Abstract
Predator–prey interactions are among the most fundamental of ecological relationships. Recolonizing gray wolf (Canis lupus Linnaeus, 1758) populations present new challenges for wildlife management in multi-prey, multi-carnivore systems. We documented diet composition and kill rates for wolves in a recently recolonized area over winter and summer seasons (2014–2015). Elk (Cervus canadensis Erxleben, 1777) were the primary ungulate prey (63%) located at wolf kill sites. Deer (mule deer (Odocoileus hemionus (Rafinesque, 1817)) and white-tailed deer (Odocoileus virginianus (Zimmermann, 1780))) were less prevalent than elk in wolf diets, but the amount of deer in diets (40%–50%) varied by pack and season. Juvenile elk were the most prevalent class of prey in wolf diets during summer (63.3%) and winter (36.3%), with adult elk (32.5%) observed nearly as often as juveniles in winter. Kill rates varied by season, with rates 2.3 times higher in summer (mean = 3.5 ungulates/week per pack) than winter (mean = 1.5 ungulates/week per pack), consistent with increased availability and use of neonate prey. Prey biomass acquisition did not vary by pack or season (summer = 243 kg/week per pack; winter = 182 kg/week per pack). Our study quantified predation patterns for a recolonizing wolf population, and patterns that we documented were similar to other multi-prey systems in North America.
Highlights
IntroductionThe number of prey an individual predator kills over time (per capita kill rates), relative to prey abundance (i.e., predator functional response), and the effects of prey availability to predator population growth (i.e., predator numerical response) are key elements needed to understand predation in a system
To properly quantify predation effects on ungulate prey populations necessitates understanding prey age class contributions to population growth relative to proportions of each age class observed as predator-killed prey (Macarthur 1960; Wisdom et al 2000; Mills 2013)
This study reports on the predation patterns of >20% of the annual number of wolf packs and pairs recorded in Oregon’s recolonizing population (ODFW Annual Wolf Reports 2014 - 2015)
Summary
The number of prey an individual predator kills over time (per capita kill rates), relative to prey abundance (i.e., predator functional response), and the effects of prey availability to predator population growth (i.e., predator numerical response) are key elements needed to understand predation in a system. To properly quantify predation effects on ungulate prey populations necessitates understanding prey age class contributions to population growth relative to proportions of each age class observed as predator-killed prey (Macarthur 1960; Wisdom et al 2000; Mills 2013). If the age classes preyed upon most frequently contribute little to population growth, effects of predation on prey populations may be minimal (Griffin et al 2011; Dellinger et al 2018; Metz et al 2020)
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