Interannual Variation in Timing and Synchrony of Parturition in Dall's Sheep

Timing and synchrony of parturition in Dall's sheep (Ovis dalli) were studied in Igloo Mountain, Denali National Park and Preserve, Alaska, from April through July 1988 and 1989. Median ±SD dates of birth were 18 May (±5.1 days) in 1988 and 27 May (±8.8 days) in 1989. Ninety percent of births occurred in a 27-day period in 1988 and in a 36-day period in 1989; interannual variation in timing and synchrony of parturition was pronounced. Mortality of young in this predator-rich environment, however, did not differ between years, suggesting climatic variability may contribute more than predation in constraining timing and synchrony of parturition in Dall's sheep.