Factors influencing elk recruitment across ecotypes in the Western United States. Issue 4 (8th March 2018)

• Record Type: Journal Article
• Authors: Lukacs, Paul M.; Mitchell, Michael S.; Hebblewhite, Mark; Johnson, Bruce K.; Johnson, Heather; Kauffman, Matthew; Proffitt, Kelly M.; Zager, Peter; Brodie, Jedediah; Hersey, Kent; Holland, A. Andrew; Hurley, Mark; McCorquodale, Scott; Middleton, Arthur; Nordhagen, Matthew; Nowak, J. Joshua; Walsh, Daniel P.; White, P. J.
• Is Part Of: Journal of wildlife management. Volume 82:Issue 4(2018)
• Page Start: 698
• Page End: 710
• Publication Date: 2018-03-08
• Subjects: carnivores -- Cervus canadensis -- climate -- elk -- forage productivity -- recruitment -- northwestern United States; Wildlife management -- Periodicals; Zoology -- Periodicals; 333.954
• DOI: 10.1002/jwmg.21438
• Languages: English
• ISSNs: 0022-541X

Abstract

ABSTRACT: Ungulates are key components in ecosystems and economically important for sport and subsistence harvest. Yet the relative importance of the effects of weather conditions, forage productivity, and carnivores on ungulates are not well understood. We examined changes in elk ( Cervus canadensis ) recruitment (indexed as age ratios) across 7 states and 3 ecotypes in the northwestern United States during 1989–2010, while considering the effects of predator richness, forage productivity, and precipitation. We found a broad‐scale, long‐term decrease in elk recruitment of 0.48 juveniles/100 adult females/year. Weather conditions (indexed as summer and winter precipitation) showed small, but measurable, influences on recruitment. Forage productivity on summer and winter ranges (indexed by normalized difference vegetation index [NDVI] metrics) had the strongest effect on elk recruitment relative to other factors. Relationships between forage productivity and recruitment varied seasonally and regionally. The productivity of winter habitat was more important in southern parts of the study area, whereas annual variation in productivity of summer habitat had more influence on recruitment in northern areas. Elk recruitment varied by up to 15 juveniles/100 adult females across the range of variation in forage productivity. Areas with more species of large carnivores had relatively low elk recruitment, presumably because of increased predation. Wolves ( Canis lupus ) were associated with a decrease of 5 juveniles/100 adult females, whereas grizzly bears ( Ursus arctos ) were associated with an additional decrease of 7 juveniles/100 adult females. Carnivore species can have a critical influence on ungulate recruitment because their influence rivals large ranges of variation in environmental conditions. A more pressing concern, however, stems from persistent broad‐scale decreases in recruitment across the distribution of elk in the northwestern United States, irrespective of carnivore richness. Our results suggest that wildlife managers interested in improving recruitment of elk consider the combined effects of habitat and predators. Efforts to manage summer and winter ranges to increase forage productivity may have a positive effect on recruitment. © 2018 The Wildlife Society. Abstract : We examined elk recruitment across 7 states in the western United States and demonstrated that elk recruitment is generally declining across the region. Forage productivity and presence of wolves and grizzly bears correlated with changes in recruitment, but the general decline existed with and without wolves and grizzly bears.