Agonistic Social Interactions Research Articles

Plant metabolites modulate social networks and lifespan in a sawfly.

Social interactions influence disease spread, information flow and resource allocation across species, yet heterogeneity in social interaction frequency and its fitness consequences are still poorly understood. Additionally, the role of exogenous chemicals, such as non-nutritive plant metabolites that are utilised by several animal species, in shaping social networks remains unclear. Here, we investigated how non-nutritive plant metabolites impact social interactions and the lifespan of the turnip sawfly, Athalia rosae. Adult sawflies acquire neo-clerodane diterpenoids ('clerodanoids') from non-food plants and this can serve as a defence against predation and increase mating success. We found intraspecific variation in clerodanoids in natural populations and laboratory-reared individuals. Clerodanoids could also be acquired from conspecifics that had prior access to the plant metabolites, which led to increased agonistic social interactions. Network analysis indicated increased social interactions in sawfly groups where some or all individuals had prior access to clerodanoids, while groups with no prior access had fewer interactions. The frequency of social interactions was influenced by the clerodanoid status of the focal individual and that of other conspecifics. Finally, we observed a shorter lifespan in adults with prior clerodanoid access when grouped with individuals without prior access, suggesting that social interactions to obtain clerodanoids have fitness costs. Our findings highlight the role of intraspecific variation in the acquisition of non-nutritional plant metabolites in shaping social networks. This variation influences individual fitness and social interactions, thereby shaping the individualised social niche.

Characterization of social behavior in a group of domestic donkeys (Equus asinus)

Although the popularity of domestic donkeys is increasing, the scientific literature on their behavior is still limited. This study investigated the social behavior of a group of 13 donkeys (10 females, 3 geldings, aged 3–13 years) stabled in an Animal Assisted Interventions facility in the North of Italy. Our first aim was to assess the distribution of donkeys’ intraspecific social behaviors during daytime and the second aim was to characterize affiliative and agonistic social interactions during peak activity times. Social behaviors were expressed more between 8 and 9 AM than the rest of daytime, mainly reflecting the expression of affiliative behavior. The latter consisted mostly of proximity (55.0% of all affiliative) and following (29.2%). In most cases affiliative behavior was expressed within preferential dyads, composed of either a mother and her offspring or two adult donkeys. This supports the idea that dyadic relationships are a predominant feature of the social organization of the species. However, dyadic interactions were not observed in the oldest sub-adults, suggesting that social preferences undergo a change around the time donkeys reach full growth. Agonistic behaviors were much less common than affiliative ones. The most expressed agonistic behavior was threat (51%), followed by displacement and bite (both 18.5%). They were less expressed by donkeys who were part of an affiliative pair, suggesting that limited expression of agonistic behavior is associated with an actual change in social preferences, not a mere consequence of fewer occasions of conflict over resources. While the study has limitations, the results provide insight into the social behavior of domestic donkeys which could represent a starting point for further research as well as relevant information for donkeys farming.

Activity Budget and Sociality of the Northern Lesser Galago, Galago senegalensis

AbstractComplex sociality in primates often is argued to have evolved after the appearance of diurnal activity. Studying the behaviour of nocturnal primates is fundamental to understanding the evolutionary origins of primate behaviour and ecology, yet much less is known about the nature of sociality in nocturnal primate species than their diurnal counterparts. We investigated group size, communication, and social interactions in free-ranging, Northern lesser galagos (Galago senegalensis) and present an activity budget and assessment of temporal variation in their behaviour. We collected continuous behavioural data using focal follows at three different stages of the night from individuals at Kwakuchinja, Northern Tanzania. We also collected group size data from Northern lesser galagos at Fongoli, Southeastern Senegal, and Lolldaiga Hills Ranch, Central Kenya. We categorised behaviours and, where sample sizes permitted, used Kruskal–Wallis tests to compare the durations of observed behaviours between the morning (pre-dawn), evening (from dusk), and later in the night. We analysed 140 focal follows (31.4 h of continuous behavioural data) and found that the proportion of time spent foraging, inactive, in locomotion, in self-maintenance, and vigilant, varied across the three stages of the night; galagos spent a great deal of their time inactive in the morning and foraging was more prevalent in the evening. Group size at Kwakuchinja was significantly larger than at Fongoli or LHR. Galagos were in groups of two or more in the majority of encounters at Kwakuchinja (55%; N = 76), rather than alone, but spent most of their nighttime activity alone at Fongoli (79%; N = 185) and LHR (80%; N = 142). Overall vocalisation rates were higher in the morning than other times throughout the night, although contact calls were relatively more frequent in the evening than other times. We recorded both affiliative and agonistic social interactions, but these contributed almost nothing to the overall activity budget. Our preliminary investigation into the social structure of Northern lesser galagos suggests that there are population differences in sociality and that overall, they connect more through vocalisations than through direct social interactions, thereby avoiding some of the potential costs associated with group-living. This variation in social organization suggests that we have more to learn about the drivers of sociality in nocturnal primates and the nature of their social structure.

