Use of food availability by guanacos (Lama guanicoe) and livestock in Northern Patagonia (Mendoza, Argentina)

Grazing areas of a guanaco population were shared with introduced livestock in a protected area of Northern Patagonia. The diet of ungulates and the availability of food were compared to recognize interspecific overlaps and to detect potential plant depletions. Seasonal faecal samples were analysed by microhistology, and food availability was analysed by point-quadrat transects in sandy and rocky habitats. Large ungulates were classified as ‘strictly grazers’, while small ungulates as ‘grazer-browsers’. Food limitations constrained ungulate feeding tendencies, in agreement with the selective quality hypothesis. Shared use with a preference of scarce items, i.e. most forbs and four grasses, suggest they are at risk of disappearance by overgrazing. Main dietary items annually shared were the grass Poa and the camephyteHyalis , the conservation of which would be essential for the guanaco population. Despite their high dietary diversity, guanacos could be affected especially by shared food use with sheep and horses in sandy habitats. Cattle would be the most affected by shared use with horses, sheep or goats. Fires and woody plant extractions caused a decrease of shrubby stratum, food diversity and patchiness, and could force an increase of competitive risks. Management priorities should be to monitor the plant cover and diversity, discourage a livestock carrying increase, avoid shrub extraction, and control fire generation