Personality Predicts Social Dominance in Male Domestic Fowl

Individuals in social species commonly form dominance relationships, where dominant individuals enjoy greater access to resources compared to subordinates. A range of factors such as sex, age, body size and prior experiences has to varying degrees been observed to affect the social status an individual obtains. Recent work on animal personality (i.e. consistent variation in behavioural responses of individuals) demonstrates that personality can co-vary with social status, suggesting that also behavioural variation can play an important role in establishment of status. We investigated whether personality could predict the outcome of duels between pairs of morphologically matched male domestic fowl (Gallus gallus domesticus), a species where individuals readily form social hierarchies. We found that males that more quickly explored a novel arena, or remained vigilant for a longer period following the playback of a warning call were more likely to obtain a dominant position. These traits were uncorrelated to each other and were also uncorrelated to aggression during the initial part of the dominance-determining duel. Our results indicate that several behavioural traits independently play a role in the establishment of social status, which in turn can have implications for the reproductive success of different personality types.     

Small Subordinate Male Advantage in the Zebrafish

Dominance is an important determinant of reproductive success in many species, and size is usually an indicator of dominance status, with larger, dominant individuals physically and physiologically preventing smaller subordinates from mating. However, small size may be advantageous in some mating contexts because enhanced manoeuvrability enables males to get closer to females during mating. Here, we determined the paternity success and testes size of dominant and subordinate male zebrafish (Danio rerio), in pairs that controlled for social status. There was no statistical difference in both body size and testes size between dominant and subordinate males. Dominant males sired significantly more offspring than subordinates, but when subordinates were small, they had a greater share of the paternity than larger subordinates. Small male advantage may be one mechanism by which variation in body size is maintained in this species.     

Two Rapidly Evolving Genes Contribute to Male Fitness in Drosophila

Purifying selection often results in conservation of gene sequence and function. The most functionally conserved genes are also thought to be among the most biologically essential. These observations have led to the use of sequence conservation as a proxy for functional conservation. Here we describe two genes that are exceptions to this pattern. We show that lack of sequence conservation among orthologs of CG15460 and CG15323—herein named jean-baptiste (jb) and karr, respectively—does not necessarily predict lack of functional conservation. These two Drosophila melanogaster genes are among the most rapidly evolving protein-coding genes in this species, being nearly as diverged from their D. yakuba orthologs as random sequences are. jb and karr are both expressed at an elevated level in larval males and adult testes, but they are not accessory gland proteins and their loss does not affect male fertility. Instead, knockdown of these genes in D. melanogaster via RNA interference caused male-biased viability defects. These viability effects occur prior to the third instar for jb and during late pupation for karr. We show that putative orthologs to jb and karr are also expressed strongly in the testes of other Drosophila species and have similar gene structure across species despite low levels of sequence conservation. While standard molecular evolution tests could not reject neutrality, other data hint at a role for natural selection. Together these data provide a clear case where a lack of sequence conservation does not imply a lack of conservation of expression or function.     

Male and Female Mating Behavior is Dependent on Social Context in the Butterfly Bicyclus anynana

Reproduction is often more costly to females than it is to males, leading to the evolution of ornamented or competitive males and choosy females. Reproduction costs to females, however, can be reduced through nuptial gifts provided by males. These gifts, by increasing female survival or fecundity, can promote the evolution of mutual mate choice, ornamentation, or competition in both sexes, as well as plasticity in mating behavior dependent on social context. We tested for plasticity in male and female mating behavior in a species of butterfly, Bicyclus anynana, where male spermatophore gifts contribute to female survival and fecundity, and where mutual mate choice and ornamentation were previously established. We examined the effect of a sexual competitor on male–female interactions by observing and comparing the behavior of male–female pairs with that of triads containing either an extra male or an extra female. In the presence of a sexual competitor both males and females copulated less than when in male–female pairs, regardless of the direction of sex-ratio skew. Active males increased their own likelihood to copulate, while active females increased their likelihood of being courted. In addition, there was an effect of social context on relative rates of male and female courting and flying. These results suggest that both males and females change their mating behavior in response to social context in the butterfly Bicyclus anynana.     