Stocking density, restricted trough space, and implications for sheep behaviour and biological functioning.

Stocking density and trough space allowance can potentially impact sheep welfare during live export voyages. The aim of this study was to assess the welfare implications for sheep housed at five allometric stocking densities, with either unrestricted or restricted trough space allowance. Merino wethers (n = 720) were housed in 40 pens of 18 heads for 18 days. Two 5-min continuous focal animal observations (n = 3/pen) were conducted on days 3, 5, 11, and 17. Scan sampling of standing and lying behaviours were conducted on the same days at hourly intervals. Live weights and immune cell counts were quantified at the start and end of the experiment, as well as faecal glucocorticoid metabolites (FGCMs), which were also assessed on days 6 and 12. Focal animals housed at higher stocking densities spent less time lying during one of the continuous observation periods, but no important effects on the overall number of animals lying or on the synchronicity of lying were evident. The scan sampling results indicated that the expression of some preferred lying positions was impaired at high stocking densities, and that high stocking densities also resulted in increased agonistic social interactions and displacement events at the start of the trial. There was a slight reduction in day 18 live weights for animals housed at higher stocking densities, but FGCM concentrations and immune cell counts were essentially unaffected. Trough space had no important effects on day 18 live weight, FGCM concentrations, or immune cell counts, and had limited effects on sheep behaviour. The lack of important impacts on biological fitness traits suggests that the behavioural responses observed were sufficient in allowing sheep to cope with their environment. However, we provide evidence that the provision of additional space is beneficial in reducing the time it takes for animals to adapt to their environment and to facilitate the expression of some preferred lying positions. While designed to emulate certain conditions relevant during live export voyages, some factors that may induce stress during this mode of transport were not present such as heat and ocean swell, so the conclusions must be interpreted in the context of the experimental conditions.

Changes in social dominance in a group of subadult white rhinoceroses (Ceratotherium simum) after dehorning

In many social species physical attributes correlate with dominance rankings and influence the outcomes of dyadic interactions. We investigated the processes that affect white rhinoceros’ social behaviour in response to a reduction in horn size asymmetries within a group of subadult individuals. We monitored agonistic social interactions and the orderliness of social rankings between six free ranging rhinoceroses before and after they underwent a second dehorning procedure. We used a modified version of Landau’s h’ to measure linearity, a score of steepness to measure power asymmetry, and a measure of triangle transitivity to assess relationships in the presence of null dyads. Agonistic social interactions were significantly greater after the monitored dehorning procedure. Hierarchies possessed significant steepness and transitivity prior to the procedure, but not after. Linearity was non-significant and rank order did not correspond with changes in horn size or age. Our results provide the first evidence of a dominance hierarchy among free-ranging white rhinoceroses outside of reproductive competition, but indicate that physical attributes alone do not explain social rankings. Rhinoceroses transitioned to a more egalitarian dominance structure than a despotic one after the procedure, but dominance ranks were only weakly differentiated within the group. Although a reduction in horn asymmetries may increase agonistic behaviours via psychosocial or behavioural changes, drier climatic conditions cannot be ruled out as the causative factor and because the subadult group stayed together, rather than dispersing, any increased fitness costs are likely to be minimal and outweighed by the benefits of group membership.

