The Relationship Of Survivorship And Body Mass Modeled By Metabolic And Vitality Theories

Abstract

The relationship between body mass and survivorship is explained by a model that merges metabolic theory relating metabolism to body mass, and vitality theory relating survival to vitality loss and extrinsic mortality. The resulting metabolic-vitality framework hypothesizes mortality results from replicative senescence of the hematopoietic system and predator-prey interactions. Fitting the metabolic-vitality model to body mass and maximum lifespan data of 494 nonvolant mammals yields allometric relationships of body mass to the vitality parameters, from which full survivorship profiles can be predicted from body mass. Comparisons of the mass-derived vitality parameters to those estimated directly from survival data identifies how intrinsic and extrinsic mortality processes of specific populations deviate from the aggregate. Highlighted findings include a mathematical explanation for the shift from Type I to Type II survivorship curves with decreasing body mass, a quantification of the impact of hunting on wild populations and a quantification of the reduce rate of primate aging relative to the aggregate of mammal populations. Finally, the framework allows explorations of the combined effects of animal aging and predation on survival patterns.