Biology subjects

Massen, J. J. M.

Publications and source records attributed to Massen, J. J. M..

10 recordsLinked to original sources

bioRxiv2026

Personality and dominance shape core area use and territory-related signalling in a feral ungulate

Space use strategies determine how animals acquire resources and encounter competitors, which ultimately influence their survival. Instead of utilising their entire range uniformly, animals typically concentrate activity in locations where resources are most valuable, and these 'core areas' provide key insights into the behavioural strategies underlying space use. Although competitive ability is often expected to influence core area use, substantial individual-level variation remains unexplained. Consistent behavioural differences among individuals, or personality, may contribute to this variation, but their role in shaping spatial behaviour under natural conditions is poorly understood. To address this gap, we observed adult males (n=24) from a free-ranging, semi-urban population of Asian water buffalo (Bubalus bubalis). We quantified individual core area size and territory-related signalling behaviour, and assessed personality from >9,300 minutes of observations. Most males (79%) shared overlapping core areas with one to five other males but with clear dominance relationships. Social engagement, reflecting a social personality, was positively associated with core area size in subordinates, but not in dominant males. Social engagement was also positively associated with territory-related signalling frequency. By contrast, a non-social personality labelled as activity-maintenance did not influence with core area size or signalling behaviour. We also found that dominant males exhibited lower signalling frequencies than subordinates. Overall, we show that personality and dominance are associated with distinct aspects of spatial behaviour. These findings demonstrate that individual spatial strategies emerge from the interplay between behavioural phenotypes and social lives, highlighting the spatial-social interface as a source of variation in animal space use.

animal behavior and cognition↗

bioRxiv2026

The social structure of a captive group of Rüppell's vultures (Gyps rueppellii)

Studies on the evolution of intelligence have so far mainly focused on mammals, primates in particular, and only few avian taxa, mainly corvids and parrots. Vultures, however, have relatively large brains too, and those of the Gyps genus are highly social. Their obligate scavenging lifestyle and sociality make them an excellent taxon for investigating the role of social and ecological selective pressures on the evolution of intelligence. However, little is known of Gyps vultures, particularly regarding their social complexity (sensu Social Brain Hypothesis). To investigate the complexity within their social structure, we studied the dominance hierarchy and social bonds of a captive group (n {equiv} 23) of Ruppell's vultures (Gyps rueppellii) over two consecutive years. Our results revealed that dominance ranks and affiliative bonds were stable, although there were some differences between breeding and non-breeding seasons. During the breeding season, pair-bonded individuals were more dominant and less social than unpaired individuals. Pair-bond status, age and season influenced dyadic bond strength. Most notably, pair-bonded dyads had substantially stronger bonds, but maintained multiple other strong bonds, too. Our results highlight that multiple forces shape the dominance hierarchy and affiliative network of captive Ruppell's vultures. Individual characteristics shape social bonds, social relationships are differentiated, and changes between the breeding and non-breeding season can result in social uncertainty, adding to the complexity of this system. The complexity of Ruppell's vultures' social structure seems comparable to that of some social corvid and parrot species, where it has been linked to their sophisticated cognition. Future socio-cognitive work on this and other less social vulture species could further identify the social challenges they face, and reveal whether a complex social environment may have been a selection pressure on the evolution of intelligence, both in general, and in this promising new taxonomic group for cognition studies specifically.

animal behavior and cognition↗

bioRxiv2025

Social status predicts self-directed behaviors, contingent on broader social dynamics

