Abstract
Abstract
The demographic buffering hypothesis builds on life history theory to propose that the vital rates most essential for population persistence will be protected against environmental variability. As a result, species with slow life histories, characterized by long lives and low fertility, are expected to exhibit reduced variation in adult survival, while species with fast life histories, characterized by short lifespans and high fertility, are expected to exhibit reduced variation in juvenile survival and/or fertility. Here, we compared mortality patterns in juveniles and adults across 372 mammalian species to test whether the variation within mammalian families conformed to the predictions of the demographic buffering hypothesis. As predicted, we found that slow-lived species exhibit less variation in adult baseline mortality and aging rates. However, fast-lived species did not show systematically reduced variation in juvenile mortality components relative to slow species. Combined, our findings provide qualified support for the demographic buffering hypothesis in mammals, with stronger evidence for buffering in the later stages of life than at its outset.