Northern right whales shout to overcome background noise, but how loud is too loud? Image credit: Wikimedia Commons
Right whales, it's believed, earned their name for being the "right whales to hunt." The whales are rich in blubber, swim slowly, and float after they have been killed—making them an easy and profitable target for whalers. These characteristics nearly led to the whale's extinction—populations were almost completely depleted in the mid-19th century—until a ban in 1937 saved the species.
Today, poaching and ship strikes continue to threaten the survival of this still-endangered species but, increasingly, the noisiness of modern oceans is also becoming a problem.Susan Parks, assistant professor of acoustics and research associate at Penn State, explained:
The impacts of increases in ocean noise from human activities are a concern for the conservation of marine animals like right whales...the ability to change vocalizations to compensate for environmental noise is critical for successful communication in an increasingly noisy ocean.
Her research, conducted with the help of the Woods Hole Oceanographic Institution, has shown that northern right whales are indeed able to increase the volume of their calls in response to increases of background noise.
Peter Tyack of the Woods Hole Oceanographic Institution discusses the incredible ways marine mammals use sound.
By attaching acoustic sensors to a group of whales with suction cups, the researchers where able to measure both the background noise and the calls from each animal. What they found, was that the majority of background noise occurred in the range of 400 Hertz, which overlaps with the frequency of northern right whale calls.
In response, the whales increase the amplitude, or energy, of their calls and keep the frequency the same. This allows their communications to travel through the background noise. The adaptation, however, does not come without a cost.
Changing their calling patterns expends more energy, slightly changes the nature of the signal—and the information it contains—, and increases the whales' predatory risk.
Furthermore, research suggested that the range of the altered calls will be reduced—which could have serious implications for feeding and mating. There is also no garuntee that the whales will continue to be able to contend with an increasingly noisy ocean. Parks commented:
Whether they can maintain their communication range in noisier environments still needs to be tested...ocean sound levels will probably continue to increase due to human activities and there is a physical limit to the maximum source level that an animal can produce.
Whales, it turns out, are versatile—but few species are prepared to contend with the intense changes occuring in the world's oceans.
Read more about noise pollution in the ocean:
TED Talk: The Incredible Ways Marine Mammals Use Sound
Lost In The Sound - New Sound Maps Show Ship Noise Blocking Whale Communication
Screaming to be Heard Over Ship Noise is Taking It Out of Killer Whales
Interactive Website Shows How "Acoustic Smog" Is Killing Whales
Noise Pollution Harms Fish Populations, Locations, Habits