Emotional states like anxiety are adaptive, assisting individuals during social uncertainty and threats. While humans can self-report anxiety, assessing comparable states in animals requires objective measures. Self-directed behaviours (SDBs), including self-scratch, autogroom, and yawn, are indicators of anxiety, particularly in nonhuman primates. Yet it is unclear whether they reflect a common underlying process or distinct responses shaped by demography, social interactions and status, and the broader social dynamics. We studied 13 macaque groups across six species along a despotic-egalitarian social style gradient to investigate the factors associated with variation in SDBs. Our findings revealed partial correlational consistency among the SDBs, where only self-scratch and autogroom positively correlated. Further, we found that males yawned more than females, and individuals receiving less aggression exhibited longer autogroom bouts. Dominance rank showed behaviour-specific effects, with weak evidence for an association with self-scratch, longer autogrooming in subordinates, and a non-linear pattern in yawning, which was lowest at intermediate ranks. Alpha status was linked to more frequent yawning than others. And finally, social style showed no consistent effects on SDBs. Our research demonstrates that SDBs in macaques reflect differential responses related to social uncertainty rather than one anxiety dimension, providing insights into primate emotion regulation.

animal behavior and cognition↗

bioRxiv2025

Despotism promotes cooperation through enhanced interdependencies in non-human primate societies

The evolutionary mechanisms of cooperation are well-studied, yet what motivates individuals to cooperate remains unclear. Although conventionally associated with enhanced social tolerance (self-domestication hypothesis) and prosociality (cooperative-breeding hypothesis), individuals belonging to species that are neither self-domesticated nor cooperatively-breeding also cooperate. An overarching interdependency hypothesis posits that inter-individual dependencies promote cooperation, but comparative evidence is lacking. We experimentally studied cooperation, prosociality, and tolerance in six macaque species along a despotic-egalitarian gradient. Within-group cooperation was higher in despotic than egalitarian societies yet restricted to few partners. Prosociality, kinship, and tolerance positively predicted cooperation success. Agent-based models consistently showed that despotic societies have fewer but more stable social bonds and, thus, higher interdependencies than egalitarian ones. Our results suggest that interdependencies facilitate the emergence and maintenance of cooperation.

animal behavior and cognition↗

bioRxiv2024

Personality assessment of synanthropic rhesus macaques: implications and challenges

"What makes animals thrive in human-dominated environments?" is a question that has been extensively researched transcending disciplines, but findings remain inconclusive. Consistent inter-individual differences or personalities can potentially explain the functional significance of habitat-specific traits and their variations that help animals successfully coexist with humans. Rhesus macaques (Macaca mulatta) are the most successful non-human primate in the Anthropocene, living in diverse climatic and environmental conditions. Studying the personalities of synanthropic rhesus macaques can provide insights into the biological traits that facilitate their success in human-dominated environments. We employed a multi-method bottom-up approach of behavioral observations and novelty experiments, standardized for assessing captive non-human primates, to evaluate the personalities of synanthropic adult rhesus macaques (N=52). To our surprise, novelty experiments encountered significant challenges, limiting their effectiveness. However, behavioral observations in the form of focal sampling revealed two repeatable traits: sociability and cautiousness. We found an effect of sex on sociability, where males were more sociable than females. In an additional analysis, we found that individuals who obtained food through contact provisioning had higher cautiousness scores than individuals who obtained food through non-contact provisioning. We discuss how the observed personality traits and their variations potentially offer adaptive advantages in human-dominated environments, where rhesus macaques face both benefits, such as anthropogenic subsidies and reduced predation, and costs, like exposure to anthropogenic stressors. We also emphasize that protocols designed for captive conditions may not be directly applicable to free-living animals. Thus, the study underscores the need to reconsider experimental designs to obtain comparable empirical evidence between captive and non-captive populations to enhance the ecological validity of personality assessments. Nevertheless, empirically identifying traits using observations in synanthropic species like rhesus macaques can still provide valuable insights into the mechanisms that enable certain animals to thrive amidst a rapid expansion of anthropogenic activities. Research highlightsStudying personalities of synanthropic animals can shed light on the biological traits that help them thrive in human-dominated environments. A bottom-up multi-method approach, standardized for assessing captive NHP personalities, was employed to study a population of synanthropic rhesus macaques. Behavioral observations captured two repeatable traits, namely sociability and cautiousness, where comparatively more cautious individuals obtained food through contact provisioning. Novelty experiments faced significant challenges.

