More than migration: Pronghorn exhibit diverse array of seasonal use behaviors

Abstract Background Considerable attention has been given in recent years to the variety of migratory behaviors that ungulates employ. However, the focus on migration ignores many other behaviors animals may exhibit to cope with seasonal changes in resource availability and mortality risk. Methods I examined daily location data of pronghorn (Antilocapra americana) inhabiting the Modoc Plateau in northern California to characterize their repertoire of seasonal use behaviors. I defined six seasonal use behaviors (resident, seasonal shift, seasonal contraction, seasonal expansion, migration, nomadism) based on patterns of home range overlap in successive seasons and identified numerous annual strategies corresponding to patterns of behaviors over the course of a year. Results Pronghorn engaged in all six behaviors throughout the year, although nomadism was observed on only four occasions. Individual pronghorn combined seasonal behaviors in numerous ways to create a wide variety of annual strategies. Individuals exhibited different annual patterns across years, while neighboring individuals exhibited different behavioral strategies in the same year. Conclusions This variety of behaviors highlights that simple categorization of seasonal use behaviors as if-when-where animals migrate is insufficient to understanding how animals respond to seasonal changes. While some ecologists have considered range residency and classical migration to be endpoints along a continuum of behaviors, the complexity of annual strategies will likely need to be considered within a multidimensional framework to understand how climate change and other anthropogenic disturbances will affect animals’ ability to respond to seasonal changes in environmental conditions.