Strongly interacting species: does puma predation on wild South American camelids structure biological diversity in the semiarid landscapes of the Andes?
The loss of species interactions, such as predator-prey relationships, may result in negative impacts that affect not only the interacting species but also other species and the biological communities and ecosystems they inhabit. For instance, the extirpation of wolves from most of North America resulted in prey species foraging in new wolf-free areas with subsequently negative impacts on tree recruitment, nesting area availability for migratory birds and plant community structure. Unlike those in North America, southern South American predator-prey systems have been disrupted mainly through the elimination of large native prey (wild South American camelids: guanacos and vicuñas) and their substitution with introduced prey species (livestock). Consequently, over vast areas of southern South America, the interaction between South American camelids and their main predator, the puma, has been disrupted with unknown consequences for biological communities. This project aimed to evaluate the community level importance of the predator-prey interaction between wild South American camelids (particularly vicuñas) and pumas in one of the last wild areas, San Guillermo National Park, where such interaction still occurs.
The main goals of this research were 1) to analyze the spatial distribution of puma predation on vicuñas in the semiarid landscapes of the Argentine Andes; specifically, to investigate whether some habitats were more or less risky for vicuñas, and 2) to evaluate whether different levels of risk perception by vicuñas resulted in a mosaic of habitats that differ in the abundance and diversity of plants, small vertebrates and invertebrates; specifically to investigate, in safe and risky habitats, vicuña foraging and vigilance behavior, and experimentally analyze vicuña grazing impact on vegetation and small fauna.
Results indicated that vicuñas were killed by pumas in canyons and meadows more often than in flat plains. Canyons (due to rocky outcrops) and meadows (due to tall grasses) present features that facilitate the ambushing strategy of pumas. Pumas were also more active in canyons and meadows and vicuñas responded accordingly by investing more time in vigilance and less in foraging in these habitats. Such behavioral responses had a clear effect on vegetation structure. When vicuñas were excluded from experimental plots (400m2-fenced areas), plant height, plant cover and plant seed production increased in flat plains but remained unchanged in canyons and meadows, suggesting that in these risky habitats pumas – by forcing increased vigilance and decreased herbivory in vicuñas – were protecting plant community structure.
Results from this research highlight the importance of conserving large predators as well as their large herbivore prey from an ecological perspective. These results will also inform evaluations of conservation actions currently underway in Argentina, such as the restoration of top predators, large prey species or both. In addition, the project increased the international visibility of the park attracting foreign researchers, which are planning to start their own research in this outstanding conservation area. This outcome is of great importance for future conservation of the area as large-scale open-pit mining operations are being developed in the surrounding landscape even inside the neighboring provincial reserve.
Donadio submitted reports to the National Park Administration suggesting that future tourist trails and roads are kept to a minimum in canyons and meadows to prevent people from scaring pumas away, thereby allowing vicuñas to graze in risky habitats and homogenizing plant structural diversity across habitats; he is hopefully that this recommendation will be incorporated into the management plan of this newly created park. The project also resulted in the filming of a documentary and the development of a field ecology teaching manual, both of which are anticipated to be completed in 2011. Donadio also noted that CREO funds contributed to the training of twenty-seven undergraduate and recently graduated biology students from seven different Argentine universities who participated in the project as lab or field technicians. One of longest-lasting outcomes of this project is likely to be the increase in local conservation research capacity. ($10,000)