Urbanization involves a drastic change of the environment and is considered one of the most important threats to biodiversity. Although there is lots of attention on how urbanization has affected behavioural changes, the effects on intra-specific behaviours like cooperation and competition has been neglected, despite its importance for fitness. In this EU funded project I use a citizen science approach, combined with new experiments to investigate the underlying mechanisms of changes in social behaviours and the long term population consequences due to urbanization.