Social Opportunity Rapidly Regulates Expression of CRF and CRF Receptors in the Brain during Social Ascent of a Teleost Fish,Astatotilapia burtoni

In social animals, hierarchical rank governs food availability, territorial rights and breeding access. Rank order can change rapidly and typically depends on dynamic aggressive interactions. Since the neuromodulator corticotrophin releasing factor (CRF) integrates internal and external cues to regulate the hypothalamic-pituitary adrenal (HPA) axis, we analyzed the CRF system during social encounters related to status. We used a particularly suitable animal model, African cichlid fish, Astatotilapia burtoni, whose social status regulates reproduction. When presented with an opportunity to rise in rank, subordinate A. burtoni males rapidly change coloration, behavior, and their physiology to support a new role as dominant, reproductively active fish. Although changes in gonadotropin-releasing hormone (GnRH1), the key reproductive molecular actor, have been analyzed during social ascent, little is known about the roles of CRF and the HPA axis during transitions. Experimentally enabling males to ascend in social rank, we measured changes in plasma cortisol and the CRF system in specific brain regions 15 minutes after onset of social ascent. Plasma cortisol levels in ascending fish were lower than subordinate conspecifics, but similar to levels in dominant animals. In the preoptic area (POA), where GnRH1 cells are located, and in the pituitary gland, CRF and CRF₁ receptor mRNA levels are rapidly down regulated in ascending males compared to subordinates. In the Vc/Vl, a forebrain region where CRF cell bodies are located, mRNA coding for both CRFR₁ and CRFR₂ receptors is lower in ascending fish compared to stable subordinate conspecifics. The rapid time course of these changes (within minutes) suggests that the CRF system is involved in the physiological changes associated with shifts in social status. Since CRF typically has inhibitory effects on the neuroendocrine reproductive axis in vertebrates, this attenuation of CRF activity may allow rapid activation of the reproductive axis and facilitate the transition to dominance.     

Social Correlates of Variation in Male Calling Behavior in Blanchard's Cricket Frog,Acris crepitans blanchardi

I studied variation in male calling behavior and its social correlates in Blanchard's cricket frog, Acris crepitans blanchardi. Calls were produced in distinct call groups, and they increased in duration and complexity from the beginning to end of a call group. Dominant frequency was the only character of 18 quantified consistently correlated with male snout-vent length. Calls from the beginning of a call group varied independently of calls from the middle and end of a call group, and only calls from the beginning of a call group exhibited significant variation among males, thus relative consistency within males. Other characters varied greatly within individual males. Unlike most other anurans, dominant frequency also exhibited tremendous within-male variation. The relative influence of caller density, local caller density, nearest neighbor distance, and nearest neighbor sound pressure level on variation in male calling behavior was examined. Nearest neighbor distance, mediated through the sound-pressure level of neighbor calls, appeared to have the greatest influence on variation in male calling behavior. The most profound changes in calling behavior occurred during aggressive encounters; males altered their calling behavior in a manner suggesting that they respond to competitors with graded aggressive signals. Furthermore, the structure of the communication system suggests that calls are graded not only in response to the level of social competition, but graded over a call group as well.     

Social Factors Influencing Russian Male Alcohol Use over the Life Course: A Qualitative Study Investigating Age Based Social Norms,Masculinity, and Workplace Context