animal behavior and cognition↗

bioRxiv2023

Personality heterophily and friendship as drivers for successful cooperation

Cooperation is widespread and arguably a pivotal evolutionary force in maintaining animal societies. Yet, proximately, what underlying motivators drive individuals to cooperate remains relatively unclear. Since free-riders can exploit the benefits by cheating, selecting the right partner is paramount. Such decision rules need not be based on complex calculations and can be driven by cognitively less-demanding mechanisms, like social relationships (e.g., kinship, non-kin friendships, dyadic tolerance), social status (e.g., dominance hierarchies) and personalities (social and non-social traits); however, holistic evidence related to those mechanisms is scarce. Using the classical loose-string paradigm, we tested cooperative tendencies of a hierarchical primate, the long-tailed macaque (Macaca fascicularis). We studied three groups (n=32) in social settings, allowing free partner choice. We supplemented cooperation with observational and experimental data on social relationships, dominance hierarchies, and personality. Friendship and dissimilarity in a non-social exploration personality trait predicted the likelihood of cooperative dyad formation. Furthermore, the magnitude of cooperative success was positively associated with friendship, low rank-distance, and dissimilarity in an activity-sociability personality trait. Kinship did not affect cooperation. While some findings align with prior studies, the evidence of (non-social)personality heterophily promoting cooperation may deepen our understanding of the proximate mechanisms and, broadly, the evolution of cooperation.

zoology↗

bioRxiv2023

Behavioural, physiological, and genetic drivers of coping

Animals regularly experience stressful situations, ranging from predation to social stress, yet successfully deal with them on most occasions. This adaptive mechanism, coping, reduces the adverse effects of stressors through behavioural and physiological efforts, failing to which may result in reduced fitness. However, considerable variation in coping is observed. Unlike in humans, coping is often considered a personality trait in non-human animals due to construct similarity, resulting in conceptual ambiguity. Besides, limited multidisciplinary research has rendered comprehending the drivers of coping in animals challenging. We assessed repetitive behavioural coping or coping styles (n=30), emotional arousal (n=12), and consistent inter-individual differences, i.e., personalities (n=32) of long-tailed macaques (Macaca fascicularis) using observations, ecologically relevant experiments, and infrared thermography. We finally investigated the association of coping with a Valine/Methionine polymorphism encoded by the Catechol-O-methyltransferase (COMT) gene (n=26), which is widely known for its involvement in human stress regulation. Our findings suggest that personality and the presence of the human equivalent COMT Val158Met polymorphism in long-tailed macaques are associated with emotion-focused and problem-focused coping styles. These coping styles were consistent with emotional arousal as measured with infrared thermography. We discuss these proximate drivers of coping for a better understanding of its evolution in primates.

animal behavior and cognition↗

bioRxiv2023

Hand preference predicts behavioral responses to threats in Barbary macaques

The structure and functioning of the brain are lateralized - the right hemisphere processes unexpected stimuli and controls spontaneous behavior, while the left deals with familiar stimuli and routine responses. Hemispheric dominance, the predisposition of an individual using one hemisphere over the other, may lead to behavioral differences; particularly, an individual may be programmed to act in a certain way concerning hemispheric dominance. Hand preference is a robust estimator of hemispheric dominance in primates, as each brain hemisphere controls the opposing side of the body. Studies have found links between hand preference and the exhibition of different behaviors in contexts such as exploring and manipulating objects. However, little is known about whether hand preference can predict behavioral variations in other ecologically relevant contexts like, for example, predation. We investigated the relationship between hand preference and the behavioral responses to two types of predator models in captive Barbary macaques (Macaca sylvanus) (n=22). Hand preference was determined by observing unimanual foraging, whereas focus and tension behaviors were quantified during experimental exposure to predator models. We found 91% of the macaques to be lateralized with no group-level bias. In contrast to their right-hand counterparts, individuals with a strong left-hand preference elicited frequent focus and tension behavior. Additionally, the behavioral response varied with predator type. We also found an interaction effect between hand preference and the predator type. Our study suggests that hand preference can reliably predict behavioral variations in the context of potential predation. While these results are consistent with the lateralized brain function, indicating lateralization as a potential neural mechanism of behavioral variation, the interaction effect between hand preference and predator type elucidates the importance of context-specificity when investigating laterality non-invasively. Future research on other non-human primates using the current framework may shed light on the evolution of laterality and underlying behavioral predispositions.

