CONICET | Buscador de Institutos y Recursos Humanos

We present preliminary data on the distribution and density of guanacos of central Isla Grande de Tierra del Fuego, assessed duringFebruary 2008. The environment is a forest-steppe transitional zone, from the forested range to the Magellan steppe and is characterizedby patches of forest interspersed with relatively flat river valleys covered with grass (vegas). The study area was divided in fourstrata: Forest, Ecotone, Steppe and inside the Provincial Reserve Corazón de la Isla. The survey was performed following a striptransect methodology, as animals move towards the vegas during noon and early afternoon. We flew along the vegas to record allanimals in a strip of 1,400m width, using a Robinson 44 helicopter, during February 14th 2008. We recorded presence and group sizeof guanaco, from pictures taken from the helicopter using a digital camera. Position of records was build from the trackline registeredby a GPS, which clock was synchronized with that of the camera. The trackline of the flight was split in transects of 550 long (basedon territory size of guanacos) for analytical purposes in a GIS framework. Density was estimated using DISTANCE software. Overallguanaco density (± SD) was 2.05 (± 0.30) guanacos/km2, in accordance with existing previous information. Density did not differsignificantly among strata (p<0.01): Forest (2.32 ± 0.85), Ecotone (2.70 ± 0.63), Steppe (2.80 ± 0.96) and Provincial Reserve (1.19± 0.31). The overall guanaco abundance for the area was estimated in 9445 ± 1382 animals. Guanacos were spread from the steppeto the forested range. These results contradict the knowledge about seasonal movements of guanacos, that would move from thelow coastal areas to the Andean range in summer. A discussion on the relationship of the distribution and abundance of guanaco withcattle and sheep is also presented

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