Factors affecting gray wolf (Canis lupus) encounter rate with elk (Cervus elaphus) in Yellowstone National Park
Abstract
Despite encounter rates being a key component of kill rate, few studies of large carnivore predation have quantified encounter rates with prey, the factors that influence them, and the relationship between encounter rate and kill rate. The study’s primary motivation was to determine the relationship between prey density and encounter rate in understanding the mechanism behind the functional response. Elk (Cervus elaphus Linnaeus, 1758) population decline and variable weather in northern Yellowstone National Park provided an opportunity to examine how these factors influenced wolf (Canis lupus Linnaeus, 1758) encounter rates with elk. We explored how factors associated with wolf kill rate and encounter rate in other systems (season, elk density, elk group density, average elk group size, snow depth, wolf pack size, and territory size) influenced wolf–elk encounter rate in Yellowstone National Park. Elk density was the only factor significantly correlated with wolf–elk encounter rate, and we found a nonlinear density-dependent relationship that may be a mechanism for a functional response in this system. Encounter rate was correlated with number of elk killed during early winter but not late winter. Weak effects of snow depth and elk group size on encounter rate suggest that these factors influence kill rate via hunting success because kill rate is the product of hunting success and encounter rate.
Résumé
Si la fréquence des rencontres est un élément clé du taux de prédation, peu d’études sur la prédation par de grands carnivores ont quantifié la fréquence des rencontres avec des proies, les facteurs qui l’influencent et la relation entre la fréquence des rencontres et le taux de prédation. La principale motivation de l’étude consistait à établir la relation entre la densité de proies et la fréquence des rencontres pour mieux comprendre le mécanisme qui sous-tend la réaction fonctionnelle. Le déclin de la population de wapitis (Cervus elaphus Linnaeus, 1758) et la météo variable dans le secteur nord du Parc national de Yellowstone offrent la possibilité d’examiner l’influence de ces facteurs sur la fréquence des rencontres de loups (Canis lupus Linnaeus, 1758) avec des wapitis. Nous avons examiné l’influence de facteurs associés au taux de prédation par des loups et à la fréquence des rencontres dans d’autres systèmes (saison, densité des wapitis, densité des groupes de wapitis, taille moyenne des groupes de wapitis, épaisseur de la neige, taille de la meute de loups et dimension du territoire) sur la fréquence des rencontres loup–wapiti dans le Parc national de Yellowstone. La densité des wapitis est le seul facteur qui présente une corrélation significative avec la fréquence des rencontres loup–wapiti, et nous avons noté une relation non linéaire dépendante de la densité qui pourrait constituer un mécanisme de réaction fonctionnelle dans ce système. La fréquence des rencontres est corrélée au nombre de wapitis tués au début de l’hiver mais non à la fin de l’hiver. De faibles effets de l’épaisseur de la neige et de la taille des groupes de wapitis sur la fréquence des rencontres semblent indiquer que ces facteurs influencent le taux de prédation par l’entremise du succès de la chasse étant donné que le taux de prédation est le produit du succès de la chasse et de la fréquence des rencontres. [Traduit par la Rédaction]
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Published In
Canadian Journal of Zoology
Volume 96 • Number 9 • September 2018
Pages: 1032 - 1042
History
Received: 21 August 2017
Accepted: 6 March 2018
Accepted manuscript online: 14 May 2018
Version of record online: 14 May 2018
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© 2018.
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H.W. Martin, L.D. Mech, J. Fieberg, M.C. Metz, D.R. MacNulty, D.R. Stahler, and D.W. Smith. 2018. Factors affecting gray wolf (Canis lupus) encounter rate with elk (Cervus elaphus) in Yellowstone National Park. Canadian Journal of Zoology. 96(9): 1032-1042. https://doi.org/10.1139/cjz-2017-0220