The behaviour of a male American black bear Ursus americanus was observed for over 2400 h across all seasons of the year. Stereotypic pacing was most frequent, oriented away from the exhibit, and performed mainly after feeding during the period May-July; from August-November pacing was oriented towards the exhibit and performed mainly around feeding time. Placing bear odors in the enclosure slightly reduced pacing and increased exploring/foraging in the late spring. Hiding small food items in the exhibit almost completely eliminated pacing in the fall and replaced it with foraging. Comparison with seasonal changes in the behaviour of wild bears suggest that the stereotypy of this bear, and probably zoo bears in general, developed from two main primary behaviours that cannot be performed in a barren zoo environment: mate-seeking behaviour predominating in the late spring and foraging behaviour in the late summer and fall.