The meaning behind cow moos has been deciphered by scientists that eavesdropped on "conversations" between calves and their mothers.
After 10 months of listening in on cows, researchers at the University of Nottingham and Queen Mary University of London found there are two distinct maternal calls.
The researchers studied the ways cows on a farm in Nottinghamshire communicate with their offspring by examining acoustic indicators of age and identity.
Findings showed that when mother and calf were separated, their calls became louder and at a much higher frequency. Calves also "spoke" to their mothers when they wanted to feed.
Study leader Mónica Padilla de la Torre said: "The research shows for the first time that mother-offspring cattle 'calls' are individualised -- each calf and cow have a characteristic and exclusive call of their own. Acoustic analysis also reveals that certain information is conveyed within the calf calls - age, but not gender."
Scientists recorded the cow moos with highly sensitive equipment. The recordings then took over a year to analyse.
Alan McElligott, at Queen Mary University of London said: "This is the first time that complex cattle calls of have been analysed using the latest and best techniques. Our results provide an excellent foundation for investigating vocal indicators of cattle welfare."