Social context information and acoustic convergence in elephant vocal choruses

Elephants use low-frequency rumbles to communicate among individuals. Rumbles occur in several patterns: as discrete, non-overlapping calls, in antiphonal sequences where individuals alternate vocalizations, and in choruses where multiple individuals produce overlapping calls. Despite the wide availability of bioacoustics tools, most studies focus on non-overlapping signals rather than on choruses. Here, we address this gap by investigating multi-caller rumble choruses recorded in several behavioral contexts. We show that behavioral context can be predicted from single (i.e., non-overlapping) and from overlapping, chorused rumbles. We find that individual rumbles in a chorus share structural similarities with single rumbles used in the same behavioral context, suggesting that choruses are composed of context-matched individual elements that together form a distinct multi-caller signal. We also find that the rumbles within choruses converge acoustically in particular behavioral contexts. Lastly, we find that the rumbles associated with various contexts vary systematically among individuals and family groups and suggest that individual acoustic differences may account for the observed family-level variation. Our findings extend previous work showing that rumbles encode behavioral context and caller identity, providing novel evidence that elephant choruses function as group signals encoding context through both their composition and patterns of acoustic convergence.