A respective animal unit (101, 102) is attached to the animals (A1, A2) in a herd of animals. Each unit (101, 102) is configured to repeatedly: emit a signal (S1 S2) representing the unit (101, 102), register a position (P1 P2) and/or register acceleration data (a1 a2) related to the animal (A1 A2) to which the unit (101, 102) is attached. A set of data read-out devices wirelessly reads out information from the set of animal units (101, 102) into a database. A data processor identifies animals potentially in heat by: - associating a respective time stamp with each entry in the database, each entry representing one event concerning an animal (A1, A2) in the herd, which event relates to an emitted signal (S1, S2), a registered position (P1, P2) and/or registered acceleration data (a1, a2) - identifying candidate mounting animals as members of a first group based on the entries in the database - identifying candidate mounted animals as members of a second group of based on the entries in the database, and - based on the time stamps, matching the members of the first and second groups with one another to determine any animals potentially in heat, wherein an animal is deemed to be potentially in heat if the animal (A1) is estimated to have been mounted by at least one other animal (A2) during a particular interval of time.Linvention concerne une unité danimal respective (101, 102) qui est fixée aux animaux (A1, A2) dans un troupeau danimaux. Chaque unité (101, 102) est configurée pour, de manière répétée : émettre un signal (S1 S2) représentant lunité (101, 102), enregistrer une position (P1 P2) et/ou enregistrer des données daccélération (a1 a2) relatives à lanimal (A1 A2) auquel lunité (101, 102) est fixée. Un ensemble de dispositifs de lecture de données lit sans fil des informations provenant de lensemble dunités danimal (101, 102) dans une base de données. Un processeur de données identifie des animaux potentiellement en chaleur en : - associant un indicateur tempor
