Singing humpback whales respond to wind noise, but not boats

Newswise — A study conducted by the University of Queensland has discovered that humpback whales increase their vocal volume in response to noisy winds, yet do not exhibit the same response to boat engines.

Dr Elisa Girola, who led the research from UQ's Faculty of Science, suggested that this particular characteristic of whale evolution may have implications for breeding patterns and behavior.

According to Dr Girola, "Humpback whales have developed over millions of years in an environment with natural sources of noise, but the noise produced by human-made vessels is unfamiliar to their instincts."

“It’s a surprising finding given engine noise has a similar frequency range to the wind.

Dr Girola suggested that the whales may be distinguishing between wind noise and vessel noise by identifying other differences. For instance, wind noise is typically broadband and consistent over vast areas, whereas vessel noise emanates from a single-point source and has specific frequency peaks.

Dr Girola further stated that it is currently unknown whether the whales' lack of response to boat noise is affecting their communication or impeding their breeding practices.

Dr Girola explained that male humpback whales' singing is likely utilized to facilitate reproductive interactions, but it is uncertain whether vessel noise is disrupting this process.

The study's audio data was gathered in late 2010 near Peregian Beach in Queensland, during the humpback whales' migration from their breeding grounds in the lagoon of the Great Barrier Reef to their feeding grounds in Antarctica.

To record the whale songs, a set of five hydrophone buoys was employed as an acoustic array, which transmitted signals back to the shore.

A 19-metre fishing boat was introduced to produce vessel noise.

The researchers have suggested that humpback whales may be utilizing alternative methods to adapt to vessel noise.

Dr Girola remarked, "Despite the presence of a noisy 19-meter boat, the whales did not increase their vocal volume."

Dr Girola added, "There are several factors at play here. The whales may be utilizing 'spatial release from masking', which involves the ability to distinguish between sound signals originating from distinct directions."

Dr Girola also suggested that another potential explanation is 'comodulation release from masking', which involves the ability to distinguish between a signal and noise when the noise has identifiable frequency components that do not overlap with the signal.

The UQ research team included Professor Michael Noad and Associate Professor Rebecca Dunlop.

The research is published in Proceedings of the Royal Society B.