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Zuberbühler, Klaus

Nom
Zuberbühler, Klaus
Affiliation principale
Fonction
Professeur ordinaire
Email
klaus.zuberbuehler@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/670
_
0000-0001-8378-088X

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  • Publication
    Accès libre
    Single Aggressive Interactions Increase Urinary Glucocorticoid Levels in Wild Male Chimpanzees
    (2015)
    Wittig, Roman M.
    ;
    Crockford, Catherine
    ;
    Weltring, Anja
    ;
    Deschner, Tobias
    ;
    Zuberbühler, Klaus 
    A basic premise in behavioural ecology is the cost-benefit arithmetic, which determines both behavioural decisions and evolutionary processes. Aggressive interactions can be costly on an energetic level, demanding increased energy or causing injuries, and on a psychological level, in the form of increased anxiety and damaged relationships between opponents. Here we used urinary glucocorticoid (uGC) levels to assess the costs of aggression in wild chimpanzees of Budongo Forest, Uganda. We collected 169 urine samples from nine adult male chimpanzees following 14 aggressive interactions (test condition) and 10 resting events (control condition). Subjects showed significantly higher uGC levels after single aggressive interactions compared to control conditions, likely for aggressors as well as victims. Higher ranking males had greater increases of uGC levels after aggression than lower ranking males. In contrast, uGC levels showed no significant change in relation to aggression length or intensity, indicating that psychological factors might have played a larger role than mere energetic expenditure. We concluded that aggressive behaviour is costly for both aggressors and victims and that costs seem poorly explained by energetic demands of the interaction. Our findings are relevant for studies of post-conflict interactions, since we provide evidence that both aggressors and victims experience a stress response to conflict.
  • Publication
    Accès libre
    An intentional vocalization draws others' attention: A playback experiment with wild chimpanzees
    (2015)
    Crockford, Catherine
    ;
    Wittig, Roman M.
    ;
    Zuberbühler, Klaus 
    A vital step in the evolution of language is likely to have been when signalers explicitly intended to direct recipients' attention to external objects with the use of referential signals. Although animal signals can direct the attention of others to external events, such as in monkey predator alarm calls, there is little evidence that this is the result of an intention to inform the recipient. Two recent studies, however, indicate that the production of chimpanzee quiet alarm calls, given to snakes, complies with some standard behavioral markers of intentional signaling, such as gaze alternation. But it is currently unknown whether the calls alone direct receivers' attention to the threat. To address this, we carried out a playback experiment with free-ranging chimpanzees in Budongo Forest, Uganda, using a within-subjects design. From a hidden speaker, we broadcast either quiet alarm 'hoos' ('alert hoos') or acoustically distinguishable hoos produced while resting ('rest hoos') and found a significant increase in search behavior after 'alert' compared with 'rest' hoos, with subjects monitoring either the call provider or the area near the call provider. In sum, chimpanzee 'alert hoos' represent a plausible case of an intentionally produced animal vocalization (other studies) that refers recipients to signalers and/or to an external event (this study).
  • Publication
    Accès libre
    Triadic social interactions operate across time: a field experiment with wild chimpanzees
    (2014)
    Wittig, Roman M.
    ;
    Crockford, Catherine
    ;
    Langergraber, Kevin E.
    ;
    Zuberbühler, Klaus 
    Social animals cooperate with bonding partners to outcompete others. Predicting a competitor's supporter is likely to be beneficial, regardless of whether the supporting relationship is stable or transient, or whether the support happens immediately or later. Although humans make such predictions frequently, it is unclear to what extent animals have the cognitive abilities to recognize others' transient bond partners and to predict others' coalitions that extend beyond the immediate present. We conducted playback experiments with wild chimpanzees to test this. About 2 h after fighting, subjects heard recordings of aggressive barks of a bystander, who was or was not a bond partner of the former opponent. Subjects looked longer and moved away more often from barks of the former opponents' bond partners than non-bond partners. In an additional experiment, subjects moved away more from barks than socially benign calls of the same bond partner. These effects were present despite differences in genetic relatedness and considerable time delays between the two events. Chimpanzees, it appears, integrate memories of social interactions from different sources to make inferences about current interactions. This ability is crucial for connecting triadic social interactions across time, a requirement for predicting aggressive support even after a time delay.
  • Publication
    Accès libre
    Urinary oxytocin and social bonding in related and unrelated wild chimpanzees
    (2013)
    Crockford, Catherine
    ;
    Wittig, Roman M.
    ;
    Langergraber, Kevin E.
    ;
    Ziegler, T. E.
    ;
    Zuberbühler, Klaus 
    ;
    Deschner, Tobias
    Animals that maintain cooperative relationships show gains in longevity and offspring survival. However, little is known about the cognitive or hormonal mechanisms involved in cooperation. Indeed, there is little support for a main hypothesis that non-human animals have the cognitive capacities required for bookkeeping of cooperative exchanges. We tested an alternative hypothesis that cooperative relationships are facilitated by an endocrinological mechanism involving oxytocin, a hormone required for bonding in parental and sexual relationships across mammals. We measured urinary oxytocin after single bouts of grooming in wild chimpanzees. Oxytocin levels were higher after grooming with bond partners compared with non-bond partners or after no grooming, regardless of genetic relatedness or sexual interest. We ruled out other possible confounds, such as grooming duration, grooming direction or sampling regime issues, indicating that changes in oxytocin levels were mediated by social bond strength. Oxytocin, which is thought to act directly on neural reward and social memory systems, is likely to play a key role in keeping track of social interactions with multiple individuals over time. The evolutionary linkage of an ancestral hormonal system with complex social cognition may be the primary mechanism through which long-term cooperative relationships develop between both kin and non-kin in mammals.
  • Publication
    Accès libre
    Generation times in wild chimpanzees and gorillas suggest earlier divergence times in great ape and human evolution
    (2012)
    Langergraber, Kevin E.
    ;
    Pruefer, Kay
    ;
    Rowney, Carolyn
    ;
    Boesch, Christophe
    ;
    Crockford, Catherine
    ;
    Fawcett, Katie
    ;
    Inoue, Eiji
    ;
    Inoue-Muruyama, Miho
    ;
    Mitani, John C. C.
    ;
    Muller, Martin N. N.
    ;
    Robbins, Martha M.
    ;
    Schubert, Grit
    ;
    Stoinski, Tara S.
    ;
    Viola, Bence
    ;
    Watts, David P.
    ;
    Wittig, Roman M.
    ;
    Wrangham, Richard W.
    ;
    Zuberbühler, Klaus 
    ;
    Paeaebo, Svante
    ;
    Vigilant, Linda
    Fossils and molecular data are two independent sources of information that should in principle provide consistent inferences of when evolutionary lineages diverged. Here we use an alternative approach to genetic inference of species split times in recent human and ape evolution that is independent of the fossil record. We first use genetic parentage information on a large number of wild chimpanzees and mountain gorillas to directly infer their average generation times. We then compare these generation time estimates with those of humans and apply recent estimates of the human mutation rate per generation to derive estimates of split times of great apes and humans that are independent of fossil calibration. We date the human-chimpanzee split to at least 7-8 million years and the population split between Neanderthals and modern humans to 400,000-800,000 y ago. This suggests that molecular divergence dates may not be in conflict with the attribution of 6- to 7-million-y-old fossils to the human lineage and 400,000-y-old fossils to the Neanderthal lineage.