A living area includes a lying and eating area and a milking area. The living area is connected to a separation area by a selection device. A subgroup of dairy animals to be separated is determined together with a desired end time at which the dairy animals to be separated should be present in the separation area. For each individual dairy animal from the subgroup to be separated, an individual separation period is determined separately which runs from the individually determined start time until the end time. A dairy animal which walks to the selection device is guided by the selection device to the separation area if the dairy animal belongs to the subgroup of dairy animals to be separated and if said dairy animal is present at the selection device during the individual separation period determined for said dairy animal. The activity of each dairy animal in the group of dairy animals is observed by an observation system while the dairy animal is in the lying and eating area. The individual separation period of each individual dairy animal from the subgroup to be separated depends on the activity of said dairy animal observed by the observation system.