Distribuzione degli insediamenti e stima della densitàdi marmotta alpine Marmota marmota) : metodi di indagine per zone campione [Répartition des installations et estimation de la densité des marmottes alpine : méthode de recherche par zone échantillon. Distribution of settlments and density estimation in alpine marmot: study method of sampling zones].

Résumé

A long term study on the behavioural ecology of alpine marmots Marmota marmota L.) was performed in the Cogne Valley, at the Gran Paradiso National Park, Italy. During this study the distribution of the colonies was determined in an area measuring 4200 hectares. Marmots were found in every grassland above the timberline (2000 m) but not in the pinewood and in stony grounds, below the pinewood (1330) few colonies were found, this was probably due to human activities. A family of alpine marmots utilizes only one hibernating burrow over the years and I suggest a density estimate calculed multiplying the number of hibernacula by the mean number of marmots in a family. In the years from 1985 to 1987 this method was carried out in the field in a smaller area measuring 375 hectares with 16% of suitable habitat for marmots (60 hectares). The mean number of 1.02, 0.91, 1.12 marmot every hectare was found in 1985, 1986 and 1987 respectively. All the field work was performed in 674h.