Empirical evidence for mammals show that population dynamics depend both on individual characteristics and environmental conditions. However, because of the scarcity of long-term monitoring, individual variation and inter-annual variability of environment are seldom quantified and almost never included in demographic models. We will work on two long-term monitoring of red deer populations, to measure the impact of climate on population dynamics. Three aspects will be investigated: (1) the relationship between age survival and reproductive history of individual; we will test whether senescence is linked with previous reproductive effort, (2) the quantification of environmental variability on survival per age and sex classes, (3) the impact of environmental variability on life history evolution. The analysis of those exceptionnally long data sets will insure new insight in life history strategies of vertebrates.