The field of animal personality has been growing rapidly in the past 10 years, yet relatively little attention has been given to development of personality through ontogeny. To understand the stability of personality traits throughout animal’s life is particularly important as behavioural tendencies are likely to change in response to the different trade-offs animals face at each stage of the life cycle. The purpose of this research was to examine the stability of personality traits in common carp but also to determine whether personality traits can affect production of induced morphological defences in this species. To investigate the presence of behavioural syndrome and the stability of individual behaviours through ontogeny, common carp were monitored for a period of 10 months. Two different tests were used to investigate cross-situational consistency in behavioural traits: exploration and risk-taking. Juvenile carp were monitored at different time intervals to assess behavioural stability. Finally, morphometric data were collected to examine the link between body morphology and behavioural traits. No initial cross-situational consistency in behaviours was observed in juvenile common carp. Ranking of behaviour traits was consistent over a period of 14-16 weeks but not when the time interval was longer. Young carp that ranked lowest in both shelter use and activity used shelter significantly more compared to those individuals that ranked highest in use of shelter and activity even after a 10 month period. Development of a deeper body was also associated with the extreme levels of shelter seeking and activity. Fish pre-determined as being “Active” increased their body depth significantly more than did “Passive” fish. To my knowledge, this is the first study directly linking personality traits and change in body morphology in an aquatic species.

Despite recent increasing interest in the existence of animal personality, i.e. intra-individual consistency and inter-individual variation in the level of a behavioural trait, the evolutionary (and ecological) consequences of these consistent behavioural differences remain poorly understood. Some recent studies have revealed that variation in animal personalities might be linked to competitive interactions, resulting from natural selection. However, since personalities might similarly affect mate acquisition and reproductive success, it seems crucial to also explore their evolution under the framework of sexual selection theory. In this thesis I investigate the influence of personality on mate choice, reproductive success, female-male and male-male interactions, using zebra finches, Taeniopygia guttata, as a model species. After (I) I review the few existing studies assessing the link between sexual selection and personality, I propose a framework on the relationship between sexual selection and personality. Subsequently, (II) I show with different experimental approaches for the first time that (a) females choose males on the basis of their behaviour per se (male behaviour was experimentally disentangled from any appearance effects) whilst considering their own personality in their choice: less exploratory females did not distinguish between exploratory and non-exploratory appearing males, whereas moderately and highly exploratory females preferred similar males. (b) These preferences have an adaptive value to the exploratory females: exploratory females which had a behaviourally similar partner raised chicks in best condition but chicks in worst condition if they had a dissimilar partner. Low exploration females always raised chicks in intermediate condition, which may explain why they did not choose males on the basis of their exploratory behaviour. (c) I provide evidence that the combination of personalities in a pair, not only in terms of the level of the behaviour but also in terms of the behavioural consistency, influence reproductive success. However, this was only true for foster but not genetic parents, suggesting that behavioural rather than genetic compatibility (for the measured personality traits) is important for reproduction. (d) Moreover, some male behavioural characteristics appear to be a signal of male quality: highly exploratory foster males raised chicks (both males and females) in best condition, which themselves raised foster chicks of increased conditions. (e) Furthermore, a number of sex differences in personality traits (both level and consistency) are identified, including different responses to social interactions. (f) Additionally, I show how females with different exploratory tendencies differ in their movement patterns during mate choice. (g) Finally, I demonstrate that in competitive male-male situations, a measurement of condition, the fat score, and aggressive behaviour are positively correlated. These findings are set into sexual selection context (but other evolutionary processes are also considered) and both their ecological and evolutionary consequences are discussed. I outline how these results make a valuable contribution to the research field and discuss their potential to indicate new directions for future studies.

