Biology subjects

Zuberbuhler, K.

Publications and source records attributed to Zuberbuhler, K..

5 recordsLinked to original sources

bioRxiv2023

Chimpanzees and bonobos reinstate an interrupted triadic game

When humans engage in joint action, they seem to so with an underlying sense of joint commitment, a feeling of mutual obligation towards their partner and a shared goal. Whether our closest living relatives, bonobos and chimpanzees, experience and understand joint commitment in the same way is subject to debate. Crucial evidence concerns how participants respond to interruptions of joint actions, particularly if they protest or attempt to reengage their reluctant or distracted partners. During dyadic interactions, bonobos and chimpanzees appear to have some sense of joint commitment, according to recent studies. Yet, data are inconsistent for triadic games with objects. We addressed this issue by engaging N=23 apes (5 adult chimpanzees, 5 infant bonobos, 13 adult bonobos) in a "tug-of-war" game with a human experimenter who abruptly stopped playing. Adult apes readily attempted to reengage the experimenter (>60% of subjects on first trial), with no group differences in the way of reengagement. Infant bonobos rarely reengaged and never did so on their first trial. Importantly, when infants reengaged passive partners, they mostly deployed (tactile) signals, yet rarely game-related behaviours (GRBs) as commonly observed in adults. These findings might explain negative results of earlier research. Bonobos and chimpanzees may thus have motivational foundations for joint commitment, although this capacity might develop over lifetime. We discuss this finding in relation to evolutionary and developmental theories on joint commitment.

animal behavior and cognition↗

bioRxiv2022

One-trial social learning of vervet monkey alarm calling

How do non-human primates learn to use their alarm calls? Social learning is a promising candidate, but its role in the acquisition of meaning and call usage has not been studied systematically, neither during ontogeny nor in adulthood. To investigate the role of social learning in alarm call comprehension and use, we exposed groups of wild vervet monkeys to two unfamiliar animal models in the presence or absence of conspecific alarm calls. To assess the learning outcome of these experiences, we then presented the models for a second time to the same monkeys, but now without additional alarm call information. In subjects previously exposed in conjunction with alarm calls, we found heightened predator inspection compared to control subjects exposed without alarm calls, indicating one-trial social learning of meaning. Moreover, some juveniles (but not adults) produced the same alarm calls they heard during the initial exposure whereas the authenticity of the models had an additional effect. We concluded that, in non-human primates, call meaning can be acquired by one-trail social learning but that subject age and core knowledge about predators additionally moderate the acquisition of novel call-referent associations.

animal behavior and cognition↗

bioRxiv2022

Socially learned arbitrary call use in a wild primate

Human speech is an unusually flexible form of primate communication. A limited repertoire of phonemes is assembled into morphemes whose combinations are linked to referents by social learning in culturally specific ways. Non-human primate vocal utterances, in contrast, are drastically less flexible at every level, i.e., acoustic diversity, combinatoriality and referential function. Here, we were interested in whether primate vocal behaviour, despite its inflexible nature, is still amenable to social learning, a well-documented, powerful mechanism in many other aspects of primate behaviour. We provided wild vervet monkeys with social learning opportunities to operate a food dispensing apparatus by uttering specific vocalisations, move-grunts, that were contextually inappropriate. In two separate experiments, subjects witnessed how another group member produced move-grunts whilst operating a food dispenser. In experiment 1, subjects only heard playbacks of the calls, followed by food release; in experiment 2, they witnessed a complete demonstration video of conspecific including the calls, followed by food release. None of the subjects learned the task in experiment 1, but 1 of 39 subjects, a juvenile female, succeeded in experiment 2 by producing move-grunts at the food dispenser to obtain food rewards. We discuss our results and behavioural observations in relation to the current theory and its eventual implications for reconstructing the evolutionary pathway to human speech.

animal behavior and cognition↗

bioRxiv2021

Dead infant carrying by chimpanzee mothers in the Budongo Forest

It has been suggested that non-human primates can respond to deceased conspecifics in ways that suggest they experience psychological states not unlike humans, some of which could indicate they exhibit a notion of death. Here, we report long-term demographic data from two East African chimpanzee groups. During a combined 40-year observation period we recorded 191 births of which 68 died in infancy, mostly within the first year. We documented the post-mortem behaviour of the mothers and describe nine occasions where Budongo chimpanzee mothers carried infants for 1-3 days after their death, usually until the body started to decompose. We also observed three additional cases of extended carrying lasting for more than two weeks, one of which was followed by the unusual extended carrying of an object and another which lasted three months. In each case, the corpses mummified. In addition, we report four instances of recurring dead infant carrying by mothers, three of whom carried the corpse for longer during the second instance. We discuss these observations in view of functional hypotheses of dead infant carrying in primates and the potential proximate mechanisms involved in this behaviour.

animal behavior and cognition↗

bioRxiv2021

Flexibility in the social structure of male chimpanzees (Pan troglodytes schweinfurthii) in the Budongo Forest, Uganda

Individuals of social species face a trade-off between the competitive costs and social benefits of group living. Species show a range of social strategies to deal with this trade-off, for example atomistic fission-fusion dynamics in which temporary social groups of varying size and membership form and re-form; or molecular fission-fusion dynamics which contain stable sets of multilevel nested subgroups. Chimpanzees are considered an archetypical atomistic fission-fusion species, using dynamic changes in day-to-day association to moderate the costs of within-group competition. It has been argued that humans highly flexible social organisation allows us to live in extremely large groups. Using four years of association data from two neighbouring communities of East African chimpanzees (Pan troglodytes schweinfurthii), we describe new levels of flexibility in chimpanzee social organisation and confirm the presence of subgrouping in a second, large community of chimpanzees. We show that males from the larger Waibira community (N males 24-31) exhibited additional levels of semi-stable subgrouping, while males from the smaller Sonso community (N males 10-13) did not. Subgroup membership showed stability across some years, but flexibility across others. Our data support the hypothesis that chimpanzees can incorporate strategies other than fission-fusion to overcome costs of social living, and that their social organisation may be closer to that of modern humans than previously described. SIGNIFICANCE STATEMENTSocial living offers benefits and costs; groups can more easily locate and defend resources, but experience increased individual competition. Many species, or individuals, flexibly adjust their social organization when faced with different competitive pressures. It is argued that humans are unique among primates in combining multigroup social organisation with fission-fusion dynamics flexibly within and across groups, and that doing so allows us to live in extremely large groups. Using four-years of association data we show new levels of flexibility in chimpanzee social organization. Males from a typically-sized community employed atomistic fission-fusion dynamics, but males in an unusually large community incorporated additional semi-stable levels of subgrouping. Our data support the hypothesis that chimpanzee males combine social organization strategies, and that doing so may allow them, like humans, to mitigate individual costs at larger community sizes.

animal behavior and cognition↗