Abstract
Shrublands and grasslands comprise over 30% of the land surface and are among the most exploited ecosystems for livestock production. Across natural landscapes, the distribution and abundance of wild herbivores are affected by interspecific competition for foraging resources, hunting and the development of infrastructure among other factors. In Argentine Patagonia, the abundance of domestic sheep grazing on native vegetation outnumbers the widely distributed guanaco (Lama guanicoe) and sheep ranching monopolizes the most productive lands. In this work, we aimed to assess the spatial variation in the abundance of guanacos in Península Valdés, a representative landscape of Patagonia, investigating the incidence of natural and human-related factors. We conducted ground surveys during the austral autumn in 2017 totaling 383.4 km along areas with and without sheep ranching. We built density surface models to account for the variation in guanaco abundance and obtained a map of guanaco density at a resolution of 4 km2. We estimated an overall density of 11.71 guanacos.km−2 for a prediction area of 3,196 km2, although the density of guanacos tripled in areas where sheep ranching was terminated (in around 20% of the surface of Península Valdés) compared to areas with sheep. Guanacos were more abundant at lower values of primary productivity and sheep stocking rates and further from inhabited ranch buildings, suggesting competition with sheep and conflict with humans. Although guanacos selected open, grass-dominated habitats across sheep-free sites, fences dividing properties and paddocks played a significant role in the spatial structure of their population in Península Valdés affecting negatively the abundance of guanacos. Our results indicate that actions to improve habitat connectivity for guanacos, favor the coexistence among guanacos and sheep ranching, and promote responsible human activities and attitudes towards wildlife are needed.
Highlights
The study of wild species distribution and abundance allows exploring the mechanisms and processes that operate in the selection of habitats and the factors related to the persistence of populations
We recorded 2.09 observations of guanacos per km surveyed across PV, the average 1.47 observations.km−1 for Sheep ranching areas (SHEEP) areas was markedly lower than 4.43 observations of guanacos per km surveyed in NOSHEEP areas
Human activities related to sheep ranching for wool production shape the spatial structure of the guanaco population across the Península Valdés landscape
Summary
The study of wild species distribution and abundance allows exploring the mechanisms and processes that operate in the selection of habitats and the factors related to the persistence of populations. The spatial structure of wild populations depends largely on biological requirements, species life history (Henle et al, 2004; Ewers & Didham, 2006; Prugh et al, 2008), capacity of dispersal, intra and interspecific interactions and evolutionary processes (Peres-Neto & Legendre, 2010). It is known that human activities affected the distribution and abundance of many wild species over time. The subsequent expansion and demographic growth of human populations imposes new uses of wild species that included domestication, for example, of the sheep (Ovis orientalis aries) from the mouflon (Ovis orientalis orientalis) among others (Olsen, 1990)
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