Interactions between wild boar and cattle in Patagonian temperate forest: cattle impacts are worse when alone than with wild boar

Abstract

The global phenomenon of introduced species has caused serious, negative impacts on biodiversity and human productive activities. Often, introduced species become invasive and impact and modifies the availability of resources in native ecosystem. Cattle and wild boar are two species that have been introduced on all continents for food and sport hunting. Both species cause detrimental changes in ecosystem processes and biodiversity. Particularly in Patagonia, it has been shown in different studies that in isolation these species can cause damage to native plants, alter the structure of the soil and its processes. This study sought to assess and compare the ecosystem impacts of cattle and wild boar upon ecosystem structure and function in different scenarios with the presence of both, one or none of these focal species. Our study area is the Nahuel Huapi National Park where both species have significant presence on temperate forest. In order to evaluate the species impact we combined experimental and observational methods across sites with the presence of one species, both species, and sites without either species. Our data showed that sites with both species or only wild boar showed fewer impacts than expected. However, when cattle is presence, this species seriously threaten the native ecosystems by affecting plant biomass, reducing the shrub cover and number of native plants, and enhancing exotic plant species. Our study found no evidence to support of additive effects or impacts a between both species, but the presence of both cattle and wild boar could have an antagonistic effect or interactions through resource competition. Although cattle and wild boar are considered valuable socio-economic resources, we believe that the free-range populations of these mammals that inhabit temperate forests of Patagonia should have focused management plans that prioritize the control of cattle, to subsequently focus on the management of the wild boar.