Effects: Whales and sonar

Whales, along with dolphins, porpoises, and other Odontoceti utilise echolocation to detect objects and orient themselves (Campbell, 2013). These creatures produce a focused beam of clicks from specialised organs found in their heads. While we humans use sight as our primary sense, whales utilise sound as the main means for observing their surroundings – it is a much more effective medium underwater (Whale.org, 2021). However, undersea vessels similarly make pulses of sounds called pings in active sonar, varying in frequency and amplitude (Campbell, 2013).

Such noise interferes with the ability of whales to perform essential life functions such as foraging, finding mates, communicating with each other, and evading predators. If a whale is within 200m of a container ship, its echolocation range is reduced by 95%, compromising its chances of locating prey (Haskell, 2022). Compounded by a decline in the numbers of Chinook Salmon in Canada, which the resident killer whales there feed on, the whale population is fragile (Haskell, 2022). This reduces their chances of survival over time.

Research off the Pacific coast of Canada has discovered that resident killer whales spent 18 – 25% less time feeding when surrounded by boat noise, compared to in the absence of boats (Jones, 2019). Beaked and sperm whales are particularly susceptible to noise generated by sonar and ocean science experiments as they are deep divers (Scott, 2004). Cetaceans have also been documented to deviate from course, and temporarily abandon areas in response to sonar transmissions (Scott, 2004).

Short and extremely loud noises are also capable of physically injuring whales, causing them to go deaf (Whale.org, 2021). In 2000, following a U.S. Navy sonar training exercise in the Bahamas, 17 animals were found beached on three nearby islands. It was suspected that the sonar had disrupted these animals’ behaviour, causing them to swim to shore. Some of the beached whales had hemorrhages near their ears and in the fluid surrounding their brains, which may have affected their hearing (Nevala, 2008). Since 1985, there have been numerous strandings that coincide with military activities and active sonar (Reynolds, 2007).

Actions

From August to October 2017, many container ships and merchant freighters travelling through the Haro Straits voluntarily slowed their speeds from as high as 18 knots to 11 knots in response to the Enhancing Cetacean Habitat and Observation programme (Jones, 2019). This reduced the noise from their engines, for some ships, reducing their speed by 3 knots was able to halve noise intensity. However, with increasing annual ship traffic, whale communication would be compromised (Haskell, 2022).

Considering the significance of sound to marine creatures like the whale, there is a need to consider the effects of anthropogenic noise pollution, and work to reduce the negative impacts on their behaviour. One of the challenges in exploring this area is that there is no baseline data, no one knows how whales behave in a quiet ocean – investigations into acoustic masking and how whales respond to anthropogenic noise began in an already noisy ocean (Whale.org, 2022). What is certain is that educating the public on this problem and looking for mitigative strategies, is key to protecting these majestic creatures.

 

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