The effect of spatial heterogeneity within the habitat on the mean life time of a population is studied by an individual-based simulation model using lizards (Lacerta agilis) as an example. We divide the habitat into zones of different mortatity. of the individuals under different environmental conditions (e.g. weather). Our results demonstrate that habitat zones which are suboptimal for an individual may be important for the survival of the population as a whole. Sometimes even a reduction of the preferred habitat zone may increase the mean life time of the population due to spreading of risk. We show that the effect of the spatial heterogeneity on the mean life time is species specific. It depends on the strategy used by the individuals to select a home range within the habitat. Thus, knowledge about this strategy is necessary to estimate the effect of. within-habitat heterogeneity on the extinction risk of a population.