Impacts of Ocean Noise

Whales face many natural and human-derived risks to their health throughout their lives. Here we describe four threats that gray whales face while feeding in Oregon waters: entanglement in fishing gear, vessel strike, elevated ocean noise, and changes to their habitat.

Gray whales have increased stress levels when there is more noise and boats in the water. More specifically, we found that the levels of the hormone cortisol in the poop of whales are correlated to the amount of noise in the ocean and boats on the water the day before the poop sample was collected. This 24-hour lag in the relationship is due to the time it takes for the hormone to be released into the bloodstream and then processed through the gut and out the other end for us to pick up. We also found that skinnier whales have a stronger stress response than fat whales, which may indicate that when whales are skinny due to low food availability, the added impacts of noise and boat traffic can cause the health of whales to decrease further. So, why does ocean noise matter to whales?

Imagine living your life at a rock concert where you can barely hear your friends talking to you and they can barely hear you. This would be really stressful, and many medical studies show that increased stress in humans is linked with increased health risks, like heart disease. We are concerned the same situation may be happening to whales living in an increasingly noisy ocean.

Listen to these two sound clips recorded off the Oregon coast to compare what it sounds like underwater with and without boats nearby.

Without boats nearby

With boats nearby

Since light does not travel well in the ocean, whales rely on sound to communicate with each other, listen for predators, find food, navigate, and find mates. However, noise levels in the Pacific Ocean have increased dramatically over the last few decades, meaning that the ability for whales to do all these important life activities is much harder now, and this may be increasing their stress levels.

Image courtesy of NOAA | Click Image for More Info

To study this relationship between ocean noise and whale stress, we record the soundscape near gray whales using hydrophones (underwater sound recorders) and we collect whale poop to examine the hormone levels of that individual, including its stress level. With these data, we have documented that the physiology of whales is impacted by ocean noise and vessel traffic, which could affect their overall health and ability to reproduce. Ocean noise increases with increased boat traffic, so we do not know yet if this rise in whale stress is related to increased collision risk or increased noise or both, but we continue to research this question.

Want to read more? Check out these resources:

Pirotta E, Fernandez Ajó A, Bierlich K, Bird CN, Buck CL, Haver SM, Haxel JH, Hildebrand L, Hunt KE, Lemos LS, New L, Torres LG (2023) Assessing variation in faecal glucocorticoid concentrations in gray whales exposed to anthropogenic stressors. Conservation Physiology 1110.1093/conphys/coad082. https://academic.oup.com/conphys/article/11/1/coad082/7410313

Lemos LS, Haxel JH, Olsen A, Burnett JD, Smith A, Chandler TE, Nieukirk SL, Larson SE, Hunt KE, Torres LG (2022) Effects of vessel traffic and ocean noise on gray whale stress hormones. Sci Rep 12:18580 10.1038/s41598-022-14510-5. https://doi.org/10.1038/s41598-022-14510-5

Blog: The effects of vessel traffic and ocean noise on gray whale stress hormones https://blogs.oregonstate.edu/gemmlab/2022/11/28/the-final-chapter-the-effects-of-vessel-traffic-and-ocean-noise-on-gray-whale-stress-hormones/