When the trumpet blows: age-sex-related differences in the acoustic properties and contexts of high-frequency vocalizations of free-ranging Asian elephants

To support their wide range of social interactions, elephants have evolved high- and low-frequency sounds for short- and long-distance communication. Our current understanding of elephant vocal communication largely comes from African elephant studies which have focused on low-frequency sounds. However, much needs to be understood about the vocal communication of the Asian elephant (Elephas maximus), both from a structural and a contextual point of view. This study aimed to provide insights into age-sex-related differences in the acoustic properties of high-frequency vocalizations and their associated contexts in free-ranging Asian elephants. We recorded trumpets, roars and a combination call, the roar-rumble, from calves (< 1 year), and female and male elephants (1–10 years and > 10 years of age) to assess the differences in their temporal and frequency parameters, and the context in which these calls were produced. The study revealed that age and sex do not influence the duration of trumpets; however, the duration of roars and roar-rumbles increases with age. The frequency parameters of measured high-frequency sounds were notably higher in calves and showed a gradual decline with age. The presence of non-linear phenomenon was observed in both trumpets and roars across age-sex classes. These differences in spectral characteristics could be attributed to variations in body size and associated sound production mechanisms across age-sex classes. Our study indicates that Asian elephants use trumpets in diverse contexts, which extends beyond previous assumptions, ranging from agonistic to social affiliative interactions. Notably, this marks the first time that combination calls have been reported from this southern Indian study population. This study underscores the importance of high-frequency and combination calls, suggesting that they may serve distinct roles within the vocal communication network of Asian elephants.