Doctorat en Sciences / info:eu-repo/semantics/nonPublished

This study compares social behavior of infants of resident mothers and infants of immigrant mothers in social groups of the mountain gorilla, Gorilla gorilla beringei. Infants of immigrant mothers spent more time in proximity to their mothers during group resting. They spent more time in solo play and less time in social play during group feeding. Their opportunity for social interaction with peers may be restricted mostly to group rest periods and their social play levels during this time are higher than infants with resident mothers. However, during both group resting and feeding they spent less time near other infants and they initiated fewer dyadic play bouts.

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Animals coordinate their behavior with each other during cooperative and agonistic social interactions. Such coordination often adopts the form of “turn-taking”, in which the interactive partners alternate the performance of a behavior. Apart from acoustic communication, how turn taking is coordinated, is not well known. Furthermore, the neural substrates that regulate persistence in engaging in social interactions are poorly studied. Here, we use Siamese fighting fish (Betta splendens), to study visually-driven turn-taking aggressive behavior. Using encounters with real conspecifics and with computer animations, we discover the visual cues from an opponent and the behavioral dynamics that generate turn taking. Through a brain-wide screen of neuronal activity during aggressive behavior, followed by targeted brain lesions, we then discover that the caudal portion of the dorsomedial telencephalon, an amygdala-like region, promotes continuous participation in aggressive interactions. Our work highlights how dynamic visual cues shape the rhythm of social interactions at multiple timescales and points to the pallial amygdala as a region controlling the drive to engage in such interactions.

The naked mole-rat (Heterocephalus glaber) is one of the most social mammals on the planet. These animals live in underground colonies consisting of a breeding female (the “queen”), 1 to 3 breeding males and up to 300 nonreproductive “workers” organized in a dominance hierarchy. In addition to their eusociality, naked mole-rats have evolved many extreme biological characteristics including an exquisite sense of touch and insensitivity to certain types of pain. However, the overlap between the social and somatosensory abilities of naked mole-rats remains mysterious. In this work, we show that naked mole-rats exhibit caste-like behavioral signatures linked to eusociality, predominantly utilize snout-to-snout interactions in social behavior and possess a somatosensory profile to mechanical stimuli distinct from mice. In the first chapter of this work, we leveraged machine learning and molecular biology tools to create a behavioral atlas of naked mole-rat behavior. We first utilized a computational pipeline of pose-tracking using SLEAP and behavioral segmentation using keypoint-MoSeq to identify 20+ behavioral syllables. This showed that the queen naked mole-rat has a distinct behavioral phenotype from the workers, consisting of faster movements, less anxiety-like freezing, and less colony maintenance behaviors such as digging. We next showed that behavioral differences exist between the workers and that the dominance rank of a given individual could be predicted by its spontaneous behaviors in an open field. Relative rank differential appeared to have relevance for social behaviors: during a tube test for dominance, pairings of a high-ranked and low-ranked animal occurred more quickly and were won more frequently by the dominant animal. Snout touch played an integral role in these dominance tests (perhaps in the communication of individual ID information). This prompted us to investigate snout-to-snout interactions in the open field. We found that two familiar naked mole-rats from the same colony engaged in hundreds of snout interactions in a 10-minute period, and the number of interactions was nearly twice as high between two foreign animals. Follow-up experiments explored the molecular basis of this snout touch and showed that mechanosensory channels (e.g. Piezo2) are likely involved in social snout-to-snout interactions. Furthermore, trimming the sensory whiskers of naked mole-rats disrupts their ability to recognize conspecifics and alters their relative dominance relationships. These findings uncover face touch as a prominent social behavior in naked mole-rats that is intimately linked to social recognition. In the second chapter of this work, we more deeply investigated naked mole-rat somatosensation by using high-speed videography. We began by determining how naked mole-rats respond to both innocuous stimuli (cotton swab, dynamic brush) and noxious stimuli (light and heavy pinpricks) when given to the hindpaw. Compared to mice, naked mole-rats showed a distinct hindpaw phenotype, never responding to innocuous touch stimuli, responding to light pinprick, but rarely responding to heavy pinprick (normally the most noxious stimulus that elicits the strongest pain response in mice). Interestingly, naked mole-rats do respond to brush stimuli to the back skin with a dorsiflexion posture. These animals also exhibit an idiosyncratic withdrawal response to a brush applied to the snout skin which appears to be highly aversive. Interestingly, the velocity of this aversive snout withdrawal appears to be socially modulated and is decreased in the presence of another naked mole-rat in the testing chamber. This phenotype does not occur in mice and provides additional evidence that the naked mole-rat snout is not only extremely sensitive but plays a role in processing socially relevant information.

