Vocal dynamics

Shouwen Ma

Social mammals and birds have a rich repertoire of communication calls. Some call types are used rarely, but in specific contexts, while others are produced in large numbers, but are not linked to a specific context. An example for the latter is the “stack” call that zebra finches utter thousands of times per day in a seemingly erratic manner. We quantified this calling activity of captive zebra finches by using on-bird telemetric microphones that permitted a precise temporal resolution. We separated the calling interactions into “reactive” and “self-contained” calls. Despite a large dynamic range in the succession of calling events, the temporal distribution of the reactive and the self-contained calls was characterized by a power-law with exponents ranging between 2 and 3. This implies that all calls in that scale have similar dynamic patterns. As birds underwent physiological and social changes, their calling dynamics changed. Power-law scaling provided an accurate description of these changes, such that the calling dynamics may inform about an individual's physiological and/or social state, even though a single “stack” call has no predetermined meaning (Ma et al., 2017)