Sexual selection and personality in zebra finches, Taeniopygia guttata

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.European Social Fun

Different or alike? Female rainbow kribs choose males of similar consistency and dissimilar level of boldness

Although the existence of consistent between-individual differences in behaviour (‘personality differences’) has been well documented during the last decade, the adaptive value of such behavioural limitations remains an open field for researchers of animal behaviour. Personalities clearly restrict individuals in their ability to adjust their behaviour to different conditions. However, sheer costs of flexibility cannot explain the polymorphism created by personality variation. In a correlative approach, we here tested whether mate choice might act as a major driving force maintaining personality variation in the monogamous, biparental rainbow krib, Pelvicachromis pulcher. We personality-typed all males and females for their boldness (activity under simulated predation risk) and allowed females to choose between two males that differed in their boldness (behavioural level and consistency). Prior to the choice, females were allowed to observe both males, expressing their natural boldness towards a video-animated natural predator. Both sexes showed personality differences in boldness over the short and long term. Furthermore, when removing side-biased females, we found a disassortative mating preference for the behavioural level and an assortative preference for behavioural consistency in boldness. These preference patterns might facilitate effective parental role allocation during offspring care and/or provide genetic benefits. Our results suggest that sexual selection plays an important role in the evolution of personality differences

Predictability is attractive: female preference for behaviourally consistent males but no preference for the level of male aggression in a bi-parental cichlid

Although personality traits can largely affect individual fitness we know little about the evolutionary forces generating and maintaining personality variation. Here, we investigated the hypothesis that personality variation in aggression is sexually selected in the monogamous, bi-parental cichlid Pelvicachromis pulcher. In this species, breeding pairs form territories and they aggressively defend their territory and offspring against con- and heterospecific intruders. In our mate choice study, we followed up two alternative hypotheses. We either expected females to show a directional preference for a high level and high consistency of aggression (potentially indicating mate choice for male parental quality). Alternatively, we expected females to choose males for (dis-)similarity in the level/consistency of aggression (potentially indicating mate choice for compatibility). Individual level and consistency of aggression were assessed for males and females using mirror tests. After eavesdropping on aggressive behaviour of two males (differing in level and consistency of aggression) females were then allowed to choose between the two males. Males, but not females, showed personality variation in aggression. Further, females generally preferred consistent over inconsistent males independent of their level of aggression. We did not detect a general preference for the level of male aggression. However, we found an above average preference for consistent high-aggression males; whereas female preference for inconsistent high-aggression did not deviate from random choice. Our results suggest behavioural consistency of aggression in male rainbow kribs is selected for via female mate choice. Further, our study underlines the importance of considering both the level and the consistency of a behavioural trait in studies of animal behaviour

Wild zebra finches do not use social information from conspecific reproductive success for nest site choice and clutch size decisions

Information about the quality of local habitat can greatly help to improve an individual’s decision-making and, ultimately, its fitness. Nevertheless, little is known about the mechanisms and significance of information use in reproductive decisions, especially in unpredictable environments. We tested the hypothesis that perceived breeding success of conspecifics serves as a cue for habitat quality and hence influences breeding decisions (nest site choice and clutch size), using the zebra finch (Taeniopygia guttata) as a model species. Zebra finches breed opportunistically in the unpredictable, arid zone of Australia. They often inspect the nests of conspecifics, potentially to prospect on conspecific reproductive success, i.e., to collect social information. We conducted a clutch and brood size manipulation to experimentally create the perception of high and low quality areas. In six areas, clutch sizes of almost 300 zebra finch nests were either all increased (N = 3 areas) or reduced (N = 3 areas) throughout one breeding season. The number of breeding pairs and sizes of newly laid clutches were not significantly affected by the manipulated reproductive success of the areas. Thus, zebra finches did not use social cues for their reproductive decisions, which contrasts with findings of species in temperate zones, and could be an adaptation to the high unpredictability of their habitat. Even the personal experience of rebreeding birds did not directly affect their clutch size. Our study suggests that zebra finches employ a high level of opportunism as a key strategy for reproduction. Further, this is the first study to our knowledge using an experimental approach in the wild to demonstrate that decision-making in unpredictable natural environments might differ from decision-making in temperate environments with seasonal breeding

