Cattle in the Patagonian forests: Feeding ecology in Los Alerces National Reserve

Cattle (Bos taurus) are the largest exotic ungulates introduced in Patagonian forest, and the most widely distributed. Although detrimental effects of cattle grazing on these forests have been documented, cattle–plant interaction has never been studied from the perspective of the feeding ecology of this ungulate. We assessed cattle diet on a seasonal basis by microhistological analysis of fecal samples in Los Alerces National Reserve, Argentina. We found that: (1) the annual diet was largely dominated by graminoids and shrubs; (2) the percentage of shrubs, forbs, and other species in the diet changed significantly across seasons; (3) cattle predominantly fed on Nothofagus spp., Berberis spp., Maytenus spp., Chusquea culeou, and Hierocloe sp.; and (4) selected more forbs than other vegetation types in warm-growing season, while highly selected graminoids and avoided shrubs during the cold-dormant season. Although these general selection patterns of plant types were observed seasonally, selection or avoidance at the species level was also recorded. Cattle have been described as grazers, suggesting that the composition of their diet should be dominated by graminoids. However, we found that cattle include significant proportions of woody plants in their diet. These results offer the first data available on diet composition and selection in a protected area in Patagonian forests, a first step towards understanding detrimental effects of cattle grazing on native forest from the perspective of their feeding ecology. Our evidence that cattle positively select Nothofagus spp. and Austrocedrus chilensis suggests that they can negatively affect the establishment and growth of these species. Given that livestock ranching is an important form of subsistence for economically disadvantaged settlers of Los Alerces National Reserve, alternatives to current ranching activities must be considered to improve their livelihood and reduce the negative effects of cattle on forests.

Research highlights
► The annual diet of cattle was largely dominated by grasses and shrubs.
► Diet composition changed significantly across seasons.
► Cattle selected forbs in warm season and selected grasses during cold season.
► The selection of tree species suggests that it can negatively affect their establishment and growth.
► These are the first data available from the perspective of the foraging ecology of cattle in Patagonian forests.