Tracking and analysing social interactions in dairy cattle with real-time locating system and machine learning

There is a need for reliable and efficient methods for monitoring the activity and social behaviour in cows, in order to optimise management in modern dairy farms. This research presents an embedded system that could track individual cows using Ultra-wideband technology. At the same time, social interactions between individuals around the feeding area were analysed with a computer vision module. Detections of the dairy cows’ negative and positive interactions were performed on foreground video stream using a Long-term Recurrent Convolution Networks model. The sensor fusion system was implemented and tested on seven dairy cows during 45 days in an experimental dairy farm. The system performance was evaluated at the feeding area. The real-time locating system based on Ultra-wideband technology reached an accuracy with mean error 0.39 m and standard deviation 0.62 m. The accuracy of detecting the affiliative and agonistic social interactions reached 93.2%. This study demonstrates a potential system for monitoring social interactions between dairy cows.

159 Differences in affiliative and agonistic social interactions in a bachelor pack and family pack of European grey wolves (Canis lupus lupus)

159 Differences in affiliative and agonistic social interactions in a bachelor pack and family pack of European grey wolves (Canis lupus lupus)

Dominance and Leadership in the Equine Social Structure: A Preliminary Study About Mules and Sex Influence

Little is known about the dominance and leadership behaviors in the social structure of mules (Equus caballus × Equus asinus). Based on the frequency of threat and aggressive behaviors, we compared the social structure, dominance, and leadership of independent groups of mules and horses (n = 11 per group), and filmed the frequency of these behaviors over a period of four days. In both groups, aggressions were uncommon and, when based on threats, the social structure was linear and consistent with males ranking higher in dominance. When compared to horses, mules exhibited some agonistic social interactions without a recognized submissive individual and displayed more specific aggressive behaviors, whereas horses presented more specific threat behaviors. Comparing between groups, mares exhibited more leader behaviors than female mules, in contrast to male horses which showed fewer leader behaviors than male mules. Regarding behaviors within the mule group, males showed more leader and threat behaviors than females, while females showed more frequent aggression. While in horses, the females showed more leader behaviors than male horses and, although there were differences in specific agonistic behaviors, both sexes presented more often threat behaviors. In this preliminary study, we conclude that the social structure of mules, although similar to those of horses, showed to be less stable, since it involves more aggression and agonistic social interactions without a submissive. Moreover, although mules did not present a sex influence on leadership as horses did, they presented it on aggression: females showed more aggression than males.

Honey bee neurogenomic responses to affiliative and agonistic social interactions.

Social interactions can be divided into two categories, affiliative and agonistic. How neurogenomic responses reflect these opposing valences is a central question in the biological embedding of experience. To address this question, we exposed honey bees to a queen larva, which evokes nursing, an affiliative alloparenting interaction, and measured the transcriptomic response of the mushroom body brain region at different times after exposure. Hundreds of genes were differentially expressed at distinct time points, revealing a dynamic temporal patterning of the response. Comparing these results to our previously published research on agonistic aggressive interactions, we found both shared and unique transcriptomic responses to each interaction. The commonly responding gene set was enriched for nuclear receptor signaling, the set specific to nursing was enriched for olfaction and neuron differentiation, and the set enriched for aggression was enriched for cytoskeleton, metabolism, and chromosome organization. Whole brain histone profiling after the affiliative interaction revealed few changes in chromatin accessibility, suggesting that the transcriptomic changes derive from already accessible areas of the genome. Although only one stimulus of each type was studied, we suggest that elements of the observed transcriptomic responses reflect molecular encoding of stimulus valence, thus priming individuals for future encounters. This hypothesis is supported by behavioral analyses showing that bees responding to either the affiliative or agonistic stimulus exhibited a higher probability of repeating the same behavior but a lower probability of performing the opposite behavior. These findings add to our understanding of the biological embedding at the molecular level.

