This article reviews the previous discussions regarding the bison migration/non-migration controversy. One hypothesis is that bison herds migrated regularly between woodland and grassland environments with the seasons. The opposing hypothesis is that bison did not migrate, engaging in no more than erratic seasonal movements. Previous discussions regarding the controversy have been based on either the historical record, or on ecological data and interpretations. The present discussion by Epp incorporates new ecological data and applies them to previously considered historic and ecological data and interpretations. Epp concludes that migratory and non-migratory behavior occurred simultaneously in the bison population, each with varying intensity depending upon forage conditions in the various parts of the overall range. According to Epp, the hypothesis that prehistoric bison on the northern Great Plains employed a dual migration/non-migration strategy, in which some herds migrated annually and others remained sedentary in suitable woodlands, is supported by ecological and historical observations. Knowledge of this dispersion behavior leads directly to human settlement hypothesis which stresses the advantages of locating habitations in topographically anomalous, wooded environments on the Plains grasslands in order to take advantage of a reliable bison supply and a high variety of vegetal and other animal resources which tended to concentrate in such places. In conclusion, some bison populations migrated while others did not.
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