Arianna De Marco

Fondazione Ethoikos

Reintroduction of separated individuals into their social group is a major problem in the management of captive group of non-human primates. Here we report a case in captive Tonkean macaques in which a female infant was abandoned by her mother after birth, then removed, hand-reared, and reintroduced after weaning to her original group in several st...

The ‘social complexity hypothesis for communicative complexity’ posits that living in a complex social system requires complex communication skills. Since the complexity of a system can be measured by the amount of uncertainty it produces, we tested this hypothesis by studying species of macaque that differ in social tolerance and uncertainty of so...

It was long assumed that only humans can distinguish the living from the dead. Renewed interest in this question over the last decade has led several authors to assert that non-human primates are also aware of death. We investigate this issue by comparing the behaviours of monkeys and great apes toward helpless conspecifics, basing our analysis on...

While there is no consensus about the definition of complexity, it is widely accepted that the ability to produce uncertainty is the most prominent characteristic of complex systems. We introduce new metrics that purport to quantify the complexity of living organisms and social organizations based on their levels of uncertainty. We consider three m...

Decision outcomes in unpredictable environments may not have exact known probabilities. Yet the predictability level of outcomes matters in decisions, and animals, including humans, generally avoid ambiguous options. Managing ambiguity may be more challenging and requires stronger cognitive skills than decision-making under risk, where decisions in...

The observation of specific reactions by animals to dead conspecifics raises questions about their capacity to understand death. We describe the behavior of a captive group of tufted capuchins in the hours following the death of an adult female. The behavior of 12 subjects was recorded over a 5-h period. Most group members displayed exploratory beh...

We tested the social complexity hypothesis which posits that animals living in complex social environments should use complex communication systems. We focused on two components of vocal complexity: diversity (number of categories of calls) and flexibility (degree of gradation between categories of calls). We compared the acoustic structure of voca...

Many studies investigate the decisions made by animals by focusing on their attitudes toward risk, that is, risk-seeking, risk neutrality, or risk aversion. However, little attention has been paid to the extent to which individuals understand the different odds of outcomes. In a previous gambling task involving 18 different lotteries (Pelé, Broihan...

Observations of animals’ responses to dying or dead companions raise questions about their awareness of states of helplessness or death of other individuals. In this context, we report the case of a female Tonkean macaque (Macaca tonkeana) that transported the body of her dead infant for 25 days and cannibalized its mummified parts. The mother appe...

Among nonhuman primates, the evolutionary underpinnings of variation in social structure remain debated, with both ancestral relationships and adaptation to current conditions hypothesized to play determining roles. Here we assess whether interspecific variation in higher-order aspects of female macaque (genus: Macaca) dominance and grooming social...

Contemporary evolutionary theories propose that living in groups drives the selection of enhanced cognitive skills to face competition and facilitate cooperation between individuals. Being able to coordinate both in space and time with others and make strategic decisions are essential skills for cooperating within groups. Social tolerance and an eg...

Does the social system have an impact on the acoustic production? We compare the tonal vocalizations of Tonkean macaques and rhesus macaques, and found a higher vocal variability and vocal repertoire for the tolerant species (Macaca tonkeana) compared to the intolerant species.

The theory of sexual selection predicts that females should be discriminatory in the choice of sexual partners. Females can express their choice in two ways. In direct mate choice, they show preferences for certain partners. In indirect mate choice, they select partners by displaying sexually attractive traits, thus eliciting contest competition be...

In several primate species, males regularly interact through ritualized exchanges known as greetings. Such interactions have mainly been reported in baboons and several species of macaques. Greetings involve various affiliative submissive signals, and can include grasps and mounts. Baboon greetings are rather tense and have a strong dominance compo...

The adolescent growth spurt in primates is defined as the temporal acceleration in the rate of growth in height and weight that occurs around the time of reproductive maturation. Whereas to date there is no evidence for the presence of human-like adolescent growth spurt in linear dimensions of nonhuman primate species, pubertal growth spurts have b...

The level of glucocorticoids, especially if obtained from noninvasive sampling, can be used as an index of animal well-being, allowing evaluation of the animal’s response to environmental modifications. Despite evidence that these hormones play a relevant role in energy metabolism regulation in perceived or real stress events, little is known regar...

The level of glucocorticoids, especially if obtained from noninvasive sampling, can be used as an index of animal well-being, allowing evaluation of the animal’s response to environmental modifications. Despite evidence that these hormones play a relevant role in energy metabolism regulation in perceived or real stress events, little is known regar...

