Subtle foodscape displacement of a native ungulate by free-ranging livestock in a forest agroecosystem

Abstract

The prevalence of livestock grazing in wildlife areas is increasing. This transformation of ecosystems into agroecosystems is concerning because the introduction of new species may cause niche displacement of the functionally related native species. We used a large-scale fence scheme and fecal analyses to study the influence of free-ranging livestock on moose diet on three boreal forest ranges. We found low interspecific diet overlap between moose and livestock (mean Pianka's O across ranges = 0.21, SD = 0.104), and the diet overlap with livestock did not differ between moose in areas with livestock and in adjacent control areas without livestock. Still, moose sympatric with livestock had less fecal nitrogen (a proxy for diet quality) than moose in the control areas. Our findings suggest that interspecific interactions other than direct food competition contributed to reduce the moose’ foraging opportunities, such as altered forage abundance and composition, or behavioral avoidance of livestock. We caution that displacement in the foodscape (i.e., spatiotemporal use of food) can occur through pathways not evident in niche indices based on composition of plant species in the diet.