Miguel Vences was dissecting a frog no bigger than his fingernail when he smelled an unusual acrid smell. “Maybe it can be compared with vinegar,” he says. “It is a totally different smell, but somehow the same kind of bitter-burning feeling when you get it into your nose.” He remembered the distinctive scent from his experiences with other species of frogs, all of which have powerful poisons in their skins. He reasoned that the species he was cutting open – a beautiful Monte Iberia eleuth – was similarly armed with toxins. A chemical analysis of its skin confirmed Rodriguez’s suspicion. The frog’s skin was laced with toxins, including a group of muscle-paralysing poisons called pumiliotoxins that are common among poison dart frogs.