Nonconsumptive impacts of competitors and predators on populations dynamics: chronic social stress in pike

Friday seminar by Eric Edeline



Chronic social stress diverts energy away from growth, reproduction and immunity, and is thus a potential driver of population dynamics. However, the effects of social stress on demographic density-dependence remain largely overlooked in ecological theory. Here we combine behavioural experiments, physiology and population modelling to show in a top predator (pike Esox lucius) that social stress alone may be a primary driver of demographic density-dependence. Doubling pike density in experimental ponds under controlled prey availability did not significantly change prey intake by pike (i.e., did not significantly change interference or exploitative competition), but induced a neuroendocrine stress response reflecting a size-dependent dominance hierarchy, depressed pike energetic status and lowered pike body growth rate by 23%. Assuming fixed size-dependent survival and fecundity functions parameterized for the Windermere (UK) pike population, stress-induced smaller body size shifts age-specific survival rates and lowers age-specific fecundity, which in Leslie matrices projects into reduced population rate of increase (lambda) by 37 to 56%. Our models also predict that social stress flattens elasticity profiles of lambda to age-specific survival and fecundity, thus making population persistence more dependent on old individuals. Our results suggest that accounting for non-consumptive social stress from competitors and predators is necessary to accurately understand, predict and manage food-web dynamics.

Eric Edeline
Assistant Professor
Ecole Normale Supérieure
46 rue d'Ulm
75230 Paris cedex 05

Published Feb. 6, 2012 12:45 PM