The massive fluctuations occurring in Russian alcohol-related mortality since the mid-1980s cannot be seen outside of the context of great social and economic change. There is a dearth of qualitative studies about Russian male drinking and especially needed are those that address social processes and individual changes in drinking. Conducted as part of a longitudinal study on men’s alcohol consumption in Izhevsk, this qualitative study uses 25 semi-structured biographical interviews with men aged 33–60 years to explore life course variation in drinking. The dominant pattern was decreasing binge and frequent drinking as men reached middle age which was precipitated by family building, reductions in drinking with work colleagues, and health concerns. A minority of men described chaotic drinking histories with periods of abstinence and heavy drinking. The results highlight the importance of the blue-collar work environment for conditioning male heavy drinking in young adulthood through a variety of social, normative and structural mechanisms. Post-Soviet changes had a structural influence on the propensity for workplace drinking but the important social function of male drinking sessions remained. Bonding with workmates through heavy drinking was seen as an unavoidable and essential part of young men’s social life. With age peer pressure to drink decreased and the need to perform the role of responsible breadwinner put different behavioural demands on men. For some resisting social pressure to drink became an important site of self-determination and a mark of masculine maturity. Over the lifetime the place where masculine identity was asserted shifted from the workplace to the home, which commonly resulted in a reduction in drinking. We contribute to existing theories of Russian male drinking by showing that the performance of age-related social roles influences Russian men’s drinking patterns, drinking contexts and their attitudes. Further research should be conducted investigating drinking trajectories in Russian men.     

Neural 22-Carbon Fatty Acids in the Weanling Rat Respond Rapidly and Specifically to a Range of Dietary Linoleic to of-Linolenic Fatty Acid Ratios

Changing the dietary ratio of the essential fatty acids (EFA), 18:2n6 and 18:3n3, while keeping the amounts of other fatty acids in the diet constant can rapidly and specifically alter the proportions of n6 and n3 22-carbon fatty acids in the brain of the weanling rat. A dietary 18:2n6/18:3n3 ratio of 165 versus 1.8 caused higher n6 and lower n3 22-carbon fatty acid levels, without changing total 22-carbon fatty acid levels, in phosphatidylethanolamine and phosphatidylcholine from several neural membrane fractions. This was apparent after only 2 weeks and showed no sign of plateauing after 12 weeks. Other neural fatty acids were essentially unaffected. The three most abundant 22-carbon fatty acids responded somewhat differently to increments in the dietary 18:2n6/18:3n3 ratio (1.8, 9, 36, and 165). Levels of 22:4n6 increased by similar absolute amounts for each four-fold increase in dietary 18:2n6/18:3n3 ratio; in contrast, the largest absolute changes in 22:5n6 and 22:6n3 levels occurred as the 18:2n6/18:3n3 ratio increased from 36 to 165. This study shows that the 18:2n6/18:3n3 ratio of diets high in fat (40% of energy) and adequate in EFA, both typical of diets in developed countries, can substantially and relatively quickly affect the 22-carbon fatty acids in the brain, even after the rapid accumulation of these fatty acids during neural growth has ceased.     

Free-Ranging Male Koalas Use Size-Related Variation in Formant Frequencies to Assess Rival Males

Although the use of formant frequencies in nonhuman animal vocal communication systems has received considerable recent interest, only a few studies have examined the importance of these acoustic cues to body size during intra-sexual competition between males. Here we used playback experiments to present free-ranging male koalas with re-synthesised bellow vocalisations in which the formants were shifted to simulate either a large or a small adult male. We found that male looking responses did not differ according to the size variant condition played back. In contrast, male koalas produced longer bellows and spent more time bellowing when they were presented with playbacks simulating larger rivals. In addition, males were significantly slower to respond to this class of playback stimuli than they were to bellows simulating small males. Our results indicate that male koalas invest more effort into their vocal responses when they are presented with bellows that have lower formants indicative of larger rivals, but also show that males are slower to engage in vocal exchanges with larger males that represent more dangerous rivals. By demonstrating that male koalas use formants to assess rivals during the breeding season we have provided evidence that male-male competition constitutes an important selection pressure for broadcasting and attending to size-related formant information in this species. Further empirical studies should investigate the extent to which the use of formants during intra-sexual competition is widespread throughout mammals.     

