The invention relates to a data network for automatically monitoring voluntary behaviors of individual animals of an animal herd. The individual animals (1) of the animal herd each have a node (3) of the data network. A further node (8) is attached at a location which an animal (1) preferably approaches in the course of a behavior to be monitored. In the event that the animal (1) approaches the node (8), communication occurs between the nodes (3, 8), in which communication one node is identified by the other node and a central data-processing system is informed that the two nodes (3, 8) have come into contact. The communication between the two nodes (3, 8) occurs by means of the transfer of electrical signals in a closed electrical alternating-current circuit, which also passes, among other things, through the body of the animal (1) as an electrical conductor.
