Guanaco’s diet and forage preferences in Nothofagus forest environments of Tierra del Fuego, Argentina

Claudia-Pamela Quinteros,Miriam-Edith Gobbi,Guillermo-Emilio Defossé,José-Omar Bava

doi:10.5424/fs/2017261-09164

Abstract

Aim of study: Guanaco (Lama guanicoe Müller), is a South American native ungulate widely distributed in Patagonia, which in the island of Tierra del Fuego (TF), extends its habitat into Nothofagus spp. forests. Within these forests, guanacos consume lenga (Nothofagus pumilio) leaves and twigs, and other understory species. The aim of this work was to determine: 1) the spring and summer diet of free ranging guanacos, and 2) which plants, grown in the forest understory, guanacos do prefer, or avoid, in these seasons of great forage abundance.Area of study: Tierra del Fuego (Argentina), on three representative areas which combined Nothofagus forests and adjacent meadows (vegas).Material and Methods: Guanacos’ diet was determined by comparing epidermal and non-epidermal plant fragments with micro-histological analyses of feces. The analysis was made from composite samples of fresh feces, collected at the seasons of maximum forage productivity (spring and summer).Main results: During spring, 48% of guanacos’ diet was composed of lenga leaves, 30% of grass-like species, 15% of grasses, and less than 7% of herbs, shrubs, and lichens. In summer, 40% of the diet was composed of grasses, 30% of lenga leaves, 25% of grass-like species and the rest corresponded to herbs, shrubs, and lichens. Within the forest understory, guanaco selected lenga leaves and twigs, grass species were consumed according to their availability (or sometimes rejected), while other herbs were not consumed at all.Research highlights: Guanacos’ consumption preference for lenga, even considering the high availability of other forages, could adversely affect forest regeneration.

Highlights

Large herbivores’ diet is often limited by the quantity and quality of available forage, and by their intrinsic anatomical adaptations that facilitate feeding (McNaughton, 1986)
According to its feeding habits, guanaco (Lama guanicoe Müller), a native ungulate widely distributed in South America, may be considered a generalist of intermediate selectivity, since its diet include most of the plants present in its natural habitat (Baldi et al, 2004)
Guanaco is the largest native ungulate that inhabits Patagonia, the region that covers the southern tip of South America in Argentina and Chile

Summary

Introduction

Large herbivores’ diet is often limited by the quantity and quality of available forage, and by their intrinsic anatomical adaptations that facilitate feeding (McNaughton, 1986). In continental Patagonia, guanaco’s habitat includes arid and semiarid grassland steppes and shrublands, and open ranges in the forest-steppe ecotone (Franklin, 1982; Baldi et al, 1997), but excludes denser forest areas dominated by Nothofagus spp. or by other tree species. In TF, Nothofagus spp. forests grow at low altitude, and their physiography present a matrix of forest embedded of open wetlands (meadows), located in depressions of the landscape. These meadows, regionally named “vegas”, highly overgrazed in the past, are sites of high potential productivity, mainly provided by tender species of the Cyperaceae, Juncaceae, and Poaceae families, which in general supply excellent forage quality (Cassola, 1988). Forst.) Oerst.] and several other low abundant shrubs, seems to constitute an important part of its diet all year round (Raedeke, 1980; Bonino & Pelliza Sbriller, 1991; Soler Esteban et al, 2011; Muñoz & Simonetti, 2013)

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