Biology subjects

Bosshard, T. C.

Publications and source records attributed to Bosshard, T. C..

2 recordsLinked to original sources

bioRxiv2024

Idiosyncrasy in gestural communication: a case study of hand-clapping in a Barbary macaque (Macaca sylvanus)

While it is well established that apes invent or individually learn new gestures, cases of development and use of novel gestures in monkeys are more rarely described. We report a case of a novel, idiosyncratic gesture in a Barbary macaque (Macaca sylvanus) at La Foret des Singes, Rocamadour, France. One adult male, Jomanix, was observed hand-clapping. To our knowledge, hand-clapping has never been described before in this species. To hand-clap, the male briefly shifted his weight onto his legs, lifted his upper body, and clapped both hands together. We recorded 30 instances of hand-clapping. Twenty-five of these hand-claps occurred in combination with other agonistic signals, such as lunges and open mouth threats. Recipients either responded with counter-aggression (N = 9) or a submissive response (N = 16). In five of the 30 events, the context was unclear. These observations suggest that the gesture constitutes an agonistic signal. According to the staff at La Foret des Singes, the hand-clapping may have been copied from staff members who occasionally hand-clap to shoo the animals away from areas where they were not supposed to be, but that notion remains speculative. In the meantime, another subject from the same group reportedly started to hand-clap, but the subject had passed away before we could document the behaviour. The observations show that Jomanix can flexibly combine a novel gesture with other established communicative signals. The hand-clap is goal-directed and fulfils the criteria for first-order intentional communication. This case, as well as anecdotal reports from a Tonkean macaque (Macaca tonkeana) hand-clapping to get attention, reveals greater flexibility in the gestural communication of this genus than previously assumed but also underscores that social learning of the production of communicative gestures occurs rarely in this taxon.

animal behavior and cognition↗

bioRxiv2024

Ecological risk-taking across age in Barbary macaques

When foraging, animals face decisions regarding unpredictable resources and varying predation risk, in which the cost-benefit trade-off must be assessed. Life-history theory focuses on resource allocation with regard to development and suggests there should be a variation in risk-taking propensity across age, manifested by a shift in goals from gain acquisition to loss aversion over time. Consequently, we aimed to assess age-related variation in decision-making strategies under risk in Barbary macaques (Macaca sylvanus) living at "La Foret des Singes" in Rocamadour, France. We experimentally varied the perceived risk and potential gains in a 2x2 design. The high-risk stimulus was a rubber snake; the low-risk stimulus a cube with a snakeskin pattern. The high-value food reward was a peanut; the low-value food reward a popcorn. In 2022, we presented 83 subjects with one of the four possible factor combinations, and in 2023, we presented 70 individuals with the inverted combination (e.g. snake-popcorn in 2022, cube-peanut in 2023). We took each monkeys propensity to retrieve the reward as a measure of risk-taking, and the latency to retrieve the reward as motivation to engage in the risky choice. Regardless of age, subjects generally retrieved the reward when placed next to the cube, whether peanut or popcorn, but were less likely to retrieve the reward placed next to the snake when this was popcorn rather than peanut. However, older individuals were faster than younger conspecifics to retrieve the reward when it was popcorn, whether paired with the cube or snake. Our results do not comply with the notion that risk-taking propensity declines with age, but rather suggest that in this paradigm, the animals assess the costs and benefits of a risky situation across age, and that the subjective value of a resource may change with age.

animal behavior and cognition↗