Experimental evidence for helping and hindering by previous offspring in the cooperative-breeding Seychelles warbler Acrocephalus sechellensis

Prebreeding Seychelles warblers (Acrocephalus sechellensis) frequently act as helpers on their natal territory, aiding in territory defence, predator mobbing, nest-building, incubation (only females) and feeding dependent young of their parents. In some cases helpers could attain breeding status (e.g. by joint-nesting) in their natal group and become co-breeders. Comparisons of group size and reproductive success on a given quality territory suggest that the presence of alloparents (helpers and cobreeders) significantly affects the reproductive success of their parents. The influence of alloparents on reproductive success was examined by removing alloparents from breeding units and comparing the success of natural-sized and artificially reduced groups. Removal experiments, controlled for territory quality, group size and breeder age, showed that the presence of one alloparent significantly improved the reproductive success of its parents. Analysis strongly suggests that this was entirely due to helping behaviour (i.e. providing care to offspring of their parents), thereby improving the helper's inclusive fitness benefits from staying at home. However, these experiments showed also that the presence of two or more alloparents in medium-quality territories significantly decreased reproductive success, compared with groups with one alloparent. Several lines of evidence suggest that this may have been due to the joint-nesting and reproductive competition that could occur in breeding groups, or simply to resource depression when a large number of previous offspring remained on their natal territory

Punish the thief:Coevolution of defense and cautiousness stabilizes ownership

Ownership of non-controllable resources usually has to be maintained by costly defense against competitors. Whether defense and thus ownership pays in terms of fitness depends on its effectiveness in preventing theft. We show that if the owners' willingness to defend varies in the population and information about it is available to potential thieves then the ability to react to this information and thus avoid being attacked by the owner is selected for. This can lead to a positive evolutionary feedback between cautiousness in intruders and aggressiveness in owners. This feedback can maintain ownership when the actual direct effectiveness of defense in reducing theft is very low or even absent, effectively turning defense into punishment. We conclude that the deterrence effect of defense in many situations could be stronger than that of prevention and that for many real-world scenarios the purpose of defense of resources might be to punish rather than to drive away intruders. Significance statement Many animals defend resources against conspecifics. Resource defense can usually only evolve if its costs are paid for by foiling attempts at theft. We show that if potential thieves can detect differences in aggressiveness between owners then cautious intruders and aggressive owners coevolve so that in the end even ineffective defense deters thieves and maintains ownership. This result greatly extends the number of situations in which we expect resource defense to evolve and has the potential to unify the concepts of defense and punishment

Why and how the early-life environment affects development of coping behaviours

Understanding the ways in which individuals cope with threats, respond to challenges, make use of opportunities and mediate the harmful effects of their surroundings is important for predicting their ability to function in a rapidly changing world. Perhaps one of the most essential drivers of coping behaviour of adults is the environment experienced during their early-life development. Although the study of coping, defined as behaviours displayed in response to environmental challenges, has a long and rich research history in biology, recent literature has repeatedly pointed out that the processes through which coping behaviours develop in individuals are still largely unknown. In this review, we make a move towards integrating ultimate and proximate lines of coping behaviour research. After broadly defining coping behaviours (1), we review why, from an evolutionary perspective, the development of coping has become tightly linked to the early-life environment (2), which relevant developmental processes are most important in creating coping behaviours adjusted to the early-life environment (3), which influences have been shown to impact those developmental processes (4) and what the adaptive significance of intergenerational transmission of coping behaviours is, in the context of behavioural adaptations to a fast changing world (5). Important concepts such as effects of parents, habitat, nutrition, social group and stress are discussed using examples from empirical studies on mammals, fish, birds and other animals. In the discussion, we address important problems that arise when studying the development of coping behaviours and suggest solutions

Keeping up with environmental change:The importance of sociality

In the current era of rapid climate change, populations are facing environments in which food availability can quickly decline or become highly unpredictable. These conditions may require a high degree of flexibility of individuals and populations to adequately respond to such changes. We propose that the evolution of such high flexibility may be facilitated in social animals that form groups and cooperate in important tasks that critically affect survival and reproduction and ultimately affect adaptive capacity. We argue that sociality is likely to be a key, yet largely overlooked factor that shapes rather than limits the potential for phenotypic plasticity. Cooperatively breeding species are most suitable for studying the influence of both the physical and the social environmental conditions on shaping the phenotypic plasticity of individuals. Cooperative breeders display variation in group size and structure, and in the extent of cooperation and competition between their members. In addition, immigrants may impose costs and/or benefits on other group members, as well as on the whole group. In cooperative breeders, we elucidate why and how group formation and interactions between group members can provide adaptive benefits to some or all individuals in the group. Observed adjustments in social behaviour may be strategic and ultimately enhance individual fitness benefits, and thus improve group and population persistence. Future studies should examine how ecology and sociality together shape the adjustment of animals to rapid and extreme environmental change. In addition to identifying how changes in physical and social factors impact individual behaviour, group formation and sociality, it is crucial to assess associated costs and benefits by exploring the life histories of all group members. Understanding this requires population models, as they integrate all the critical life-history phases, and different types of sociality. We are confident that future research into the ecology and social dynamics will reveal new avenues for the adaptive ability of cooperative breeders and other social species