BODY-MASS AS AN INDEX OF PHYSICAL CONDITI ON DURING WINTER IN THE ISARD, RUPICAPRA-PYRENAICA (ARTIODACYLA, BOVIDAE)

The physical condition of Isard (Rupicapra pyrenaica) during winter wa s estimated from 1984 to 1995 in two neighbouring sectors of the Pyren ees National Park on the basis of the body mass of both 152 captured i ndividuals by means of footsnares and 37 fresh and whole carcases of d ead animals. We found that the growth of isard ended at ca. 7 years ol d. The growing and the full growth animals having different energetic expenditures, these two categories were then considered separately. Th e body mass of captured isards was found not to be related to their se x or to the location. A strong linear relationship was observed for th e growing animals between their body mass and the natural log-transfor mation of their age, more than the four fifths of the variability in b ody mass can be explained by age variation (r(2) = 0,814). Kids attain a body weight half that of their maximal weight at 8 months old. Sign ificant differences in the physical condition of isards occurred betwe en the years of capture. Nevertheless, growing and full growth animals may react differently in similar weather conditions, the first catego ry being more affected by low temperatures and the second by steady sn ow on ground. Whatever the year of discovery, the carcases of dead ani mals weighted ca. 20 % less than the body mass of captured animals wit h similar age class.