Individuals in social species commonly form dominance relationships among each other, and are often observed to differ in behaviour depending on their social status. However, whether such behavioural differences are a consequence of dominance position, or also a cause to it, remains unclear. In this thesis I therefore investigated two perspectives of the relationship between social dominance and personality in the domestic fowl (Gallus gallus domesticus), a social species that forms relatively stable dominance hierarchies. In paper I I investigated the influence of social status on the expression and consistency of behaviours by experimentally changing status between repeated personality assays. The level of vigilance, activity and exploration changed with social status, while boldness and territorial crows appeared as stable individual properties, independent of status. These results showed that social status contribute to both variation and consistency in behavioural responses. Social status should therefore be taken into account when investigating and interpreting variation in personality. In paper II I showed that behaviour in a novel arena test and during encounter with an opponent can predict social status, more specifically that fast exploration and aggressiveness predicted a dominant social position. Together, these results highlight the dynamics of the two-way relationship between social position and individual behaviour and indicate that individual behaviour can both be a cause and a consequence of social status.

Social dominance relationships are formed within numerous animal species and reduce costly fights over resources. Dominant individuals often enjoy greater access to important resources such as food and mating partners, and are generally more aggressive, bold, active and explorative compared to subdominant individuals. These behavioural traits can differ among individuals, but they can also be consistent within the individual, thereby describing the individual’s personality type. However, the causal direction of the observed correlation between dominance and personality is not well studied. One possibility is that some personality types have higher chances of obtaining a dominant social position. This would suggest that personality has consequences for fitness. Another possible explanation is that possessing different social positions gives rise to consistent behavioural differences among individuals on various timescales. If social status has a lasting effect on behaviour, social status would constitute a ‘stable state’ that explains some of the diversity of personality types that has been observed in a multitude of animal species. Dominance and personality may also share underlying proximate factors. In this thesis, I investigate the relationship between social dominance and personality using male domestic fowl, Gallus gallus domesticus. The species is group-living with pronounced dominance hierarchies, and dominance increases male access to mating partners. I show that some aspects of personality, exploration, vigilance and in particular aggressiveness, increased a male’s chances of obtaining dominance (paper III, IV, V), and that aggressiveness can be even more important than body weight and ornament size (comb size, paper V) or recent experience of winning or losing (paper IV). Winning a social interaction resulted in an increase in aggressiveness, while a decrease was seen in males that experienced a loss (paper IV). By observing behaviour before and after changes in male dominance relationships, I further show that a recent (2 days earlier) change in social status induced behavioural adjustments to the new social status in activity, exploration and vigilance (paper I). By extending the time of the new social relationship to 3 weeks, I show that such behavioural changes did not continue (paper II). Finally, I show that the social environment during juvenile development had little impact on adult male competitiveness (paper V). Social interactions appear to have several short-term effects on behaviour, but did not contribute significantly to variation and long-term consistency of personality in male fowl. Instead, a male's personality, and in particular his aggressiveness, affected the outcome of dominance interactions. Overall, my studies reveal important consequences of individual differences in behaviour, and contribute to the highly sought-after empirical testing of hypotheses explaining variation in animal personality. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 5: Manuscript.</p>

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Territorial fights between males are frequently observed among insects. However, despite the existence of theoretical models directed at explaining the possible rules adopted to decide the winner, there is little empirical support for these models. The low empirical support may be explained by difficulties in identifying traits that determine the male fighting capacity (RHP- or Resource Holding Potential) and also by the lack of simultaneous tests of different models. In this study we evaluated males traits that may determine RHP in the dragonfly Diastatops obscura. Also, we evaluated the relationship between such characteristics and duration of disputes between pairs of males to test predictions derived from the models War of Attrition (GDA), Sequential Access Information (ASI) and Cumulative Access Information (ACI). Male weight was the main feature related to the winning chances. The dispute duration decreases with increasing weight and presented the opposite pattern for the loser male, rejecting the GDA as the decision rule adopted by males to settle territorial interactions. In addition the duration of the dispute