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Increasing global food demand requires the exploration of agricultural production systems that minimise the conflict between food production and biodiversity conservation. Cattle ranching is a main land-use in tropical and sub-tropical South American semi-arid ecosystems, such as the Chaco eco-region of sub-tropical Argentina, one of the most active frontiers of land-use change. Despite open habits being a key component of the Chaco landscape, conservation studies and policies have focussed on forests. In this study, bird and mammal communities of three different open-canopy livestock-producing systems in the semi-arid Argentinian Chaco: natural grasslands, sown non-native pastures and silvopastoral systems are discussed. Diversity (Inverse Simpson index) and species composition (multivariate ordinations) were measured and species identified that characterise each system (indicator species). The three livestock systems did not significantly differ in terms of diversity but showed differences in the composition of bird communities. Natural grasslands had the highest number of bird and mammal indicator species (including Myrmecophaga tridactyla, a high conservation-value species). These results highlight natural grasslands as a landscape unit with a high conservation value and indicate that they should be explicitly targeted by conservation and land-use policies, particularly because they represent a small and rapidly decreasing proportion of the semi-arid Argentinian Chaco.