The diets of cattle and guanaco in the relict Chacoan savannahs of Bolivia

Overlap in resource use between cattle and wild herbivores have implications for conservation, particularly if food is limited. The aim of this paper is to investigate the diets of a wild and a domestic herbivore living in sympatry in plant communities degraded by woody encroachment. Dung samples from both species were subjected to microhistological analysis, making of this work the first study describing and comparing the diet of sympatric guanacos and cattle in the Chaco region. We found a relatively high richness of 53 plant species in the diets of both herbivores, and 4 species were exclusive to cattle. A clear separation between the diets of guanaco and cattle was observed at two levels using analysis of similarity (ANOSIM): a) species level (r=0.52, p=<0.0001) and b) at ecological group level (r= 0.3312, p=<0.001). Cattle appear to forage mostly on the colonial woody species mainly responsible for the reduction of open areas while guanaco diets include more of the native grass most characteristic of the shrinking Chacoan savannahs. Our study raises questions for further research that could form core elements of future conservation plans for the guanaco population in the study area and beyond.