En este trabajo evaluamos si un depredador de emboscada-el puma ( Puma concolor )-afecta las respuestas antidepredador de su presa principal-la vicuña ( Vicugna vicugna )-con efectos de cascada sobre la vegetación (i.e., graminoides). Si los grandes carnívoros terrestres afectan indirectamente la vegetación vía cambios en el comportamiento de sus presas es controversial porque la evidencia existente es largamente correlacional, y experimentos de campo recientes encontraron una débil asociación entre el riesgo de depredación y las respuestas de la vegetación a la presión de pastoreo. However, primary productivity modulated the strength of such effects, with high primary productivity dampening the observed cascading effects. Our results show that large ambush carnivores can positively affect vegetation via nonconsumptive effects on their prey, and that these effects are habitat mediated. In 1 habitat deemed as risky, however, cascading effects were offset likely because water and nutrients were readily available to plants and regrowth was rapid. Here, vicuñas relaxed antipredator behaviors and exclosures had strong effects on vegetation. Conversely, a safe habitat presented low structural complexity, a disproportionately low number of vicuñas killed by pumas, and low relative abundance of pumas. In these habitats, vicuñas displayed strong antipredator behaviors and exclosures did not affect vegetation, suggesting that pumas indirectly protected plants. Risky habitats presented high physical complexity, a disproportionately large number of vicuñas killed by pumas, and high relative abundance of pumas. We also examined habitat-specific rates of vegetative regrowth. In 3 different habitats, we evaluated the relationships among predation risk, vicuña behavior, and-by deploying vicuña exclosures-vegetation structure and productivity. We predicted that strong protective effects of pumas on vegetation would be most apparent in habitats where cover and terrain (i.e., physical complexity) facilitated the ambushing strategy of pumas.
We combined observational data and a field experiment to test whether an ambush predator-the puma ( Puma concolor )-affected the antipredator behavior of its primary ungulate prey-the vicuña ( Vicugna vicugna )-which in turn had cascading effects on vegetation. Whether large carnivores indirectly influence vegetation via prey behavior remains controversial because available evidence is largely correlational, and recent field experiments have found weak associations between risk experienced by prey and vegetative responses to herbivory.
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