How an animal copes with its biological characteristics and environment is one of the most interesting questions within animal behavior. To get detailed insights into a species behavioral routines and natural needs, the analyses of activity budgets of an animal species is a reliable ethological tool. By analyzing the activity budgets of more than 30 mammalian species, our research group focuses primarily on determining nocturnal behavioral rhythms. Further, it is of great interest which biological and environmental factors cause adaptations or changes in these species specific rhythms. To analyze these complex interrelations, we collect data from more than 25 EAZA zoos. In addition, we combine zoo-based analyses with data collected from the wild. Using state of the art methods such as artificial intelligence allows us to create a bigger picture on animal behavior. Our multi-zoo and long-term studies provide detailed insights into a time of day that has been overlooked and underestimated by ethologists for too long. The results of this holistic approach expand our knowledge of the nocturnal behavior of endangered species, highlight factors that influence it, and thus enable the continued development of animal welfare assessments and management guidelines.