Distribution of Alpine marmot (Marmota marmota) in Cerdanya, Southern Pyrenees. Distribution de la marmotte alpine (Marmota marmota) en Cerdagne (Sud des Pyrénées).

Résumé

The present population of Alpine marmot in the southern Pyrennes comes from the Alps. Several releases of marmots in the french slope of the Pyrenees were carried out between 1948 and 1983 in order to feed the golden eagles and the brown bears, both endangered species, and to decrease the predating pressure of eagles on Alpine chamois. The preference of marmots for southern slopes has facilitated their expansion along the Pyrenees, and the last estimates establish their population in around 10000 individuals. Although the presence of marmots can be problematic in agricultural fields and gardens, a moderate population has benefits on the environment, mostly through soil fertilization, but also as food for the golden eagle, fox and other predators. Given the high expansion capacity of this species in the Pyrenees and the lack of knowledge of its distribution, an study was carried out in order to update the knowledge on this species in the catalan region. During spring-summer of 2007, we visited several plots in La Cerdanya to make census of this species. Census were made in a total of 69 square plots of 1 km2 of area. In each plot, we searched for all the family units, we located them with GPS, and we measured the following variables: number of adults/youngs, numer of burrows, orientation, slope, number of stone blocks, percentge of small stones, percentage of forest surface, and plant species. In order to assess which of these characteristics were most important when selecting a site to establish, we measured, in the same plots, the same variables in as many randomly chosen points without marmots as marmot family units we found. Preliminar results show that the density of marmots in La Cerdanya is very high, specially in the northern site, where there are almost no valleys without marmots. We censed more than 300 family units. More than half of them (55%) were located in alpine meadows, and 17% were found in mixed sites of alpine meadow and spots of high quantity of big rocks. On average, they were installed in areas with 30% of the surface covered by small stones, and with a mean slope of 19%, but ranges are wide in all these variables. We have also stated that they mostly etablish in sothern slopes (22%), east (18%) and south-east (16%). Most probably, the high density we have found has driven the species to establish in sub-optim habitats for they fitness like, areas very close to towns or near heavily densed roads.Resum (catalan)Les marmotes que avui habiten als Pirineus provenen dels Alps. Els alliberaments de marmotes al vessant francès es van dur a terme des del 1948 fins el 1983 per alimentar les àguiles daurades i els óssos, aleshores a punt d'extingir-se, i disminuir l’atac d’aquesta rapinyaire sobre els isards. La preferència de les marmotes per les vessants solanes ha facilitat una ràpida expansió arreu del Pirineu. Des d'aleshores, la marmota ha proliferat amb tanta força als prats pirinencs que les últimes estimacions en comptabilitzen més de 10000 individus. Tot i que la presència de marmotes pot causar danys als camps d'agricultura o jardins, o ser problemàtica per la ramaderia i la maquinària agrícola, una població moderada pot ser beneficiosa per l'entorn. Les seves defecacions a dintre dels caus fertilitzen enormement el sòl, i l'activitat excavadora de les marmotes l'aireja i el remou. L'abundància de marmotes beneficia la guineu, el duc, el trencalòs i, especialment, l’àguila daurada, un dels seus principals depredadors naturals. Donada l'enorme capacitat d’expansió que ha demostrat aquesta espècie al Pirineu i al profund desconeixement que se'n té, vam considerar necessari actualitzar el coneixement de l'estat d'aquesta espècie al territori català. Durant la primavera-estiu del 2007, vam visitar nombrosos punts de La Cerdanya per censar-ne les colònies. Així, vam fer batudes en 69 quadrats d'1 km2 escollits a l'atzar, la majoria amb presència de marmota. A cada quadrat, vam buscar totes les unitats