Behaviour 2019
Non-linear Phenomena are Common Features in Dolphin (Tursiops) Signature Whistles
Jessica J. Sportelli, Brittany L. Jones, Sam H. Ridgway. National Marine Mammal Foundation, San Diego, CA, United States

Non-linear phenomena (NLP; biphonations, chaos, sidebands, and subharmonics) are common in the vocalizations of animals. NLP have been used to aid in diagnosing illness, but were also found in healthy individuals. Some hypotheses for NLP use include gaining attention, signaling urgency, and individual recognition. Vocalizations from nine dolphins at the US Navy Marine Mammal Program were opportunistically recorded. Signature whistles for each dolphin were identified by recording them away from other dolphins. Then signature whistles were recorded from dates when each animal was in good health, as confirmed by the Navy’s health database. NLP were common across whistles and occurred on average in 53% of signature whistles. While there were individual differences between dolphins, all nine animals produced NLP. Sidebands were the most common (25%), followed by subharmonics (18%), chaos (18%) and biphonations (12%). Multiple NLP types were commonly emitted over the course of a single whistle, with some overlapping in time. These results suggest that the prevalence of NLP in dolphin whistles may be a commonly overlooked feature that could be salient for dolphin communication.