UW Aquatic & Fishery Sciences Quantitative Seminar
UW QERM / School of Aquatic & Fishery Sciences
The vitality model: a way to understand population survival
A model that describes survival processes in terms of vitality dependent and vitality-independent processes is used to characterize population survival of animals. The vitality independent process characterizes the rate of mortality independent of animal age or condition. The vitality-dependent processes describe mortality as the absorption of survival capacity, i.e. vitality, into a killing boundary. Trajectory of vitality to the boundary depends on its mean rate of loss, the initial distribution of vitality, and an evolving variance in vitality with age. The model provides a clear characterization of population heterogeneity through the initial and evolving heterogeneities. Using example populations we demonstrate how each process uniquely contributes to the patterns of survival. We suggest that this four-parameter characterization of survivorship provides a fundamental and powerful perspective in which to view mortality processes across all taxa.