Resumen

GOMEZ VINASSA, M. Laura  y  BEATRIZ NUNEZ, M.. Dieta estacional de guanacos (Lama guanicoe) y burros ferales (Equus asinus) en un ambiente semiárido de San Luis, Argentina. Ecol. austral [online]. 2016, vol.26, n.2, pp.178-188. ISSN 1667-782X.

Seasonal diet of guanacos (Lama guanicoe) and feral donkeys (Equus asinus) in a semiarid environment of San Luis, Argentina. In the province of San Luis (Argentina), in an ecotonal area between Monte and Dry Chaco regions, populations of guanacos and feral donkeys coexist. Since sympatric herbivores with similar body masses may incur in interspecifc competition for food, the food habits of guanacos and donkeys was determined to evaluate the degree of trophic overlap. Feces of each species were collected and relative food availability in the environment was measured in the dry (DS) and wet (WS) seasons. Relative frequency (%RF) of each vegetal item in scats was determined by microhistological analysis. According to our results, donkeys' diet showed seasonal variation in the consumption of monocots and was correlated with the available resources in the environment in DS. It was mainly composed of grasses (75% in DS and 50% in WS), with an increase in consumption of epiphytic plants in the genus Tillandsia spp. in the rainy season (40%). Guanacos' diet also showed seasonal variation and was signifcantly related to environmental supply in WS. It contained about 60% of woody plants throughout the whole year, with a higher percentage of epiphytes and cactus in DS. The similarity in the total compositions of the diets was 20% in DS and 40% in WS, with higher values of similarity for epiphytes (74%) and cactus (64%) in WS. The rest of the year diets mostly difered in composition and proportion of plant items, so we conclude that the trophic overlap between these species in the study area is low.

Palabras clave : Sympatry; Herbivory; Food habits; Native ungulates; Exotic mammals.