Dietary overlap among cattle and cervids in northern Idaho forests

Abstract

Botanical composition of diets and dietary overlap were investigated among free-ranging cattle (Bos taurus), Rocky Mountain elk (Cervus elaphus nelsoni), and white-tailed deer (Odocoileus virginianus) in coniferous forests of northern Idaho. The study was conducted within the Abies grandis/Clintonia uniflora (grand fir/queencup beadlily) and Thuja plicata/Clintonia uniflora (western redcedar/queencup beadlily) habitat types. Botanical composition of ungulate diets was determined via microhistological analysis of fresh fecal samples collected in early summer, mid-summer, and early fall of 1987 and 1988. Dietary overlap was examined using Kulcyznski's similarity index. This formula also was used to compare the botanical composition of ungulate diets vs. plant community composition at 5 different seral stages: herb-shrub, sapling, pole, mature, and potential natural community. Cattle consumed graminoid-dominated diets from within early successional communities. Elk also foraged predominantly on graminoids, but elk foraging habits were more diverse and more variable amongst seasons than cattle. White-tailed deer diets were dominated by forbs and shrubs from within late successional communities. Competition for forage between cattle and elk was more likely in the grand fir habitat type, while forage competition between elk and white-tailed deer was more likely in the redcedar habitat type. There was little evidence of potential forage competition between cattle and white-tailed deer in either habitat type.