BIOLOGY OF TWINNING AND ORIGIN OF AN UNUSUALLY HIGH TWINNING RATE IN AN INSULAR MOUFLON POPULATION

Twins have rarely been reported from wild populations of European mouf lons (Ovis ammon musimon), and this subspecies is commonly regarded as monotocous. During the winter of 1994, we autopsied 71 pregnant femal es in a population established on Ile Haute, a small island of the sub antarctic Kerguelen archipelago. Though pregnant yearlings always bore single fetuses, the twinning rate reached 36% among pregnant adult fe males. The study population was founded by two individuals, originatin g from the Vincennes Zoo (France). Our analysis of the birth registers revealed that multiple births were common in this zoo herd, and a fou nding effect may explain the high twinning rate observed during this s tudy. Crossings with sheep (O. ammon f. aries) and oriental mouflons ( O. ammon orientalis) during the recent history of the mouflon in conti nental Europe are probably responsible for the occurrence of twinning in the Kerguelen population, as well as in some captive mouflon popula tions.