Humpback whales emit two main communication sounds; vocal sounds and sounds generated on the surface (by breaching and slapping their pectoral and tail fins). Groups of whales tend to switch their communication strategy, from using primarily vocal sounds, to using primarily surface-generated sounds, in higher wind noise. Whales also emit vocal sounds at higher levels in increased wind noise and therefore utilise two different methods to overcome potential deleterious effects communicating in noise. However, whales must also consider their social environment when signalling. Groups (especially females with a nursing calf) emit vocal sounds at lower levels in the presence of singing whales, despite the song being a potential source of noise. This is presumably to avoid the unwanted attention of a singing male. Therefore there are two competing effects; wind noise causing an increase in vocal level, and singing whales causing a decrease in vocal level. It is unknown, however, if whales emit fewer surface-generated sounds in the presence of singing whale (potentially to avoid the unwanted attention of the male), and if noise levels change this response. This project will test the hypothesis that nearby singing whales reduce the use of surface-generated sounds in female-calf humpback whale groups. It will also consider the potential effect of noise within this response to their social environment.

Supervisor: Rebecca Dunlop