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The Effect of Noise Pollution on Humpback Whales

Noise pollution might be most associated with nuisance neighbors and living beneath flight paths. In the oceans, however, the noise from ships, military activities and mining is a conservation issue. Excess noise in the seas could be having serious effects on ocean wildlife, including humpback and other whales. Whales use sound to communicate, navigate and locate food. It appears that noise pollution has the potential to cause these animals serious problems.

Physical
- Noise-related injury is a risk factor for all marine life, from near-microscopic fish larvae to humpback whales. Very high levels of noise can cause physical injury to animals, notably to their brains and hearing structures. Post-mortems of beached whales have revealed brain hemorrhages. The fact that some of these beachings were associated with high levels of military or shipping activity suggests a possible connection between the injuries and the noise.
Communication
- The great baleen whales, including humpbacks, use sound to communicate with one another over vast reaches of ocean. Noise pollution interferes with the songs, affecting the whales' breeding and social behavior. Each whale may have to expend more energy in singing to overcome the background noise, or may be deafened completely. One study on humpback whales in Hawaii showed the animals spent 29 percent more time singing when exposed to low frequency sonar. The expenditure of more energy and time on an activity does not help the survival or reproduction rates of wild animals.
Feeding
- Humpback whales feed on plankton and don't use the very advanced form of sonar that dolphins and some smaller whales employ to detect prey, although they may use a more rudimentary form. However, it appears that noise pollution may affect small animals, such as the members of the zooplankton, as seriously as large ones. Some marine larvae have shown physical damage after being exposed to high noise levels, and others use noise to navigate. What affects the humpbacks' food supply will eventually affect the whales. If food supplies become limited and difficult to find, some humpbacks might struggle to survive.
Navigation
- Noise pollution has been linked to mass strandings of whales, suggesting that it interferes with the whales' ability to navigate the oceans. These strandings primarily have affected toothed whales, a group that includes dolphins, rather than the baleen whales. The toothed whales use echolocation to navigate. Humpback whales may or may not employ sound for their migrations of thousands of miles each year. If sound does play an essential navigational role for humpbacks, noise pollution could impact their ability to locate feeding and mating grounds.

Animals & Science