Acoustic signatures in a multi-functional humpback whale ( Megaptera novaeangliae ) call type

In many animal communication systems, signals serve both intentional functions and incidental byproduct roles shaped by evolutionary pressures. Humpback whale (Megaptera novaeangliae) “whup” calls exemplify this duality. Ubiquitous across populations and stable across generations, this stereotyped call functions as both a contact call mediating social interactions and a recurrent song unit within male breeding displays—making it ideal for exploring how selection acts on both functional and incidental acoustic traits. Using focal recordings from 2011–2024 off the Big Island of Hawai‘i, we tested for individual vocal signatures in whup calls from known singers. Using calls isolated from song sequences, we extracted traditional spectro-temporal features and mel-frequency cepstral coefficients (MFCCs), the latterdesigned to approximate human auditory perception. Across 1,000 random forest iterations, MFCC-based models achieved 82% classification accuracy, outperforming traditional features (59%). These results show that even stereotyped calls encode individuality, likely as a byproduct of vocal production mechanisms. The whup call’s intentional function as a contact signal may coexist with incidental cues enabling individual recognition. Such recognition may confer fitness benefits to singers (via mate attraction or male assessment) and social receivers—positioning the whup call as a model for studying signal evolution under multiple selective pressures.