Gorillas have a more extensive repertoire of gestures than any other mammal bar humans, according to researchers at the University of St Andrews. They found that ape gestures, all 102 of them, are carried out with close attention paid to the audience: silent ones were made only when other apes could see them. Researchers found that juvenile and adolescent animals, aged between three and ten, used the highest number of different gestures. Richard Byrne, professor of psychology and leader of the St Andrews study, said that each population of gorillas used a different repertoire, suggesting that they had learnt their gestures. However, there was no sign of local "dialects".