|Research Focus Two stressors are far deadlier than one

Natural organisms often face a barrage of stressors, both natural and human induced. Two known stressors that impact amphibian populations are pesticides and predators. Recent work by Relyea and by Mills and Relyea reveals strikingly strong, synergistic negative effects of these two factors on amphibian larvae. Add-ing predation risk on top of supposedly sublethal con-centrations of a common pesticide caused a massive increase in larval mortality. Interestingly, the increased mortality did not require exposure to actual predation. That is, simply the ‘smell of danger ’ (predator chemical cues) caused 80–90 % of larvae that were held in other-wise ‘safe ’ levels of the pesticide to die. Notably, this effect occurred in some species, but not in others. These new studies highlight the need for furthe