Environmental change poses challenges to many organisms. The resilience of a species to such change depends on its ability to respond adaptively. Social flexibility is such an adaptive response, whereby individuals of both sexes change their reproductive tactics facultatively in response to fluctuating environmental conditions, leading to changes in the social system. Social flexibility focuses on individual flexibility, and provides a unique opportunity to study both the ultimate and proximate causes of sociality by comparing between solitary and group-living individuals of the same population: why do animals form groups and how is group-living regulated by the environment and the neuro-endocrine system? These key questions have been studied for the past ten years in the striped mouse Rhabdomys pumilio. High population density favours philopatry and group-living, while reproductive competition favours dispersal and solitary-living. Studies of genetic parentage reveal that relative fitness of alternative reproductive tactics depends on the prevailing environment. Tactics have different fitness under constrained ecological conditions, when competitive ability is important. Under conditions with relaxed ecological constraints, alternative tactics can yield equal fitness. Both male and female striped mice display alternative reproductive tactics based on a single strategy, i.e. all individuals follow the same decision rules. These changes are regulated by endocrine mechanisms. Social flexibility is regarded as an adaptation to unpredictably changing environments, selecting for high phenotypic flexibility based on a broad reaction norm, not on genetic polymorphism for specific tactics. Social flexibilityBehavioural ecology seeks to understand how animals survive and reproduce in their natural environment. However, the environment is not static, but changes in predictable and unpredictable ways (Wingfield, 2003). Long-term field studies are needed to understand individual responses to changing environments and how these may affect the evolution of social behaviour (Clutton-Brock & Sheldon 2010). Natural environments are predicted to change faster in the future due to anthropogenic induced climate change (Friedlingstein 2008), testing the limits of behavioural adaptation and resilience of natural populations.The term social flexibility is generally used to describe modifications of individual social behaviours, but its usage differs among authors. A search in the ISI Web of Science for the term 'social flexibility' revealed 276 publications in the field of Zoology for the period 1900 to 2010. Most papers were about 'behavioural flexibility' of non-social behaviours, only 84 papers were about flexibility in social behaviour and no clear difference was made between 'social flexibility', 'intra-specific variation in social behaviour', and 'alternative reproductive tactics'. Used in such a way, the term 'social flexibility' simply means that social behaviour is flexible, which is true for nearly all social behavi...

Summary 1.The time at which animals enter puberty and become sexually mature is a significant life-history trait, influencing lifetime reproductive success. Great variation exists both between and within species. 2. The proximate mechanisms regulating the time at which a male enters puberty are not wellunderstood. Environmental cues are predicted to provide the relevant information on resource availability and opportunities for reproduction. When these are good the onset of puberty begins whereas at other times investment in survival becomes more important. 3. Male African striped mice ( Rhabdomys pumilio ) demonstrate large variation in the age at which they enter puberty, with grassland populations starting at 4 weeks old and semi-desert populations at over 10 weeks old. 4. We predicted that differences in the availability of food, social organization and population density could explain these differences. 5. Using data on 170 individual males from 4 years of field studies in a semi-desert population, we found that males became scrotal at a younger age when no breeding male was present in their group and when food was abundant, while population density had no effect. 6.In laboratory experiments we demonstrated that males fed with poor protein food, that regularly encounter larger unfamiliar males (mimicking high population density), and that live in family groups with their father present, become scrotal at a significantly later age, independent of their growth rate. 7. Males housed in family groups have lower testosterone but higher corticosterone levels than singly housed males, indicating they are sexually suppressed. When they become scrotal in their family group, their testes are only half as large as those of their singly housed brothers, and they contained significantly less sperm. 8. We conclude that male striped mice have a flexible response to the onset of puberty, and that the onset of sexual maturity is dependent on several environmental cues. Our results indicate that there is no threshold body mass, which, when reached, would automatically trigger puberty in male striped mice. 9. Male helpers in some species are reproductively suppressed, but ours is the first study that demonstrated the importance of different ecological factors in the timing of puberty in male helpers in a facultative cooperatively breeding species.

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International audiencePersonality in free-living individuals has predominantly been measured under standardized laboratory conditions. Such measurements have been then linked to life-history traits, fitness and survival. Yet, it remains unclear how such personality measurements reflect the variation shown by free-living individuals, if the same measurements were taken directly in their natural environment. Here, we used free-living African striped mice to test whether the personality traits of activity, boldness, exploration and aggression are consistent when measured in the laboratory and in the field contexts. First, we established whether personality traits were repeatable and consistent within one context. Next, we compared measurements across the two different contexts. Additionally, we established whether personality traits were correlated with one another in behavioural syndromes and assessed whether the resulting syndromes were consistent across the two contexts. All personality traits in the laboratory were measured using classical personality tests. The same tests were then modified and used to measure personality of the same individuals in the field. All personality traits were highly repeatable and consistent within the same context. In addition, individuals behaved consistently for all the behaviours measured both in the laboratory and in the field. Further, we found that the presence of two correlated context-specific separate latent variables (one for the field and one for the laboratory) underpinned all the behaviours measured, indicating that there is a context-specific syndrome in this species. Overall, our results confirm that measurements of personality traits of wild striped mouse individuals recorded in the laboratory environment are consistent with the traits that the same individuals show under natural conditions