Timing of maternal nest building and perinatal offspring survival in a group-living small mammal

Maternal care frequently includes the construction of a burrow or nest where mothers will raise their young. Delays in the timing of such complex sequences of building behavior might potentially interfere with mothers’ successful reproduction. By analyzing a long-term data set (11 years) from a study on European rabbits Oryctolagus cuniculus, we tested whether late maternal burrow and nest building increases the occurrence of perinatal offspring mortality. Additionally, we aimed to identify causes for the occurrence of such late burrow and nest building behavior. In the majority of cases, mothers dug their nursery burrow and constructed a grass nest inside well before the last 24 h prior to parturition. During the last pre-partum day, mothers usually lined the nests with their abdominal hair. However, when mothers carried out of all these activities during the last 24 h pre-partum (“late burrow and nest building”), perinatal mortality was significantly increased. Social constraints might have affected the temporal aspects of females’ display of nest building. Thus, in social groups occupying smaller territories, late burrow and nest building occurred with a significantly higher probability when several females of that group gave birth within a period of a few days (“concurrent parturition”). Behavioral observations suggested that concurrent parturition was associated a higher level of intra-sexual competition, since a significantly increased frequency of agonistic interactions among females was observed in these conditions. The results suggest a mechanism by which the mothers’ social environment influences perinatal mortality, thus adding to our knowledge on drivers of maternal fitness. Differences in the timing of maternal care behavior can strongly affect offspring survival. We investigated this link in a long-term study of a colony of European rabbits. In this species, the young are born and raised in nests situated in nursery burrows dug by the mother. Females which dug their burrow and constructed the nest during the last night before giving birth showed a higher perinatal offspring mortality than mothers that dug their burrow earlier. Furthermore, we explored potential causes of such delays in the timing of burrow and nest construction. Agonistic social interactions between females were increased when different females of a group reproduced at around the same time. Overall, the findings support the conclusion that competition for breeding resources, in particular within smaller group territories, was an important driver for delays in maternal burrow and nest building.

Corticosterone: a costly mediator of signal honesty in sand lizards.

The mechanisms underlying honest signal expression remain elusive and may involve the integration of social and physiological costs. Corticosterone is a socially modulated metabolic hormone that mediates energy investment and behavior and may therefore function to deter dishonest signal expression. We examined the relationship between corticosterone and green badge coloration in male sand lizards (Lacerta agilis), hypothesizing that physiological and behavioral costs resulting from elevated baseline glucocorticoids function in maintenance of honest signal expression. We found that large‐badged males had higher corticosterone titer, with this relationship apparent at the end of the season and absent early in the season. Large‐badged males also suffered higher ectoparasite load (number of tick nymphs), despite being in better condition than small‐badged males. Ectoparasite load was positively related to corticosterone titer early in the season at the time of badge formation. High‐condition individuals had lower corticosterone and lower numbers of ectoparasites than low‐condition individuals, suggestive of conditional variation in ability to withstand costs of corticosterone. We found an opposing negative relationship between corticosterone titer and endoparasite load. Corticosterone titer was also negatively associated with male mobility, a fitness‐determining behavior in this species. Because badge size is involved in mediating agonistic social interactions in this species, our results suggest that badge‐dependent variation in corticosterone is likely reflective of variation in social conditions experienced over the course of the season. Our results implicate corticosterone in maintenance of signal honesty, both early in the season through enforcement of physiological costs (ectoparasite load) and during the season through behavioral costs (male mobility). We propose that socially modulated variation in corticosterone critically functions in mediation of signal honesty without requiring a direct role for corticosterone in trait expression.

Dynamic Status Signal Reflects Outcome of Social Interactions, but Not Energetic Stress

Social defeat induces stress-responses in a wide array of vertebrates and can generate winner-loser effects. Dynamic condition-dependent signaling systems that reflect preparation for subsequent agonistic interactions, and thereby mediate winner-loser effects, should be more sensitive to competitive history than to non-social sources of stress. Bill color of female American goldfinches (Spinus tristus) is a dynamic condition-dependent ornament that functions as a signal of competitive status and mediates intrasexual agonistic social interactions. We tested the “social experience signaling hypothesis” in female goldfinches by (1) manipulating a non-social energetic stressor by experimentally elevating flight costs via wing-clipping in free-ranging birds, and (2) manipulating social experience by staging competitive interactions among captive birds. Bill color change did not differ between wing clipped and non-clipped females, even though stress-response, as measured by the heterophil to lymphocyte (H:L) ratio, increased significantly in clipped females relative to unclipped females. In contrast, winners and losers in the social experience experiment differed significantly in the degree and direction of bill color change following social contests, with bill color increasing in winners and decreasing in losers. These results suggest that dynamic bill color of female American goldfinches signals recent social history, but is less sensitive to some stressors stemming from non-social sources, and thereby suggest that signals can evolve sensitivity to specific types of processes relevant to the context in which they are used.

