We compared the activity patterns of coyotes (Canis latrans) in a suburban/agricultural area to those in an adjacent undeveloped area in northwest Wyoming from August 1998 to August 1999. Activity patterns were recorded using variable-pulse radio-collars. Correlation of recorded activity and observed activity indicated differences in the sensitivity of the collars. The mean percent of active signals for coyotes in the suburban/agricultural area was significantly lower during diurnal periods and significantly higher during nocturnal periods than the mean percent of active signals in those periods for coyotes in the undeveloped area. No differences between the two areas were observed during crepuscular times. Environmental stimuli, such as human activity, increased the amplitude of the circadian rhythms of coyotes. This increase in amplitude is a result of increased nocturnal activity and decreased diurnal activity.