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Social species rely on acquiring appropriate social skills to navigate their social environment. Developmental plasticity allows individuals to develop an appropriate phenotype by receiving cues from their social and nonsocial environment. However, committing to a specific phenotype early in life may prove maladaptive if there is a mismatch between the early and future environment. To address potential mismatches, multiple or extended sensitive periods provide opportunities for individuals to gather the necessary information in changing and predictable environments. Cooperative breeders, like the highly social cichlid Neolamprologus pulcher , typically experience changing environments especially during dispersal. While we know that early development is critical for the acquisition of social competence, it remains uncertain whether a second or extended sensitive period exists around the time of dispersal decisions in cooperative breeders. Here we manipulated the early and late life social environment of N. pulcher and asked whether individuals retain plasticity to adjust their social phenotype around sexual maturation. Juveniles were raised for 2 months with or without adults and tested for social competence. Shortly before reaching sexual maturity, they were randomly assigned to be housed alone, with siblings or with a social group for an additional 2 months before undergoing further social competence testing. Aggressive and submissive behaviours were assessed in two social contexts. Fish raised with a large group exhibited greater social competence compared to those raised only among siblings, regardless of subsequent social experiences. This suggests that either early life cues reliably predict future environments in nature or that constraints on late life plasticity exist. • We study the acquisition of social competence in cooperatively breeding fish. • We investigate whether sensitive periods exist early and late in life. • Early development is critical in acquiring social competence in Neolamprologus pulcher. • Later development does not influence the social competence in N. pulcher. [ABSTRACT FROM AUTHOR]

The ability to flexibly adjust behaviour to social and non-social challenges is important for successfully navigating variable environments. Social competence, i.e. adaptive behavioural flexibility in the social domain, allows individuals to optimize their expression of social behaviour. Behavioural flexibility outside the social domain aids in coping with ecological challenges. However, it is unknown if social and non-social behavioural flexibility share common underlying cognitive mechanisms. Support for such shared mechanism would be provided if the same neural mechanisms in the brain affected social and non-social behavioural flexibility similarly. We used individuals of the cooperatively breeding fish Neolamprologus pulcher that had undergone early-life programming of the hypothalamic–pituitary–interrenal axis by exposure to (i) cortisol, (ii) the glucocorticoid receptor antagonist mifepristone, or (iii) control treatments, and where effects of stress-axis programming on social flexibility occurred. One year after the treatments, adults learned a colour discrimination task and subsequently, a reversal-learning task testing for behavioural flexibility. Early-life mifepristone treatment marginally enhanced learning performance, whereas cortisol treatment significantly reduced behavioural flexibility. Thus, early-life cortisol treatment reduced both social and non-social behavioural flexibility, suggesting a shared cognitive basis of behavioural flexibility. Further our findings imply that early-life stress programming affects the ability of organisms to flexibly cope with environmental stressors. [ABSTRACT FROM AUTHOR]

The early social environment can have substantial, lifelong effects on vertebrate social behaviour, which can be mediated by developmental plasticity of brain gene expression. Early-life effects can influence immediate behavioural responses towards later-life social challenges and can activate different gene expression responses. However, while genomic responses to social challenges have been reported frequently, how developmental experience influences the shape of these genomic reaction norms remains largely unexplored. We tested how manipulating the early social environment of juvenile cooperatively breeding cichlids, Neolamprologus pulcher, affects their behavioural and brain genomic responses when competing over a resource. Juveniles were reared either with or without a breeder pair and a helper. Fish reared with family members behaved more appropriately in the competition than when reared without. We investigated whether the different social rearing environments also affected the genomic responses to the social challenge. A set of candidate genes, coding for hormones and receptors influencing social behaviour, were measured in the telencephalon and hypothalamus. Social environment and social challenge both influenced gene expression of egr-1 (early growth response 1) and gr1 (glucocorticoid receptor 1) in the telencephalon and of bdnf (brain-derived neurotrophic factor) in the hypothalamus. A global analysis of the 11 expression patterns in the two brain areas showed that neurogenomic states diverged more strongly between intruder fish and control fish when they had been reared in a natural social setting. Our results show that same molecular pathways may be used differently in response to a social challenge depending on early-life experiences. [ABSTRACT FROM AUTHOR]

