Cetaceans, which include whales, dolphins, and porpoises, communicate using underwater echolocation, which can take the form of high-frequency clicks and whistles, to low-frequency hums. These beautiful, peaceful creatures have faced a vast number of challenges over the centuries, from whale hunting, to oil spills, and climate change – and now one of the most prominent anthropogenic impacts on the ocean is the altered soundscapes.
It is well known that human noise pollution from boats and military sonar disrupts cetacean communication, and is responsible for mass stranding events, such as in 2018 when 150 Short-finned Pilot Whales (Globicephala macrorhynchus) became stranded and tragically died on Australia’s Western coast. Cetaceans are known to be very intelligent, and have been observed exhibiting signs of emotions such as grief. Therefore, mass stranding events caused by noise pollution are likely to be distressing, and if individuals from the pod are lost, then others are likely to show signs of grief.
During the coronavirus lockdown, David Barclay and his group seized the opportunity to look at how the lack of boats and machines operating in the seas around the world was impacting whales, and although their paper is still undergoing review, it supports findings from 2001 when marine noise pollution decreased as a result of 9/11.
Rolland’s paper in 2012 showed that increased background noise from anthropogenic processes includes habitat displacement, behavioural changes, and alterations in vocalisation. Following 9/11, a reduction in ship traffic in the Bay of Fundy, Canada, led to a significant decrease in low-frequency background noises. By analysing levels of the faecal glucocorticoid (fGC) stress hormone over four years from 2001, Rolland showed that the reduction in anthropogenic noise in the sea corresponded with a significant reduction in fGC. Glucocorticoids are naturally secreted in response to natural stressors such as predators, social aggression, starvation, and drought, as well as in response to anthropogenic disturbances. They are released from the adrenal cortex within minutes or hours of the animal expressing the stressor, and in the short-term it would allow the animal to respond to the threat appropriately, as well as mobilising energy reserves for a flight-or-fight response. However, anthropogenic noise pollution means that glucocorticoids are released over the long-term, meaning cetaceans suffer from chronic levels of the stress hormone, which can suppress growth, depress the immune system, and decrease reproductive success, as well as increasing stress-induced mortality. Rolland’s study was based on the opportunities provided by a tragic event, and therefore its results have been unrepeatable until this year. Although the 2020 coronavirus pandemic has been a global tragedy, it has provided an opportunity for wildlife to thrive with reduced anthropogenic stresses, and for the impact of humans on wildlife to be studied.
As life begins to return to normal, noise pollution is returning to our oceans – but it doesn’t have to be this way. In 2014, the WWF produced a report which looked at how to reduce anthropogenic noise, and its impact on cetaceans. It considers solutions such as using quieter electric engines in boats and ships rather than diesel engines, and reducing our reliance on oil, which would not only decrease the noise produced from oil drilling, but also the noise and traffic of ships transporting oil, as well as reducing the likelihood of oil spills occurring.
Rolland and Barclay’s research on anthropogenic noise pollution and cetaceans is important as it not only helps give us an insight into the delicate and complex world of cetacean communication, but it also shows us how fragile marine ecosystems are, and how humans are leaving no ecosystem or sensory system unaffected. Without us, these gentle giants of the ocean would continue their lives peacefully – and therefore it is our responsibility to help reduce marine noise pollution, and protect cetaceans from this invisible killer.
During the coronavirus pandemic, people around the world have been engaging more with nature and wildlife, and although studies of the so-called “anthropause” are only just beginning, I hope that our appreciation of nature will continue even after lockdown has ended. Furthermore, I hope that the coronavirus pandemic acts as a wake-up call, showing us the urgent need to protect nature on land, in the air, and in our oceans - to protect our cetaceans from the damaging and stressful effects of anthropogenic noise pollution.
NOTE TO READER
This blog post was written as part of the British Ecological Society Undergraduate Summer School 2020. All the content in this blog post was correct at the time of writing (July 2020).
REFERENCES AND FURTHER READING
Chinea A. (2017) "Is Cetacean intelligence special? New perspectives on the debate", Entropy; Volume 19, Issue 10; Available: https://www.mdpi.com/1099-4300/19/10/543/htm
Cockburn H. (2020) Coronavirus: Scientists to study great "human pause" of pandemic and impact on wildlife, Available: https://www.independent.co.uk/environment/coronavirus-lockdown-animals-anthropause-study-wildlife-natural-world-a9580691.html
McVeigh K. (2020) Silence is golden for whales as lockdown reduces ocean noise, Available: https://www.theguardian.com/environment/2020/apr/27/silence-is-golden-for-whales-as-lockdown-reduces-ocean-noise-coronavirus
Rolland R.M. et al. (2012) "Evidence that ship noise increases stress in right whales", Proceedings of the Royal Society B: Biological Sciences; Volume 279, Issue 1737; Available: https://royalsocietypublishing.org/doi/full/10.1098/rspb.2011.2429#d3e740
Thomson J. (2020) "An important time to listen": ocean scientists race to hear the effects of coronavirus underwater, Available: https://thenarwhal.ca/an-important-time-to-listen-ocean-scientists-race-to-hear-coronavirus-under-water/
Whales UK (2020) Scientific Evidence for Whale and Dolphin rights, Available: https://uk.whales.org/whale-culture/scientific-evidence-for-whale-and-dolphin-rights/#:~:text=The%20evidence%20suggests%20that%20whales,experiencing%20a%20range%20of%20emotions.
Wright A. J. (2014) "Reducing Impacts of Noise from Human Activities on Cetaceans", WWF: Switzerland; Available: https://www.wwf.de/fileadmin/fm-wwf/Publikationen-PDF/Report-Reducing-Impacts-of-Noise-from-Human-Activities-on-Cetaceans.pdf
Yong E. (2018) Once again, a massive group of Whales strands itself, Available: https://www.theatlantic.com/science/archive/2018/03/whales-mass-stranding-australia/556400/