Bande, N. | Search bioRxiv

bioRxiv2025

Living with urban fear: vervet monkey response to an evolutionarily new predator

Humans have facilitated contacts between prey and predator species that have originally not co-evolved, reshuffling the prey-predator arms race. How do prey cope with an evolutionarily new predation risk? We tracked three vervet monkey troops in a South-African semi-urban habitat for 14 months to study their response to domestic dogs. We show that monkeys responded to dogs with a two-pronged behaviour: they emitted alarm calls, and became more vigilant and displayed aggressive behaviours towards the dogs. While their movement highlighted risk-prone behaviour, they appeared to have mapped and planned for risk, as they reacted more strongly when risk was unexpected. The response intensity was further modulated by risk labels typically encountered in their natural environment, but not by labels uniquely associated with dogs. This highlights that vervet monkeys responded with ingrained behaviour to this evolutionarily new threat, anticipating risk based on long-term spatial memory, but failed to integrate evolutionarily new information. TeaserVervet monkeys fear domestic dogs but fail to adjust their antipredator response by discriminating evolutionarily new risk labels.

animal behavior and cognition↗

bioRxiv2025

Rule-based sequences in sooty mangabey vocal communication

Investigating how non-human animals produce call sequences provides key insights into the evolutionary origins of meaning in vocal communication, including syntax. Many species combine calls into structured sequences, often following specific rules, yet most studies focus on only a few sequences per species. This limits our understanding of their ability to combine calls and convey meaning through sequences. Our study addresses this gap by documenting the vocal sequence repertoire and underlying rules of sooty mangabeys (Cercocebus atys), a West African monkey species. We collected and analysed 1,672 recordings from two wild groups in the Tai National Park, Ivory Coast. Sooty mangabeys frequently combine calls but rely on a limited set of sequences. Within these, we identified rules of call ordering, recurrence and hierarchical structuring. Notably, they produced hierarchically structured sequences using only two call types, a previously unreported system in animal communication. Our findings suggest that sooty mangabeys use both structured and unstructured sequences, likely encoding different types of information. While context of production remains essential for determining meaning, our results highlight how a whole-repertoire approach reveals the full range of rule-based sequences and their potential for meaning expansion beyond the number of individual calls available in the repertoire.

animal behavior and cognition↗