On sustainable grazing and the conservation of Patagonian rangelands: Self-regulation of population density by free-ranging guanaco

M. VICTORIA RODRÍGUEZ; ANDREA MARINO; GUSTAVO PAZOS

Quintay

Congreso; Grant Recipients Conference; 2015

Costa Humboldt y Centro de Investigaciones Marinas de Quintay

The guanaco is the dominant native herbivore inhabiting the Patagonian steppe and a potential productive alternative to the traditional sheep-ranching that has produced massive habitat degradation across the region. However, local people perceive this herbivore as a threat to livestock production. Hypothetical overgrazing-risks exhort current culling initiatives planned by government agencies aimed at hindering the perceived guanaco overpopulation. Since there is a lack of empirical knowledge on the processes linking native herbivores, vegetation and livestock within this system, grazing impact by guanacos and sheep is often confounded and management plans are susceptible to be founded on wrong assumptions. To address these interactions in the context of the study of the processes that regulate guanaco density, we assessed the response of a guanaco population and the main vegetation communities within a traditional sheep ranch of Northeastern Patagonia that was turned into a wildlife reserve. We recorded the rapid increase in guanaco density coupled with augmented forage cover after livestock removal. The observed density stabilized below the environmental carrying capacity predicted by an equal share of available forage. These results, in addition to our measure of vegetation performance, are consistent with the hypothesis of a self-regulatory mechanism that prevents overgrazing, which challenges major assumptions of classic regulation models for large herbivores in predator-free populations. Besides the critical implications for the conservation and management of South-American camelids and austral rangelands, our results are an important contribution to the understanding of the processes shaping the distribution of territorial herbivores and their grazing impact across the landscape.