Comparative biology of aging in birds: an update

The long life spans and slow aging rates of birds relative to mammals are p aradoxical in view of birds' high metabolic rates, body temperatures and bl ood glucose levels, all of which are predicted to be liabilities by current biochemical theories of aging. Available avian life-table data show that m ost birds undergo rapid to slow "gradual" senescence. Some seabird species exhibit extremely slow age-related declines in both survival and reproducti ve output, and even increase reproductive success as they get older. Slow a vian senescence is thought to be coupled evolutionarily with delayed maturi ty and low annual fecundity. Recent research in our lab and others supports the hypothesis that birds have special adaptations for preventing age-rela ted tissue damage caused by reactive oxygen species (ROS) and advanced glyc osylation endproducts, or AGEs, as well as an unusual capacity for neurogen eration in brain. Much of this work is in its early stages, however, and re liable biomarkers for comparing avian and mammalian aging need more thoroug h development. (C) 2001 Elsevier Science Inc. All rights reserved.