Bag-of-calls analysis reveals group-specific vocal repertoire in long-finned pilot whales

TL;DR

This study uncovers a complex, group-specific vocal repertoire in long-finned pilot whales using an innovative automated analysis method, demonstrating that vocalization patterns can distinguish whale groups without knowing individual identities.

Contribution

The paper introduces the bag-of-calls method, a novel automated approach to analyze and quantify group-specific vocal differences in marine mammals.

Findings

Identified 140 call types in pilot whale vocalizations

Demonstrated group-specific vocal patterns using statistical analysis

Validated the bag-of-calls method for distinguishing whale groups

Abstract

Besides humans, several marine mammal species exhibit prerequisites to evolve language: high cognitive abilities, flexibility in vocal production and advanced social interactions. Here, we describe and analyse the vocal repertoire of long-finned pilot whales (Globicephalus melas) recorded in northern Norway. Observer based analysis reveals a complex vocal repertoire with 140 different call types, call sequences, call repetitions and group-specific differences in the usage of call types. Developing and applying a new automated analysis method, the bag-of-calls approach, we find that groups of pilot whales can be distinguished purely by statistical properties of their vocalisations. Comparing inter-and intra-group differences of ensembles of calls allows to identify and quantify group-specificity. Consequently, the bag-of-calls approach is a valid method to specify difference and concordance in acoustic communication in the absence of exact knowledge about signalers, which is common observing marine mammals under natural conditions.