“Indris are the only lemurs that communicate with songs,” says De Gregorio, a primatologist at the University of Turin, in Italy, and lead author of a new study on indri rhythms, published today in Current Biology.

In this case, De Gregorio refers to the animals’ tendency to harmonize in duets and even choruses of more than two animals. The animals sing to find family members that have become lost, lay claim to patches of forest, and even perform “vocal battles” with their neighbors, De Gregorio says in an email.