Due to a stabile social hierarchy, guinea pigs rely on their intuition to decide whether to compete or to escape. So far, there has been limited research on how the sexual cycle may shape female social behaviour in animals. Researchers from the University of Veterinary Medicine, Vienna, and the University of Vienna showed now that flight was the preferred strategy during experimental confrontation of two females during oestrus. If the animals were not ready to mate, however, their stress hormone level increased stronger and physical contact was more frequent.