animal behavior and cognition↗

bioRxiv2022

Prosociality in a despotic society

Humans possess remarkable prosocial tendencies beyond the confinement of kinship, which may be instrumental in promoting cooperative interactions and sociality at large. Yet, prosociality is an evolutionary conundrum as it does not provide immediate benefits to the actor. The domestication and cooperative-breeding hypotheses postulated that enhanced social tolerance and inter-individual dependence could nonetheless facilitate the evolution of prosociality. However, inconsistent results due to varying experimental paradigms, and restricted focus of research on tolerant and cooperatively breeding species, have impeded our understanding so far. Albeit counterintuitively, despotic societies with relatively low social tolerance levels represent an excellent opportunity to investigate prosociality due to their kin favoritism and potential interdependence among individuals in terms of social support. Japanese macaques (Macaca fuscata) live in strictly hierarchical matrilineal societies, where kin members have strong social bonds. Additionally, support from non-kins can be crucial to form coalitions and rank up in the hierarchy. Using a group-service paradigm, we tested prosociality in a semi-free-ranging group of Japanese macaques. In contrast to currently existing evidence, we found that individuals (n=25) can act prosocially and at comparably high rates as cooperative breeding- or self-domesticated species. The macaques benefitted not only their kin members but other individuals to whom they showed relatively high social tolerance. We emphasize the roles of complex socio-ecological conditions in facilitating individual prosocial tendencies. Furthermore, these results call for a novel evolutionary framework regarding prosociality that focuses on different forms of interdependence and expands beyond cooperative breeding- and (self-)domesticated species. Significance statementWhat made humans so incredibly prosocial? Examining the evolutionary trajectory of prosocial acts led comparative psychologists to explore various taxa. Empirical evidence so far suggests that enhanced social tolerance and interdependence among individuals facilitate prosociality. Conventionally, despotism is characterized by low group-level tolerance, yet kin favoritism, nepotism, and high interdependence (in support and coalition formation) are also fundamental properties of despotic societies. Under such complex socio-ecological conditions, individual prosocial acts could thus be vital. We found, for the first time, high levels of prosociality in the very despotic Japanese macaques. Individuals benefitted both kin-relatives and others to whom they showed relatively high dyadic social tolerance. This study signifies that prosociality can be favored even in a highly despotic society.

animal behavior and cognition↗

bioRxiv2021

Individual repeatability, species differences, and the influence of socio-ecological factors on neophobia in 10 corvid species

Behavioural responses to novelty, including fear and subsequent avoidance of novel stimuli, behaviours referred to as neophobia, determine how animals interact with their environment. Neophobia aids in navigating risk and impacts on adaptability and survival. There is variation within and between individuals and species, however, lack of large-scale, comparative studies critically limits investigation of the socio-ecological drivers of neophobia. In this study, we tested responses to novel objects and food (alongside familiar food) versus a baseline (familiar food alone) in 10 corvid species (241 subjects) across 10 labs worldwide. There were species differences in the latency to touch familiar food in the novel object and food conditions relative to the baseline. Three of seven socio-ecological factors influenced object neophobia: 1) use of urban habitat (vs not), 2) territorial pair vs family group sociality and 3) large vs small flock size (whereas range, caching, hunting live animals, and genus did not); while only flock size influenced food neophobia. We found that, overall, individuals were temporally and contextually repeatable (i.e. consistent) in their novelty responses in all conditions, indicating neophobia is a stable behavioural trait. With this study, we have established a network of corvid researchers, demonstrating potential for further collaboration to explore the evolution of cognition in corvids and other bird species. These novel findings enable us, for the first time in corvids, to identify the socio-ecological correlates of neophobia and grant insight into specific elements that drive higher neophobic responses in this avian family group.

animal behavior and cognition↗