Responses to Variation in Song Length by Male White‐Crowned Sparrows

Bird song has the potential to convey a variety of information about the singer, including the singer’s current motivational state. A recent review by Searcy & Beecher (2009) (Anim. Behav. 78, 2009; 1281) emphasized how little is currently known about whether song functions as an aggressive signal in territorial interactions. A recent observational study of song length variation in the Puget Sound white‐crowned sparrow reported that males shorten the terminal trill in their single song type while singing close by another male, and shorten the trill even further immediately before chasing the opponent. Here, we report the results of two song playback experiments designed to test whether males distinguish the differences in song length that occur in agonistic and non‐agonistic contexts. We found that males gave stronger responses, as measured by close approach distances, to either a series of songs increasing in duration (compared to a series decreasing in duration), or to long loud songs (compared to short soft songs). In both experiments, males gave weaker responses to the stimuli hypothesized to be more aggressive. Males shortened their songs in response to both simulated intrusions. Combined with the observational data on song variation in different contexts, these experiments support the conclusion that song length variation contains information about aggressive motivation in the white‐crowned sparrow.     

Social Modulation of Circulating Hormone Levels in the Male

SYNOPSIS. In many species, social interactions rapidly modulatecirculating hormone levels in the male. Sexual interaction ormere exposure to a conspecific female results in rapid, transientelevation of both plasma luteinizing hormone and testosteroneconcentrations in a variety of species. In contrast, aggressiveinteractions result in decreased plasma gonadotropin and testosteronelevels and increased levels of adrenal corticoids. In general,these changes are more profound and of longer duration thanthose accompanying sexual interactions, particularly among subordinatemales. These fluctuations in circulating hormone levels appearto be related to an individual's behavioral responsivity. Forexample, plasma concentrations of luteinizing hormone duringa social encounter are positively correlated with the degreeof sexual arousal shown by a male during the interaction. Similarcorrelations have been found between plasma androgen or corticoidlevels and patterns of behavior shown by males during both sexualand aggressive interactions. The causal relationship betweensuch rapid hormone fluctuations and behavior remains unclear.Are fluctuating hormone levels causing differences in behavioror aredifferent patterns of behavior causing differences inplasma hormone levels between males? Or is the correlation betweenthese two variables caused by their relationship to anotherunidentified factor? There are some data favoring the firstpossibility. Increasing the magnitude of socially induced hormonefluctuations during an aggressive encounter or preventingsuchfluctuations entirely significantly alters an animal's behavior.These data suggest that the endocrine system may play a moreimportant role in an individual's minute-to-minute responseto critical social stimuli than was previously realized.     

Seasonal Variation in Female Response to Male Calling Song in the Field Cricket, Gryllus rubens

Conspicuous traits that make males attractive to females may make them vulnerable to predators. Females that approach conspicuous males may increase their risk of predation. This means that selection for reduced male conspicuousness in the presence of predators may be due to sexual selection resulting from altered female behavior in the face of increased predator risk. We examine this hypothesis in the field cricket, Gryllus rubens, in which male calling song attracts both conspecific females for mating and parasitoid flies (Ormia ochracea) which kill their hosts within a week. Female crickets are also parasitized by these flies as a result of associating with calling males. In northern Florida crickets that emerge in the spring are not subject to fly parasitism whereas autumn crickets encounter large numbers of flies. We predicted that autumn females should be less attracted to male song than spring females. We tested female response to male calls in a rectangular arena in which male calling song was broadcast from a speaker. Spring females readily approached the speaker but autumn females were less likely to approach and remain in the vicinity of the speaker. These results emphasize the importance of considering how risk affects the evolution of conspicuous male behavior both directly through its effect on the male and indirectly through its effect on female responses to males.     

Does the Giant Wood Spider Nephila pilipes Respond to Prey Variation by Altering Web or Silk Properties?

Recent studies demonstrated that orb‐weaving spiders may alter web architectures, the amount of silk in webs, or the protein composition of silks in response to variation in amount or type of prey. In this study, we conducted food manipulations to examine three mechanisms by which orb‐weaving spiders may adjust the performance of webs to variation in prey by altering the architectures of webs, making structural changes to the diameters of silk threads, and manipulating the material properties or amino acid composition of silk fibers. We fed Nephila pilipes two different types of prey, crickets or flies, and then compared orb structure and the chemical and physical properties of major ampullate (MA) silk between groups. Prey type did not affect orb structures in N. pilipes, except for mesh size. However, MA silk diameter and the stiffness of orbs constructed by spiders fed crickets were significantly greater than for the fly group. MA fibers forcibly silked from N. pilipes fed crickets was significantly thicker, but less stiff, than silk from spiders fed flies. Spiders in the cricket treatment also produced MA silk with slightly, but statistically significantly, more serine than silk from spiders in the fly treatment. Percentages of other major amino acids (proline, glycine, and glutamine) did not differ between treatments. This study demonstrated that orb‐weaving spiders can simultaneously alter some structural and material properties of MA silk, as well as the physical characteristics of webs, in response to different types of prey.     

