Reproductive behavior and related social organization of the muskox on Nunivak Island

Abstract

The sexual behavior and social organization of the muskox (Ovibos moschatus wardi Zimmerman) were studied on Nunivak Island, Alaska, in fall 1972 and summer and fall 1973. Observation effort was concentrated on a single harem group for two months, during the height of courtship activity. Movements and fluctuations in the structure of this group are documented. There was no significant change in mean herd size as a result of the rut, suggesting the existence of a basic social unit independent of the influence of harem bulls. Harem bulls were in the 6-10 year age class. They exerted a stabilizing influence on the harem but did not direct its movements. The rut extended from early July to mid-October. Copulation occurred on September 4 and 5. General patterns of sexual and agonistic behavior are described. Changes in activity patterns as a result of the rut are shown. Bulls displayed more marked changes than cows or juveniles. The proportion of time allocated to sexual and agonistic behavior increased at the expense of maintenance activity as the rut progressed.