Noise Pollution is a Buzzkill for Killer Whales Looking for Lunch
Featured Image Caption: Orcas travel great distances to hunt prey using echolocation. They are social animals that hunt in groups. Orcas communicate through a range of clicks, whistles, and buzzes. “Killerwhales jumping” by Robert Pittman. Photo is public domain from US National Oceanic and Atmospheric Administration, via Wikimedia Commons
Primary Source Article: Tennessen, J. B., Holt, M. M., Wright, B. M., Hanson, M. B., Emmons, C. K., Giles, D. A., Hogan, J. T., Thornton, S. J., & Deecke, V. B. (2024). Males miss and females forgo: Auditory masking from vessel noise impairs foraging efficiency and success in killer whales. Global Change Biology, 30(9), e17490-. https://doi.org/10.1111/gcb.17490
Secondary Source Articles: Erbe, C., Marley, S. A., Schoeman, R. P., Smith, J. N., Trigg, L. E., & Embling, C. B. (2019). The Effects of Ship Noise on Marine Mammals—A Review. Frontiers in Marine Science, 6. https://doi.org/10.3389/fmars.2019.00606
https://www.noaa.gov/news-release/us-marine-economy-continues-upward-trend
According to the National Oceanic and Atmospheric Administration (NOAA), the marine economy contributed to $476 billion in economic impact in 2022. This marine economy is made up of different sectors: tourism and recreation, national defense and public administration, transportation and warehousing, transportation of offshore minerals, and technical services, to name a few. Although increased marine traffic is a good sign for the economy, it comes at a cost to marine mammals. According to senior research scientist Jennifer Tennessen, vessel noise is a threat to marine ecosystems. In a study this year, Dr. Tennessen studied killer whales and found that vessel noise interferes with whales successfully capturing prey.
Tennesson and colleagues studied fish eating killer whales in British Columbia, Canada, and Washington, USA. Whales were tagged at the base of their dorsal fin to track the whale’s location and to identify the vessel type that was close to the whale when they surfaced. After tagging, a VHF receiver was used to find and retrieve data from the tags. They looked at foraging behavior and ambient noise to determine whether there was a link between vessel acoustic noises and the killer whales’ success rate at capturing prey. Sounds simple enough, but how did they accomplish this task
Measuring Foraging Behavior and Ambient Noise
According to the study, foraging is identified in 3 distinct phases: searching, pursuit, and capture. The researchers looked at different sounds that were being produced by the killer whales: echolocation clicks, buzzes, and prey handling sounds such as tearing and crunching. Movement data was also recorded using triaxial accelerometers and magnetometers to show body accelerations and changes in the body’s position to confirm foraging behavior. Using recordings they collected from the study, they used software to filter out noise not associated with human activity. Using methods from previous studies, they used software to pay attention to noise between 15 and 45 kHz. This is the range of pitch that is associated with vessel noise and human activity.
Researchers found that echolocation clicks were more likely to happen as the dive depth and noise levels increased. There were sex differences between noise levels and hunting. Females were less likely to pursue prey when noise level increased. Males were more likely to pursue prey in noisy conditions. The researchers mention that these differences could be due to females having to tend to calves and males having a higher lung capacity for increased dives. However, in spite of these differences, both sexes were overall less likely to capture prey in increased noise levels.
All motorized boats and ships produce noise at varying levels. Small crafts can generate 130-160 dB while larger vessels can produce 200 dB and above. For comparison, a thunderclap produces 120-140 dB. The noise source comes from the propeller when it cavitates. This noise can increase or decrease depending on the speed, size, and load of the watercraft. In addition, the engine and machinery on the ship can produce noise that can emit frequencies into the water. For animals that are trying to listen to audio cues, this can have a negative impact. Marine animals rely on echolocation and vocalizations for communication, hunting, and mating. Killer whales are not the only marine animals affected by noise pollution. There are documented negative impacts on bowhead whales, humpback whales, and sea lions.
Can We Keep the Economy Strong and Protect Marine Mammals?
Whales play an important role in balancing the marine food chain and the environment. They regulate population of prey, provide food to scavenger animals when they die, and transport nutrients from deep waters to surface waters via waste. Whale watching is also important to the the tourism industry and contributes to the economy. Traditionally, topics on the economy and the environment are often spoken of as if they are on opposing sides. However, both economy and the environment are intertwined.
The marine economy makes up roughly 2% of the US GDP. Although halting watercraft activities altogether is not a viable solution, there are some measures that can be taken to protect marine wildlife. According to the study, sound can be managed by increasing distances between vessels and whales, reducing vessel speeds to reduce noise impact, and rethinking the design of vessels to reduce cavitation noise. This study highlights the importance of regulating human activities that is not only sustainable for the economy, but for the environment as well.
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