While the gestural communication of apes is widely recognised as intentional and flexible, their vocal communication still remains considered as mostly genetically determined and emotionally bound. Trying to limit the direct projections of linguistic concepts, that are far from holding a unified view on what constitute human language, this thesis presents a detailed description of the pant-grunt vocalisation usage and development in the chimpanzees (Pan troglodytes schweinfurthii) of the Budongo forest, Uganda. Pant-grunts are one of the most social vocalisations of the chimpanzee vocal repertoire and are always given from a subordinate individual to a dominant. The question of how such a signal is used and develops is critical for our understanding of chimpanzee social and vocal complexity in an ontogenetical and phylogenetical perpective. Results suggest that pant-grunt vocalisations can be used in a flexible way, both in their form and usage within a social group. More specifically, chimpanzees seemed to take into account the number and identity of surrounding individuals before producing these vocalisations. At the acoustic level, pant-grunts seem to be very variable vocalisations that corresponded to different social situations commonly encountered. Grunts are one of the first vocalisations produced by babies but they are not first produced in social contexts. Although some modifications of the social grunts form and usage could not entirely be attributed to maturation only, the role of the mother seemed to be restricted. Her direct influence was perhaps more visible in the rhythmic patterns of chorusing events. Taken together, this thesis suggests that chimpanzee vocalisations are more flexible in their usage, production and acquisition than previously thought and might therefore be more similar to gestural communication.

Vervet monkeys (Chlorocebus pygerythrus) are generally described as a territorial species, though variations in territoriality have been observed. This research examined the impact of high population density, large group sizes and extensively overlapping home ranges on the expression of territoriality in a population of vervet monkeys. Over a period of eighteen months, data were collected on three large troops of vervet monkeys (PTN = 31, RBMN = 39, RSTN = 57) on the Samara Game Reserve, South Africa. I examined the spatial dynamics demonstrated in this population, assed the extent and use of home range overlap and examined the occurrence of intertroop encounters in relation to mate defence, resource defence and home range defence. The home ranges of the troops in this study population overlap substantially, and overlap areas are exploited extensively. The frequency of occurrence of intertroop encounters does not increase in the mating season, nor is there evidence of the defence of particular food patches or home range defence. The findings from this thesis emphasize the importance of examining the expression of territoriality of a population within the context of its environment. / xvi, 125 leaves : ill. ; 29 cm

Forest elephant (Loxodonta africana cyclotis) sociality is relatively little-studied due to the difficulties of making direct observations in rainforests. In Central Africa elephants aggregate at large natural forest clearings known as bais, which have been postulated to offer social benefits in addition to nutritional resources. This thesis explores the role of these clearings as social arenas by examining bai use within three main themes; ecology, sociality and risk factors. Seasonal changes in elephant use of the Maya Nord bai (Republic of Congo) are described, along with the demography of the visiting population. Elephant visit rate was highly variable; the number of elephants using Maya Nord in an observation day ranged from 0 to 117 animals. This variability was unrelated to local resource availability and productivity suggesting that bai use occurs year round. Elephants in Odzala-Kokoua do not show high fidelity to a single clearing; 454 elephants were individually identified and re-sighted an average of 1.76 times (range 1-10) during the twelve month study period. Previous bai studies have yet to quantify how elephants associate with one another within the bai area. This study examines socio-spatial organisation and associate choice using two measures of association within the 0.23 km2 bai area; aggregations (all elephants present in the clearing) and parties (elephants spatially co-ordinated in activity and movement) and distinguishes these from parties that range together (i.e. arrive and leave together). Social network analyses (SocProg) were used to describe inter- and intra-sexual multi-level organisation in the bai environment, and to illustrate the non-random nature of elephant aggregations and parties. Bais were shown to function as social arenas; female elephants showed active choice of certain associates and active avoidance of others when creating parties, whereas males were less discriminatory. Parties formed in the clearing (mean size= 3.93, SE= 0.186) were larger than ranging parties (mean size= 2.71, SE= 0.084) and elephants stayed for 50% longer in the clearing when they associated with individuals from outside their ranging party. Inter- and intra-sexual relationships were maintained within the clearing, and these are suggested to offer elephants essential opportunities for social learning. The patterning and nature of the relationships observed at the Maya Nord clearing indicates that forest elephants use a fission-fusion social structure similar to that of savannah elephants (Loxodonta africana africana); relationships are significantly structured by age- and sex- and underpinned by individual identity. Old experienced females hold key roles for forest elephants, and male relationships are superimposed on the network of female associations. Odzala-Kokoua elephants use bais to maintain their social relationships despite being highly sensitive to the anthropogenic risks involved in using these open areas. The results of this study suggest that forest and savannah elephants lie on the same social continuum, balancing social “pulls” to aggregate against the ecological “pushes” that force groups to fission. Previous models of savannah elephant sociality construct levels of association and social complexity upwards from the basic mother-calf unit (e.g. Wittemyer & Getz 2007). My results suggest that it may be more appropriate to consider elephant sociality and associations as in dynamic equilibrium between social and ecological influences acting at all levels of grouping, and to explicitly test how these underlie the opportunity costs that elephants are willing to pay in order to maintain social groupings.

