Trophic utilization of a montane/subalpine forest by chamois (Rupicapra pyrenaica) in the Central Pyrenees

Abstract

We have determined the annual variations in the diet of a dense chamois population inhabiting the northern face of the Arazas Canyon (679 ha), in the Ordesa National Park (Spanish Pyrenees), in order to assess the trophic relationship between chamois and forest. Altitudes range between 1050 and 2200 m. Excluding rock, woodland occupies 81% of the trophically useful surface for chamois, and open habitats (forest clearings, pastures, screes, gullies, avalanche corridors and subalpine shrubland) occupy 19%. Woodland is made up of a mixed forest of Pinus sylvestris, Fagus sylvatica and Abies alba at middl heights, and by a P. uncinata forest in the subalpine belt. Feeding regime was estimated by means of micrographic analysis of faeces. The three most important species in the diet were Festuca rubra, Sesleria coerulea and Pinus sylvestris. These three accounted for 50% of the fragments identified in the faeces for the annual average. Although the proportion of the two grass species was fairly constant throughout the year, the proportion of P. sylvestris varied greatly, reaching a maximum value in winter (39%) and a minimum value in the summer (1%). The percentage of browse increased in the winter, coinciding with the altitudinal descent of the population. The opposite tendency was observed in the forb percentage. The results coincided with those attained from other populations in the Alps. Despite their capability for living in forestal habitats and incorporating a relatively high proportion of browse into their diet, chamois seem to prefer open habitats where, presumably, more digestible food can be obtained.