The invention relates to a data network for automatically monitoring voluntary behaviors of individual animals of an animal herd. The individual animals of the animal herd each have a node of the data network. A further node is attached at a location which an animal preferably approaches in the course of a behavior to be monitored. In the event that the animal approaches the node, communication occurs between the nodes, in which communication one node is identified by the other node and a central data-processing system is informed that the two nodes have come into contact. The communication between the two nodes 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 as an electrical conductor.