This thesis examines the relationship between individual differences in learning, personality, and social success in two groups of brown capuchin monkeys (Sapajus sp.) housed at the “Living Links Centre for Human Evolution” at Edinburgh Zoo, UK. Being able to learn quickly and efficiently likely helps primates achieve social success (defined here in terms of centrality within a social network), such as acquiring knowledge of others or learning social skills. Therefore, individuals that are better at learning were predicted to have greater social success than other group members. This prediction, however, contrasts with hypotheses generated from two other disciplines at the individual level: 1) the study of behavioural innovation, and 2) the study of individual differences, i.e. “personality”. In terms of behavioural innovation, better learners should have less social success than other group members because they are expected to rely more on problem-solving, rather than physical combativeness or status, to gain access to socioecological resources. In terms of personality, learning should have little or no direct relationship with social success because other individual differences, like sociability and fearfulness, should mediate primates’ social decision making. This thesis investigates each of these hypotheses. Personality was assessed in 127 capuchins from 7 international sites using the Hominoid Personality Questionnaire, and then validated at Living Links (LL) using behavioural codings; this was the first-ever description of personality structure in brown capuchins. Brown capuchins have five personality dimensions: Assertiveness, Openness, Sociability, Neuroticism, and Attentiveness. Ratings were consistent across observers, and predicted relevant behaviours among the LL capuchins over a year later (e.g. scores on Sociability predicted time spent in close proximity to others). “Social success” in the LL capuchins was assessed in terms of centrality in spatial proximity networks. Individual scores on social network centrality were significantly correlated with scores derived from a Principal Components Analysis of eight affiliative and agonistic behaviours among the LL capuchins, indicating that spatial proximity is a reliable measure of the quality of subjects’ social embeddedness within their groups. Social rank and two personality traits (Assertiveness and Sociability) were positively related to network centrality, while another personality trait (Neuroticism) was negatively related to centrality. Sociability was a significant predictor of network centrality even after controlling for social rank and the other personality traits, highlighting the importance of this personality trait in shaping the social success of capuchins beyond that of basic social rules (e.g. kinship, sex, and rank). Individual learning was assessed in the LL capuchins by administering two operant tasks to subjects under conditions of free choice participation. In Task 1, thirteen monkeys participated, and eight individuals met learning criteria (i.e. >80% trials correct over 3 consecutive sessions). In Task 2, fifteen monkeys participated, and five individuals met learning criteria; the monkeys that learned this second task were also among those individuals that learned Task 1. For monkeys that regularly participated in both tasks (i.e. >50% of sessions), their average performances (i.e. % trials correct) were significantly correlated with individual scores on Assertiveness, but not the other four personality traits, or individual differences in attention span during testing, the percent of sessions subjects participated during testing, the amount of scrounging events subjects directed towards others within their social group, or the percent of observation time subjects spent feeding within their main indoor/outdoor enclosures. In terms of social success, relatively better learners had lower social rank and network centrality compared to relatively poor learners. Also, compared to poorer learners, better learners were generally less likely to direct affiliative acts (e.g. grooming, food sharing, coalitionary support) to other group members. Controlling for Assertiveness (i.e. the only variable related to individual differences in subjects’ average learning performance), individual differences in learning performance were no longer significantly related to social rank, network centrality, or the amount of affiliative acts subjects initiated with others. Collectively, such findings contrast the hypothesis that better learners should (concurrently) be more socially successful than poorer learners, and instead are more reflective of hypotheses pertaining to behavioural innovation and/or the study of individual differences. Social rank and certain traits of personality (Assertiveness, Openness, Neuroticism, and Sociability) appear to interact with capuchins’ patterns of social interaction, and one personality trait (Assertiveness) may mediate how individual differences in learning are associated with differences in social success.

Synchrony between Atlantic spotted dolphins (Stenella frontalis) is crucial for successfully fending off bottlenose dolphins (Tursiops truncatus) during interspecies aggression. The present study examined synchrony in adult Atlantic spotted dolphins during aggressive encounters with bottlenose dolphins. Across group size, aggressive behavioral events increased preceding synchrony, peaked during synchrony, and decreased dramatically after synchrony. Although smaller groups (< 10 dolphins) became synchronous more frequently than larger groups (> 10 dolphins), larger groups remained synchronous longer; however, smaller groups exhibited more frequent aggressive behavioral events during synchrony, suggesting that additional aggressive behaviors may be necessary to compensate for the small group size, whereas larger groups may be able to rely on synchrony alone. Disorganized squawk bouts synchronized as physical synchrony began, but only if coupled with escalating aggressive behaviors. The synchrony during aggressive episodes observed in adult Atlantic spotted dolphins can be used as a baseline to determine the process of the development of this critical skill in juveniles. / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2015 / FAU Electronic Theses and Dissertations Collection