ON THE REPRODUCTIVE-PERFORMANCE OF THE FR EE-RANGING ALPINE IBEX POPULATION (CAPRA I IBEX L) AT ALBRIS (GRISONS, SWITZERLAND)

In order to evaluate the reproductive performance of alpine ibex (Capr a i. ibex L.), the uteri and ovaries of 80 females were investigated. The animals came from the colony at Albris (Grisons, Switzerland) and samples were collected during the months December to June in 1989-1990 and 1990-1991. The females conceived between December 1 and january 2 1. The earliest age of females to conceive was 2 years with a concept ion rate of 0.13. Conception rate in 3 year old females was 0.56 and o f 4 year old females 1.00. Gravidity rate amounted to 0.88. For 70 fem ales older than 2 years 48 viable embryos could be determined (fecundi ty rate = 0.69). For the-age class 4-13 years fecundity rate equalled 0.83. At 14 years of age a probably age dependent decrease of fecundit y was observed (fecundity rate of females 14-16 years old = 0.40). Amo ng 59 mature females 48 viable embryos were found (natality 0.81) and fertility was 0.25. Twins were observed in only 1 out of 52 cases inve stigated. The reproductive performance detected in this study clearly surpasses the one previously described for this population, which is a pproaching the carrying capacity of its habitat.