Abstract. – Around 500 individuals of Alpine marmots were re-introduced in the French Pyrenees between 1954 and 1988. Marmots soon crossed the mountains to settle in the sunniest southern slopes. After 40 years or so, estimations of the marmot population in the Pyrenees suggested that there were 10 000 individuals. Queries about the presence of marmots in Cerdanya, a 595 km² region of southeastern Pyrenees, were given to forest services and mountain guides and sites visited to verify data. Afterwards, sixty-four plots of 1 km² that contained marmot populations were intensively sampled in search of burrow sites. GIS-based analysis was performed for the whole area in order to compare 1 km² plots with and without marmots. Regression trees and Generalized Linear Models showed that the marmots positively selected plots with low mean March temperatures, small areas of calcareous soils and big areas of meadows. Furthermore, the density of burrow sites was positively associated with the presence of talus and wetland vegetation.