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Accueil du site → Doctorat → Argentine → Live-shearing effects on population dynamics of wild guanacos (lama guanicoe) and mortality associated with wire fences in livestock ranches of northern Patagonia, Argentina

Universidad de Buenos Aires (2010)

Live-shearing effects on population dynamics of wild guanacos (lama guanicoe) and mortality associated with wire fences in livestock ranches of northern Patagonia, Argentina

Rey, Andrés

Titre : Live-shearing effects on population dynamics of wild guanacos (lama guanicoe) and mortality associated with wire fences in livestock ranches of northern Patagonia, Argentina

Efectos del manejo sobre la dinámica de poblaciones de guanacos silvestres (Lama guanicoe) y mortalidad por enganches en alambrados en campos ganaderos de Patagonia Norte, Argentina

Auteur : Rey, Andrés

Université de soutenance : Universidad de Buenos Aires

Grade : Doctor en el área de Ciencias Biológicas 2010

Résumé
Live-shearing effects of wild guanacos could work as a complementary activity to livestock ranching and contribute to conserve their populations. The objective of this thesis was to evaluate the effects of live-shearing wild guanacos. The study was conducted successively in two ranches of Northern Patagonia, where live-shearing of wild guanacos was conducted, through line transects to estimate abundance and social structure, capture-recapture data to estimate survival, radio-tracking of captured guanacos, and behavioural observations. In Southern Neuquén (Alicura ranch), abundance and social structure was compared between areas with and without shearing, and individual activities were analysed before and after a shearing event, between August 2004 and December 2005. Abundance of guanacos remained similar after the shearing event. Social structure did not differ from other populations. Family groups were the most frequent social structure and the size of male groups was smaller in spring than in winter. Foraging was the main activity throughout the day and resting was positively associated with temperature in summer. In the centre of Rio Negro (Cabeza de Vaca ranch), abundance and survival was estimated in a repetitively managed population (7 events) throughout 5 years, and its reproduction and population trend was compared with a guanaco population coexisting with livestock, between January 2003 and January 2009, during normal climatic conditions and a drought (since December 2006). No movements of guanacos outside the managed area were observed and in only one occasion abundance decreased immediately after shearing, related to sampling design and evasive behaviour. Survival of the managed population was similar between sexes and ages, was constant throughout the study, and was lower than survival in non-managed populations. Reproduction in the managed population did not differ with reproduction in the population coexisting with livestock, and other non-managed populations. Population trend was similar between the managed population and the one coexisting with livestock, being stable during normal climatic conditions but declining during a drought. Additionally, in this ranch, mortality associated with wire fences was estimated by registering all carcasses found on fences and its characteristics. Mortality due to fences had a higher impact on juveniles than on adults. Juveniles died mainly on sheep fences (93 cm) while adults mainly died when trying to jump on cattle fences (113 cm). Results suggest that repeated management caused no movements outside the area, nor higher mortality or reduction in reproduction that could generate declining population trends during normal climatic conditions. However, shearing events should be avoided during post-partum periods (summer) and adverse climatic conditions (e.g. drought). Further studies are necessary to evaluate sustainability of live-shearing and its value as a conservation tool for guanaco populations.

Mots clés : ESQUILA ; ESTRUCTURA SOCIAL ; GUANACOS SILVESTRES ; LAMA GUANICOE ; MORTALIDAD POR ALAMBRADOS ; PARAMETROS POBLACIONALES ; PATRON DE ACTIVIDAD ; TENDENCIA POBLACIONAL ; USO SUSTENTABLE ; SHEARING ; SOCIAL STRUCTURE ; WILD GUANACOS ; LAMA GUANICOE ; MORTALITY IN WIRE FENCES ; POPULATION PARAMETERS ; ACTIVITY PATTERN ; POPULATION TREND ; SUSTAINABLE USE

Présentation (Biblioteca Digital)

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Page publiée le 27 septembre 2017, mise à jour le 12 février 2020