a b s t r a c tGuanaco populations face different feeding constraints along their altitudinal migrations in Andean mountains. The guanaco's diet and food availability were analyzed using microhistological analysis and point-quadrat transects at four sampling sites from the summer range, and four sites from the winter range of a High Andean migratory population. Significant differences were detected with Kruskal-Wallis ANOVA, feeding selection by the 2 test, and dietary preferences by Bailey's confidence interval. Summer range was characterized by having higher plant diversity with more availability of grass-likes (Ciperaceae and Juncaceae) and forbs, compared to winter range. Sites with vegas (moist areas associated to streams and ponds, with dense hydrophytic vegetation) showed higher plant cover and diversity, also diet diversity was higher. Diet was dominated by grass-likes and grasses at sites with wetlands, only by grasses at the other sites, especially in winter. The highest diet-availability similarity occurred in the vega microhabitat, but species from slopes were also eaten at sites with wetlands. Grasses were preferred and shrubs were avoided in both seasonal ranges. The narrower guanaco's diet in winter, and the higher dietary diversity where plant cover and diversity are higher, both agree with the hypothesis of selective quality. A summer opportunistic feeding behavior shifts to a more selective behavior during winter. Winter browsing barely occurred, and grasses prevailed in the diet of both seasons. Altitudinal migration, forced by the deep snow, could favor guanacos to maintain a grazer strategy year round. Vegas and grasslands, in the summer and winter ranges, have a high feeding relevance for this guanaco population, and connectivity between both ranges is essential for their survival.
The brown hare, a Leporid widespread in the world, is now dispersed across Argentina after its introduction at the end of the 19th century. Studies on hare feeding ecology are important to evaluate a potential competition with domestic and native wild herbivores. This study analyses the brown hare diet in relation to food availability, and dietary overlaps with several herbivores in northern Patagonia. Food availability was estimated by point-quadrat transects, and hare diet by microhistological analysis of faeces, carried out in five habitats in five seasonal samplings. Significant differences were detected by Kruskall-Wallis ANOVA with multiple comparisons by Tukey test. Feeding selection was detected by w 2 test, and dietary preferences by the confidence interval of Bailey. Grasses and chamaephytes were the most available plant categories, with Stipa, Panicum and Acantholippia as main species. Grasses and phanerophytes were the main dietary categories, including Poa, Panicum, Bromus, Adesmia and Prosopidastrum. The phanerophytes Prosopidastrum and Ephedra were more eaten in winter, when the main food item (Poa) presented lower availability. A higher dietary proportion of the chamaephyte Acantholippia occurred in rocky habitats, where the coarse dominant grasses were always avoided. Hares shared most food items with several wild and domestic herbivores in northern Patagonia. The lack of preference for forbs differentiates brown hares from other herbivores. However, hares exhibited important dietary similarities with plain and mountain vizcachas, goats and horses, and an interspecific competition for food is highly probable.
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