Seasonal Anointment with Millipedes in a Wild Primate: A Chemical Defense Against Insects?
Members of a wild group of wedge-capped capuchin monkeys (Cebus olivaceus) intentionally anoint themselves with millipedes (Orthoporus dorsovittatus). Chemical analysis revealed these millipedes secrete two benzoquinones, compounds known to be potently repellent to insects. We argue that the secretion that rubs off on the monkeys in the course of anointment provides protection against insects, particularly mosquitoes (and the bot flies they transmit) during the rainy season. Millipede secretion is so avidly sought by the monkeys that up to four of them will share a single millipede. The anointment must also entail risks, since benzoquinones are toxic and carcinogenic. We suggest that for capuchins the immediate benefits of anointment outweigh the long-range costs.