Does food abundance determine the diet of the Puna Rhea (Rhea tarapacensis) in the Austral Puna desert in Argentina?

摘要

The Puna Rhea (Rhea tarapacensis) is a large, flightless herbivorous bird found in the Andes Mountains of four countries, namely Argentina, Chile, Bolivia and Peru. Despite its ample distribution range, little is known about the ecological requirements of the species. In this work, the diet and food selection behaviour of the Puna Rhea in the Argentine Puna desert were analysed. From 2011 to 2014, throughout the dry and wet periods of each year, fresh faeces were collected and vegetation cover was simultaneously recorded. Diet composition was determined by microhistological analysis of the faeces and diet selectivity was established statistically by the Bonferroni method. The diet of the Puna Rhea was completely herbivorous and mostly folivorous, consisting of 51% of the plant species in the study area. This species was highly selective, consuming scarce shrub and herbaceous species and rejecting grasses or graminoids. The strongly selective foraging strategy presented by the Puna Rhea was therefore unrelated to the abundance of particular species but probably influenced by factors such as nutritional value, mainly in terms of fibre content and plant secondary compounds, and predation risk. Consequently, conservation efforts aimed at the Puna Rhea should be focused on maintaining the availability of the few preferred plant species and reducing possible competition with other generalist herbivores.