Australian snubfin vocal activity is influenced by behavioral state and group characteristics

Abstract

Acoustic communication is an important aspect of life for marine mammals, as their environment often limits the reliability of visual cues. However, there is little information regarding the acoustic communication and behavior of Australian snubfin dolphins (Orcaella heinsohni). This study was designed to determine if call rate and type were significantly affected by the behavioral state, group size, and cohesion of snubfin dolphins in the Fitzroy River in Queensland, Australia. We found that dolphins significantly modified both call rate (calls/hour/individual) and call type among behavioral states. For example, call rates were higher when dolphins were foraging versus resting or traveling. We also found that group size and cohesion had minimal effects on call rate, but significantly affected the predicted probabilities of call type production. For example, the probability ratio of burst pulse to whistle production is estimated to be highest when groups are widespread (>10 m), indicating the potential importance of burst pulses in maintaining contact between dispersed individuals. This study presents the first comprehensive analysis of snubfin dolphin communication under natural noise conditions in relation to behavioral context, which provides a foundation to explore how anthropogenic acoustic masking and behavioral disturbances may affect these dolphins in the future.