Heard, D. C., T. M. Williams, and D. A. Melton. “The Relationship Between Food Intake and Predation Risk in Migratory Caribou and Implications to Caribou and Wolf Population Dynamics”. Rangifer, vol. 16, no. 4, Jan. 1996, pp. 37-44, doi:10.7557/2.16.4.1219.