Behaviour 2019
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A mechanistic understanding of how elk balance risks and rewards when crossing highways
Marie-Pier Poulin1, Seth G. Cherry2, Jerod A. Merkle1. 1University of Wyoming, Laramie, WY, United States; 2Parks Canada Agency, Yoho National Park, BC, Canada

Roads and their associated traffic represent modern risks for wildlife. Yet, a detailed and mechanistic understanding of the individual and group decision-making processes underlying road crossing behavior in animals is still lacking. We investigated how elk (n=12, representing >80% of the adult population) balanced the risks of vehicle traffic and forage benefits of crossing a major highway in Yoho National Park (Canada) during winter. Using hidden Markov movement models and step-selection functions, we found that the probability of crossing the highway increased with the average time gap between vehicles, the amount of available biomass of herbs and shrubs at their target location, and an interaction between the two. Elk habitat selection with respect to the highway also varied strongly among individuals. Our work demonstrates that most elk are strategically balancing risks and rewards to select for safer and more profitable crossing opportunities. Our study helps understand how decision-making processes related to available food resources and traffic levels dictate road crossing behavior, and thus the mechanisms underlying wildlife-vehicle interactions on highways.