Behavioural profiles are shaped during ontogeny - the time from the moment the egg is fertilized until the death of an individual. To increase their fitness, subjects have to adjust themselves to their abiotic as well as to their biotic environment. The latter does not only consist of inter- but also intraspecies interactions which can be defined as social environment. The social environment can support welfare and health. However, it can also result in severe stress, eventually leading to diseases and even death. Thus, the social environment represents a most influential stressor, which, during pregnancy, can even be crucial for the development of the offspring as well. For example in wild cavies, instability of the social environment during pregnancy and lactation affects the development of the offspring: Daughters of mothers living in an unstable social environment exhibit a profound behavioural masculinization in contrast to daughters of mothers which had lived in a stable social environment [1].

In the present study, we investigated whether daughters of mothers living in unstable social environments have advantages over daughters of mothers living in stable social environments in situations where resources are scarce. The idea of this experiment is that high population density situations are characterized by a high degree of instability and scarce resources, whereas low population density situations are characterized by a high degree of stability and sufficient resources. Thus, in situations in which resources are limited, competitive abilities are important and masculine traits facilitate the attainment of dominant social positions which in turn help to secure resources more efficiently. Under such conditions masculinized females might fare better than non-masculinized ones. We analysed cortisol reactivity, body weight development and dominance establishment and will discuss whether the different behavioural phenotypes are caused by maternal effects and may represent adaptations to prevailing and future environmental conditions. [2]