Demographic Aging in Captive Birds and Mammals

University Of Missouri-St. Louis, Saint Louis MO

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Abstract

DESCRIPTION (provided by applicant): This project takes advantage of a unique data resource to characterize variation in rates of aging in captive populations of vertebrates (mammals, birds, and reptiles) in zoological institutions. We define rate of aging as the increase in mortality rate as a function of age, or actuarial senescence (AS). Previous analyses have shown that AS in both natural and captive populations of mammals and birds varies by nearly an order of magnitude and that mortality resulting from aging processes is generally similar in natural and zoo environments. This suggests that aging-related mortality results primarily from unique intrinsic causes of death (e.g., vascular disease, malignancies, autoimmune disease) rather than increasing vulnerability to extrinsic causes of mortality (predation, accident, contagious disease, weather-related starvation) owing to general deterioration of physiological function. Demographic patterns of aging will be compared by analyzing data in the International Species Information System (ISIS), which is the major international data base for zoological institutions. The data include age at death, reproductive history, and genealogy. We use the Weibull function to quantify actuarial senescence. Rate of AS for each species will be related to other aspects of life history, including sex, early experience (wild versus zoo born), body mass, brain mass, metabolic rate, development period, age at maturity, diet, and mortality rates in the wild. We shall additionally determine whether birds exhibit reproductive menopause and whether a trade-off exists between reproduction and aging. Ages at death will be compared among siblings and half-siblings to estimate its heritability. Medical records of zoos will be analyzed to determine how causes of death change with age. The ultimate goals of this study are to establish a comparative database for actuarial senescence in captive populations of vertebrates, to identify model organisms for further research on the physiology of aging, and to determine the feasibility of involving zoological institutions in collaborative, non-invasive research on aging.