Temporal changes in key factors and key age groups influencing the population dynamics of female red deer

1. We use structured demographic accounting to decompose the contribution t o the variance in relative population growth between 1971 and 1997 in femal e red deer on Rum, Scotland, in terms of different fitness components and a ge categories. 2. During the first 10 years (1971-80) the variance in relative population growth was small (0.00246) as the population grew from 58 to 148 having bee n culled previously. After this the relative variance in population growth increased to 0.00575 between 1981 and 1989, and increased again to 0.00848 between 1990 and 1997. 3. in the first phase of population growth (1971-80) changes in the birth r ate contributed most to the variance in relative population growth (30%), t hen adult winter survival (23%), with calf summer and calf winter survival contributing less than 10%. Birth rate tended to covary strongly with adult winter survival, and to a lesser extent with calf winter survival. 4. The contribution of birth rate to the variance in relative population gr owth diminished to less than 5% in both the periods 1981-89 and 1990-97. In contrast, the contribution of adult winter survival increased to 36% in 19 80s and 40% in 1990s. At the same time, the covariation of adult winter sur vival with calf winter survival increased successively to reach 40% in 1990 -97. 5. Changes in population age structure were small and contributed little to the variance in relative population growth (approximate to 1% over the ent ire study). In the 1970s the 5-7-year-old group contributed most (23%) to t he variance in relative population growth, though this covaried with 8-12-y ear-olds. In the 1980s the 8-12-year-olds contributed most (27%) and now th e covariation was with older animals (>12-year-olds). This pattern persiste d in the 1990s, though there was covariation with 5-7-year-olds too. 6. Birth rate, calf winter survival and adult winter survival were all dens ity-dependent. The strength of density dependence within each vital rate di d not differ between the 1970s, 1980s and 1990s; however, there were differ ences in the means of these vital rates relative to population size between the three periods. 7. The implications of temporal changes in the most important vital rates, the 'key factors', contributing to the variance in relative population grow th rate are discussed.