Long-term effects of supplementary feeding of moose on browsing impact at a landscape scale

Abstract

Supplementary feeding of wildlife is a common management practice, increasingly used to reduce or divert herbivore impact from sensitive habitats, forestry or agriculture. The landscape-scale spatial distribution of herbivory in relation to supplementary or diversionary feeding stations is of particular relevance to wildlife and land management, yet has never been quantified. We considered multiple hypotheses, based on central-place foraging theory, to investigate how landscape-scale browsing impact changed as a function of distance from feeding stations and thereby test the effectiveness of diversionary feeding. We assessed the landscape-scale browsing impact of moose by quantifying browsing patterns and moose density in commercially-valuable young Scots pine stands in an area of south-east Norway with a long history of winter feeding. We also used positions from GPS-collared female moose to investigate the spatial distribution of individuals across the landscape. Moose density and browsing impact at a fine spatial scale (<1km) followed an exponential decrease with distance from diversionary feeding stations. However, at a landscape scale (1-10 km), browsing impact did not show any relationship with distance to feeding stations. Leader stem browsing on Scots pine trees was high at both the local (< 1 km; 68 ± 12 %) and landscape (1- 10 km; 56 ± 7 %) scales. In addition, browsing on commercially valuable Norway spruce, which is normally avoided by moose, was locally high around feeding stations. As currently practiced, long-term diversionary feeding of moose was ineffective in diverting browsing impact from young pine stands at the landscape scale. Browsing on commercially-important tree species was sufficiently high that economic consequences could be expected. To avoid further conflict, we suggest a combination of reducing the moose density and increasing the availability of natural or more attractive supplementary forage.