Ecological determinants of one of the last massive guanaco migrations in Patagonia

NOVARO, A.J., M.J.BOLGERI, C. ZAMBRUNO, P. CARMANCHAHI, M. FUNES, S. WALKER

Mendoza

Congreso; International Mammalian Congress; 2009

Most massive ungulate migrations around the world have been lost and little is known about ecological factors and threats affecting remaining migrations. Guanacos (Lama guanicoe) have been found to be mostly sedentary, but this may be due to barriers to movement such as fences and livestock grazing imposed in the last century in South America. We studied seasonal movements through radiotelemetry of 27 guanacos, assessed plant productivity with remote sensing using the Enhanced Vegetation Index (EVI) and estimated seasonal abundance of guanacos and livestock using transect counts during 2005-9 in the 450,000-ha Payunia reserve of Mendoza, Argentina. Seventeen (63%) of the radiocollared guanacos migrated seasonally between summer and winter ranges along treks that ranged between 15 and 75 km-long. We evaluated causes of this migration by building a logistic model based on seasonal patterns of EVI and abundance of competing livestock to predict presence of guanacos along the migration route. The Payunia migration involves several thousand guanacos and may be the largest migration remaining for the species. Even the extensive Payunia reserve, however, may be insufficient to conserve this migration in the long term as access to the summer range is being restricted by oil development in the outskirts of the reserve, access to winter range is threatened by livestock grazing and fences, and a drying climate may shift forage availability in the coming decades.