Natural populations are persistently exposed to environmental pollution,which may adversely impact animal physiology and behaviour and even compromise survival.Responding appropriately to anystressorultimatelymight tip the scales for survival, asmistimedbehaviourandinadequatephysiological responsesmay be detrimental. Yet effects of legacy contamination on immediate physiological and behavioural stress coping abilitiesduring acute stress are virtuallyunknown. Here,we assessed these effects in barnacle goslings (Branta leucopsis) at a historical coalmine site in theArctic. For threeweekswe ledhuman-imprinted goslings, collected from nests in unpolluted areas, to feed in an abandoned coal mining area, where theywere exposed to tracemetals. As controlwe led their siblings to feed on clean grounds. After submitting both groups to threewell-established stress tests (group isolation, individual isolation, on-back restraint), control goslings behaved calmer and excreted lower levels of corticosteronemetabolites. Thus, legacy contamination may decisively change stress physiology and behaviour in long-lived vertebrates exposed at a young age. [ABSTRACT FROM AUTHOR]