title: Body downsizing caused by non-consumptive social stress severely depresses population growth rate.
abstract: 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 per cent. 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 37-56%. 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.
authors.affiliation: UPMC-Paris 6, UMR (CNRS) 7618, Laboratoire Biogéochimie et Ecologie des Milieux Continentaux, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris cedex 05, France. edeline@biologie.ens.fr
authors.forename: Eric
authors.initials: E
authors.lastname: Edeline
authors.forename: Thrond O
authors.initials: TO
authors.lastname: Haugen
authors.forename: Finn-Arne
authors.initials: FA
authors.lastname: Weltzien
authors.forename: David
authors.initials: D
authors.lastname: Claessen
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Winfield
authors.forename: Nils Chr
authors.initials: NC
authors.lastname: Stenseth
authors.forename: L Asbjørn
authors.initials: LA
authors.lastname: Vøllestad
mesh_terms: D000818:Animals; D049628:Body Size / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D017859:Esocidae / Q000097:blood / Q000254:growth & development / Q000502:physiology*; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D016014:Linear Models; D008099:Liver / Q000502:physiology; D008297:Male; D008954:Models, Biological; D009929:Organ Size / Q000502:physiology; D011158:Population Growth; D011235:Predatory Behavior / Q000502:physiology*; D013315:Stress, Psychological / Q000503:physiopathology*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D014284:Triiodothyronine; D013974:Thyroxine; D006854:Hydrocortisone