Polaris, Dipper and the Death of the Southern Resident Killer Whales: Part 4: Noise Pollution
Polaris, Dipper, and the Death of the Southern Resident Killer Whales:
Part 4: Noise Pollution
Guest Blogger: Courtney Halvorson
Humans live in a visual world, but whales live in an acoustic one. Killer Whales use sound like we use our eyes. By forcing air through their sinuses a clicking sound is created. This sound is focused out the front of the whales’ head using a fatty organ called a melon. This sound goes out into the environment and the echo is received through the whales’ jaw bone which is hollow and full of oil. This echolocation ability allows the whales to see - just with sound. Their echolocation is so good that scientists believe they can detect the larger sized swim bladder inside a Chinook Salmon and therefore know to target them.
Using sound to locate prey, navigate and communicate makes these Killer Whales incredibly sensitive to noise pollution. The Juan de Fuca Strait, Strait of Georgia and Puget Sound make up the largest shipping lanes on the Pacific seaboard. We have tankers, container ships, cruise ships, and pleasure boaters constantly travelling through the same waters as the whales.
Current research suggests that the whales need to alter the sound frequency and duration of calls to adapt to this noise. This noise can cover up calls or a call frequency change may alter the intended message. A study done right in the Salish Sea by Christine Erbe in 2002 suggested that small fast boats can be heard by killer whales 16km away and can actually cover calls from 14km away. Slow boats seemed to have less impact becoming audible at 1km away and masking calls from that distance. Hundreds of boats from small pleasure boats to tankers the size of towns travel the Salish Sea every day and this impact on the Killer Whales is becoming more drastic.
Courtney Halvorson is a PNW educated Marine Biologist, Wildlife Photographer and Marine Naturalist for Orca Spirit Adventures in Victoria, British Columbia.
Photo By: Susanne Davies