was not related to the loser male weight when we considered only pairs of rivals who presented similar weight differences. This indicates that the rivals make mutual assessment of RHP, as assumed by the model ASI. Since wings are highly melanized, we suggest that males may perform rival assessments of RHP based on wings traits, as occur in odonate species. / Apesar das brigas entre os machos serem frequentes e de existirem modelos teÃricos que postulam possÃveis regras usadas para decisÃo do vencedor, pouco suporte empÃrico direcionado ao entendimento das brigas tem sido encontrado. Provavelmente esse fato ocorre devido à dificuldade em identificar quais caracterÃsticas determinam a capacidade de luta (RHP - Resource Holding Potential) dos indivÃduos e na escassez de testes simultÃneos de diferentes modelos. Neste trabalho, usamos machos da libÃlula Diastatops obscura para identificar caracterÃsticas determinantes do RHP. Posteriormente usamos informaÃÃes sobre a relaÃÃo entre tais caracterÃsticas e a duraÃÃo das disputas entre pares de machos para testar previsÃes derivadas dos modelos Guerra de Atritos (GDA), Acesso Sequencial de InformaÃÃo (ASI) e Acesso Cumulativo de InformaÃÃo (ACI). O peso representou a principal caracterÃstica determinante da chance de vitÃria em uma disputa. A duraÃÃo da disputa diminuiu com o aumento do peso do vencedor e aumentou com o aumento de peso do perdedor, refutando o modelo GDA como explicaÃÃo das regras de resoluÃÃo das brigas. Adicionalmente a duraÃÃo da disputa nÃo esteve relacionada com o peso do macho perdedor quando consideramos apenas pares de rivais que apresentaram diferenÃas semelhantes de peso. Isso indica que os rivais fazem avaliaÃÃo mÃtua do RHP, como presumido pelo modelo ASI. Uma vez que as asas sÃo fortemente melanizadas, sugerimos que eles podem realizar avaliaÃÃes da capacidade de luta ao obter informaÃÃes sobre a coloraÃÃo das asas, como ocorre em outras espÃcies de libÃlulas.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Em muitas espÃcies animais, os machos brigam por territÃrios os quais aumentam as chances de cÃpulas. Os comportamentos de luta dos machos podem variar desde embates sem contato fÃsico atà lutas com injÃrias e possÃveis mortes. Existem pelo menos trÃs modelos propostos para explicar as regras usadas pelos machos para decidirem o vencedor de um confronto territorial: Guerra de Atritos (GDA), Acesso Sequencial de InformaÃÃes (ASI) e Acesso Cumulativo de InformaÃÃes (ACI). PorÃm, para sermos capazes de testar tais modelos à necessÃrio identificar primeiro quais traÃos dos machos determinam funcionalmente sua capacidade de luta (RHP). Para isso, usamos machos da libÃlula Macrothemis imitans para avaliar duas hipÃteses: 1) se as brigas ocorrerem com contato fÃsico, caracterÃsticas ligadas ao tamanho determinarÃo o RHP e 2) se os machos nÃo exibirem contato fÃsico durante as brigas, caracterÃsticas que conferem maior resistÃncia determinarÃo o RHP. Realizamos coletas de campo em campanhas de dois dias seguidos. Nessas campanhas realizamos captura, marcaÃÃo, observaÃÃo comportamental e recaptura de duas categorias de machos: os que possuÃam posse dos territÃrios (machos residentes) e os machos que ocuparam o local apÃs a remoÃÃo experimental dos machos residentes (machos substitutos). ApÃs a recaptura, levamos os machos residentes e substitutos para laboratÃrio para realizar as medidas: Ãrea alar, peso fresco, massa muscular torÃcica e quantidade de gordura. Os resultados indicaram que os machos residentes apresentaram maior quantidade de massa muscular e possivelmente gordura do que os substitutos. Uma vez que as brigas ocorreram com contato fÃsico, a maior quantidade de massa muscular e gordura dos machos residentes indica que a relaÃÃo funcional entre comportamento de luta e traÃos determinantes do RHP deve ser rejeitada. Alternativamente, à possÃvel que a maior quantidade de mÃsculo proporcione maior desempenho para causar injÃrias nos rivais ou evitar acÃmulo acelerado de danos. / In many animal species, males fight for the possession of territories that increase their mating chances. The fighting behavior of males may range from conflicts without physical contact to disputes with injuries and possible deaths. There are three models aiming to explain the rules adopted by males to decide the winner of a contest: war of attrition (WOA), sequential assessment model (SAM) and cumulative assessment model (ACM). However, to be able to test these models it is necessary to identify male traits functionally related to fighting ability (RHP). In this sense, we used males of the dragonfly Macrothemis imitans to evaluate two hypotheses: 1) if contests occur with physical contact, traits related to the size define RHP and 2) if disputes occur without physical contact, traits which confer endurance define male RHP. We did field experiments during campaigns with two consecutive days. In each campaign we captured, marked, made behavioral observations and recaptured males that were defending a territorial site (resident males) and males that stablished territories in this sites after the experimental removal of the resident male (substitute males). After recapturing, we transported all males them to lab to measure total wing area, male fresh weight, muscle mass and fat content.The results indicated that resident males presented higher muscle mass and probably fat content than substitute males. Since disputes occurred with physical contact, these differences in muscle mass and fat content indicate that the functional relationship between fight behavior and traits linked to RHP should be rejected. Alternativelly, it is possible that the higher muscle mass confers higher ability to cause injuries or to avoid damage accrual.