A University of Queensland study found that humpback whales sing louder when the wind is roaring, but don’t have the same reaction to boat engines.
This aberration in whale evolution could have consequences for reproduction and behaviour, said lead researcher Dr Elisa Gerola, from the University of Queensland’s College of Science.
“Humpback whales have thrived over millions of years with noise from natural sources, but the noise from human-made ships is alien to their instincts,” said Dr. Gerola.
“It’s a surprising finding since engine noise has a similar frequency range to wind.
“It is possible that whales pick out other differences such as wind noise being broadband and the same over large areas, while ship noise is generated from a single point source with specific peaks in frequency.
“We don’t know yet if this lack of response to boat noise makes whales communicate less effectively or makes breeding practices more difficult.
“It is likely that male humpback whale vocalization is used to mediate reproductive interactions, but we cannot say whether vascular noises interfere.”
Acoustic data for the study were collected in late 2010 off Peregian Beach in Queensland, during the whales’ southward migration from their breeding grounds in the Great Barrier Reef lagoon to their feeding grounds in Antarctica.
The whale songs were recorded using an acoustic array of five water buoys, which sent signals ashore.
A 19-meter fishing boat was entered to make noise from the ship.
It’s possible, the researchers say, that humpback whales use other strategies to compensate for ship noise.
“Even with a 19-meter boat making noise, the whales didn’t sing any louder,” said Dr. Gerola.
“There are a few things going on — they might be using ‘spatial release from masking’, which is the ability to distinguish between acoustic signals coming from different directions.
Or there is a “combination release from masking” which is the ability to distinguish signal from noise when the noise has distinct frequency components and at least some of these components do not interfere with the signal.
“There is still a lot of research to be done.
“Understanding humpback whales’ response to noise is important for developing mitigation policies for human activities at sea.
“I am sure that these beautiful and mysterious creatures will continue to surprise and fascinate us.”