The social intelligence hypothesis suggests that an increase in social complexity drove the evolution of cognitive flexibility in primates. Here we aimed at testing whether social tolerance, used as a proxy of social complexity, might have shaped cognitive skills. Using the Primate Cognition Test Battery, we tested 39 subjects from 4 different maca...

Whereas most experiments indicate that monkeys have no theory of mind, a study carried out by Wood and collaborators (2007) claimed that they can make inferences about the intentions of another individual. We applied the experimental procedure devised by these authors to investigate whether monkeys can recognize goal-directed actions. We tested 16...

By distinguishing the attentional cues of their mates, animals can learn what part of their environment is of potential interest. However, recognizing the attentional states of others through auditory perception appears to be difficult, since these states are generally not accompanied by ostensive signals liable to reveal them. In this context, one...

Measuring variations in body mass is necessary to gain a deeper understanding of the evolution of lifehistory patterns, and it provides information on the timing of sexual maturity and the development of sexual dimorphism. In this study, we collected longitudinal data on body mass from infancy to adulthood in a captive population of Tonkean macaque...

Many animal species use a variety of cognitive strategies to locate food resources. One strategy is to make inferences by exclusion, i.e., perceiving the absence of reward as a cue that another location should be investigated. The use of such advanced cognitive strategies may be more prominent in species that are known to frequently solve social ch...

Why regularities in personality can be described with particular dimensions is a basic question in differential psychology. Nonhuman primates can also be characterized in terms of personality structure. Comparative approaches can help reveal phylogenetic constraints and social and ecological patterns associated with the presence or absence of speci...

EFP 2015

By distinguishing the attentional cues of their mates, animals can learn what part of their environment is of potential interest. However, recognizing the attentional states of others through auditory perception appears to be difficult, since these states are generally not accompanied by ostensive signals liable to reveal them. In this context, one...

Males living in multi-male groups are both strong rivals and potential allies. In several primate species they regularly interact through ritualized exchanges known as greetings. We studied five captive groups of Tonkean macaques (Macaca tonkeana) to test five hypotheses regarding the social function of greetings. We found that greetings were mostl...

In nonhuman primate social groups, dominance ranks are usually assigned to individuals based on outcomes of dyadic agonistic encounters. Multiple approaches have been used, but currently there is no consensus. One approach, David's Scores (DS), offers dual advantages of yielding cardinal scores that may in turn be used to compute hierarchical steep...

Highlights ► We used network analysis to investigate variations in the social style of macaques. ► We studied two intolerant species and two tolerant species. ► We showed that top-ranking individuals were more central in intolerant species. ► We found that networks had higher modularity in intolerant species. ► This study shows the efficiency of ne...

Celebrations and bursts of communal joy can occur spontaneously in human communities based on mechanisms of emotional contagion. Some examples of similar collective excitement have been reported in animals when they reunite or anticipate rewards, but little is known about the processes and meaning of these multiple interactions. We experimentally s...

eigenvector centrality Macaca social network social relationship subgroup In group-living species, individuals gain significant advantages from establishing an extensive network of social relationships. This results in complex organizations that are difficult to quantify in a comprehensive manner. In this respect, network analyses are an ideal mean...

Sexual competition is potentially disruptive for the cohesion of social groups because stress and conflicts can extend to other group members. The displays and interactions of sexual partners are liable to influence the behavior of group-mates, which may need to observe them to anticipate possible consequences. We studied 2 captive groups of Tonkea...

Aggression is potentially disruptive for social groups. Although individuals witnessing a conflict are not directly threatened by aggressive interactions, the aftermath of aggression appears to be a period of social instability. We expected bystanders to respond to conflicts by affiliating with other group members and so reducing social tension. To...

Aggression is potentially disruptive for social groups. Although individuals witnessing a conflict are not directly threatened by aggressive interactions, the aftermath of aggression appears to be a period of social instability. We expected bystanders to respond to conflicts by affiliating with other group members and so reducing social tension. To...

Systematic studies on facial displays in capuchins are limited and based mainly on studies of tufted capuchins (Cebus apella). Despite the great social-morphological variability within Cebus suggesting possible morphological and functional variations in the facial displays of different species, no study has considered thoroughly visual communicatio...

Facial displays are important for communication, and their ontogeny has been studied primarily in chimpanzees and macaques. We investigated the ontogeny, communicative function and target of facial displays in Cebus apella. Our results show that facial displays are absent at birth and develop as infants grow older. Lip-smacking appears first (at ab...