Overmarking occurs in high rate in equids. Despite the fact, that many hypotheses explain the phenomenon no one fitted well for overmarking in equids. In this research, we observed 140 individuals of all three zebra species (Grévy’s zebra, mountain zebra, and plains zebra) and African wild ass spread in five Czech zoos. We found that overmarking serves to express social bonds between individuals and to strengthen the group cohesion. On the other hand, the time of exploration and investigation of the elimination is most likely associated with reproductive behaviour.