Many animal societies rely on highly influential keystone individuals for proper functioning. When information quality is important for group success, such keystone individuals have the potential to diminish group performance if they possess inaccurate information. Here, we test whether information quality (accurate or inaccurate) influences collective outcomes when keystone individuals are the first to acquire it. We trained keystone or generic individuals to attack or avoid novel stimuli and implanted these trained individuals within groups of naive colony-mates. We subsequently tracked how quickly groups learned about their environment in situations that matched (accurate information) or mismatched (inaccurate information) the training of the trained individual. We found that colonies with just one accurately informed individual were quicker to learn to attack a novel prey stimulus than colonies with no informed individuals. However, this effect was no more pronounced when the informed individual was a keystone individual. In contrast, keystones with inaccurate information had larger effects than generic individuals with identical information: groups containing keystones with inaccurate information took longer to learn to attack/avoid prey/predator stimuli and gained less weight than groups harbouring generic individuals with identical information. Our results convey that misinformed keystone individuals can become points of vulnerability for their societies.

The proximate causes triggering nest abandonment are unclear for most species, including the Yellow Warbler (Dendroica petechia), which abandons nests parasitized by cowbirds (via burial or desertion). Cowbird parasitism and rejection of parasitism are costly to some hosts; therefore cues affecting their responses have important evolutionary implications. Manipulative experiments showed that experimentally adding a cowbird egg elicited similar rejection frequencies (2008: 31.8%; 2009: 26.1%) as naturally laid eggs (2008: 27.1%; 2009: 20.0%). In 2008, interaction with an egg-removing model increased the probability of abandonment and the most aggressive individuals were more likely to bury the model cowbird egg. In 2009, eggs added to nests before sunrise were rejected at a frequency (29.7%) similar to eggs added to nests after sunrise (22.9%). Warblers returning to nests after egg addition peered significantly longer at their clutch than at control nests, shuffled their bodies more frequently when on the eggs and spent more time probing eggs with their bill once settled on their parasitized clutch. Furthermore, although non-mimetic blue eggs were not abandoned significantly more frequently than cowbird eggs (blue 31.1% versus cowbird 21.4%), only blue eggs were ejected from some nests. Thus, warblers use both tactile and visual cues to detect the presence of a parasitic egg in their nest. Eggs added to nests were not rejected at a lower frequency than naturally parasitized nests, as was recorded in a previous study. It is difficult to know whether this increase in abandonment of experimental eggs is due to phenotypic plasticity, genetic changes, or other factors. Egg recognition abilities may have changed because I have shown that the warblers’ behaviour changes before versus after egg addition, whereas no changes were recorded in an earlier study. Finally, not all individuals that buried eggs for the first time in 2009 (21.4%) buried again after being re-parasitized (5.3%), when less time remained in the breeding season relative to the first parasitism event. This suggests that egg rejection and host responsiveness in warblers, and likely other avian hosts that use abandonment as a form of rejection, is affected by environmental cues which may act as genetic expressers.

The proximate causes triggering nest abandonment are unclear for most species, including the Yellow Warbler (Dendroica petechia), which abandons nests parasitized by cowbirds (via burial or desertion). Cowbird parasitism and rejection of parasitism are costly to some hosts; therefore cues affecting their responses have important evolutionary implications. Manipulative experiments showed that experimentally adding a cowbird egg elicited similar rejection frequencies (2008: 31.8%; 2009: 26.1%) as naturally laid eggs (2008: 27.1%; 2009: 20.0%). In 2008, interaction with an egg-removing model increased the probability of abandonment and the most aggressive individuals were more likely to bury the model cowbird egg. In 2009, eggs added to nests before sunrise were rejected at a frequency (29.7%) similar to eggs added to nests after sunrise (22.9%). Warblers returning to nests after egg addition peered significantly longer at their clutch than at control nests, shuffled their bodies more frequently when on the eggs and spent more time probing eggs with their bill once settled on their parasitized clutch. Furthermore, although non-mimetic blue eggs were not abandoned significantly more frequently than cowbird eggs (blue 31.1% versus cowbird 21.4%), only blue eggs were ejected from some nests. Thus, warblers use both tactile and visual cues to detect the presence of a parasitic egg in their nest. Eggs added to nests were not rejected at a lower frequency than naturally parasitized nests, as was recorded in a previous study. It is difficult to know whether this increase in abandonment of experimental eggs is due to phenotypic plasticity, genetic changes, or other factors. Egg recognition abilities may have changed because I have shown that the warblers’ behaviour changes before versus after egg addition, whereas no changes were recorded in an earlier study. Finally, not all individuals that buried eggs for the first time in 2009 (21.4%) buried again after being re-parasitized (5.3%), when less time remained in the breeding season relative to the first parasitism event. This suggests that egg rejection and host responsiveness in warblers, and likely other avian hosts that use abandonment as a form of rejection, is affected by environmental cues which may act as genetic expressers.

