Within a view field, a camera records image data representing a body portion of an animal. A reader unit registers identity data from a data carrier on the animal and a data processor associates the recorded image data with the registered identity data. A passageway only allows a single animal at the time within the camera's view field. The camera is arranged so that the view field covers an identification zone within the passageway. To reduce the risk that the reader unit interferes with other nearby equipment, the data processor detects the presence of any animal within the view field of the camera based on the recorded image data, and activates the reader unit only when an animal is detected within the identification zone.