Photo credit: ArtHouse Studio
by Arline L. Bronzaft, Ph.D., Board of Directors, GrowNYC, Co-founder, The Quiet Coalition, and Honorary Chair, Quiet American Skies
We learn in this article by James Urton that the sounds from both large and small ships are creating a noisy underwater environment for orcas. Urton informs us of research conducted by Jennifer Tennessen and her associates at the University of Washington that looks at how loud sounds from shipping vessels make it difficult for orcas to carry out their life activities.
The Salish Sea is the home to two populations of fish-eating orcas: northern and southern orcas. We learn from Tennessen’s research that northern orcas have grown in number in the last century, but southern orca numbers are low. To live and grow in number, orcas need an environment that permits them to successfully hunt for fish. However, the loud sounds from nearby ships in the southern part of the Salish Sea, where the southern orcas live, is so loud that they have difficulty capturing the fish they need to survive because ship sounds are intruding upon their signals to seek out prey.
The researchers tagged the orcas with digital tags to collect data on the sound levels to which they were exposed. This is how they were able to identify how shipping vessels raised the sound level. These tags also identified orcas’ hunting attempts. One interesting finding was the more negative impact the ship noise had on female orcas. The researchers hypothesized that females may be less reluctant to leave young calves for lengthier searches for food. While we learn that orcas share prey with each other, the researchers believe that additional stress brought on by difficulties of getting food may be linked to higher rates of pregnancy failure for southern resident female orcas.
So what can be done to save southern orcas? Reduced vessel speed resulting in quieter waters. However, the article lets us know there are other reasons for reduced southern orca numbers, like water pollution, salmon habitat destruction and more. The reality is that all these intrusive factors must be addressed to protect the southern orcas.
