Dynamics of a harvested moose population in a variable environment

1. Population size. calves per female, female mean age and adult sex ratio of a moose (Alces alces) population in Vefsn, northern Norway were reconstr ucted from 1967 to 1993 using cohort analysis and catch-at-age data from 96 % (6752) of all individuals harvested. 2. The dynamics of the population were influenced mainly by density-depende nt harvesting, stochastic variation in climate and intrinsic variation in t he age-structure of the female segment of the population. 3. A time delay in the assignment of hunting permits in relation to populat ion size increased fluctuations in population size. 4. Selective harvesting of calves and yearlings increased the mean age of a dult females in the population, and, because fecundity in moose is strongly age-specific, the number of calves per female concordantly increased. Howe ver. after years with high recruitment, the adult mean age decreased as lar ge cohorts entered the adult age-groups. This age-structure effect generate d cycles in the rate of recruitment to the population and fluctuations intr oduced time-lags in the population dynamics. 5. An inverse relationship between recruitment rate and population density, mediated by a density-dependent decrease in female body condition, could p otentially have constituted a regulatory mechanism in the dynamics of the p opulation, but this effect was counteracted by a density-dependent increase in the mean age of adult females. 6. Stochastic variation in winter snow depth and summer temperature had del ayed effects on recruitment rate and in turn population growth rate: appare ntly through effects on female body condition before conception.