Animals embedded in food webs must generally balance two simultaneous co-evolutionary arms races, with their resource and natural enemy species. Venomous animals may use venom components to mediate both arms races. To evaluate this hypothesis, we investigated rapid changes in scorpion venom composition by manipulating experimental scorpions’ exposure to a surrogate vertebrate predator, and providing either live or dead prey. After six weeks scorpions exposed to the surrogate predators exhibited significantly different venom chemical compositions compared to naïve scorpions. In contrast, reducing the need for venom use by providing dead, rather than live prey did not lead to changes in venom composition. The observed rapid changes in venom composition in response to increased predator exposure may increase the stability of food webs and suggest that arms races within food webs should not be viewed in isolation.