Niche Segregation between Wild and Domestic Herbivores in Chilean Patagonia

Abstract

Competition arises when two co-occuring species share a limiting resource. Potential for competition is higher when species have coexisted for a short time, as it is the case for herbivores and livestock introduced in natural systems. Sheep, introduced in the late 19th century in Patagonia, bear a great resemblance in size and diet to the guanaco, the main native herbivore in Patagonia. In such circumstances, it could be expected that the two species compete and one of them could be displaced. We investigated spatial overlap and habitat selection by coexisting sheep and guanaco in winter and in summer. Additionally, we studied habitat selection of the guanaco in a control situation free from sheep, both in summer and winter. We also determined overlap between species in areas with different intensity of use (named preferred and marginal areas) in order to further detect the potential level of competition in the case of overlapping. Guanaco and sheep showed significantly different habitat preferences through all seasons, in spite of their spatial overlap at landscape scale. Additionally, the habitat used by guanaco was similar regardless of the presence or absence of livestock, which further indicates that sheep is not displacing guanaco where they coexist. These results suggest that habitat segregation between guanaco and sheep is due to a differential habitat selection and not to a competitive displacement process. Therefore, the potential for competition is considered low, contrary to what has been previously observed, although this could be a density-dependent result.

Livestock and the functional habitat of vicuñas in Ecuador: a new puzzle

“…So far, outcome of our study of vicuñas in the CFPR matches another disparate result from a study of guanaco and sheep coexistence in Patagonia, which the authors speculate owes to high habitat heterogeneity and very fine‐scale niche segregation (Iranzo et al. ). To explore further how context affects ecological interactions, a wider and more precise sampling of densities of sympatric large herbivores may be required to specify thresholds for habitat homogeneity at which negative interactions disappear.…”

“…, Arzamendia and Vilá ), as habitat selection and other behavioral changes in sympatric ungulates are density dependent (Iranzo et al. , van Beest et al. ).…”

“…In Patagonia, guanaco (Lama guanicoe, another free-ranging camelid) declines in areas of coexistence with livestock, particularly sheep, have been assumed due to dietary overlap and potential competition (Baldi et al 2004). Many authors describe similar net negative effects of livestock on camelids, but the effect vanishes at low livestock densities, perhaps due to habitat segregation or the ability of native camelids to persist in habitats that are suboptimal for livestock (Borgnia et al 2008, Iranzo et al 2013, Wurstten et al 2014, Arzamendia and Vil a 2015. Our case is of a vicuña population that continues to grow exponentially into habitat that is restricted in extent, occupying foothills rather than altiplano, and where space sharing with livestock is common (Figs.…”

Predator occurrence and perceived predation risk determine grouping behavior in guanaco (Lama guanicoe)

“…A detailed description of survey methodology is provided in Iranzo et al. (, ), and Traba, Iranzo, Carmona, and Malo ().…”

Influencia de factores bióticos y abióticos en el crecimiento de la regeneración pre- y post-cosecha en un bosque de Nothofagus pumilio

“…Si bien el guanaco es un componente natural de estos bosques, se ha sugerido que sus poblaciones pueden poner en riesgo la regeneración de estos bosques (Cavieres y Fajardo 2005) debido a que las poblaciones son segregadas por el ganado doméstico hacia el bosque (Iranzo et al 2013). Por otra parte, la regeneración establecida también es vulnerable a daños abióticos debido a heladas o desecamientos durante la temporada de crecimiento (Bannister 2007, Martínez Pastur et al 2016a, pudiendo en algunos años afectar a un mayor porcentaje de plántulas que el ramoneo, y cuyos efectos (ramoneo y años por heladas/desecamientos) suelen confundirse en el tiempo (Martínez Pastur et al 2016a).…”