Begging calls provide social cues for prospecting conspecifics in wild zebra finches

Social information can spread fast and help animals adapt in fluctuating environments. Prospecting on the breeding sites of others, a widespread behavior, can help to maximize reproduction by, for instance, settling in the same area as other successful breeders. Previous studies have shown that successful broods have the highest number of prospectors and that they are visited most when offspring in nesting sites are already old, making the information more reliable. In this field study, we experimentally tested how prospectors are attracted to successful nest sites. We presented wild Zebra Finches (Taeniopygia guttata) with different visual or acoustic cues in nest boxes, simulating the presence of small or large clutches or broods. More Zebra Finches visited experimental nests that were associated with playback recordings of begging calls of large broods (7 chicks) as opposed to begging calls of small broods (3 chicks) and controls (white noise and silence). On the other hand, visual cues (nests with different numbers of eggs or rocks), representing nests at early stages, did not influence either the probability of visits, nor number or duration of visits. We present the first evidence that begging calls of chicks in the nest, a signal intended for kin communication, can also provide social information to unrelated prospecting conspecifics. This information could potentially be used for a fast initial assessment of the quality of a breeding site

Nosy neighbours: large broods attract more visitors. A field experiment in the pied flycatcher, Ficedula hypoleuca

Life is uncertain. To reduce uncertainty and make adaptive decisions, individuals need to collect information. Individuals often visit the breeding sites of their conspecifics (i.e., “prospect”), likely to assess conspecifics’ reproductive success and to use such information to identify high-quality spots for future breeding. We investigated whether visitation rate by prospectors and success of visited sites are causally linked. We manipulated the reproductive success (enlarged, reduced, and control broods) in a nest-box population of migratory pied flycatchers, Ficedula hypoleuca, in Finland. We measured the visitation rates of prospectors at 87 nest-boxes continuously from manipulation (day 3 after hatching) to fledging. 302 adult pied flycatchers prospected 9194 times on these manipulated nests (at least 78% of detected prospectors were successful breeders). While the number of visitors and visits was not influenced by the relative change in brood size we induced, the resulting absolute brood size predicted the prospecting behaviour: the larger the brood size after manipulation, the more visitors and visits a nest had. The parental provisioning rate at a nest and brood size pre-manipulation did not predict the number of visitors or visits post-manipulation. More visitors, however, inspected early than late nests and broods in good condition. Our study suggests that individuals collect social information when visiting conspecific nests during breeding and provides evidence that large broods attract more visitors than small broods. We discuss the results in light of individual decision-making by animals in their natural environments

High air temperatures induce temporal, spatial and social changes in the foraging behaviour of wild zebra finches

Understanding how heatwaves affect organisms is becoming an important issue in animal behaviour, given the changing climate. Exposure to high air temperatures can lead to lethal hyperthermia, when individuals are no longer able to maintain body temperature within their optimal physiological range. Animals will rapidly adjust their behaviour, prioritizing heat dissipation through activities such as drinking and sitting in shade to maintain their body temperature over other activities, such as foraging. Here, we used an automated logging system to consider both the spatial and temporal foraging patterns under a range of different air temperatures at an individual level, in a strictly granivorous species in the wild. We continuously monitored individual foraging activity of wild zebra finches, Taeniopygia guttata, a species well adapted to arid conditions, in an Australian arid area across two heatwave events. High air temperatures significantly reduced foraging activity, with the extent of this effect depending on the time of day. They also led to a significant decrease in the number of birds foraging together and to birds spending a higher proportion of their foraging activity close to a water supply. As temperatures exceeded 35 °C we saw a significant escalation of heat dissipation behaviour. Our results indicate that extreme air temperatures significantly affected temporal, social and spatial characteristics of zebra finch foraging behaviour and these are likely to adversely reduce an individual's capacity to forage efficiently, and consequently its food intake in the short term, while also potentially having implications for both reproduction and survival in the long term

Do female rainbow kribs choose males on the basis of their apparent aggression and boldness? A non-correlational mate choice study

