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

Abstract

The prevalence of livestock grazing in wildlife area s is increasing. This transformation of ecosys- tems into agroecosystems is concerning because the intr oduction of new species may cause niche displacement of the functionally related native species. We used a la rge-scale fence scheme and f ecal analyses to study the in fl uence of free-ranging livestock on moose diet on thr ee boreal forest ranges. We found low interspeci fi cdiet 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 live- stock. Still, moose sympatric with livestock had less fe cal nitrogen (a proxy for diet quality) than moose in the control areas. Our fi ndings suggest that interspeci fi c interactions other than direct food competition contributed to reduce the moose ’ foraging opportunities, such as altered forag e abundance and composition, or behavioral avoidance of livestock. We caution that displacement in the foodscape (i.e., spati otemporal use of food) can occur through pathways not evident in niche indices based on composition of plant species in the diet.