group formation is one of the most striking patterns in the natural world. elk (cervus elaphus and c. canadensis) are well known for their social and gregarious nature, but motivations for this behaviour are not fully understood. in particular, how elk perceive and deal with predation risk and modify foraging behaviour as group size changes requires further study. this thesis begins by describing how group behaviour might add to the security of individuals, using a model that varies adult elk survival with group size. the model might explain why a lake of the woods, ontario, elk population (c.canadensis manitobensisi) declined following re‐introduction in a translocation program that occurred between 2000 and 2001. the population suffered initially from high levels of predation, possibly due to the predator‐naïve nature of the source population from elk island national park, alberta. a model forcing elk into one of several group sizes, each varying in degree of predation risk describes the predator‐naïve nature of introduced elk as contributing to the decline. if individuals adapt to novel predation risks by joining larger groups with higher survival, the population stabilizes and eventually increases.