The Face of the Emperor in Philo’s Embassy to Gaius

In this paper I will show how Philo shapes his narrative in the Embassy to Gaius to highlight the role of the emperor in rupturing traditional forms of political representation, which anticipates later assessments of the principate but is surprising in an author usually thought to be favorable to monarchy. Philo should therefore be considered an important witness to the evolving views of a pan-Mediterranean aristocracy on the changes wrought by the imposition of Roman imperial authority. In constructing his narrative, Philo exploits long-standing norms of physical comportment associated with oratory and engages with the art of physiognomy, which was then approaching the peak of its popularity, by heavily emphasizing the visual elements of the political situations he describes. In particular, Philo uses facial expressions and bodily movements as markers of status and sites of agonistic social interaction to show that the unprecedented power of the imperial position, combined with the malice of Gaius, rendered personal political appeals, including his own embassy, futile, thus furthering the exculpatory purpose of the treatise.

Sex, Love, or War? A Representation of 20 Years of Research on the Social Interactions of Animals

To navigate through a social world, animals may form temporary or long-term associations with others, recognize kin and discriminate between familiar and unfamiliar conspecifics, protect themselves and their resources, fight and compete for the best mates, and produce offspring that require various forms of care. The purpose of the current paper was to summarize the publication trends of research investigating animal social interactions over the last 20 years. We selected 8 journals for their diverse representation of animal taxa and examined the number of published articles representing research on affiliative, agonistic, and sexual social interactions. Out of 18,993 published articles, social interactions (N = 4,273) were studied 5.5% to 30.8% of the published articles per journal between 1993-2013. Agonistic social interactions (43%) were the most frequently published topic with affiliative social interactions representing less than a third (30%) of the articles and sexual social interactions accounting for the remaining articles (27%). Mammalian social interactions were investigated the most (38.5%) with invertebrate (22%) and avian (21%) social interactions following closely behind. Observational research and experimental research designs were divided almost equally across different social interactions except for affiliative interactions. Social interactions were studied most often in laboratory settings (45%), then semi-natural field settings (32.5%), and less often in natural habitats (19%). Interestingly, the rates of the different types of social interactions, certain taxa, type of research study, and research setting remained relatively consistent across the 20 year period. Some fluctuations occurred in the frequency of specific topics and taxa within various years; however, research on mate choice, parental care, environmental influences, and group composition was consistently conducted across the years. While many aspects of social interactions in a broad range of taxa have been studied, there are many areas that are still sparse and in need of additional research.

Introducing young dairy goats into the adult herd after parturition reduces social stress

The aim of this experiment was to compare social stress, as measured by social behavior and adrenocortical activity, in young dairy goats during the first week after introduction into a herd of adult goats either during the dry period of the herd (i.e., all goats in the herd being pregnant or dry: PD) or shortly after parturition (i.e., all animals lactating or with their kids: LK). Thirty-two young goats that had had no contact with adult goats from the age of 7 wk were introduced into adult goat groups. Adult goats were kept in 2 groups of 36 animals each. Young goats were introduced (in groups of 4 animals each) into each of these 2 groups either during the PD period (2 repetitions) or during LK (2 repetitions); goats with different rearing experience were balanced over introduction periods. Young goats were more often receivers of agonistic social interactions when introduced during PD than during LK. Irrespective of the period of introduction, young goats had other young goats as neighbors more frequently than expected by chance alone, although this was even more distinct during PD. Cortisol metabolite levels increased markedly from baseline during PD, but not after parturition. Rearing showed an effect only on the nearest neighbors, with mother-reared young goats staying closer together. Our results indicate that young goats experience less social stress when being introduced into a herd of adult dairy goats shortly after parturition and with kids still present rather than during the dry period. Whether this effect is due to the period and lactational stage itself or to the presence of kids needs to be tested in future studies.

