Age-related variation and temporal patterns in the survival of a long-lived scavenger
Résumé
Although senescence has been described for various fi tness components in a wide range of animal species, few studies havestudied senescence in long-lived species, and little is known about its interactions with varying environmental conditions.Using a 32 year capture – mark – recapture dataset on the griff on vulture Gyps fulvus , we examined the demographic patternsof actuarial senescence and the patterns of year-to-year variation in survival rates. We found a signifi cant, surprisingly late,decrease of annual survival probabilities from the age of 28 years onward and divided individual lifetimes into to threecategories (juvenile, mid-age and senescent birds). In agreement with the environmental canalization hypothesis, our analysesuncovered 1) higher temporal variation of annual survival probabilities in both the juvenile and senescent age classescompared to the mid-age class and 2) low sensitivity of the population growth rate to the survival of both the juvenile andsenescent age classes. Our results further suggested that the temporal variation in the survival of senescent birds might berelated to intra-annual changes in air temperature amplitudes. Finally, using population dynamics modeling, we revealedcontrasting eff ects of the inclusion of the senescent age class on predicted population growth, depending on how survivalrates were modeled. Altogether, our results demonstrate the existence of a class of senescent birds that exhibit distinctdemographic properties compared to juvenile and mid-age classes.