The rate of ageing in a long-lived bird is not heritable

A senescent decline in performance occurs in late age in many organisms, and is thought to be partly due to additive genetic effects. Here annual fitness, estimated as the age-specific sum of survival and reproduction, was used to test for genetic variance in ageing in a population of common gulls, Larus canus. Data on 3986 individuals collected over a 34-year period indicate a dramatic senescent decline in late life. We also find that annual fitness is heritable and that individuals vary in their rates of ageing. However, counter to theoretical expectations, we find no support for a heritable component to the variance in rates of senescence. Increases in the among-individual (permanent environment) and residual variance components initiate an increase in the total phenotypic variance for annual fitness with age. This finding suggests that older birds are more sensitive to environmental effects, and that old age causes an overall pattern of declining h(2) of annual fitness. Our findings suggest that individual-specific factors do have a role in determining the rate of senescence in this population, but that additive genetic variance for the rate of senescence is either absent or small.