Over the past month, I have been reading the book ‘Of Orcas and Men: What Killer Whales Can Teach Us’ by David Neiwert. The book paints killer whales (or orcas) as beautiful, intelligent creatures and brings up a number of impacts that humans have had on their species, including boat-engine noise, a less-talked-about type of marine pollution.
Orcas have amazing echolocation abilities, which they use to navigate, communicate and hunt. They produce directional and amplified clicking sounds that can travel up to 800 metres in water and bounce on objects back to the orca (OrcaNation, 2019). This allows orcas to get a mental picture of the shape of the object, as well as what is inside it. Other marine animals like bottlenose dolphins and sperm whales also use echolocation for hunting.
With the rise in popularity of whale-watching tours, orcas are often exposed to boats all day during summer. Most whale-watching boats are not exceptionally noisy, but the sheer number of boats has the potential to affect their communication and hunting. Smaller, private recreational boats may also have a greater disruptive effect on orcas, as they produce higher-frequency noises that are closer to the orcas’ frequency signals. Large ships produce lower-frequency noise, but they are louder and often go on for longer durations. The book also mentions that the orcas sometimes just stay silent as large, noisy ships pass by them.
An orca, with a large ship in the background (photo by Ryan Stone)
The noisy conditions from the mix of boats and ships may require orcas to make louder vocalisations in order to communicate (Holt et al., 2009), which means a greater amount of energy spent. The underwater noise also reduces the range of echolocation, affecting orcas’ ability to detect prey (Holt, 2008).
New rules for boats have been introduced recently in U.S. and Canada to protect the Southern Resident orcas. They include keeping a distance, slowing down or turning off the engine when in the proximity of orcas. Along with education and outreach efforts, it is hoped that the extent and impact of noise pollution on the orcas will be reduced.
Infographic summarising the new rules for boating around orcas (by Be Whale Wise)
References
Holt, M.M. (2008). Sound exposure and Southern Resident killer whales (Orcinus orca): A review of current knowledge and data gaps. U.S. Department of Commerce, National Oceanic and Atmospheric Administration Technical Memorandum NMFS-NWFSC-89.
Holt, M.M., Noren, D.P., Veirs, V., Emmons, C.K. & Veirs, S. (2009). Speaking up: Killer whales (Orcinus orca) increase their call amplitude in response to vessel noise. The Journal of the Acoustical Society of America, 125(1): EL27-32.
OrcaNation (2019). The social intelligence of orcas and communication – Orca series II. Retrieved from https://www.orcanation.org/2019/10/10/the-social-intelligence-of-orcas/ on 20 February 2022.