Evidence for semantic communication in titi monkey alarm calls

► Black-fronted titi monkeys produce acoustically distinct calls to predators. ► Alarm calls are untypically quiet, high-pitched & morphologically simple. ► Monkeys respond to playbacks of different calls in predator-specific, adaptive ways. ► Neotropical primates are critical for evolutionary theories of communication. ► Call morphology is evolutionarily more variable than call use or perception.