Role of immigrant males and muzzle contacts in the uptake of a novel food by wild vervet monkeys.

The entry into and uptake of information in social groups is critical for behavioral adaptation by long-lived species in rapidly changing environments. We exposed five groups of wild vervet monkeys to a novel food to investigate the innovation of processing and consuming it. We report that immigrant males innovated in two groups, and an infant innovated in one group. In two other groups, immigrant males imported the innovation from their previous groups. We compared uptake between groups with respect to the initial innovator to examine the extent to which dispersing males could introduce an innovation into groups. Uptake of the novel food was faster in groups where immigrant males ate first rather than the infants. Younger individuals were more likely overall, and faster, to subsequently acquire the novel food. We also investigated the role of muzzle contact behavior in information seeking around the novel food. Muzzle contacts decreased in frequency over repeated exposures to the novel food. Muzzle contacts were initiated the most by naïve individuals, high rankers, and juveniles; and were targeted most towards knowledgeable individuals and high rankers, and the least towards infants. We highlight the potential importance of dispersers in rapidly exploiting novel resources among populations.

Raw-material selectivity in hook-tool-crafting New Caledonian crows.

Animals that manufacture foraging tools face the challenge of identifying suitable raw materials among a multitude of options. New Caledonian crows exhibit strong population-specific material preferences for the manufacture of hooked stick tools, but it is unknown how they identify their favourite plants. We investigated experimentally whether crows pay attention to the stems of plants (from which the tools are made) and/or their leaves (which are usually discarded during manufacture but may enable rapid and reliable species identification at a distance). Subjects were highly selective in choice trials with multiple plant species. Two additional treatments with experimental leaf-stem combinations revealed that birds can identify their preferred plant species by its stems alone, and possibly also its leaves. These findings encourage future experiments that investigate whether New Caledonian crows attend to features of the stem that are required for the production of efficient hooked stick tools. Our study provides one of the most detailed assessments to date of how non-human animals identify raw materials for tool manufacture.