Laughing,Smiling, and Talking: Relation to Sleeping and Social Context in Humans

The propabilities of laughing, smiling, or talking during a given hour and in various social environments were investigated by having undergraduate college students record their performance of these activitics in a log book during a one-week period. All three activities were least likely to occur during the hours immediately before bedtime and after waking and were most frequent in social situations. Smiles and laughs, like talking, were performed primarily during social encounters and were often part of verbal and nonverbal conversations. Because laughing and smiling are phasic social acts, they are of limited value as indices of ongoing (tonic) emotional state. The role of laughing, smiling, and talking in communication, the production of mood, and social bonding is considered.     

So Close to a Deal: Spatial-Distance Cues Influence Economic Decision-Making in a Social Context

Social distance (i.e., the degree of closeness to another person) affects the way humans perceive and respond to fairness during financial negotiations. Feeling close to someone enhances the acceptance of monetary offers. Here, we explored whether this effect also extends to the spatial domain. Specifically, using an iterated version of the Ultimatum Game in a within-subject design, we investigated whether different visual spatial distance-cues result in different rates of acceptance of otherwise identical monetary offers. Study 1 found that participants accepted significantly more offers when they were cued with spatial closeness than when they were cued with spatial distance. Study 2 replicated this effect using identical procedures but different spatial-distance cues in an independent sample. Importantly, our results could not be explained by feelings of social closeness. Our results demonstrate that mere perceptions of spatial closeness produce analogous–but independent–effects to those of social closeness.     

Bonobos Respond to Distress in Others: Consolation across the Age Spectrum

How animals respond to conflict provides key insights into the evolution of socio-cognitive and emotional capacities. Evidence from apes has shown that, after social conflicts, bystanders approach victims of aggression to offer stress-alleviating contact behavior, a phenomenon known as consolation. This other-orientated behavior depends on sensitivity to the other''s emotional state, whereby the consoler acts to ameliorate the other''s situation. We examined post-conflict interactions in bonobos (Pan paniscus) to identify the determinants of consolation and reconciliation. Thirty-six semi-free bonobos of all ages were observed at the Lola ya Bonobo Sanctuary, DR Congo, using standardized Post-conflict/Matched Control methods. Across age and sex classes, bonobos consoled victims and reconciled after conflicts using a suite of affiliative and socio-sexual behaviors including embracing, touching, and mounting. Juveniles were more likely to console than adults, challenging the assumption that comfort-giving rests on advanced cognitive mechanisms that emerge only with age. Mother-reared individuals were more likely to console than orphans, highlighting the role of rearing in emotional development. Consistent with previous studies, bystanders were more likely to console relatives or closely bonded partners. Effects of kinship, affiliation and rearing were similarly indicated in patterns of reconciliation. Nearby bystanders were significantly more likely to contact victims than more distal ones, and consolation was more likely in non-food contexts than during feeding. The results did not provide convincing evidence that bystander contacts served for self-protection or as substitutes for reconciliation. Overall, results indicate that a suite of social, developmental and contextual factors underlie consolation and reconciliation in bonobos and that a sensitivity to the emotions of others and the ability to provide appropriate consolatory behaviors emerges early in development.     

Ethnography and Human Development: Context and Meaning in Social Inquiry

Ethnography and Human Development: Context and Meaning in Social Inquiry. Richard Jessor. Anne Colby. and Richard Shweder. eds. Chicago: University of Chicago Press, 1996. pp. 516.