Immunohistochemical localization of serotonin in the brain during natural sex change in the hermaphroditic goby Lythrypnus dalli

The neurotransmitter serotonin (5-HT) may play a central role in the inhibition of socially regulated sex change in fish because of its known modulation of both aggressive and reproductive behavior. This is the first study to use immunohistochemical techniques to examine the morphometry of serotonergic neurons at different times during sex change. Using a model species wherein sex change is socially regulated via agonistic social interactions (the bluebanded goby, Lythrypnus dalli), we sampled brains of males and females with different social status, and of females at different times during sex change. Consistent with previous studies on other teleosts, immunoreactive neurons were found in the posterior periventricular nucleus (NPPv), the nucleus of the lateral recess (NRL), the nucleus of the posterior recess (NRP) and in the raphe nucleus. We measured the total area of NPPv, NRL, NRP, and the number and mean cell area of serotonergic neurons in the raphe nucleus. There was no significant difference in any of the brain regions between males, females or sex changing fish, but there was a slight increase in the number of dorsal raphe neurons in the brain of sex changers 2 h after male removal. The results show that in L. dalli the serotonergic system does not present any morphological sex and status differences, nor any dramatic modifications during sex change. These data, together with previous results, do not support the hypothesis that serotonin inhibits socially regulated sex change.

Effects of an estrogen receptor alpha agonist on agonistic behaviour in intact and gonadectomized male and female mice

Gonadal hormones mediate both affiliative and agonistic social interactions. Research in estrogen receptor alpha (ERα) or beta (ERβ) knockout (KO) mice suggests that ERα increases and ERβ decreases male aggression, while the opposite is found for female ERαKO and ERβKO mice. Using a detailed behavioural analysis of the resident-intruder test, we have shown that the ERβ selective agonist WAY-200070 increased agonistic behaviours, such as aggressive grooming and pushing down a gonadectomized (gonadex) intruder, in gonadally intact but not gonadex male and female resident mice, while leaving attacks unaffected. The role of acute activation of ERα in agonistic behaviour in adult non-KO CD1 mice is presently unknown. The current study assesses the effects of the ERα selective agonist 1,3,5-tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT) on the social and agonistic responses of gonadally intact and gonadex male and female CD1 mice to a gonadex, same-sex intruder. PPT had few effects in gonadally intact mice, but seems to increase sex-typical aggression (i.e., attacks in males, other dominance-related behaviours in females) in gonadex mice. In untreated mice, we confirmed our previous findings that gonadally intact males attacked the intruder more than females, but females spent more time engaged in agonistic behaviour than males. As in our previous results, we observed that gonadex mice generally show behaviour patterns more like those of the gonadally intact opposite sex, while leaving overall levels of agonistic behaviour unaffected. Taken together, our current and previous results show that exogenous activation of ERα had no effects in gonadally intact mice, but increased sex-typical agonistic behaviour in gonadex mice, while ERβ had no effects in gonadex mice, but increased non-attack agonistic behaviour in gonadally intact animals. This suggests that, as in social recognition, ERα may be necessary for the activation of agonistic responses, while ERβ may play a modulatory role.

Agonistic behavior in males and females: Effects of an estrogen receptor beta agonist in gonadectomized and gonadally intact mice

Affiliative and agonistic social interactions are mediated by gonadal hormones. Research with estrogen receptor alpha (ERalpha) or beta (ERbeta) knockout (KO) mice show that long-term inactivation of ERalpha decreases, while inactivation of ERbeta increases, male aggression. Opposite effects were found in female alphaERKO and betaERKO mice. The role of acute activation of ERalpha or ERbeta in the agonistic responses of adult non-KO mice is unknown. We report here the effects of the ERbeta selective agonist WAY-200070 on agonistic and social behavior in gonadally intact and gonadectomized (gonadex) male and female CD-1 mice towards a gonadex, same-sex intruder. All 15min resident-intruder tests were videotaped for comprehensive behavioral analysis. Separate analyses assessed: (1) effects of WAY-200070 on each sex and gonadal condition; (2) differences between sexes, and between gonadally intact and gonadex mice, in untreated animals. Results show that in gonadally intact male and female mice, WAY-200070 increased agonistic behaviors such as pushing down the intruder and aggressive grooming, while leaving attacks unaffected. In untreated mice, males attacked more than females, and gonadex animals showed less agonistic behavior than same-sex, gonadally intact mice. Overall, our detailed behavioral analysis suggested that in gonadally intact male and female mice, ERbeta mediates patterns of agonistic behavior that are not directly involved in attacks. This suggests that specific aspects of aggressive behavior are acutely mediated by ERbeta in adult mice. Our results also showed that, in resident-intruder tests, female mice spend as much time in intrasexual agonistic interactions as males, but use agonistic behaviors that involve extremely low levels of direct attacks. This non-attack aggression in females is increased by acute activation of ERbeta. Thus, acute activation of ERbeta similarly mediates agonistic behavior in adult male and female CD-1 mice.

