The Evolution of Avian Senescence Patterns: Implications for Understanding Primary Aging Processes

SYNOPSIS. The long life spans of birds relative to those ofmammals are intriguing to biogerontologists, particularly inlight of birds' high body temperatures, high blood glucose levels,and high metabolic rates—all of which should theoreticallyincrease their biochemical liability for rapid aging. The comparativelongevity of birds and other flying homeotherms is consistentwith evolutionary senescence theory, which posits that specieswith low mortality rates from predation or accident will bereleased from selection for rapid maturity and early reproduction,and will exhibit retarded aging. Comparative analyses of avianlife history parameters to date, although not as extensive asthose for mammals, broadly support an association between lowmortality rates, slow reproduction, and long lifespan. The diversityof bird life histories suggests the importance of developinga diversity of avian models for studies of aging mechanisms,both proximate and ultimate, and for using wild as well as domesticrepresentatives. Birds studied in the laboratory thus far showmany of the same manifestations of aging as mammals, includinghumans, and many ornithologists are beginning to document actuarialevidence consistent with aging in their study populations. Weencourage greater communication and collaboration among comparativegerontologists and ornithologists, in the hope that the studyof aging in birds will lead to an integrated understanding ofphysiological aging processes well grounded in an evolutionaryparadigm.