Humpback whales fail to respond to vessel noise

A recent study led by the University of Queensland (UQ) in Australia has found that, although humpback whales sing louder when the wind is noisy, they do not have the same reaction to noise from boat engines. 

According to the experts, this quirk of whale evolution could have significant consequences for their behavior and breeding practices. The research is published in the journal Proceedings of the Royal Society B: Biological Sciences.

“Humpback whales evolved over millions of years with noise from natural sources but noise from man-made vessels is foreign to their instincts. It’s a surprising finding given engine noise has a similar frequency range to the wind,” said study lead author Elisa Girola, an expert in Bioacoustics and Conservation at UQ.

“It’s possible the whales are picking out other differences such as wind noise being broadband and the same over large areas, while vessel noise is generated by a single-point source with specific peaks in frequency.”

By using an array of five hydrophone buoys that sent signals back to the beach, the researchers collected audio data in late 2010 off the Peregian Beach in Queensland, during the humpback whales’ southward migration from their breeding grounds in the lagoon of the Great Barrier Reef to their feeding grounds in Antarctica. In addition, a 19-meter fishing boat was introduced to test whales’ reactions to vessel noise.

The investigation revealed that, even with this massive boat producing loud noises, the whales did not sing any louder, suggesting that they may be using other strategies to compensate for such artificially produced sounds. 

“There are a few things going on – they might be using ‘spatial release from masking,’ which is the ability to discriminate between audio signals coming from different directions. Or there’s ‘comodulation release from masking’ which is the ability to discriminate between signal and noise when the noise has distinctive frequency components and at least some of these components are not overlapping with the signal,” Girola explained.

It is not yet clear whether this lack of response to boat noise is diminishing the effectiveness of whale communication or making breeding practices more difficult. Although male humpback whale singing is likely used to mediate reproductive interactions, the ways in which vessel noise is interfering with these processes requires further investigations.

“There’s still so much more research to be done. Understanding humpback whales’ response to noise is important for developing mitigation policies for human activities at sea,” Girola concluded.

More about whales and noise pollution 

Noise pollution, particularly from human activities such as shipping, construction, and oil drilling, can have significant impacts on marine life, including whales. The noise can interfere with the whales’ communication, navigation, feeding, and mating behaviors. Below are some of the specific effects:

Communication Disruption

Whales use sound to communicate with each other. Noise pollution can interfere with these communications, causing confusion and distress.

Navigation and Foraging

Many species of whales use echolocation to navigate and find food. This involves producing sounds and then listening for their echoes to determine the location and distance of objects. Noise pollution can disrupt this process, making it difficult for whales to navigate or find food.

Stress and Physical Harm

Prolonged exposure to loud noise can cause stress in whales, which can lead to changes in behavior, decreased immune response, and other negative health effects. Extremely loud noises can even cause physical harm, such as hearing loss.

Displacement

Noise pollution can make certain areas inhospitable for whales, forcing them to move to other, potentially less suitable areas. This can result in increased competition for resources, changes in prey availability, and other negative impacts.

Stranding

There have been instances where intense underwater noise events, such as naval sonar use or seismic testing, have been associated with mass strandings of beaked whales, although the exact mechanisms are still not fully understood.

Efforts are being made to mitigate the impact of noise pollution on whales and other marine life. For example, some shipping companies are modifying their vessels to be quieter, and certain areas are being designated as protected, with restrictions on the amount of noise that can be produced. 

However, more work is needed to fully understand the impact of noise pollution on marine life and to develop effective mitigation strategies.

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By Andrei Ionescu, Earth.com Staff Writer

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