Typically, animals spend a considerable portion of their time with social interactions involving mates, offspring, competitors and group members. The social performance during these interactions can strongly depend on the social environment individuals have experienced early in life. Despite a considerable number of experiments investigating long-term effects of the early social environment, our understanding of the behavioural mechanisms mediating these effects is still limited, mainly for two reasons. (1) Only in few experimental studies have researchers actually observed and quantified the behaviour of their study animals during the social treatment. (2) Even if differences in social interactions between social rearing treatments are reported, these differences might not be causally linked to any observed long-term effects later in life. The aim of this review was to investigate whether behavioural records of animals during the experimental manipulation of their social environment can help (1) identifying behavioural mechanisms involved in a long-term effect and (2) obtaining a better understanding of the long-term consequences of early manipulations. First, I review studies that manipulated the social environment at an early stage of the ontogeny, observed the social interactions and behaviour during the social experience phase and subsequently tested the performance in social and non-social behavioural tasks at a later life stage. In all reviewed studies, treatment differences were reported both in social interactions during the social experience phase and in social and/or non-social behaviours later in life. Second, I discuss four classes of behavioural mechanisms that can cause the reported long-term effects of social experience, namely learning by experience, social learning, sensory stimulation and social cueing. I conclude that social interactions during the social experience phase should always be recorded for at least two reasons. Knowledge about how the social interactions differ between rearing treatments (1) permits researchers to formulate hypotheses about candidate mechanisms causing long-term effects on behaviour and (2) can help to interpret unexpected outcomes of developmental experiments. Finally, I propose that as a crucial ultimate step towards understanding effects of the early social environment, we should develop targeted experiments testing for the causality of identified candidate mechanism. [ABSTRACT FROM AUTHOR]

Social competence is defined as the ability of an animal to optimize the expression of social behaviour as a function of the available social information. The social environment encountered early in life can affect the expression of various social behaviours later in life. We investigated whether early social experience can affect social competence. In the cooperatively breeding cichlid Neolamprologus pulcher, we tested whether individuals reared with older brood-caring conspecifics persistently perform better in a series of tasks (1) simulating different social contexts, (2) assigning individuals different social roles and (3) exposing them to an unknown social situation. Fish that had been reared together with older conspecifics showed more appropriate behaviours both as winners (more aggressive displays) and as losers (more submissive displays) when aggressively competing with peers over a resource, and when trying to be accepted as subordinate group member and prospective brood care helper by an unfamiliar dominant pair (more submissive displays near shelters), a situation they had never encountered before. In both tasks fish that had grown up with older fish were tolerated better by conspecifics than fish reared with same-age siblings only. We detected effects of the early environment on social behaviour in the juvenile and adult stages of the test fish. Our results suggest that growing up in more complex social groups fosters a general social ability (i.e. social competence) in N. pulcher that improves their performance across different social roles and contexts, and which may provide fitness benefits. [Copyright &y& Elsevier]

Behavioural interactions between conspecifics rely on the appreciation of social cues, which is achieved through biochemical switching of pre-existing neurophysiological pathways. Serotonin is one of the major neurotransmitters in the central nervous system responsible for the modulation of physiological and behavioural traits, in particular social behaviour. The relative importance of serotonin in modulating optimal social responses to the available social information (i.e., social competence) is yet unknown. Here we investigate how serotonin and the serotonin 1 A receptor (5-HT 1A) modulate social competence in a competitive context. In the cooperatively breeding cichlid Neolamprologus pulcher , we pharmacologically manipulated the serotonin availability and 5-HT 1A activity to test their effects on social behaviours during an asymmetric contest between the owner of a defended territory containing a shelter and an intruder devoid of a territory. In this contest, the adequate response by the intruders, the focal individuals in our study, is to show submissive behaviour in order to avoid eviction from the vicinity of the shelter. While the serotonin enhancer Fluoxetine did not affect the frequency of submission towards territory owners, reducing serotonin by a low dosage of 4-Chloro-DL-phenylalanine (PCPA) increased submissive behaviour. Furthermore, threat displays towards territory owners were reduced at high dosages of Fluoxetine and also at the lowest dosage of PCPA. 5-HT 1A activation increased threat displays by intruders, indicating that this receptor may not be involved in regulating social competence. We conclude that serotonin, but not its receptor 5-HT 1A plays an important role in the regulation of social competence. [ABSTRACT FROM AUTHOR]