Évaluation du régime alimentaire de base par analyse du comportement de Marmota bobac Müll. Foraging base evaluation by means of Marmota bobac Müll. behaviour analysis.

Résumé

Three types of areas were identified depending on the anthropogenic influence on phytocoenoses (hay-making, grazing): the plots without any hay-making and grazing, the plots characterized by moderate grazing and regular hay-making and those areas which may be identified as active grazing plots. The observation indicated that the population density of marmots attains its maximum within the plots of the third type whereas the plots of the first type are, as a rule, avoided by the animals.Observations on animals foraging in cages without bottom indicated that their diet was mainly determined by the abundance of various foraging plant species available and to the lesser extent by their phytomass. Marmots may, not "notice" separate plants usually preferred by them as fodder, e.g., some species of Trifolium L., Chichorium intybus L. etc. growing in the nearest vicinity of them. Even when their cage remains stationary on one and the same place the animals eat up no more than 50% of fodder available within this limited area. To compare the phytocoenoses studied for their evaluation as M. bobac foraging base the main fodder plant phytomass was calculated in % or the total aerial phytomass, also taking into in account the diet of parts of the plants (because the latter together with the plants not used as fodder limit the foddder plant accessibility for the animals). This value was: for the first area 10% in 1992 and l8% in 1993, for the second area 22% and 19%, respectively, 38% and 52% for the third one. It allows to suggest that the third type of areas was the most attractive for M. bobac. This was confirmed by the highest population density and breeding of animals within the areas of active grazing and the tendency of the animals to use similar areas as foraging base. Alternatively, marmots may use agrocoenoses (kitchen-gardens, crops, etc.).