Behavior: A Relevant Tool for Brain‐immune System Interaction Studies

Neuroimmunomodulation describes the field focused on understanding the mechanisms by which the central nervous system interacts with the immune system, potentially leading to changes in animal behavior. Nonetheless, not many articles dealing with neuroimmunomodulation employ behavior as an analytical endpoint. Even fewer papers deal with social status as a possible modifier of neuroimmune phenomena. In the described sets of experiments, we tackle both, using a paradigm of social dominance and subordination. We first review data on the effects of different ranks within a stable hierarchical relationship. Submissive mice in this condition display more anxiety-like behaviors, have decreased innate immunity, and show a decreased resistance to implantation and development of melanoma metastases in their lungs. This suggests that even in a stable, social, hierarchical rank, submissive animals may be subjected to higher levels of stress, with putative biological relevance to host susceptibility to disease. Second, we review data on how dominant and submissive mice respond differentially to lipopolysaccharide (LPS), employing a motivational perspective to sickness behavior. Dominant animals display decreased number and frequency in several aspects of behavior, particularly agonistic social interaction, that is, directed toward the submissive cage mate. This was not observed in submissive mice that maintained the required behavior expected by its dominant mate. Expression of sickness behavior relies on motivational reorganization of priorities, which are different along different social ranks, leading to diverse outcomes. We suggest that in vitro assessment of neuroimmune phenomena can only be understood based on the behavioral context in which they occur.

Circadian Regulation of Agonistic Behavior in Groups of Parthenogenetic Marbled Crayfish,Procambarus sp.

Crustaceans have frequently been used to study the neuroethology of both agonistic behavior and circadian rhythms, but whether their highly stereotyped and quantifiable agonistic activity is controlled by circadian pacemakers has, so far, not been investigated. Isolated marbled crayfish (Procambarus spec.) displayed rhythmic locomotor activity under 12-h light:12-h darkness (LD12:12) and rhythmicity persisted after switching to constant darkness (DD) for 8 days, suggesting the presence of endogenous circadian pacemakers. Isogenetic females of parthenogenetic marbled crayfish displayed all behavioral elements known from agonistic interactions of previously studied decapod species including the formation of hierarchies. Groups of marbled crafish displayed high frequencies of agonistic encounters during the 1st hour of their cohabitation, but with the formation of hierarchies agonistic activities were subsequently reduced to low levels. Group agonistic activity was entrained to periods of exactly 24 h under LD12:12, and peaks of agonistic activity coincided with light-to-dark and dark-to-light transitions. After switching to DD, enhanced agonistic activity was dispersed over periods of 8-to 10-h duration that were centered around the times corresponding with light-to-dark transitions during the preceding 3 days in LD12:12. During 4 days under DD agonistic activity remained rhythmic with an average circadian period of 24.83 +/- 1.22 h in all crayfish groups tested. Only the most dominant crayfish that participated in more than half of all agonistic encounters within the group revealed clear endogenous rhythmicity in their agonistic behavior, whereas subordinate individuals, depending on their social rank, initiated only between 19.4% and 0.03% of all encounters in constant darkness and displayed no statistically significant rhythmicity. The results indicate that both locomotion and agonistic social interactions are rhythmic behaviors of marbled crayfish that are controlled by light-entrained endogenous pacemakers.