Monkey as seed dispersers of Neotropical <i>Vanilla</i> involves social learning

Social learning comprises the processes by which individuals acquire new information about environment and behaviour through observation and interaction with their parents and members of their community. In the orchid genus Vanilla, seed dispersal is mediated by vertebrates. Although primates have never been observed consuming vanilla pods under experimental conditions, monkeys have been proposed as possible seed dispersers of Vanilla in Central Brazil. Here, I investigate mechanisms involved in the attraction and rewarding of seed dispersers of a Neotropical Vanilla based on field observations, morpho-anatomy of fruits and seeds, analysis of fragrances, reward substances, and examination of seed viability through the digestive tract. In addition, an experiment has been conducted to examine whether fruit consumption in Vanilla may involve some kind of social learning. Dehiscent fruits of V. pompona are consumed by mammals: monkeys, rats, and marsupials. Besides providing nutritive rewards in the placenta and funiculus, the fruit wall is rich in calcium oxalate crystals, which are toxic to mammals. Consequently, seed dispersers access the fruit cavity through the fruit valves. While primates are the main seed dispersers in natural populations, no monkeys consume fruits outside the Vanilla habitat. Vanilla fruits are consumed by both diurnal and nocturnal mammals, evidencing the importance of both visual and olfactory cues in the attraction of seed dispersers. Unrecognized or harmful fruits seem to be a poor choice for consumption in resource-rich environments. Monkeys require a period of resource scarcity to be stimulated and learn how to safely consume Vanilla fruits. After incorporating such fruits into the diet of knowledgeable individuals, the information is transmitted to naïve individuals through social learning. This is the first study to describe monkeys as seed dispersers in orchids.