Featured Image: GREMM
By: Kira Krall
We know of many obvious sources of pollution: trash, runoff, and greenhouse gas emissions. These are all pollution sources that we can see. But one source of pollution challenges that definition: Noise pollution.
If you’ve seen Finding Dory, you have an idea of how echolocation works. Marine mammals use an organ in their forehead called a melon to emit a frequency. That frequency bounces off objects and returns to the animal and creates a mental picture for the marine mammal.
Echolocation success depends on the ability of the initial soundwave to return to the animal that created it. Noise pollution can disrupt the echolocation process and leave mammals like belugas unable to navigate. If they can’t echolocate, whales and dolphins can end up in waster that are much too shallow for them to navigate safely.
Image Credit: Prince of Wales Northern Heritage Centre
Out of the ocean bunch, beluga whales are characteristically chatty. They have a variety of clicks and whistles imbedded from birth and even have the ability to mimic hundreds of different sounds. This communication can easily be disrupted by the sound of ships in the narrow rivers of Canada.
This is a problem because beluga whales, like most toothed whales, form tightly-knit pods of relatives. They rely on physical contact and verbal communication to maintain these pod bonds.
Image Credit: Ansgar Walk via Wikipedia
In 2015, 14 beluga whales were found stranded on the banks of the St. Lawrence estuary. Of those 14, six were newborn calves. None of these newborn carcasses had any sign of injury, emaciation, or infection, which lends credit to the theory that noise pollution could have separated the calf from its mother.
Belugas frequent the area of Saint Lawrence River and are forced to cohabitate with the river’s noise pollution. Boat noise in the Saint Lawrence River is so loud, humans would be required to wear ear protection if they were subject to the same decibel level.
That’s detrimental to a creature that relies mostly on its hearing to get around and to communicate with other whales. Beluga whale calves soft whistles are easily masked by the rumbling of passing ships, boats, and ferries.
Image Credit: Feather in Flight Productions
Decibel level and frequency are both factors. Soundwaves made by ships are low frequency, while belugas communicate and echolocate using high frequency calls. Because of the difference in frequency, the sounds actually don’t intersect. What’s really happening is that the low-frequency sounds are masking the high-frequency sounds and making high-frequency sounds imperceptible to the belugas.
One study tracked belugas in relation to sources of noise pollution and found that the whales were within a half mile of the noise source. The whales could even be sustaining ear damage due to the decibel level and proximity to the noise.
Even though us humans can’t see it, whales are under auditory attack.
You can read more about noise pollution here.