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Abstract: Primates understand the meaning of their own and other species' alarm calls, but little is known about how they acquire such knowledge. Here, we combined direct behavioural observations with playback experiments to investigate two key processes underlying vocal development: comprehension and usage. Especifically, we studied the development of con- and heterospecific alarm call recognition in free-ranging sooty mangabeys, Cercocebus atys, across three age groups: young juveniles (1-2y), old juveniles (3-4y) and adults (> 5y). We observed that, during natural predator encounters, juveniles alarm called to a significantly wider range of species than adults, with evidence of refinement during the first four years of life. In the experiments, we exposed subjects to leopard, eagle and snake alarm calls given by other group members or sympatric Diana monkeys. We found that young juveniles' locomotor and vocal responses were least appropriate and that they engaged in more social referencing (look at adults when hearing an alarm call) than older individuals, suggesting that vocal competence is obtained via social learning. In conclusion, our results suggest that alarm call comprehension is socially learned during the juvenile stage, with comprehension preceding appropriate usage but no difference between learning their own or other species' alarm calls. Significance statement: Under natural conditions, animals do not just interact with members of their own species, but usually operate in a network of associated species. However, ontogenetic research on primate communication frequently ignores this significant element. We studied the development of con- and heterospecific alarm call recognition in wild sooty mangabeys. We found that communicative competence was acquired during the juvenile stages, with alarm call comprehension learning preceding appropriate vocal usage and with no clear difference in learning of con- and heterospecific signals. We also found that, during early stages of life, social referencing, a proactive form of social learning, was key in the acquisition of competent alarm call behaviour. Our results show that primates equally learn to interpret alarm calls from their own and other species during their early stages of life and that this learning process is refined as the animals mature. Supplementary Information: The online version contains supplementary material available at 10.1007/s00265-023-03318-6.

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Protest in response to unequal reward distribution is thought to have played a central role in the evolution of human cooperation. Some animals refuse food and become demotivated when rewarded more poorly than a conspecific, and this has been taken as evidence that non-human animals, like humans, protest in the face of inequity. An alternative explanation-social disappointment-shifts the cause of this discontent away from the unequal reward, to the human experimenter who could-but elects not to-treat the subject well. This study investigates whether social disappointment could explain frustration behaviour in long-tailed macaques, Macaca fascicularis. We tested 12 monkeys in a novel 'inequity aversion' paradigm. Subjects had to pull a lever and were rewarded with low-value food; in half of the trials, a partner worked alongside the subjects receiving high-value food. Rewards were distributed either by a human or a machine. In line with the social disappointment hypothesis, monkeys rewarded by the human refused food more often than monkeys rewarded by the machine. Our study extends previous findings in chimpanzees and suggests that social disappointment plus social facilitation or food competition effects drive food refusal patterns.

RESUMEN

How do animals learn to classify the world and what is the role of social learning during this process? Here, we show that young sooty mangabeys, Cercocebus atys, of Taï Forest, Côte d'Ivoire, learn to rapidly classify an unfamiliar predator by attending to others' alarm calls and that such knowledge is retained over long periods. We experimentally exposed subjects to chimeric predator models with both snake- and leopard-like features, combined with playbacks of conspecific snake (N = 12) or leopard alarms (N = 13). Adults classified the chimeras as non-threatening but for juveniles, we found that one single alarm call exposure was sufficient to allocate the chimera to the snake or leopard category, suggesting plausibility judgments in experienced adults. We then retested N = 10 juveniles with the same models more than a year after their first experience and found that they continued to show their original response, indicating long-term retention of socially learned predator categorisation.

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The understanding that the perceptual appearance of the environment can differ in several ways from the reality underlies the ability to discriminate appearance from reality. Being able to realize when a misperception can lead us to behave in inappropriate ways confers an evolutionary advantage and may be a prerequisite to develop a Theory of Mind. Understanding that our own perception can differ from reality seems indeed necessary to attribute to others perceptions or beliefs different than ours. This appearance-reality discrimination ability has recently been demonstrated in great apes but no information is currently available regarding this ability in other nonhuman species. In a comparative study, we tested Tonkean macaques (Macaca tonkeana), an Old World primate species, and brown capuchins (Sapajus apella), a New World primate species. We provided monkeys with two experiments using visual illusions of size and quantity to test their ability to discriminate appearance from reality, with an experimental setup similar to the one developed by Krachun et al. (2016) on chimpanzees. A large number of brown capuchins, from different ages and both sexes, as well as two Tonkean macaques succeeded in the two experiments. By ruling out all alternative explanations (i.e. visual tracking or associative learning), our study brings the first evidence that some Old World and New World monkeys are able to discriminate appearance from reality. Our results suggest moving the evolutionary apparition of this cognitive ability earlier in time. Finally, it suggests that humans could share more Theory of Mind components with more nonhuman species than we previously thought.

Asunto(s)

Ilusiones , Pan troglodytes , Animales , Cebus , Femenino , Haplorrinos , Masculino , Desempeño Psicomotor

RESUMEN

Lytic transglycosylases (Lts) are involved in recycling, cell division, and metabolism of the peptidoglycan. They have been understudied for their usefulness as potential antibacterial targets due to their high redundancy in Gram-negative bacteria. Bulgecin A is an O-sulphonated glycopeptide that targets primarily soluble lytic tranglycosylases (Slt). It has been shown that bulgecin A increases the efficacy of ß-lactams that target penicillin bindings proteins (PBPs). Here, we present the high-resolution crystal structure of LtgA from Neisseria meningitidis strain MC58, a membrane bound homolog of Escherichia coli Slt, in complex with bulgecin A. The LtgA-bulgecin A complex reveals the mechanism of inhibition by bulgecin A at near atomic resolution. We further demonstrate that bulgecin A is not only a potent inhibitor of LtgA, but most importantly, it restores the efficacy of ß-lactam antibiotics in strains of N. meningitidis and Neisseria gonorrhoeae that have reduced susceptibility to ß-lactams. This is particularly relevant for N. gonorrhoeae where no vaccines are available. This work illustrates how best to target dangerous pathogens using a multiple drug target approach, a new and alternative approach to fighting antibiotic resistance.