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

RODRÍGUEZ, MARIA VICTORIA; MARINO, ANDREA; PAZOS, GUSTAVO

Quintay

Congreso; Rufford conference 2015; 2015

Rufford fundation

The guanaco isthe dominant native herbivore inhabiting the Patagonian steppe and a potentialproductive alternative to the traditional sheep-ranching that has producedmassive habitat degradation across the region. However, local people perceivethis herbivore as a threat to livestock production. Hypothetical overgrazing-risksexhort current culling initiatives planned by government agencies aimed athindering the perceived guanaco overpopulation. Since there is a lack ofempirical knowledge on the processes linking native herbivores, vegetation andlivestock within this system, grazing impact by guanacos and sheep is oftenconfounded and management plans are susceptible to be founded on wrongassumptions. To address these interactionsin the context of the study of theprocesses that regulate guanaco density, we assessed the response of a guanacopopulation and the main vegetation communities within a traditional sheepranchof Northeastern Patagonia thatwas turned into a wildlife reserve. We recorded therapid increase in guanaco density coupled with augmented forage cover afterlivestock removal. The observed density stabilized below the environmentalcarrying capacity predicted by an equal share of available forage. Theseresults, in addition to our measure of vegetation performance,are consistentwith the hypothesis of a self-regulatory mechanism that prevents overgrazing,which challenges major assumptions of classic regulation models for largeherbivores in predator-free populations. Besides the critical implications forthe conservation and management of South-American camelids and australrangelands, our results are an important contribution to the understanding ofthe processes shaping the distribution of territorial herbivores and their grazingimpact across the landscape.