Abstract: Consistent between-individual differences in behaviour, known as personality differences, are heritable and have consequences for individual survival and reproductive success. Therefore, it is likely that personality differences are not just under natural but also under sexual selection. Indeed, the recently developed idea that individuals choose their mate based on its personality finds empirical support. However, most studies on mate choice based on personality traits are correlative pioneering work and there is a paucity of experimental studies that test for causality by disentangling personality measures from other, potentially correlated traits that may be important during mate choice. Here, we tested female preference for the apparent level and consistency of either male aggression (measured as mean distance of approach towards an animated opponent, manipulated by locating males at a fixed distance) or male boldness (measured as activity under a simulated predation threat, manipulated using a gradient in ambient water temperature) in a bi-parental West African cichlid, Pelvicachromis pulcher. Females could observe the apparent behaviour of paired stimulus males and were allowed to choose between the two stimulus males in a subsequent choice test. We found no direct effect of male apparent aggression/boldness on female choice, but an indirect effect such that female preference for the apparently bold male increased with increasing within-male pair contrast in their apparent level of boldness. Our results indicate females consider male boldness per se during mate choice, suggesting male boldness is sexually selected in our study species. Significance statement: Ever since Darwin introduced the concept of sexual selection, female choice has been studied extensively. However, the hypothesis that consistent between-individual differences in behaviour (known as personality differences) affect mate choice is relatively new. Correlative studies support this idea but provide only suggestive evidence. Here, we used behavioural manipulations in order to disentangle male behaviour from other, potentially correlated male traits, allowing us to test for causality between female choice and personality differences in male aggression and boldness (both in level and consistency of behaviour) in a bi-parental cichlid. We found no overall female preference for male apparent behaviour, but female preference for the bold-appearing male increased with increasing between-male contrast in apparent boldness. Our results indicate a causal link between female choice and male boldness. In future, behavioural manipulations using a temperature gradient could provide further valuable insights

Early-life social environment predicts social network position in wild zebra finches

Early-life experience can fundamentally shape individual life-history trajectories. Previous research has suggested that exposure to stress during development causes differences in social behaviour later in life. In captivity, juvenile zebra finches exposed to elevated corticosterone levels were less socially choosy and more central in their social networks when compared to untreated siblings. These differences extended to other aspects of social life, with ‘stress-exposed’ juveniles switching social learning strategies and juvenile males less faithfully learning their father's song. However, while this body of research suggests that the impacts of early-life stress could be profound, it remains unknown whether such effects are strong enough to be expressed under natural conditions. Here, we collected data on social associations of zebra finches in the Australian desert after experimentally manipulating brood sizes. Juveniles from enlarged broods experienced heightened sibling competition, and we predicted that they would express similar patterns of social associations to stress-treated birds in the captive study by having more, but less differentiated, relationships. We show striking support for the suggested consequences of developmental stress on social network positions, with our data from the wild replicating the same results in 9 out of 10 predictions previously tested in captivity. Chicks raised in enlarged broods foraged with greater numbers of conspecifics but were less ‘choosy’ and more central in the social network. Our results confirm that the natural range of variation in early-life experience can be sufficient to predict individuals' social trajectories and support theory highlighting the potential importance of developmental conditions on behaviour

Sex-specific covariance between metabolic rate, behaviour and morphology in the ground beetle Carabus hortensis

Background Individuals within the same species often differ in their metabolic rates, which may covary with behavioural traits (such as exploration), that are consistent across time and/or contexts, and morphological traits. Yet, despite the frequent occurrence of sexual dimorphisms in morphology and behaviour, few studies have assessed whether and how sexes differ in metabolic trait covariances. Methods We investigated sex-specific relationships among resting or active metabolic rate (RMR and AMR, respectively) with exploratory behaviour, measured independently of metabolic rate in a novel environment, body size and body mass, in Carabus hortensis ground beetles. Results RMR, AMR and exploratory behaviour were repeatable among individuals across time, except for male RMR which was unrepeatable. Female RMR neither correlated with exploratory behaviour nor body size/body mass. In contrast, AMR was correlated with both body size and exploratory behaviour. Males with larger body sizes had higher AMR, whereas females with larger body sizes had lower AMR. Both male and female AMR were significantly related to exploratory behaviour, though the relationships between AMR and exploration were body mass-dependent in males and temperature-dependent in females. Discussion Differences between sexes exist in the covariances between metabolic rate, body size and exploratory behaviour. This suggests that selection acts differently on males and females to produce these trait covariances with potentially important consequences for individual fitness