Nutritional Consequences of Partial Migration in the North Sapphire Elk Herd
In collaboration with Montana Fish, Wildlife and Parks and the North Sapphire Elk Research Project, we conducted a study on the North Sapphire elk herd in the Bitterroot Valley of Montana. The herd provides important hunting and recreational opportunities, but changing elk distributions in recent years have become a potential source of concern for local landowners and sportsmen. Using GPS collar locations of elk and forage plant data from ground plots, we assessed the prevalence of migratory behavior in the population and determined whether elk that migrated had access to the same quality of nutrition as elk that did not migrate. We found migrants had access to lower forage quality during late summer than elk that did not migrate. Relatively high forage quality in irrigated agricultural areas contributed strongly to these nutritional differences, although recently-burned higher-elevation forested areas dominated by Douglas fir or Ponderosa pine provided equivalent forage quality to that of irrigated agriculture. Excluding elk from irrigated agricultural areas may help encourage migratory behavior by reducing nutritional incentives for elk to remain resident in low elevations year-round. Further, fire may help temporarily increase forage quality for elk on native forests and improve nutritional benefits for migrants.