Interindividual differences in animal behaviour that are relatively consistent over time and context are referred to as animal personality. Personality has been recognized throughout the entire animal kingdom, in an array of species like molluscs, arthropods, fish, birds and mammals. The personality of non-human animals has been suggested to vary along five different axes, or continua; boldness-shyness, avoidanceexploration, activity, sociability and aggressiveness. Having a relatively fixed personality may seem nonadaptive compared to infinite behavioural plasticity so the individual would be able to respond adaptively to any changes in the environment. There can be physiological limitations to the phenotypic expressions of any trait, including behaviour. Variation in neuroendocrinology may thus explain why animals have personality. A candidate neurochemical that potentially proximately influences and forms personality, is serotonin (5- HT), one of the most omnipotent neurotransmitter of the animal body. In the many realms of the serotonergic system, there may arise individual differences which forms a proximate basis for differences in personality. In this review paper, I discuss the impact of the serotonergic system on a few different personality traits. Depending on the individual’s motivational state, serotonin can dampen or enhance aggression. Serotonin correlates negatively to anxious traits. Feeding behaviour is affected by serotonin in seemingly opposing directions. Overall, serotonin seem to underlie many behaviours that describe animal personality.

Correlated individual differences in behaviour across ecological contexts, or behavioural syndromes, can theoretically constrain individuals' ability to optimally adjust their behaviour for specific contexts.Female Anelosimus studiosus exhibit a unique behavioural polymorphism: 'social' females are tolerant of conspecifics and aggregate in multi-female colonies, while 'solitary' females aggressively defend their singleton webs from intrusion by adult female conspecifics. Previous work found that social females are also less aggressive toward prey and are more fearful of predators.In this study we quantify potential fitness consequences of these correlated behaviours by examining the potential and realised fecundities of the two phenotypes in naturally occurring colonies, and by quantifying their ability to rear offspring as singleton individuals.There were no differences in the fecundities of laboratory-reared females between the phenotypes, nor were there differences in field-collected brooding females from naturally occurring solitary and social nests.Brooding females from solitary and social colonies that were isolated in new nests for the growing season were both capable of rearing their broods; however, females from solitary nests had significantly greater success.These results suggest a fitness consequence to the reduced-aggression syndrome of social females that may represent a general impediment to the evolution of sociality in spiders.

<p>In this thesis, I experimentally investigate feeding selectivity in fallow deer (Dama dama), with respect to plant secondary compounds, especially tannins, which can decrease the quality of foods. I found that fallow deer avoided foods with higher amounts of tannic acid and Quebracho tannin, even though the deer ate some high-tannin food. The food choice was strongly dependent on the context in which the food was presented, so that the food choice in relation to tannin content was relative rather than absolute. When high-tannin food occurred at low frequency, the deer ate proportionally less from this type of food, at least when the difference in tannin content between the two foods was large. A basic implication is that an unpalatable plant type could benefit from its unpalatability, especially when occurring at low frequency. In experiments with two patches, the finding of a stronger within- than between-patch selectivity was mirrored in associational effects. First, low-tannin, palatable food was more eaten when occurring in a high-tannin patch, which corresponds to neighbour contrast susceptibility. Second, high-tannin, unpalatable food in a less defended patch was less eaten, which corresponds to neighbour contrast defence. A proximate cause of the associational effects can be the presence of a simultaneous negative contrast, which was experimentally demonstrated in an additional study. Individual differences in selectivity were present early in life and were consistent over five years, and selectivity was correlated with foraging exploratory behaviour. The results from this thesis suggest that fallow deer are selective in their food choice with respect to tannins from the beginning, and that the frequency of occurrence of different foods, but also the distance between foods and the complexity of presentation, influence the food choice. It is also suggested that a foraging behavioural syndrome is present in mammalian herbivores.</p>

