The contribution of longevity to population death rates

The magnitude of a population's per capita death rate depends on the maximum age at death and the intensity or schedule of mortality of its members. Knowing the maximum possible lifespan that an animal can achieve when raised under defined conditions makes it possible to calculate the component of per capita death rate due to longevity alone. This component is most important to slow-growing populations of animals with relatively short lifespans. Life-table experiments with two rotifer species and a cladoceran indicate that the short lifespans of these animals account for moderate proportions (up to 37.2%) of their population death rates. Decomposing per capita death rates into two components, one due to maximum length of life and another due to differential mortality of animals of different ages, may therefore be a useful way to examine how deleterious processes, such as predation and starvation, limit growth of zooplankton populations.