was detected.