<p>Syftet med denna studie var att undersöka om det fanns olika personlighetstyper hos mjölkkor av raserna SRB och SLB och om dessa personlighetstyper skilde sig mellan ras, ålder och vilken sida djuren stått på i lösdriften. Korna observerades i tre olika testmiljöer för att se huruvida konsistenta de var i deras beteenden: ostörda i lösdriften, vid mjölkning och med ett främmande objekt i lösdriften. Beteenden som studerades var normala beteenden, sociala beteenden, tramp och sparkningar vid mjölkning och interaktioner med det främmande objektet. Tolv beteendevariabler användes i en PCA (principal component analysis) och visade två komponenter som tillsammans kunde förklara 51,2 % av den totala variansen. Den första komponenten speglade aggression och extraversion, som ingår i medgörlighet och extraversion i den mänskliga femfaktorsmodellen. Den andra komponenten speglade ett mer introvert beteende och rädsla, som går under extraversion och neuroticism i samma modell. Oberoende T-test visade inga signifikanta skillnader mellan någon av komponenterna och ras eller sida i lösdriften p>0,05, däremot en tendens till skillnad mellan den första komponenten och ålder, där den äldre gruppen individer visade tydligare personlighetsdrag p<0.1. Tidigare studier har visat att personlighetsdimensioner som medgörlighet, neuroticism och extraversion ofta förekommer bland flera arter. Då olika personligheter hanterar stressfulla situationer på olika sätt, är detta ämne av stor vikt när det gäller förbättrandet av djurens välfärd.</p> / <p>The purpose of this study was to investigate if different personality dimensions existed in dairy cows of two breeds (SRB and Holstein) and if these personality dimensions differed between breed, age and how the animals were placed in the loose housing system. To investigate behavioural consistency, the cows were observed in three different situations: uninterrupted in their home pen, during milking and with a novel object in their home pen. Normal and social behaviour was observed as well as stepping and kicking during milking and interactions with the novel object. Twelve behavioural variables were used in a principal component analysis, which showed two components that together explained 51,2 % of the total variance. The first component reflected aggression and extraversion, which are included in agreeableness and extraversion in the human five-factor model. The second component reflected fear and introversion, which are included in neuroticism and extraversion in the same model. Independent-samples T test showed no significant differences between any of the components and breed or placement in the loose housing system p>0,05, however there was a tendency between the first component and age, where the older group showed a more defined personality p<0,1. Other studies have showed that personality dimensions such as agreeableness, neuroticism and extraversion often exist in several species. Different personalities cope with stressful situations in different ways, making this topic relevant to the improvement of animal welfare.</p>

In this thesis, I experimentally investigate feeding selectivity in fallow deer (Dama dama), with respect to plant secondary compounds, especially tannins, which can decrease the quality of foods. I found that fallow deer avoided foods with higher amounts of tannic acid and Quebracho tannin, even though the deer ate some high-tannin food. The food choice was strongly dependent on the context in which the food was presented, so that the food choice in relation to tannin content was relative rather than absolute. When high-tannin food occurred at low frequency, the deer ate proportionally less from this type of food, at least when the difference in tannin content between the two foods was large. A basic implication is that an unpalatable plant type could benefit from its unpalatability, especially when occurring at low frequency. In experiments with two patches, the finding of a stronger within- than between-patch selectivity was mirrored in associational effects. First, low-tannin, palatable food was more eaten when occurring in a high-tannin patch, which corresponds to neighbour contrast susceptibility. Second, high-tannin, unpalatable food in a less defended patch was less eaten, which corresponds to neighbour contrast defence. A proximate cause of the associational effects can be the presence of a simultaneous negative contrast, which was experimentally demonstrated in an additional study. Individual differences in selectivity were present early in life and were consistent over five years, and selectivity was correlated with foraging exploratory behaviour. The results from this thesis suggest that fallow deer are selective in their food choice with respect to tannins from the beginning, and that the frequency of occurrence of different foods, but also the distance between foods and the complexity of presentation, influence the food choice. It is also suggested that a foraging behavioural syndrome is present in mammalian herbivores.